texts: Why is there a positive charge at the cathode electrode of a battery in a closed circuit?

texts:
Consider a simple circuit that has a resister and a voltaic battery.

Here is what (I think) I know to be true:

If I draw an arbitrary shape around the battery, the net charge enclosed in that battery is zero.
At the anode, electrons are being generated from an oxidation event. Rather than accumulate on the anode electrode, the electrons from the anode electrode enter the wiring that is connected to the cathode of the battery. As electrons enter the wire (from the anode electrode) they can be thought of as "pushing" electrons throughout the wiring towards the cathode electrode of the battery, where a reduction event takes place. The anode is therefore a source of electrons, and the cathode is a sink of electrons.

Here is where I get confused.

Why does the anode hold a negative charge and the cathode hold a positive charge? If the moment electrons are generated at the anode electrode they are shuttled away from the electrode, why would this scenario result in any different charge than what is observed at the cathode electrode?

The only way I can think of mechanistically explaining this is that the anode does, in fact, accumulate some small portion of electrons even when the wire is present / circuit is closed (i.e. some small negative charge is statically present at the anode electrode). Conversely, no such accumulation occurs at the cathode electrode...perhaps, even a "baseline deficit" exists at the cathode.

Is this correct way of thinking about it?


texts: Can I use a PLL to generate the *phase* component of an SSB signal?

texts:
I want to use Kahn's method of Envelope Elimination and Restoration (EER) to produce a single-sideband, supressed-carrier (SSB) signal. Kahn simply clipped a low-level SSB signal, but I wonder if it isn't possible to use a PLL in this application.

Knowing the quadrature components of the input signal (I,Q), it seems one should be able to calculate the instantaneous frequency that corresponds to the time-varying phase (phase = arctan(Q/I)) and apply it to the VCO in a PLL that uses the carrier frequency as its reference.

Any ideas?


texts: Using a GPIO pin as GND is noisy... why?

texts:
I've experienced the following on both an STM32F4, and in my recent experiments with a Pi Pico.
(My goal, which isn't particularly relevant to the question is to create a -12V to +12V square wave using an H-bridge. To drive it I use the 2 microcontroller pins)
When one of my GPIO pins is high, the other is low. (They will feed into the INA1 and INA2 of the H-bridge)
The outputs of the microcontroller are the default Push-Pull. My understanding is that when LOW, it should be switched to GND.
Here is the output when I connect the scope to my two alternating GPIO pins

And here is the output when connecting to 1 of my GPIO pins and actual GND

So why all the extra noise when using a GPIO pin as a ground, and can I do anything about it?
UPDATE
In addition to the comment replies I have made, the issue is power supply related. In both examples the microcontroller (a raspberry pi pico in this case) was being powered through USB. When I removed USB power and connected a buck convertor, the output across the 2 GPIO pins becomes a nice noise-free square wave. While I can't explain the exactly why this works (I would probably need to understand the pi pico build-in power suppy), I am happy that my design will work.


texts:
How do ESD monitors work? Especially those dealing with one wired ESD wrist band. All I've been able to grasp is that the human body acts as a capacitor between the wrist band and the ground. But I don't understand how you can detect if an operator is wearing the wrist band or not. Should you run a current through him?
If anyone knows the answer a detailed explanation would be very appreciated.


texts: Why can optical usb cables not operate below 0°C?

texts: The specifications of this optical usb cable specify operating conditions of more than 0 °C. What is the physical reason behind this?


texts: Turning a USB drive on/off w/out unplugging it

texts:
I have a camera that uses a USB flash drive to store images. The startup sequence for the camera requires that the USB drives NOT be plugged in on startup... only after the camera boards have initialized. I am triggering the camera with an arduino, but would also like to be able to power-cycle the camera via the arduino in case something goes wrong during operation (I'll be monitoring the camera remotely).

The power situation is manageable via a relay and hacking into the shutdown switch on the camera; where I get stuck is the USB drives. I need to be able to "unplug" the USB flash drives while the camera goes through its startup sequence. My current idea is to put a short male-to-female USB cable between the flash drive and the port on the camera, then tap into the power wire in that cable. If I run that through a transistor or opto-isolator and break the power circuit, will the camera think that the USB is unplugged?

I'd love any thoughts on how to get this right!


texts: Old used electronics, can I re-use them for other purposes?

texts:
I have taken apart and had a look at a small dashboard camera which was broken due to the solders on the button going loose and detaching. Upon inspection, I could turn the camera on without it's casing however the screen would just turn white and nothing would happen.

I want to use this as a SD card reader since I don't think I will get the camera to work, the problem is that whenever I try to access the SD card it crashes my explorer due to incorrect drivers. Is there anyway I can make this work or should I just throw this junk away?

Idea of what the situation looks like:


texts: How to connect a Microchip ENC28J60 to 3 port stand alone unmanaged switch chip with out using MCU

texts:
I have a working design running a Microchip PIC24 with TCP IP stack using the ENC28J60 chip. I am new to switching, and would like to add a second port for daisy chaining multiple devices without having to run ethernet cable back to original source.
I've been looking at all kinds of data sheets trying to understand the networking lingo like a KSZ8794 series chips from Microchip, but can't seem to wrap my head around ( as of now) how to go about having the ENC28J60 chip connect to a switch in unmanaged mode / standalone mode. Then once find a compatible chip, then of course next step would be from the switch to the 2 ports.
Can't seem to find any reference designs, with application notes to understand.
I may be looking too deep, and need a higher level understanding before I can get back deep and choose the proper ethernet switch chip, and reference design.
The ENC28J60 is Fully Compatible with 10/100/1000Base-T Networks and Supports Full and Half-Duplex modes.
Thanks for any links, direction and feedback. Needs to use ethernet cable and not wireless for FYI.


texts: Using an active bandpass on a very small signal

texts:
I am trying to design a active bandpass filter for an electret microphone (the output will then be read through a microcontroller to control some LEDs)

(Image source - Electronics Tutorials)

I want to use the following design so that I can replace R3 with a potentiometer to change the gain for different volumes of music, without changing the properties of the bandpass. However, is there a possibility that having the electret microphone feed straight into the high pass filter could cause the signal to suffer, before it has been amplified? Op-amps aren't really my forte yet, so any pointers in the right direction would be greatly appreciated!

Many thanks.

(Image source - RS Components part number 780-0725 datasheet, linked from this product page)


texts:
I want to design a schmitt trigger which triggers 3.3V above -8V (independent of whether inverting or non-inverting schmitt trigger) when the input voltage is greater than 14V and less than -6V. my total supply voltages are +15V and -8V and 3.3V above -8V (i-e -4.7). My comparator is a open collector comparator which can be connected to 3.3V to match to the output logic. The output signal of Schmitt trigger should go to microcontroller.

simulate this circuit – Schematic created using CircuitLab

As my output voltage is allowed to be in range of -8V and -4.7V (uC GND is -8V and Vcc = -4.7V), I dont know how to calculate R1 and R2 to reach this. If I calculate using +Vsat = -4.7V and -Vsat = -8V, I get negative values of Resistors.

e.g to trigger at upper threshhold of +14V.

14V = -4.7V (10K) / 10K + R1 => R1 = -13.35 KOhm

Could you please tell me where I am wrong. How to do this ?
Should I use voltage divider at inverting input to scale +15V - (-8V) = 23V to 3.3V frame  ?

I expect hysteresis like shown in a graph.

Thanks.


texts: Is this ADC circuit safe for when my Pro Micro is off?

texts:
I have the following little circuit:

This voltage divider is used by my Pro Micro to detect when CB_VCC is powered. CB_SENSE leads to an ADC pin on my Pro Micro.

Is this circuit safe for when the Pro Micro is off, but CB_VCC is powered? I'm dealing with 3.3V (that's what's powering the Pro Micro and CB_VCC). Do I need a series resistor before the ADC pin?


texts:
I want a RPi to act as a SPI master and be able to communicate with 24 SPI slaves. The SPI connection is full-duplex. The SPI slaves are about 50 cm away from the master (SPI runs on wires to an other PCB board not considered here).
The 24 slaves will be Blue Pill STM32 boards, I have to use DMA on the SPI slave (CPU is very busy).

I have successfully communicated using SPI with 50 cm unshielded cables with a reasonable enough baud-rate for my application (9 MHz).

I'm pretty sure (though I have not tested) I will run into problems because of the multiple SPI slaves and long wires so I designed a schematic and I would like you to tell me what may work and what may not. There is also probably room for simplifications.

Design

I plan to use 3 daisy-chained 74HC595 shift registers to generate 24 outputs that will determine to which SPI slave the RPi will be connected to.
I plan to use CD54HC125 quad tri-state buffers to isolate the other SPI slaves when connected to one, these would be driven by the shift registers outputs.

Raspberry Pi

SER, SRCLK and RCLK drive the shift registers
SPI_CS, SPI_MISO, SPI_MOSI and SPI_SCLK drive the SPI communication (RPi is the master)

Shift registers

SER, SRCLK and RCLK driven by the RPi
Daisy chained
Each SPI_x output will drive a tri-state buffer

Tri-state SPI buffers

There are 24 similar blocks like this, only the SPI_x changes
Each 01x04 male connector leads to one SPI slave
Output enable is driven by one of the shift register output (here SPI_0)
SPI_MISO is inverted because it is an output pin of the slave

This is my first KiCAD design, review and comments would be much appreciated before I buy components and try to test on a breadboard! After that I plan to layout the PCB and get it manufactured.

Edit ( July 2018): Real world test

I have just tested the communication between one Raspberry Pi (master) and 6 blue pill (STM32) boards, full-duplex.

Without any additional device and despite the poor wiring the communication works at 10 MHz reliably; 99.6% over 12 000 messages (checked with a Flechter sum)

Whether this scales up to 24 device or not remains a question :)


texts:
When i tried to code the below flip flop, the program failed. I'm using altera .

module DFF_SYNC_RESET(Din, nRst, Dout, Clk);
output Dout;
input nRst,Clk,Din;

wire D;
assign D= Din & nRst;

always@(posedge Clk)
 begin
  Dout<= D;
end

endmodule

Can you please tell my failure in the code?

Edit: After i encountered to another problem which is the same as in this page, the problem was solved

https://stackoverflow.com/questions/25832326/altera-quartus-error-12007-top-level-design-entity-alt-ex-1-is-undefined


texts: What are the items you have in your personal electronics tool kit?


texts: error in dimension for adder in negative feedback loop

texts: im a universiity student i was trying to model this state space with simulink i tried to use the state block but got the same error i think i need to use mux i already checked the dimensions for A B C and Kc can anyone help?


texts: What is the control Input of the small signal current mode PWM switch

texts:
I am trying to simulate the open loop transfer function of my system. My system is really classic. A converter (the plant transfer function), a sensor and a corrector which is a simple Integrator (1/(1+s/wp)). My corrector is a discrete transfer function. But I use the inverse bilinear transform to get it in the S domain. (I do not think that it is possible to simulate discrete transfer function in LTspice). My problem is the following, it doesn't work. When I simulate it with a transient analysis "trans", the duty cycle given is not correct and the output of my controller does not move in function of the output where as the output is really moving correctly because I used a method which set automatically the operating point #ChristopheBasso. I would like to be sure to what I have to apply on the control input of the PWM switch.
If I used the UC384X, from my side, I think the Input control of the average PWM switch is equal to the input of the comparator as it is shown above.

So after my corrector, I have to simulate the error amplifier? Isn't it? The model that I have of the error amplifier is clearly not representative of the real model. I saw when I looked the bode diagram of the error amplifier. But I do not think that It will prevent to make my simulation work. Then I should got add the real model if I want to obtain the correct open loop transfer function.
Here is how I set the error amplifier.

Have a nice day!


texts:
Can you please help me identify these components and state their function?
These were taken from the inside of a digital thermometer.


texts: Why is it good to slow down digital lines with resistors?

texts:
I've heard that sometimes it is recommended to "slow down" a digital line by putting a resistor on it, let's say a 100 ohm resistor between the output of one chip and the input of another chip (assume standard CMOS logic; assume the signalling rate is pretty slow, say 1-10 MHz). The described benefits include reduced EMI, reduced crosstalk between lines, and reduced ground bounce or supply voltage dips.

What is puzzling about this is that the total amount of power used to switch the input would seem to be quite a bit higher if there is a resistor. The input of the chip that is driven is equivalent to something like a 3-5 pF capacitor (more or less), and charging that through a resistor takes both the energy stored in the input capacitance (5 pF * (3 V)2) and the energy dissipated in the resistor during switching (let's say 10 ns * (3 V)2 / 100 ohm). A back-of-the-envelope calculation shows that the energy dissipated in the resistor is an order of magnitude greater than the energy stored in the input capacitance. How does having to drive a signal much harder reduce noise?


texts:
I'm in a CMOS class and we are currently going through the second order effects of a NMOS. I have a few questions.

When the body isn't connected to the source, the threshold voltage increases. Meaning as VGate increases, Vsource will eventually level off.

And when the body is connected to the source the threshold voltage stays constant, meaning as VGate increases, VSource increases as well.

What I do not understand is why isn't the body always connected to the source? Is there a downfall from always having the two connected?


texts: Problem with overvoltage protection circuits limits

texts:
I have a circuit which input voltage shouldn't exceed 50 V, I can't use neither of available overvoltage protection circuits because of the limits each have;

Crowbar circuit. While this is a good approach, the fuse in the circuit is 10 A. What if overvoltage condition occurred but the source supply can't provide 10 A to blown the fuse? For example if the input voltage is 60 V and supply can only provide a maximum current of 5 A, that's 300 W on the SCR and fuse is not going to open.

P-channel MOSFET based overvoltage protection. This circuits working condition is depended on the gate voltage and is not a sharp cut off like crowbar circuit. assuming the mosfet have 50 mΩ RDSon with 10 A over it, that's 5 W of power loss, not to mention the price on low RDSon p-channel MOSFETs.

How do I protect the input from overvoltage condition and overcome the problems described? is there a better approach?

Input source can be a battery or power supply of any kind (DC), input voltage shouldn't exceed 50 V and maximum current is limited to 10 A both by a fuse and design.


texts: Is there any real world difference in upgrading TL071 to OPA314?

texts:
I have a DIY made guitar amp in which there is a TL071 preamp section.  I read various opinions about how upgrading op amp improves that sound and how it doesn't do anything really...  I'm quite confused - would upgrading TL071 to OPA134 make a distinctive difference in sound and quality? And if not is there any other advantages in upgrading?  And what other op amps would you recommend that would be a 'direct' replacement for TL071 instead of OPA134  (I don't plan to spend big so it should be on the cheap (up to 3-4$).
Another thing which I could not find myself is whether a 'better' op amp improve the output level? Bigger output really wouldn't hurt for my little amp - there would be lots of more headroom for various instruments :)
  I think I should mention that two inputs goes to the preamp  (connected by two resistors).


texts:
What prevents someone with some funding from creating and selling their own hardware? Let's ignore the legal side of things and assume the only limit is technology.

Could someone create something akin to a 1995-2000 time period processor without specialized equipment? What about slightly earlier, like the "computer pioneers" did?


texts:
I was given in class a problem about power transform but I don't understand which current is used in a stage of the resolution. It is asked to find the efficiency of a transformer in a period of a day (24 hours) given that;

\$S_{N}=110kVA\$
\$2200V/110V\$
\$ 60~ Hz\$
\$R_{1}=.22\Omega\$
\$R_{2}=.5m\Omega\$
\$X_{1}=2\Omega\$
\$X_{2}=5m\Omega\$
\$R_{c}=5.5k\Omega\$
\$X_{m}=1.1k\Omega\$
with this power cycle
4 hrs with no load
8 hrs at 1/4 full load and pf .8
8 hrs at 1/2 at pf 1
4 hrs at full load and pf 1
Constant core loss of 1.346 kW
Both in the resolution given and my idea  is to make this fraction

\$\eta=\frac{output@24hrs}{input@24hrs}\$

first
\$output=(4\times0+8\times.25\times.8+8\times.5\times1+4\times1\times1)=1056kWh\$
then the core loss is
\$1346\times24=32.3kWh\$
and finally the ohmic losses in the windings

8 hrs at .25 full load
(\$250^2\times0.005+14.1^2\times.22)8=2.85\$
4hrs at .5 full load
(\$500^2\times0.005+26.6^2\times.22)4=5.62\$
8hrs at full load
(\$1000^2\times0.005+51.7^2\times.22)8=44.70\$

but I don't understand why 14.1, 26.6 and 51.7, isn't supposed to be the nominal current on the high voltage side
\$I_{1N}=\frac{110000}{2200}=50A\$?

and that would be

8 hrs at .25 full load
(\$250^2\times0.005+12.5^2\times.22)8=2.85\$
4hrs at .5 full load
(\$500^2\times0.005+25^2\times.22)4=5.62\$
8hrs at full load
(\$1000^2\times0.005+50^2\times.22)8=44.70\$

If not then which current is this and how to calculate?

UPDATE
the total ohmic loss will be 53.17kWh and then

\$\eta=\frac{1056}{1056+32.3+53.17}=92.5\%\$
But I still don't get how the 14.1...and respective currents are calculated


texts: High speed logic level converter circuit

texts:
I have been trying to make a 3.3V circuit controlled by an Arduino (5V logic.)
I have used a logic converter circuit similar to the SparkFun/Adafruit ones. My problem is that whenever i try to increase the clock speed of the main circuit up to 1MHz, the circuit does not work.
What options are there for high speed logic conversion? I don't necessarily need bidirectional conversion, however it would be nice if it would be bidirectional.


texts: I'm looking for an IC that will give me a minimum of 6 independent PWM channels for motor control, preferably with an SPI interface but this isn't critical. My micro will be busy with floating point calculations etc so I don't want to risk tying it up. Any suggestions?


texts:
I use a SainSmart UNO with LCD4884 and HC-SR04 Distance sensor and an Arduino Shield Plus SD (SD-card module with RTC-DS1307) to measure the water level of a well. The calculation and LCD4884 display works well. But as soon as I initialize the SD card, the program does not work. I've also tested the "SD Arduino Shield Plus" individually and the read and write and it works on an SD card without problems. I got a short program, where the same effect occurs when the line "SD.begin" fits. What can be the cause?

#include
const int input = 13;
const int output = 12;
unsigned int duration, inches;

void setup() {
    Serial.begin(9600);
    // SD.begin(10); <- When I use this line paste like this, it does not measure the distance.
}

void loop() {
    pinMode(output, OUTPUT);
    digitalWrite(output, LOW);
    delayMicroseconds(2);
    digitalWrite(output, HIGH);
    delayMicroseconds(5);
    digitalWrite(output, LOW);
    pinMode(input, INPUT);
    duration = pulseIn(input, HIGH);
    inches = duration / 74 / 2;
    Serial.println(inches);
    delay(1000);
}


texts: Capacitor in series with transistor base

texts:
I am fairly new to electronics and just had a quick question. I saw the following suggestion for a one shot trigger to wake up an ESP from for example a PIR sensor with one shot trigger and to read the data on another pin:

I do not understand how current can reach the base of the transistor and make the collector emitter path conductive. I always was under the impression that capacitors do not let current flow in a DC circuit and just charge up. I would have expected the capacitor in parallel to the base emitter path, so it would charge up and delay the current flow to the base and the resistor in series from interrupt signal to base to limit the base current. Any answer is greatly appreciated!
I am sorry if my English is not the best, it is not my first language.


texts: Switched capacitors using MOSFETs in filter design

texts:
I'm designing a State Variable Filter design using switched capacitors to control cut-off and resonance. Simulating this using idealized switches yields excellent results. See attached schematic

After that I proceeded to replace one of the integrators with a MOSFET version (the center-right part of the circuit). This doesn't work. I'm using a parasitic-insensitive switched cap implementation as you can see. See attached schematic

I tried a couple of implementations for the switches. First of all the parasitic sensitive version, and after that several parasitic-insensitive versions like this one. I've also tried several different NMOS models.

Can anybody tell me what I'm doing wrong here?


texts: Informations about FT2232H as programmer

texts:
I was looking on a EVB that use FT2232H chip to program an SPI ram used in second time to programm another device.

My question is, if I copy the circuit that programm this SPI ram and use the same programmer provided by producer of EVB, it will work or FT2232H is a programmable chip with some kind of blocks or periferical selection?

Here's schmatics of USB interface and SPI flash connections:


texts: What's the need of translating the virtual address to physical address?

texts:
These are the points I read in the Memory Management Unit of ARM architecture:

Virtual addresses (or logical addresses) are addresses provided by the OS to processes.
One virtual address space per process
Programs use virtual addresses. As a program runs, the hardware (with help
from the operating system) converts each virtual address to a physical address.
The conversion of a virtual address to a physical address is called address
translation
When the MMU is turned off, the virtual acts as output onto the physical address.

After reading the fifth point, I want to understand why do the address translation is required? Is it because the size of virtual memory is smaller than physical memory? And why/when would the MMU is turned off?


texts: Charging laptop using external 18650 cells

texts:
I happened to be given 7 laptops that were destined for the landfill. All of them came without DC power adapters. Realising it would take a long time to receive DC power adapters by mail, I looked around.

Looking through my excessive 5v - 12v power adapters I found DC jacks that fit each of the laptops and cut each of them off.

The laptops I wanted to charge all required 19v inputs.

I placed 5 18650 cells in series, soldered wires them to the DC jacks, added a diode to the positive end and checked with a multimeter to get a voltage around 19.5v (inner being positive and outer shield ground.)

However, once I plugged the batteries into the DC jacks of each of the laptops, nothing happened. Except for one laptop which consumed ~10mAh from the five 18650 cells, but that was it.

Is there more to a DC power adapter? Why do (good quality) 18650 cells not work for the job?


texts:
I'm trying to work out whether I can talk via SPI without level conversion between a PIC at 5V and an MCP3202 ADC at 4.096V (Vref and Vdd share a pin on the ADC).

I looked at the data sheet for the ADC and found the following:

I'm a bit confused by the "Low Level Input Voltage" line, for example. You see, normally I'd interpret the 0.3Vdd in the Max. column as saying "Every chip has a low level input of at most 0.3Vdd". But that doesn't help me - I want to know (for example) that my PIC's low-level output (guaranteed <=0.6V) is less than the low-level input.

Now, I presume that I'm reading things backwards, and the "Low level input voltage" line means "As long as the voltage is below 0.3Vdd, the MCP3202 will regard it as a digital zero". After all, that's the only useful spec I could imagine. However, this is backwards from what Max. and Min. for other specs tends to mean (for example, the Input Leakage Current is guaranteed to be less than 10µA, not at least 10µA!)

Have I understood this correctly?


texts: Bipolar stepper motor: What should the sequence timing be?

texts: What I mean is, how long should a coil be energized before it's de-energized. Also how long should the coil stay de-energized before I power it in the reverse direction. Where can I find this timing information for stepper motors. I've been having trouble googling stepper motor sequences. I have a H-Bridge connected to a bipolar motor and to an AVR. If the coil isn't powered long enough, the stepper motor might not fully jump to the next position, right?


texts:
How does a Vector Network Analyzer (VNA) measure S parameters actually?

Namely we have equations:

\$b_1=S_{11}a_1+S_{12}a_2\$

\$b_2=S_{12}a_1+S_{22}a_2 \$

In theory, if i wanted to calculate scattering parameters I would have to be able to make perfect matching on the source (\$a_1=0\$) and on the load side (\$a_2=0\$).

Unfortunately I do not understand how is this done inside the VNA. If I want to measure scattering parameters of a random network with input and output impedance different than 50ohm, how is in this case achieved \$a_1=0\$ and \$a_2=0\$?


texts: VNA measurement of a domestic 3 wire AC cable used as a parallel transmission line

texts:
I am currently working on power line communication techniques for low and medium bandwidth applications. I was curious to calculate Z0 on a 3 wire, 1.5mm2 power cable. The theoretical impedance of a parallel transmission line calculation works only for 2 wires, and since there is a protective earth conductor, I doubt it could be calculated easily.
So I'll need to measure it. (open circuit, then short circuit of phase/neutral)
After that I will perform real world measurements (S11/S21) on a live cable/outlet, and i will use a 275V AC 0.044uF filter capacitor and a pulse 1:1 transformer t3001nl for each port as a HPF and then work on from here. If the 50 Hz / 230V AC is sufficiently attenuated, I should not fry my VNA.
Then I will make more measurements on different outlets in the house.
Since it is an improvised transmission line with branchings at the power panel, I'll expect to have wildy variable measurements.
my frequencies of interest are in the 2 Mhz to 900 Mhz range. I don't want to pass too much low frequency in my filter to keep AC 50 hz levels low.
Any safety advice or other tips for that kind of measurements ?


texts: Sensing weight with strain gauge, InAmp, ADC & Pi

texts:
I have an SEN-10245 sensor for weighing objects (essentially a strain gauge). The goal is to capture data with a Raspberry Pi, so the signal from the weight sensor needs to be amplified and then ran through an Analog to Digital converter. I have the AD620 InAmp paired with a 47 Ohm resistor to set the gain to ~1000, which is then ran through the MCP3008 Analog to Digital Converter. I then hooked the converter up to the Raspberry Pi following this Adafruit tutorial

Question: Where should the red black and white leads of the load sensor be connected; this is the signal that needs to be amplified by the InAmp.

AD620 Data Sheet

MCP3008 Data Sheet

The pictures below illustrate my current setup:


texts: How to Turn off a PIC Microcontroller in high capacitance circuit?

texts:
Below image is the input voltage VDD to PIC16F18326. I am turning off (Switching off the mains supply) my circuit at point A (see image). Due to large capacitance at load, which is required in my circuit to reduce large current ripples, the VDD to microcontroller is OFF after 8Sec. But I want to turn off my microcontroller immediately (within 1 sec) after I turn off the mains.

I have tried to change the capacitance placed across the VDD. No big changes in the time taken to turn off.

The VDD is supplied and controlled by a LinkSwitch (LNK304) which is fed from the output. I tried to control the feedback FB of LNK304. But the large capacitors at the output has high influence on this as well.

Any simple idea, how to Pull Down this VDD when my I switch off the mains? (Any suggestion on Addition of a component at VDD? for eg. Logic level MOSFET?)

Thanks in advance.

update: µC schematic (not complete) (VDD is supplied by LNK304)


texts: RS485 half duplex mode in full duplex IC

texts:
Datasheet link
I am unsing full duplex RS485 feature IC.

Please confirm below

To use this IC in half duplex mode I need to short Pin B to pin z and Pin A to Pin Y.
Since thease pins are internally not shorted ( beacuse it is full duplex feature IC).


texts:
I am using a TI CC1120 + CC1190 combination to transmit data wirelessly using Sub 1 GHz link. My output power is about 27dBm according to the CC1190 SOC.

I want to determine the maximum power (an approximate) that I would be able to see (through RSSI readings) of the receiver circuit (another CC1120 + CC1190) if the boards are about 1-2 meters apart.

I currently receive about -25 - -30 dBm when I keep them a couple of meters apart but I intend to know a usual ballpark RSSI figure that can be read from a receiver when the tx is about 27dbm.


texts: How can a ring oscillator work without burning?

texts:
I built this ring oscillator and it works fine. After a while I wondered how can it work without breaking.
I am powering it with 5 volts so at start let's say capacitor is charged with 0 volts and a blue node is at 0V. So capacitor starts to charge via R1. When it reaches Vih min (~3.2 V) for IC2A the voltage level is flipped (so voltage at blue node will become high) and now is a red node at Voh + Vih (5 + 3.2 = 8.2 V) which is much higher than allowed from datasheet. This voltage is connected via R2 to input pin.
I've used this oscillator for maybe a year now and it's working fine. The IC is an SN74HC00N.
What I am missing?


texts: Understanding the application of a switching regulator as a constant current LED driver

texts:
There is an application note from ON-semiconductors which provides a few diagrams to use a well known MC34063 switching regulator as LED driver. it's around the idea of setting the 1.25v feedback value using the voltage drop of a series, current sense resistor :

further, it suggests using a transistor to "shift levels"(as it says) so the current sense resistor doesn't have to be that big to provide 1.25v drop; now it needs a voltage drop of about 0.65v, and less power is wasted in the resistor:

how this transistor provides 0.6v (1.25-0.65) so the resistor is less burdened? does it have anything to do with base-emitter voltage drop ?
there are many adjustable regulators with the same feedback setup (e.g. LM2596 or the linear LM317). does this idea (either the one with the transistor or the one without) work on them too?
does it work on the same MC34063 configured as step up? to drive LEDs from a single cell lithium ion battery for example?
can we use another component to provide more drop so the power dissipation of current sense resistor is decreased even further?

regards


texts: What is the difference between using an USB Logging Software and Logic Analyzer for signal sent to the printer?

texts:
In my recent pursuit in exploring the workings of an inkjet printing head, I need information like the default firing voltage and waveform set by the printer's manufacturer for different instructions sent to each pin on the printing head.

Assuming that the printer is connected to the computer via USB, can I use an USB Logging Software (eg. USBlyzer etc.) installed on the computer, in place of a Logic Analyzer or Oscilloscope(probing the pins of the printing head) to get the information for the purpose above?

What is the main difference between such a software and hardware approach of measurement, apart from the cost?


texts: Just chopped two USB cables,but one of them looks unusual

texts:
I just chopped two USB cables but one of them has three white cables and one grey. The other wire has normal colouring of:-Black, Green, White, Red
First wire:

White

White(has single orangestrand)

White(has orange strand too)

Grey

Could someone tell me what combination should is use to connect them to each other.
I am connecting microUSB to USB 2.0.


texts: How to record input from multiple microphones so there is no latency between microphones due to writing to memory

texts:
I am going to be doing some beam forming. I understand the concept and plan to record all the data then analyze the signals from multiple microphones to figure out locations of some noises (there will be multiple locations per trial). I am stuck on how to record the data from multiple microphones at the same time. I can use a computer or a designated micro controller to do this. I plan on using 3 to 10 microphones.

Thank you in advance.


texts: What limit switches would be necessary for use in series with a DeWalt 20V cordless drill battery?

texts:
I am on a senior design team at school. We have designed a mechanical system that uses a DeWalt 20V drill motor to drive the system. It is powered by the stock lithium ion batteries. I need to implement a few limit switches. I think 4 will do the trick, two of them will be SPST and two will be SPDT. I ran some tests with an ammeter and found the drill is pulling 17 amps without a load. When loaded, there were a few 100 amp spikes. What limit switches can I use that will handle this sort of power? (I am assuming 20 V * 100 Amps = 2000 Watts) I need them to have a fairly small footprint. Is this even possible to accomplish? Thanks in advance for any help.

I have added a wire schematic, maybe this can help. It was a bit dicey how I measured the current. I pulled the battery out of the drill, and completed the connection with wire and an ammeter to get power to the drill from the battery which was laying on a table. It was crude, but the motor came on, and the ammeter spit out a reading.


texts: FTDI chip based custom board. Driver not working

texts:
I designed a board containing a USB to UART bridge in order to program a ATmega microcontroller. I copied the schematic of this breakout board from Sparkfun

https://www.sparkfun.com/products/9716

This is my schematic:

I install FTDI drivers from this link:

http://www.ftdichip.com/Drivers/VCP.htm

in "windows - setup executable". It doesn't work. My computer doesn't recognize it. I have windows 8.1 and I think it could be related. I disabled device driver signatures.

I don't know what to do now. I don't think it's related with my schematic, but I can't solve this problem.

Any idea?

Thank you.


texts:
I got a MSP432P401R LaunchPad and wrote/ran some applications with it.

What if I want to use it in a real life application. How can program the MCU when I design my own circuit and place it on the pcb. My guess I need to connect programming pins of the mcu to some pin headers and connect an external programmer to those pins, when the code is uploaded the pcb will be ready to work.

My question; what is the minimum connection I need to do between the programmer and the MSP432P401R, which pins are the programming pins and what kind of external programmer I would need?


texts: Simplify a logic expression - Where have I gone wrong?

texts:
I am trying to simplify a logic expression but I think I simplified it too much. The expression is as follows:

$$\overline{\overline{(A \cdot B)} \cdot C \cdot (\overline{A}+\overline{(B+C)})}$$

This is what I got after I did the simplification:
But Logic Friday says that the answer should be:

$$A \cdot B+A \cdot C+\overline{C}$$

Which one is correct? Am I allowed to do the manipulations I did in this case?


texts:
LG has this Wi-Fi module:

This is a 2X2 Dual Band AC Wi-Fi / BT module. You will see two folded WiFi antennas on upper side and one bluetooth PCB trace antenna at the lower right side.

I found this PCB very interesting because of the weird shapes/prints on all over it. For example:

What does this two stubs do? They are GND layer (I checked with measurement. It is GND layer). The same shape also is on Top layer too. Is that supposed to achieve something? I really would like to understand if it is so.

another example is this one.

This is basically a dead copper. I checked many times. It has no connectivity to any other conductive. It is just below one of the Wi-Fi folded atnennas. If it is there for some reason, I'd like to know why.

3rd example is this one:

This is another stub. Just below the same Wi-Fi antenna. It can be seen that this is connected to GND layer.

4th example is these slots:

Maybe, it is a long shot but maybe, the one slot that is closer to Bluetooth antenna has something to do with its impedance, but the other is definetely not near to any antenna or any RF trace.

The last example is on the TOP Layer were the Wi-Fi antennas are.

You will notice that the symmetry is broken on the upper side stubs. One is 'L' shaped where the other is straight 'I'. Also there are L shaped cuts on the GND layer.

Can you explain me the purposes of this weird modifications on the PCB? I don't need the equations, just sensible explanations will be more than enough for me. Thanks.


texts: Changing an active low decoder to active high?

texts:
I apologize if my question sounds stupid, but I'm a novice and trying to explore all of my options. I currently have a 4/16 decoder, but I did not realize it was active-low and what I really need is an active-high decoder. How might I go about fixing this without putting an inverter on every output? Thanks!

(datasheet: https://datasheet.octopart.com/NTE74HC154-NTE-Electronics-datasheet-22129262.pdf)


texts:
Let me say to set the scene, that I am a complete beginner with electronics, not having done anything since my school days.  I can write code, but hardware is another thing entirely.

I got myself an Arduino, and bought a breadboard from Maplins. The only thing is, the layout is very different to what I see on most tutorials, and I don't want to risk damaging anything.

Can anyone link to any tutorial which uses this breadboard layout?


texts: What does the logic statement "F = AB" mean? Bitwise A AND B?

texts:
On an ALU data sheet there are logic formulae showing the results that will be output for various inputs.

http://www.farnell.com/datasheets/1840939.pdf

(Second from last row on page 3.)

I assume that A+B means bitwise A OR B, this would follow, as the plus in a circle is XOR.

Does AB mean bitwise A AND B?


texts: About capacitors the formula Ic = C*dV/dt refers to the displacement current or to the current which charges/discharges the capacitor?


texts:
I was during a 868MHz transmitter layout, and as always, I have placed the filter and matching inductors and capacitors in a "straigt line" from the TX output pin to the antenna. See picture below.

I was once told by and more expirienced RF guy, that TX outputs should always be in a straigt line to the antenna, if possible, because sharp turns in the signal path, could cause several dB of loss. But, say that due to limited space, it was not possible to make the TX signal path a straight line.

Would it still be possible to make a good RF design, if not using a straight line, and what are the best design principles in such case ?

EDIT: After feedback, I have changed the layout to the following:

Is this more correct now ?

Should I worry about orientation of inductors in relation to there magnetic fields, I have seen application notes from manufactures where they pointed out, that it was very important to orient inductors correctly, or else there magnetic field would effect the inductor behaviour?
Snapshot from TRC105 reference design (NOT the chip I am using for this design):


texts: Two varying & equal opposing Induced EMF's and a converter in between?

texts:
This question is to touch base on the understanding and knowing limits of a DC converter when in a complex and odd situation.

From this schematic:

simulate this circuit – Schematic created using CircuitLab

A battery of constant voltage is in series to a conductor that is placed in a changing magnetic field over time, inducing an EMF with a polarity as indicated in the circuit as "Induced EMF(1)", both the battery and the induced EMF(1) are in series as the input voltage to the DC converter, the intention is to increase or decrease the applied voltage and ultimately the current(if there is a load). The outputted voltage( BAT + Induced EMF(1)) is opposed by Induced EMF(2) that is exactly the same in magnitude to the induced EMF(1), both I-EMF(1) AND I-EMF(2) are induced at the same time.
I'm confused as to how things would turn out due to the converter, in a general sense what might happen?

If I excluded the DC converter like so:

simulate this circuit

It would be easy, the net voltage would be: BAT + Induced EMF(1) - Induced EMF(2) = BAT.
Since Induced EMF(1) = Induced EMF(2). However, what if the convert is in between as the first schematic? And lets say the inputV(to the converter circuit)>outputV or vice versa intputV < outputV? The result is the same?

Edit: In a case of a boost converter:

simulate this circuit

Where Vout(Vemf(1) + Vbatt) < V(emf(2). However, the output current is higher than inputted now, my goal is to cancel out the induced EMF(since they are equal) I think adding an inductor would solve that? Due to the higher magnetic field caused by the higher current outputted?

Edit(2): Without changing the properties of the given magnetic field that created EMF(1) and EMF(2) for the case of a buck-converter specifically I propose adding an inductor to compensate(and if possible) cancel out EMF(2) from the output voltage:

simulate this circuit

Since the output is of a higher current(do to Vbatt + Induced EMF(1)) the conductor would create a considerable magnetic field to maintain the current, when the  Induced EMF(2) induced, it should compensate for the loss?


texts: Transistor system like a shift-register?

texts:
I'm new to electronics and need a name for a type of component that I seek.

I want to find a component that act as a shift register but with a transistor result rather than the voltage output that the shift register have.

The reasons for this is that I want to make a hack on a remote that has a HT6222 matrix keyboard decoder with IR output for remote control applications. I want to control the connections between the C and R inputs of the HT6222 (for rows and columns of keyboard).


texts:
I am building a smart door at home. One of the features I am using is a PIR to detect if someone is staying behind the door. Unfortunately due to the facilities constraints the PIR and its cables will have be exposed.

I would like to make sure that I build a circuit resistant against malicious use. For example, someone connects the PIR wires into a 220V power plug.

Below you can see how I place all the components in my circuit:

I made sure to use some diodes and a resistor to ensure my Raspberry Pi doesn't get damaged. Is it enough to protect my system?


texts: Transistor parrallel to Voltage Regulator

texts:
I'm encounter following schematic in a product.

It gets 110VAC and provide 5V DC to the board. After many inspection I still can't understand what Q2 and R4 do in this design.

First of all after T1, Voltage down convert to 27.5 volt. If we assume D1, R3 and D2 reduce at most, Vin at Voltage Regulator will at least be 25V in no load which is very higher than LM123 Vin Absolute Maximum (Specified 20V in Datasheet)

And another mystery is, if we assume 5V at the LM123 output, Base-Emitter junction of Q2 will have 20V on it :|. So IMO either of Q2 or LM123 will explode.

So the question is where am I going wrong?


texts: Removing/Subtracting Lead Resistance Using Op Amp Circuit

texts:
I'm working with RTD sensor, and need to use Op Amp circuitry.

Can someone explain to me how this Op Amp circuit work to remove the lead resistance?

So that Rw1, Rw2, and Rw3 vanish, hence the output from Op Amp Vout3 = IREFF * RTD

along with the calculation please if possible...


texts: Resistor causing problems when in series with LED

texts:
I am wanting to dim the light on my computers power light, its just a 5mm LED what i am guessing gets 5v from the motherboard to power it

The problem I am having is that when adding a 100R resistor in series with the LED it randomly turns on and off and sometimes flickers, then at other times it is fine

I tried with a different 68R resistor but the same issue occurs?

any ideas?


texts: VHDL - Unable to correctly implement complex scheduling of data lines to Inputs of multiplexers

texts:
In my design, I have two configurable parameters

R = 4  = Number of Multiplexers
L = 16 = Number of data lines
W = 16 = bit-width of each data line
M = 4 = Number of input data lines per multiplexer = L/R

My design has following ports

fir_in = x[n] as W-bit input
fir_out = y[n] as W-bit output

I obtain L-data lines using L registers:

x[n-1], x[n-2], ..., x[n-L+1], x[n-L]

VHDL code to generate this is as follows:

type  t_reg_x is array ( 0 to L-1 ) of signed( W-1 downto 0 );
signal reg_x : t_reg_x                     := ( others => ( others => '0' ) );

-- Generate x[n-1],x[n-2]...x[n-L+1], x[n-L]
process ( clk, reset_n )
begin
    if ( reset_n = '0' ) then
        for i in 0 to (L-1) loop
            reg_x(i) <= ( others => '0');
        end loop;
    elsif ( rising_edge(clk) ) then
        reg_x(0) <= signed(fir_in);
        for i in 1 to (L-1) loop
            reg_x(i) <= reg_x(i-1);
        end loop;
    end if;
end process;

I then divide my L-data lines across R multiplexers such that each multiplexer has M=L/R data inputs. However I am scheduling my delayed x[n] data lines to multiplexer input in following fashion:

-- Allocate following data lines as inputs to the rth multiplexer:
--              m = 0    m = 1         m = M-1
--  r = 0   :   x[n-1]   x[n-1-R]  ... x[n-1-RM+R]
--  r = 1   :   x[n-2]   x[n-2-R]  ... x[n-2-RM+R]
--  r = 2   :   x[n-3]   x[n-3-R]  ... x[n-3-RM+R]
--  ..
--  r = R-1 :   x[n-R]   x[n-R-R]  ... x[n-R-RM+R] = x[n-RM]= x[n-L]

The VHDL code to do this is as follows:

type t_array_mux_in_x is array ( 0 to L-1 ) of signed( W-1 downto 0 );
signal sig_array_mux_in_x : t_array_mux_in_x := ( others => ( others => '0') );

process( reg_x )
begin
    for r in 0 to R-1 loop
        for m in 0 to M-1 loop
            sig_array_mux_in_x( r*M + m ) <= reg_x( m*R + r );
        end loop;
    end loop;
end process;

Using the generic parameter values as listed above, I expected following signal assignments to be generated:

r = 0
sig_array_mux_in_x(0) = reg_x(0)
sig_array_mux_in_x(1) = reg_x(4)
sig_array_mux_in_x(2) = reg_x(8)
sig_array_mux_in_x(3) = reg_x(12)

r = 1
sig_array_mux_in_x(4) = reg_x(1)
sig_array_mux_in_x(5) = reg_x(5)
sig_array_mux_in_x(6) = reg_x(9)
sig_array_mux_in_x(7) = reg_x(13)

r = 2
sig_array_mux_in_x(8) = reg_x(2)
sig_array_mux_in_x(9) = reg_x(6)
sig_array_mux_in_x(10) = reg_x(10)
sig_array_mux_in_x(11) = reg_x(14)

r = 3
sig_array_mux_in_x(12) = reg_x(3)
sig_array_mux_in_x(13) = reg_x(7)
sig_array_mux_in_x(14) = reg_x(11)
sig_array_mux_in_x(15) = reg_x(15)

In my testbench, I first rest my design for 1.5 clock cycles. The I disable the rest, enable the filter and set the fir_in to constant value of 2.

I run the simulation until this constant value of 2 is shifted across all L registers from x[n-1] to x[n-L]. As much as I would have hoped, the simulation results donot seem to match the expectations.For example, after enabling the filter and setting fir_in to 2, I expect that in next clock cycle, all sig_array_mux_in_x signals should be set to 0 except sig_array_mux_in_x[0] which should be set to 2. However, not only sig_array_mux_in_x[0] but sig_array_mux_in_x1, sig_array_mux_in_x[2] and sig_array_mux_in_x[3] are also set to 2 in the same clock cycle.

I donot know what is wrong with my VHDL code. Here is the link to my VHDL code: https://www.edaplayground.com/x/2_xm


texts: Is there anything glaringly wrong or bad with this circuit?

texts:
I'm changing out the pump for a pond and I am looking for an objective set of eyes to either confirm that my idea will work or to tell me it won't and why.  I've attached a diagram to help explain things.
The new pump (I) is rated 12V 10A and indicates 16A maximum, which I take to mean that when starting up it may/will draw up to 16A.  (The old pump was rated for 12/24V and was submersible but didn't work well.)
The pump (I) will be switched on for a period of time (about 10-12 minutes) per hour to pull 100-150 gallons of dirty water from the pond where dirty bits are separated out from the water and then clean(er) water is returned to the pond via gravity.
To handle the scheduling of the pump I am (initially) planning to use an Arduino (D) and a relay (E) to control power to the pump.  A sketch in the Arduino will handle signalling the relay.
I've got a Fuse Block (B) that I'm using to also split up the circuit and independently power the electronic bits and the pump.
The pump isn't rated for 24V so I need to step the voltage down to 12V and that is handled by a pair of DC-DC converters that take 24V and output 12V 10A each. (F and G)
My intention at (H) is to take the two 12V 10A lines and tie them together to give me enough amps for the 16A max that the pump may want.  I think if I only use one of those converters (F or G) then I'm not going to have enough amperage when it starts up.
Intuitively this makes sense to me but I'm not an electrical engineer so I'd appreciate some feedback on this.  I am waiting on some parts so I have wired this all up yet.


texts: Choosing a linear regulator vs. switching regulator for low-power application?

texts:
I have a 3.6 V battery that I want to regulate down to 3.3 V and 1.8 V rails. I have already asked about the configuration of the two rails here.

My question here however is whether I should use a linear regulator or switching regulator. I know that regulating from 3.6 V down to 3.3 V results in fairly high efficiency with a low dropout regulator (3.3 / 3.6 = 91.67 %), but going to 1.8 V results in half the power being wasted as heat (1.8 / 3.6 = 50%).

I want to compare this 50% loss in using a linear regulator vs. using a switching regulator. This involves considering whether or not the extra power needed to power the regulator itself is greater than the power conserved in using it.

How would I go about calculating this power lost vs. power conserved in order to compare it with the linear regulator?

I know that the power wasted in a linear regulator can be calculated simply by (Vout - Vin) * current drawn, but how do I calculate this for a switching regulator?

What kinds of switching regulators would be best for this application? (Buck regulator?)


texts: What are the steps for a beginner to electronics to get custom PCBs made for a simple adapter?

texts:
I need to make an adapter between two 14-pin board-to-board connectors, one being a MicroMatch and the other being a JMC.

What is the most straightforward way to get a PCB designed and ordered so that I only need to solder those connectors?

P.S.: I'm a computer science guy, so please excuse my ignorance :)


texts: Grounds in a linear bipolar power supply for audio?

texts:
I've purchased a linear power supply, as surplus, from a local electronics dealer.  It's a Condor AA15-0.8, made to supply ±15VDC at 0.8A or ±12V at 1A; as far as I can tell, it's a standard regulated design (though quite old; the regulator chips are actually UA723s, for instance). The metal frame/chassis of the power supply is not electrically connected to the output common/ground.

(Photo taken from an online auction.)

The difficulty comes in connecting the thing to wall power.  I'm in the US, so the intent is the standard wall 110VAC, and the transformer's lugs are already jumpered for that. The writing on the chassis recommends a 0.5A fuse.  My current intent is to solder to the transformer lugs a fused IEC socket, so I can mount the socket and supply solidly into a wooden case.  I've got a Corcom 5EFM4S for this purpose (which incidentally includes a switch and RF filters); as I understand it, I just need to connect the transformer lugs to either the D and F terminals or the C and E terminals --

-- but I am concerned about grounding. The 5EFM4S filter has capacitors that connect from each line to a common ground.  By the schematic, that ground is also the IEC cable's mains ground, and both connect to terminal G.
Because this is going to be used in an audio application (I'm meaning to use it to power DIY and commercial Eurorack modular synthesizer modules), I have heard a lot of conflicting things about grounding; for instance, I've read that I shouldn't ground the chassis to avoid ground loops, and I've read that I should ground the chassis for safety. If I should ground the chassis, I'm not sure which ground it should use -- the output common, or the socket's terminal G.  I don't know whether to connect that terminal G to the DC common, either.
Part of the concern is that I'm intending to connect the modules powered by this to separately powered systems, and I've heard, but only vaguely, about damage being caused by systems having grounds at differing potentials.  If there's not a clear-cut answer to these questions, are there resources out there to help in understanding these problems and making these decisions?


texts: Beginner - Why do voltage/current behave this way

texts:
I was checking falstad and came around this resistor circuit which lost me completely :

Knowing that input voltage is 5v and current is 17mA :
1- Why is the voltage 0 after the 200Ohm resistor knowing that It's 3.4V before It ?
2- Why is the current flowing without voltage ? (here is the animation for those interested
3- When the current arrives at the first junction, 15mA take the first route, and 2mA take the 2nd route, why is that ?
4- Check this 2nd circuit :

Why closing the right bottom switch drops the voltage to 0 after the 100/400/800 resistors ?


texts: Can you make an electric gamma ray emmiter by adding up frequencies with freq. mixers up until you reach gamma ray herz quantities?

texts: I just thought this up. Theoretically if you can add freq numbers you can get to large quantities like in a calculator, only this time mixing electric frequencies using amounts of circuitry right? Is this possible? Can you make up for the losses in load?


texts: How to build a multi LED blink circuit triggered by vibration sensor?

texts:
I'm wondering how to build a module just like the ones that are in kids shoes that light up. I've taken a few of these out and would like to make my own circuit but I'm not sure if it is possible. I've made blinking LED circuits before but they had an on/off switch. I like how the sensor turns it on and does the flashing cycle then turns itself off.

I'd like to make the battery replaceable and change the pattern of the LED blinks. My plan was to embed it into my kids bike and other things.

My guess is that a special machine or tool is needed to embed the cycle onto the circuit but I hope there is a different method to achieve the same result without using a power hungry microprocessor.

I've checked youtube but I haven't found anything similar to this.

If anyone can steer me in the right direction that'd be awesome.

I found the modules for sale here, 2018 popular shoe decorations vibration sensor flashing led shoe sole lights

Vibration/Shake Sensor from ebay, 10PCS Vibration Switch Shake Sensor Switch for Skates Gyro output Shake Rod 9P9


texts:
In this question I have already found the current in the three meshes given using mesh analysis, they are (i1 = top mesh , i2 = bottom left, i3 = bottom right).
How to find the power supplied by the ideal current source?


texts: Appropriate relay for water heater rated for 220VAC/1500W

texts:
I've created a complete hardware platform using a Raspberry Pi as master/controller, an Arduino nano and two RF24l01 transceivers, which should control some household electrical appliances. The software part and the "low voltage" circuitry is ready and tested but now I'm stumbled on the appropriate relay for higher power appliances, i.e an electric water heater of 50 liters rated for 1500Watt, taking account of a 220V mains voltage. Currently I have two Arduino compatible modules, one rated for 16A at 250VAC (normally-open) and a second one with two channels each rated for 10A at 250VAC as the attached picture below.

The doubt comes in considering that normally water heater uses bipolar switches (I would leave the existent one in place), so the question is simply, should I use:

the first relay (16A, left side of the picture) interrupting only the phase line

or

should I take advantage of the two channels using them one for phase and one for neutral lines?

Any consideration will be really appreciated!


texts: Error: constant value required while compiling with avr-as in linux

texts:
Im trying to compile the following simple assembly program but there is a problem with the compiler that i cannot find its reason and fix it.

So here is the code :

  1 #define __SFR_OFFSET 0
  2 #include <avr/io.h>
  3
  4
  5 rjmp Init
  6
  7 .global Init
  8
  9 Init:   sbi _SFR_IO_ADDR(PORTB),5
 10         rjmp In

and when im going to compile it with
avr-as -c -mmcu=atmega168a -o ledON.o ledON.s

i am getting this error:

ledON.s: Assembler messages:
ledON.s:9: Error: constant value required
ledON.s:9: Error: `,' required
ledON.s:9: Error: constant value required
ledON.s:9: Error: garbage at end of line

I also change a little bit the code as you can see above but there is still an error

  1 ;#define _SFR_OFFSET 0
  2 #include <avr/io.h>
  3
  4 rjmp Init
  5
  6 .global Init
  7
  8 Init:   sbi PORTB,0x05
  9         rjmp Init

  ledON.s: Assembler messages:

  ledON.s:8: Error: constant value required

Any ideas?


texts: The blue text is mine and the black text is given by my teacher


texts: SMPS 5V without load, fluctuation on load TOP258PN

texts:
I am using PI Expert Online (this) to design a smps circuit for 5V, 2.5A output. I already have TOP258PN IC with me so built circuit for that.

Change from schematics: I am not using choke and using SR360 as output diode.

I am able to get 5V output when no load is connected. But as soon as I add load (5 ohm test load for 1 A current), I get current at right value but within few second voltage drops to zero and transformer makes noise. And then it again goes up and then down and it continues. Just before transformer goes to zero, it makes sound. I made transformer design as given by the PI Expert software (which says Design Passed).

Is it problem in transformer or some other thing like switching?

Leakage inductance is estimated to be 93 uH but is 124 uH in real. Will that be a problem?


texts: In theory, is it possible to make a logic gate that uses zero current?

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CMOS greatly reduces the current draw of ICs because one of the complementary FETs is always in the non-conducting mode, so there is only a flow of current during the transition between states, which is just the amount of charge on the gate's equivalent capacitance and maybe some leakage when both gates are open momentarily.

Is it theoretically possible to make a logic gate that has zero leakage while changing states (using any realistic technology), and the signal is just passed through the circuit as changes in voltage causing other changes in voltage?  If not, what's the theoretical minimum?


texts: Help identifying proper connection of pressure transducer?

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I am using a US381-0000005-100PA pressure transducer. The datasheet.

The '8' indicates its the 5-20 mA current loop type. The transducer has four wires - red, white, green, and black, but the diagram on page 5 only shows the current loop type to have two wires - red and black.

Why is this, does it not matter with which polarity I connect the white and green (which I infer is where the current loop happens)?


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I want to build a Tesla coil with mains voltage. I found a schematic online but it uses an irfp460n MOSFET which can handle 500v (Vdss) but I only have couple of irfp260n and irf250n MOSFETs with 200v max Vdss. I will be using 230v half wave rectified dc.
The question is, Can I increase the max Vdss of MOSFETs by connecting them in some configuration and also how to connect them?


texts: Limiting DC motor's stall current draw from power source

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I've got a power supply that'll deliver 0.5-1A (depending on a later design decision), and a motor that will normally draw about 150mA, but its stall current is a whopping 2.1A.  In my application I shouldn't stall very often or for more than very brief periods of time, but I may stall nonetheless, and it's very important that I don't draw too much current from my power source.
I can only assume this is a common problem with a simple solution that I'm unaware of because I'm a total newb.  My instinct is to provide a secondary source of power that can supply 2.1A momentarily, like a battery or a big juicy capacitor, and something to sense current from the normal power supply and cut it off or limit it if it gets too high.  I'm really rather radically unprepared for coming up with a way to do this on my own, however.

Any suggestions?


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I've had to make a series for physics and now we're being made to compute for cost of electrical consumption over 2 hours

The series is as follows:

9 volt battery (standard Everready)
1000 ohms resistor
2 volt yellow LED, 20 mA maximum current
3.2 volt white LED, 20 mA maximum current
2 volt yellow LED, 20 mA maximum current
switch

How do I compute for kwh?

One person said current= 0.0018 amps because the voltage that gets to the resistor is 1.8 V (9V-2-3.2-2) and divide that by 1000 ohms. If that's the case, is power in the entire system .0018 amps * 1.8 volts? Or .0018 amps * 9 volts because the battery is 9V? Or is it .0018 amps * 7.2 Volts because the lamps are 7.2 volts total?

Or is power 7.2 V (3.2+2+2) so it's (7.2 V/1000 ohms)*7.2 V?

Or is power 9 V so it's (9 V/ 1000 ohms)*9 volts?

Or is it 7.2 V * 20mA?

Not in the textbook, I've scoured through the internet and I've phoned-a-friend and I'm nowhere near the answer


texts: I made a fluctuating circuit that controls an LED to be on or off, How does it work?

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I have this circuit,
The two ends represent the positive and negative terminals of the battery.
Values

R6-4.7K
R1-470K
R2-470K
R3-4.7K
C1-.1 uf
C2-.1 uf

All transistors are NPN. Can someone please explain how this circuit causes fluctuations?I have no idea whats going on here. please help


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I saw in datasheet of L293D that maximum current per channel is 650mA. I have two dc motors that draw within that limitation. Most of the time, measured current is around 1.1A (sum for both motors). Under heavier load it could probably rise few hundreds of mA.

With usage of heatsink would that limitation be extended ? Am i on the safe side ?


texts: Unexpected behaviour in Altera clock crossing FIFO

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As far as I am aware, in a FIFO as we keep reading it will eventually become empty i.e no more data inside and its output shall become 0x0. If we keep reading it after it has become empty, we shall cause an "underflow".

I am new to using Altera (Clock Crossing) FIFOs and what I have noticed in simulation is that the FIFO does NOT get completely empty i.e the last data word written to it stays at the output q even after empty is asserted by the FIFO itself and even if more rdreq is sent to this empty FIFO, the output simply does not become 0 which in my understanding would mean no more data inside.

Here is result of simulation I did with the FIFO on its own:

In the megawizard, I did not find any option that controls this aspect of the FIFO behaviour. I have not yet done hardware simulation using signal tap II on a real FPGA to see what happens in it. What am I missing/misunderstanding here?


texts: Can a resettable thermal fuse be soldered?

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Earlier related questions:

How to solder a 70 °C (158 °F) thermofuse
Using a thermal fuse in a PCB terminal block?

History: I 'normally' soldered a nonresettable thermal fuse, which (of course) failed after soldering.

I have ordered a resettable thermal fuse RY Tf, for 73 degrees (Celcius), after getting a comment from PlasmaHH in question 2 that such components exists.

However, I'm wondering, what happens if I solder these? During soldering, the temperature will go much further than 73 degrees, but will it 'reset' or keep on resetting until the soldering process is finished and it has cooled down enough. Thus will the thermal fuse function normally after soldering?


texts: What's the middle terminal in the VN2222 MOSFET?

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In the VN2222 MOSFET below (diagram is from PSPICE), what is the terminal with the arrow pointing in? The one to the left is the gate, above and to the right is the drain and at the bottom is the source. What's the terminal in the middle, though? Under what circumstances should it be grounded?

Thanks!


texts: Actual power consumption of a smartphone charger

texts: When I search on the Internet "How much power does a smartphone charger consume?" it shows "3-7W". I know Power = Voltage x Current. Based on the equation and the input ratings (110-240V, 0.5A) on my smartphone charger if I calculate, the power consumption equals 220V x 0.5A = 110W. Can someone explain this? Note that the voltage in India is 220V, alternating at 50Hz per second.


texts: I am attaching a motor to an ATmega32 chip. I want to build an H-bridge but before doing that, I want to control the motor using the chip. I bought few NPN Transistors from RadioShack. I have 5V running though the breadboard. I attached Vcc to the Collector, Base to the Pin, and Emitter to the motor. And other wire of motor is hooked up to Ground. Unfortunately, the power coming out of the transistor is too low, the motor is barely moving (As opposed to when I hook up my motor straight to 5V). What is wrong? Do I need a different transistor or is my setup wrong? If it is the transistor, can you please recommend the right one, I am not too good at those.


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I'm trying to replace an existing ESD diode(PESD1CAN) in my application CAN circuitry due to some reasons, I've found an alternative ESD diode(RSB27C2), but compared to the diode that I already have in my circuit, it's not that great clamping negative voltages as depicted in the below picture.THe above graph is for the new diode that I'm considering and the below one is for the already existing diode in my circuit. I'm assuming that the negative scale is not shown but the green curves denote the clamped voltage during a negative ESD pulse and the horizontal axis is the timescale : 50ns per division, so I see that for about 100ns the clamped voltage would be about -75V , whereas my existing diode is better at clamping it to -45V.

What I'm interested in knowing is how this would affect the components on the line where the voltage is being clamped,

In my understanding, the negative clamped voltage would appear at CANL and Gnd, and how this extra negative voltage for a very short time(100ns) would impact C418, R413, R414, C410 and the common mode choke L400


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I am trying to make a discrete component linear power supply. This schematic seemingly works but it doesn't work when I build it on my breadboard.

I am taking 110 volts through a transformer down to 6 volts AC. I added a full bridge rectifier and then a 4700uF capacitor and I get about 8 volts out.

After wiring up the mosfet, the 2 volt zener clamp with a capacitor to create a reference voltage for the inverting input of the op amp. I add a 250k and 10k pot in series on the source of the mosfet.

The power goes from the capacitor to the drain of the mosfet and the output of the opamp goes to the gate of the mosfet.

The opamp reference voltage is created by the zener clamp described above; the positive rail of the zener comes from +8 volt after the rectifier capacitor and the negative rail goes to ground.

When I turn the poteniometer, I don't see any variation in the output from the opamp.

I also notice some voltage movement when I touch the potentiometers but not from actually turning them.

For a simple linear regulator like this that I want to take from 0-5V, why isn't it working?

The first step was drawing out the schematic:

Then I wired it up

Here's a cleaner schematic

simulate this circuit – Schematic created using CircuitLab

It seems like there are many different ways to design a circuit but so far this circuit comes down to a few basic blocks.

There's the current pass element; This can be almost any transistor.
There was a comment about me using the n channel mosfet in the incorrect position. I now realize that this has to do with high side [the positive rail] vs low side [the ground rail] switching.
It seems as though low side switching can be easier to wire up but causes issues with ground. High side switching is more stable and safe but more complicated to drive; usually there's a NPN type transistor driving the a PNP high side transistor.

Then there's the reference voltage; there was a answer that says the output voltage cannot be lower than the reference voltage in certain configurations.

With this updated schematic I think I have worked out a lot of the errors in the earlier one, although I am still a bit unsure about driving the mosfet with the smaller transistor.

simulate this circuit


texts: How many ground and power pins to have in a connector?

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I'm designing a daughter board for a project. There are 35 I/O pins that need to go to the board. How do I determine the number of ground and power pins to include? How do I determine the placement of those pins throughout the connector?

I know something like this would be bad, as I was told:

P IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO
G G  IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO

I'm guessing something like this isn't much better:

P IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO G
G G  IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO IO P

The board is for a microprocessor, I'm going from a breadboard to a PCB and am trying to learn as I go :)

23 pins are address lines, 8 data lines and 4 signal lines (Read, Write, Chip Enabled and Direction). There is no clock line on this board but there might be on others I'll be making. The clock of the microprocessor will be 50MHz or less, down to <1MHz. The connector itself will be a standard .1" pins.


texts: Im currently working on setting up led blinking on the board but the human's eyes cannot see it but when i record using camera i can see the blinking (after extracting the frames) . i believe our eyes can only see up to 24fps ~30 fps and the frequency is 60hz. Also, from what I understand from some research 20% duty cycle at 100 hz will look steady compared to 20%duty cycle at 10hz which will look like it on and off. I also read somehwere online that if 75% duty cycle the LED does not blink at all compared to 50% duty-cycle. can you explain more about this? do i need to change the duty cycle or the frequency to make the led only visible to camera but not to our eyes?


texts: Is using a capacitor to transfer a 0.1 V differential between voltage levels reasonable?

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The temperature of a terminal at -600 V and 500 deg C needs to be measured. I am using a thermocouple for this, and to achieve the most accurate reading the couple must be physically connected to the -600 V terminal.

The two leads on the thermocouple will be at approximately -600.0 V and -600.1 (for example). How can I transfer this voltage difference to ground so I may measure it with a ADC?

The way I am considering at the moment is to charge a capacitor with the small current from the thermocouple (sample rate can be in the range of tens of seconds). Then, using relays, disconnect the capacitor from the thermocouple and using a second relay to connect it to my ADC at ground level.

I thought about this since it is similar to how bootstrap capacitors are used to drive high side loads - charging a cap with low voltage, and then connecting it to the high rail in order to charge a mosfet gate.

Is this reasonable? Or are there other more traditional ways to do this? Thank you.


texts: How to use a supernode or supermesh with regard to this circuit?

texts: Is the two ohm resistor in parallel with the dependent current source disregarded when using a supermesh? I have not gotten the correct answer of Va=1V Vx=-4 . What are the steps?


texts: Determine if motor is "stepper motor" or "DC motor"

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Stepper motors I have used before and I also know the basics of how it works. I have make one spin with an arduino by turning a pin on and off with 500 seconds of microdelay. I remember that the higher the delay the slower the motor spins.

With DC motors I just have used them by applying voltage to them.

I found some old battery electric drills on my house. I dissembled them in order to remove the motor.

1) The first drill that I dissembled had this motor:

If I connect a battery to the cables the rotor spins. This is therefore a DC motor and it works great.

2) The second drill had this motor inside. I messed up ripped a board that was connected to the top and I was left with this:

When I ripped the board that was on top I circled in yellow the cables that where attached to it. Is this a stepper motor? It looks like one to me but I think a drill should have a dc motor no? How can I make this motor work? What do you guys recommend?

Edit

I forgot to mention that this are connected:

1 - 4

2 - 5

3 - 6

Also I can tell there is a strong magnet inside even when it is not connected.


texts: In its former, pre-burnt-out life, was this thing a capacitor?

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I've a problem with a ventilation system that stopped working shortly after power-on. I've pulled out what I believe is the power supply board and I can see an obvious problem, but I'm not entirely sure what the component is near the center that set on fire. Physically it seems virtually identical to a blue disc-shaped, two-legged one on the far left of the board between U4 and U3. That component is labelled C15, and the burnt out one is labelled RV1. Is there any hope of identifying the damaged one or do I need a manufacturer schematic to know the specifics (E.g. capacitance)?

And a closeup with flash:

Edit: couple of additionals

Edit2: my neighbour has an identical unit. I was able to photo his board without disturbing it, alas no markings:


texts: Does A20 line only disable 20th it or all bits from 20th and above?

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According to this picture:

Only the 20th bit is disabled until we enable it with keyboard controller (or BIOS). Based on the diagram, I think that the wrap around feature is retained for old programs by always set A20 to 0, effectively prevent carry bit from bit 19th and achieve a wrap around after a calculation. However, when we set bits 21th and above, those bits can still be used as normal for calculation, since they are not masked out.

But some resources state that A20 line disables 20th and above bits. Which is correct?:


texts: Measuring power with a current transformer

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I'm working on a project at the moment to measure power through a current sensor.

I posted a similar question before, and received very helpful advice which I have tried to heed.

I have improved the design (I hope) by incorporating a precision rectifier.

I still need to get at the voltage waveform of the household supply. My thinking is that the phase will be constant at any point in the household circuit (assuming the house is on a single phase) and so I was thinking of getting a transformer from something like a cellphone charger and plugging it into a wall socket, and measuring that in the same way as I am measuring the current. Here is a diagram:

Is this a good way to do it? What factors do I need to keep in mind? Is there a better way?


texts: Powering a servo from a 5v, 3.3 amp power supply

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I am building a Mearm robot using an Arduino to control it. The kit came with 4 servos which are rated at 5v. The Arduino doesn't output enough power to power all 4 servos so it suggests buying an external power supply.

I did this, my power supply outputs 5v and when I measure on my ohmmeter it says it's outputting 3.3 amps. The problem is I connect the live and ground servo wires to the positive and negative pins on the power supply and the control wire to the Arduino and nothing happens apart from a very small sound from the servo. I think I also blew one up trying this as now it doesn't even work from the Arduino.

They all worked perfectly when powered from the Arduino which output5 5v also, but only 0.3 amps when I measured it. I thought the current didn't matter if the voltage was correct? Am I blowing them up because of too much current?

Thanks


texts: Minimum voltage rating for output capacitor for use with LTC3525-5 boost voltage regulator

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I'm (still) selecting parts to build a 3 to 5V boost DC-DC converter using the LTC3525-5. The board I'm planing to build is based on the typical application shown in page 11 of the aforementioned datasheet, which schematic I reproduce below:

I'm having trouble finding the right output capacitor. The closest match I can find at my local suppliers is this 10uF X5R capacitor (JMK212BJ106KD-T) rated at 6.3V, but I think that's too close to the 5V output.

So, my questions are:

Is the 6.3V capacitor appropriate for my application? If not, what would be a suitable replacement?
What will be the maximum voltage I should expect at the output capacitor terminals? What would be the minimum voltage rating for such capacitor?

I tried, but couldn't find such information on the datasheet or elsewhere.


texts: Arduino TMP36 not enough resolution -- how to improve

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I have connected a TMP36 to an Arduino Uno, and eventually figured that the 10-bit resolution allows for the smallest step to be 4.8mV. Using the proper conversion results in half degree temperature steps. Since the TMP36 changes 10mV per degree this makes sense.
However, this is simply not good enough for a smooth transition in the first decimal digit.
What do I need to do to:

spread -- say -- -10 to 40 deg C over the 1024 steps, or
increase the bits in the A/D converter, or
use an extra/external A/d with higher resolution,

... to achieve a higher resolution?

What I figured is that in other posts, resolution is mistaken for accuracy. I am after a higher resolution; e.g. 4096 steps would be close to 1mV steps. I reckon even more is required for smooth transitions.

Any help appreciated... as I am sort of to new to this.


texts: how to control a DC supply's voltage using a micro controller

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Im trying to complete a home project and I have run into a problem.  I want to control the output of two 18650s to a simple resistor circuit.  I want the output to change based on the changing resistor value that is being read.  I think the best way involves a micro controller and possible  Mosfet. The ohms meter doesnt sound hard due to a simple voltage divider. However controlling power does.  Im using a Cerebot Mx7 and C if this helps.

Thanks in advance.


texts: Does pulsing an LED at higher current yield greater apparent brightness?

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This question implies two assumptions:

The frequency of a switched LED driver is high enough that average power, not instantaneous power, should be used to determine maximum drive current.
The limiting factor which determines maximum current at any duty cycle is average power dissipation.

After these assumptions, it is obvious that the current through an LED at maximum power dissipation is inversely related to the duty cycle.

Is the apparent brightness (not necessarily the luminosity) increased, decreased, or not affected by pulsing an LED at higher current and lower duty cycle?

I do not have any particular LEDs or driver topologies in mind, but would welcome references to real parts, datasheets, or appnotes.  I would also be interested in knowing if this varies between low-power (say, 20mA) indicator LEDs and high-power, high-brightness lighting LEDs.


texts: Induction Motor Poles and Drive Configuration

texts: If an IM is driven by a VVVF drive and the poles of the motor do not match with the drive configs.. eg., IM is 4 poles but the drive setting is 2 poles.. or the other way around.. then can it create a hazard condition leading to accident or will it be only less efficient motor control?


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Does the 15A amperage rating for screw terminal blocks such as the ones shown below refer to each pole or to the entire product?

I have a project that will require 5A on each pole. Would this block work for me?


texts: RGB LED Driver (with PWM) not working as expected

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I'm working on an RGB LED project for which I have designed a driver (Original Design). Everything seems to be in place but there is some problem that is causing the Drains/Output to be always High even though I've not connected the Gates of transistors with any input source. I'm planning to use it on arduino and PWM signals to be fed in from the Digital Pins.

The Transistors (Q1, Q2, Q3) are IRF540N and Resistance (R1, R2, R3) are 22K Ohms. Ground of driver will be connected to Ground of arduino and +ve of Power source (J2). Please suggest if there is an issue in the schematic below.


texts: Can I deal with the differents standards of 3G? And of 4G?

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I have a very popular device (a smartphone) which works on 3G: TD-SCDMA 1880/2010 standards and 4G: LTE 1900/2300/2600. I want to turn it compatible with 3G: UMTS 900/2100 or, if not possible, with 4G: LTE 1800/2100.

To solve that two things came to my mind.

The first one consists in the fact that there is already another device which is absolutely identical to mine but with the antenna that I desire. Then, I suppose I can try to buy the other's model antenna and try to solder it by myself, but I have no experience dealing with such small circuits. If I could do that, I think I would also need to reprogram the device, to recognize its new antenna.

The later is to try to design a board to successful read and then transcripts and generates a signal on a standard that my device can read. Since, relative to 3G, the devices use not only different frequencies but also standards, is it hard to transcript the signals? It would be a lot easier to deal with the 4G possibility? Are only the frequencies different in 4G and is it possible to convert them without problems?

Sorry if the question seems a little abstract. I think is very probably that either ideas are not cost efficient and would demand tons of work. So I wanted to check with all of you if that worth further researches on those possibilities and which one seems better. Also, where can I learn technical parameters about those telecommunications standards?


texts: Coax characteristic impedance measurement

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How is physically possible to get the value of the characteristic impedance of a certain coaxial cable?

Precisely, in my case I have a coax of 50Ohm impedance, and I need to cut it and connect some alligator clips or some tester leads. Now I thought that this variation maybe will change the characteristic impedance of my coax. Since the device I would connect to it gives an accurate value only if connected to 50Ohm cable, do this variation modify it a lot?

Is there a kind of measurement I can do?


texts:
In a circuit schematic of a stereo audio amplifier, I found the following component:

It is the potentiometer used for the balance. Upper line is one of the channels, lower line is the other one. Central, bold line is ground. The variable resistor seems to be "bridged" between the two lines.

1) Conventional potentiometers have a simple, unique output which is a fraction of the input voltage; but this one needs to have two complementary outputs. Does such a potentiometer have a specific name?

2) Removing this potentiometer (which is very similar to this image), the amplifier still works, with just one channel. How is it possible? Looking this part of the schematic, after removing the variable resistor, both the channels should be isolated with respect to ground: so, they should exhibit the same behaviour.


texts: General protocol for data transfer from one system to another?

texts: What is the general protocol to send information from one system to another? For example, let's say we have some information collected from microcontroller over a length of time that we want to send to another microcontroller. I've heard of SPI and I2C interfaces, but I am unclear when you use one method over another and how you implement it. Are there other methods besides SPI and I2C that are common? Is the implementation process similar for different microcontrollers? Is it basically parsing bytes of data that I am doing on the receiving microcontroller?


texts:
I have an application for a backup power supply, which requires guaranteed energy available, but very infrequently, think burglar alarm. I would naturally gravitate towards lead acid as it has a well defined float charge protocol. However my client wants to use lithium, probably for cost in the small size that's required.

My first port of call was batteryuniversity.com, and the various battery manufacturers. The BU papers 409, 808 and 808b cover charging and longevity of lithium cells.

The classic cyclic charge protocol is to charge to 4.2V, terminating when the current is around 0.04C, then let the cell decline to a lower voltage, before repeating. Keeping the cell at 4.2v would accelerate the cathode oxidation wear mechanism.

This protocol makes the cell's full capacity available at the time of the charge, but when it drops to a lower voltage, less capacity is available. The guarranteed capacity is therefore with respect to the lower voltage.

Improved lifetime can be obtained by using lower end-point voltages, and various sources mention voltages of (end_point/recharge_point) of 4.20/4.05, 4.10/3.90, 4.05/4.00. BU808 plots the highest lifetime as a cycle between 75% and 65% SoC, which equates roughly to 4.00/3.90. I'm not sure that's the highest possible, only the highest of the options they considered.

Where hi-rel is required, satellites for instance, NASA apparently charge to 3.92V, which is a compromise between a higher voltage which induces cathode oxidation, and a lower voltage, which loses capacity via SEI (solid electrolyte interface). However, this is still cyclic use. Dr Dahn (who's he?) suggests that below 4.1v, the oxidation mechanism is not significant.

Getting near to the question.

Nowhere have I seen (apart from a few questions on AllAboutCricuits or Instructables, which were not answered satisfactorily) a discussion about whether float charging to a low voltage is ever permissible.

Consider a 4.05/4.00 top-up protocol. Now compare and contrast to a 4.00 float charge.

the minimum voltage, so the guaranteed energy, is the same
the cell reaches a higher voltage with the top-up protocol
the cell is cycling with a top-up, but not with a float

That seems to me to be a draw, then two wins for floating, IF floating is permissible.

In one case, I'm supplying just enough charge over a long period in bursts to keep the voltage at 4v or above, in the other case I'm supplying just enough continuous current to keep the cell at 4v or above. Given that cell leakage is higher at higher voltages, and charge efficiency is less than 1, I would expect to be supplying less total charge over time when floating than with topping up.

Question - When you are well below the maximum voltage, say in the 3.9V to 4.0V range, is there still the prohibition about applying a small continuous current that there quite rightly is at 4.2v?

Question - different wording - When at a low voltage, does applying a lower charge continuously actually damage the cell more than bursting the charge, which involves a higher peak voltage and cycling?


texts: Transformer - If the Output V number matches, does it matter that the A numbers are different"

texts: The transformer that came with my Kinkle Fire say "DC Output: 5V1.8A".  I want to install some Fastmac Usockets in my house but their specs say "Output: 5VDC 2.4A".  Do the different A numbers matter?  I don't want to damage the Fire.


texts: How to convert a voltage range to LED brightness without a microcontroller?

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I have a hall effect sensor which outputs 0V when on the North pole of a magnet, 5V when on the South pole. It idles at 2.5V.

I want to connect 2 LEDs to show the reading, one activated from 0-2.5V, the other from 2.5V to 5V.

I could use the ADC on a microcontroller to read the sensor then drive the LEDs with two PWM channels. But, this seems like overkill to me.

Can anyone suggest a better way? Without using a microcontroller?


texts: What is the impedance of two transmission lines in parallel?

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Lets say we have two transmission lines in parallel as shown in the figure below, what will be the total impedance of their combination? That rectangle is the way I am representing TL and Z is the characteristic impedance and theta is the electrical length.

I was thinking whether I can use the same formula as for the case of resistors. So, the characteristic impedance of two parallel transmission lines will be as shown below and electrical length is the same, theta:
$$
Z_{total} = \frac{Z_1*Z_2}{Z_1+Z_2}
$$
Is this correct?


texts: Electronics riddle: After dropping on the floor, LED flashlight only works with a 3V supply instead of its normal rated 1.5V

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I'll keep it brief. I've dropped a flashlight on the floor, after which the casing broke a bit. The flashlight normally works with a single 1.5V 'D' battery. I was looking into it and tried these steps in a chronological order (number 1 is the one I tried first):

1) Connected a 1.5V 'D' battery (with juice left in it) directly to the circuit with no luck.
2) Connected my power supply set at 3V (that's the MIN voltage I can set it at) directly to the circuit and the LED worked.
3) Connected x2 1.5V 'D' batteries, as a test and worked again.

So after the drop the LED lights up only with x2 batteries at a total of 3V instead of its original 1.5V.

There is nothing wrong with the PCB (it's a very basic design); to test this I repeated 1-3 with wires directly touching the LED. Same results again. So I guess something must have 'changed' in the LED. Is this possible? It's all a bit strange and interesting at the same time :). Some photos follow.

This is my first post here, so I hope all is clear!


texts:
Has anyone been able to convert shapes from DXF file to pads in Eagle? Is it possible to convert circles to Eagle pads?

I have just arranged and positioned things using Fusion360 and now I want to convert it to proper things in Eagle.

So far I have manually edited .lbr file (converted <circle> to <pad>) but I'm looking for something more convenient.

Before: <circle x="-22.86" y="10.49" radius="0.45" width="0.001" layer="17"/>
After:  <pad name="AP0 x="-22.86" y="10.49" drill="0.9"/>

If somebody is interested:

Datasheet:
https://datasheet.lcsc.com/szlcsc/CONNFLY-Elec-DS1131-S80BP_C77853.pdf
Fusion360: https://a360.co/2SxftLv

Regards, Paweł


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I'm trying to use a D flip-flop 7474 for my project.
When I tried to simulate it, this warning appears (see picture.)
My parameters for input clock are:

OFFTIME = 0.1S
ONTIME = 0.1S
DELAY = 0
STARTVAL = 0
OPPVAL = 1.

Can someone explain why this warning appears?


texts: Why is the following AC analysis of CMOS inverter resulted in zero AC gain (vout/vin) ?


texts: Wiring diagram for USB-C to USB-A cable?

texts: I make USB cables (USB-A to Mini or Micro primarily), but don't have any experience with USB-C. I would like to create a cable that has a USB-A (2.0) connector on one end, and a USB-C connector on the other (mainly for connecting keyboards to CPUs, and charging devices). How do I wire this properly (typically I use a 4-core 28AGW cable)? Thanks in advance for any help, please let me know if I need to clarify further!


texts: Confusions with placing and sizing the flyback diode, TVS and Zener

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I have couple of questions regarding the location of flyback diode and sizing and locating the Zener and TVS diodes. For example below at the far end there is a magnetic relay which is controlled by a MOSFET. Power supply is also close to the MOSFET.

simulate this circuit – Schematic created using CircuitLab

To make it clear I divide the question into two separate ones:

1-) Should the TVS be placed on the power supply side or at the relay side(between the relay terminal? Or TVS at both?
And if the power supply is lets say 24V what should be the rating for the TVS?

2-) This is very confusing because sometimes they use flyback on the top of the MOSFET and sometimes a Zener which is across the source and the drain.
I put both in my figure above. I also found out using only Zener is creating faster falling edge proportional to its rating

About the diode: Should the flyback diode be close to the MOSGET as in my figure or should it be across the relay terminals but in the vicinity of the relay at far end?

About the Zener: If the Zener is used how is its rating determined? Becuase if its max voltage is given as 100V and I choose a 36V Zener this kind if scares me.


texts: What determines the output voltage of this SMPS?

texts:
This website http://danyk.cz/impulz4_en.html says that the output voltage is due to the zener diode that has a forward voltage drop of 18V. But zener diode is just a clipper that regulates the output voltage so, What is the component that really produce (or specify or determine) the output voltage? Is it the transformer or the IC?

Also, What is the 180V of the transil? Is it the maximum forward voltage or the reverse voltage drop? I think it is the reverse voltage drop due to the diode.

Can I replace BA159 with 1n4007?

Thank you very much,


texts: What exactly is blocking voltage in relation with Metal-semiconductor junction diodes? Is it related to breakdown voltage?


texts: How are some electronics with physical on/off switches turn off with a tune/message?

texts:
Like this:
A toy says "See you later!" when the switch is turned off.
The Bose Qc35 plays tones then shuts off when the switch is turned off.
How can I mimic this in my BT speaker circuit?


texts: Boost converter extremely low efficiency

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I'm trying to use a boost converter from Pololu that steps up my 1.25 input voltage from a AAA battery to 5V in order to power an Arduino. I have found that my Arduino needs .03A to be powered.
I understand that if the boost converter were 100% efficient and when using (V*I)in = (V*I)out, I would need .12A to be drawn from my AAA battery into the boost converter. However, when measuring the current drawn directly from the battery using a multimeter, I find that 1.05A is leaving my battery and entering the boost converter, while .03A is leaving the boost converter and entering the Arduino. This implies that my boost converter is about 11% efficient. The voltage seems to be stepped up fine from 1.25V to 5V.
This efficiency is concerning since the Polulu component has an input current limit of 1.2A, and I also need to drive a small motor. I am wiring the positive and negative terminals of my AAA battery to "Vin" and "GRD" on the boost converter respectively, and then wiring the "Vout" and "GRD" pins to the "5V" and "GRD" pins respectively on my Arduino. I am not using the "SHDN" pin.
So, am I wiring the boost converter incorrectly, or is this efficiency typical?


texts: Microprocessors for multiple (~40) SPI devices?

texts:
I'm looking at building a product that combines over 40 LCD pushbutton switches (example here that communicate via SPI). I've been looking at microprocessors to handle this, but I am running into trouble finding any. The highest that Atmel offers is 12 devices (as found here), and ARM isn't looking better.

What is the best way to go about controlling this many SPI devices? Do I need to link several processors together into a master?


texts: What's all this Voltage Coefficient stuff, Anyhow? (*)

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Rocket Surgeon posted this as a comment to this question. It's from (an older copy? of) the Art of Electronics, and is about permanent (memory effect) and non permanent change in resistance over 400V and varistor effect.

I hear from different people questions what it's all about? Is this true, still true? Do resistance values shift under high voltage?

I've worked for 10 years with a colleague who designed high power dimmers for 400V AC. I've never heard him mention Voltage Coefficient. Never heard about it when I was a student either.

Is there somebody who can shed light on this?

(*) After the late Bob Pease


texts:
I'm trying to make a circuit that will press the reset button on the device after a power failure.

This should reset the device when the power is restored and remains inactive until the next power failure.

This is my first idea but with this scheme the device is reset every 2 minutes.