texts: What does it mean when a charger supports n cells

texts:
I want to preface this by saying that I'm a beginner and this might be a very silly question but I've spent a while looking at datasheets and online forums and I still don't get this.

I'm trying to select a charger for a project where I'll be charging a Li-ion battery pack with a dynamo hub installed on a bike. Most of the charger ICs I've come across say that they support n cells in series where 1 <= n and at most I've seen 8 or 6 cells being supported by the charger IC.

The typical circuits in the datasheets for these charger ICs show n cells connected in series. My question is, if a charger supports 2 cells does that mean it can support both 2 cells in series and alternatively 2 cells in parallel? I'm confused because if you connect two cells in parallel the charger would see about 3.6V across them and it sees 7.2V if you have 2 in series. In the parallel case, does the charger know that its actually two cells or does it think its one cell with twice the capacity of a single cell?


texts: I have some circuits and I want to get and reuse some of its components. How can I determine if I can still use that capacitor, diode,resistor, thermistor and many more components by using a multitester?


texts: Using individually addressable 8806 LED as digital output

texts:
I plan to drive 4 relays from an ESP8266, which already have some pins used for temperature and wind sensors, so I'm a little low on pins.

I've been searching for 1-wire digital output (DS2408) as the temperature sensor is already 1-wire, but they are ratherr expensive (and most also require SMD soldering, which I'm not to keen on trying)

So now I wonder if I could use a piece of addressable LED strip. The LPD8806 is relatively old, but the strips contain individual driver chips and leds, not like newer 5050, where LED and controller is on the same chip.

The relay board I Intend to use have optocouplers in the input, so I guess I can just solder a thin wire on each LED pin.

I'll be using two pins on the ESP for this, better than using 4.

In theory one could control thousands of didital (or even analog) outputs with this.

Any reason not?


texts: Why in Digital Design only Capacitive load?

texts: Why in designing of CMOS logic we only consider the capacitive load of fanout? There is some wire resistance. So, why don't we consider resistive load?


texts: What kind of Ultrasonic Transducer is capable of 85db at 25khz-40khz using 5vdc and is 1cm diameter?

texts:
I'm building a dog training device. I don't want to zap or shock the dog, but just produce an ultra-sonic sound that will discourage current behavior.

I tried an online schematic and it didn't get any reaction from the dog. I was using one of these. I think that's a fixed frequency, so it doesn't work.

I need it to be very small (1cm diameter 1cm tall), but loud enough to make the dog notice and deter her behavior. What kind of transducer is capable of this? It needs to put out about 85db I am looking for something between 25khz and 40khz.

UPDATE:
From the comments and some more research, it looks like what I need is an "Ultrasonic Air Transducer".  Is that the right term?  I'm looking for something around 1cm in diameter and 1cm tall.  Is this the right terminology for such a device, or are there other names I can search on?

It needs to be operational at 5vdc.  Do they make such things?  Do they make them with a variable frequency, or are they pretty much tuned in on either 25khz or 40khz?

Thanks for your help!!


texts: Analog differential line driver and receiver circuit

texts:
I want to do a "simple" task of transmitting 0-5v analog voltage from a potentiometer to a microcontroller 15ft away in a very noisy environment.
the available supply is 5V only (no negative voltage).

My idea is to use something like the digital line Driver/Receiver (AM26C31/AM26C32) but made for analog signals . Is this possible ? Which circuit could achieve this?

Does the signal have to be scaled down to 1/2 then use a 2.5V voltage reference, in order to avoid using a -5v negative supply?

EDIT : according to answers by NEIL and OLIN , This is how i understand the circuit should be at the sender side, is this the schematic correct  ?


texts:
I have an 11.1v LiPo battery that has be working just fine and it recently dropped to 8.3 volts as it normally does during use. However this time when I plugged it into the charger the charger started to blink meaning either the battery is too low to charger or there is a problem with the battery. When I checked the battery's individual cells I made note of their individual charges

Cell1: 4.15v
Cell2: 4.15v
Cell3: 0.0v

How is this even possible? Is my battery toast? It's new and was working fine until this happened.
NOTES

This battery has a balance charging connection w 1 blk & 3 red wires to the connector
I only have only ever used balanced charging for this battery
This battery has 16 gauge red/back wires connected to a deans connector for use
I use this battery with a quad copter uav.
This battery was freshly charged and only lasted ~1 minute the last time it was used
I was changing pitch/roll/yaw settings on last use and at one point an ESC started causing a motor to be jittery (happens a lot). As I was throttling down/up (4/5 times) to get the motor to spin correctly the low voltage signal kicked in.
I was using this batter with my quad copter last night when I got the "low voltage" cut off from my ESCs. Instead of charging this battery I charged another battery and left this one sitting on my counter (room temperature) over night.

Edit
I just ran a multimeter on each of the wires coming out of the balanced charge connection and here's what I found:

Wire1(c1): 4.16v
Wire2(c1+c2): 8.33v (4.16v from cell1 + 4.17v from cell2)
Wire3(c1+c2+c3): 8.43v (4.16v from cell1 + 4.17v from cell2 + 0.1v from cell3)

Edit
Using a suggestion in the comments I was able to get a voltage readout of 41.2mV for cell 3. This extremely low as it close to 3.7V.


texts: Verilog style: one large always block vs multiple small always blocks?

texts:
Say I have multiple registers set up to update on the same clock, based on different conditions.

I could set this up as a series of multiple always blocks:

reg [7:0] counter;
reg output_even;
reg output_multiple_of_5;

always_ff @ (posedge clk)
   if(reset)
       counter <= 0;
   else
       counter <= counter + 1;

always_ff @ (posedge clk)
   if(reset)
       output_even <= 0;
   else begin
       if(counter % 2 == 0)
           output_even <= 1;
       else
           output_even <= 0;
   end

always_ff @ (posedge clk)
   if(reset)
       output_multiple_of_5 = 0;
   else begin
       if(counter % 5 == 0)
           output_multiple_of_5 <= 1;
       else
           output_multiple_of_5 <= 0;
   end

Alternatively, I could set this up as a single always block with multiple conditions:

reg [7:0] counter;
reg output_even;
reg output_multiple_of_5;

always_ff @ (posedge clk)
   if(reset) begin
       counter = 0;
       output_even = 0;
       output_multiple_of_5 <= 0;
   end
   else begin
       counter = counter + 1;

       if(counter % 2 == 0)
           output_even <= 1;
       else
           output_even <= 0;

       if(counter % 5 == 0)
           output_multiple_of_5 <= 1;
       else
           output_multiple_of_5 <= 0;

   end

I suppose one way of looking at this is whether I should use separate always blocks for separate clocks, or for separate registers.

Is there any difference between how these two code blocks will be synthesized? Extra clock cycle, implied latch, etc, or are they functionally equivalent?
Is there any stylistic or code-maintenance  reason to prefer one style vs the other?


texts: Beginner Led Soldering Connection Project

texts:
So I have my own project that I want to make.
In this Project i want to light up 7 led diodes (1 contains 3,0-3,6V each).

To light up 7 led diodes, how much voltage do i need (min to max) and how big of a resistor is required (min to max)? Any sort of assistance would be appriciated!


texts:
I'm currently working on building a density based traffic light model. I want to use the magnetic hall effect sensor to detect the number of the cars passing, so the idea that I have is to place the sensor under the road surface which will be made of wooden material, then place magnets under the cars.
I'm not really sure if this will work because the road surface will be between the sensor and the magnet! Any idea if this gonna work or not?


texts: Why does this resistor affect this transimpedance circuit in this way?

texts:
I am working with the following circuit

simulate this circuit – Schematic created using CircuitLab

It's a transimpedance amplifier with a clamping circuit to limit the output to a diode drop.

The idea is once the base of Q1 is at -0.7V, it turns on, shunting the photodiode current away from the op amp.

The circuit kind of works. It clamps at -.7V, but it rings and then overshoots as seen in the oscilloscope trace below (taken at the output of the op amp).

Adding a resistor in series with the photodiode fixes the problem, but slows things down a lot as seen in the circuit and scope trace below.

simulate this circuit

Why is the resistor changing the output in such a way? I was not able to derive the loop gain for this circuit.

I don't think the lower speed is because the 100 ohm series resistor is making the photodiode current shunt into its capacitance, since the time constant of 10 ohm * photodiode capacitance is much faster than the bandwidth of the amplifier.

Thanks for your help.


texts: Information about time-to-digital converters (TDCs)

texts:
I'm going to measure short times (max 150 microseconds). To do this I will use time-to-digital converters (TDCs). They don't seem to be very common and it's hard to find information about them on internet. I wonder if someone here can answer my questions.

Which companies make these things? So far I've only found Acam. Is there more manufacturers?
They are connected with SPI. Can I connect six of them to a single MCU? The problem is that all six can sometimes send the measurement at the same time. What happens then?
Is there an alternative which would do the same? A resolution needed is 50 nanoseconds.


texts:
I am designing an IR demodulator circuit to replace the one shown in this question. Basically I want to demodulate a simple IR signal modulated at 32.678 kHz. I just need to know if the signal is present. No packets. Just IR present or not present.

Below is what I have so far...

I have tried simulating this in LTspice with no success so I am not sure if I've done something very wrong in spice or in my circuit. I am no pro with LTspice.

R1 N001 N006 2.49K tol=1 pwr=0.1
R2 Output N003 1Meg
R3 N006 N005 1Meg
C1 N005 N004 470pF
C2 N003 N001 220pF
C3 Output N001 220pF
V1 N006 0 2.5
V2 N002 0 5
V3 N004 0 PULSE(0 .05 0 0 0 0.0000152587890625 0.000030517578125 200)
XU1 N005 N003 N002 0 Output LT1722
.tran 12ms
.lib LTC.lib
.backanno
.end

I have a few questions:

How best do I determine the value for R34? I have left it at 22k simply because the previous circuit used this value.
C16 and R31 set the high pass knee point. What would be a wise choice for this value?
The overall gain of the circuit is approximately 400 by my calculations. So, in choosing my op amp I would need a GBWP of 14 MHz or greater? Any other critical op amp specifications for this application? Note the amp showed is just a place holder until I choose the op amp.
If I wanted to increase my gain beyond what is shown (~1000) would it be best to break this up into several stages?


texts: Calculating the True Power Factor in non-linear loads

texts:
In my circuit I am taking in 60 Hz 120 VAC from the power company and hooking it up to a AC/DC non-linear switching buck converter I am designing.

I know that:
true power factor = (displacement power factor) x (distortion power factor)
But how can I calculate the displacement power factor for a non-sinusoidal or transient current?

Example waveform:


texts: Driving a common cathode 8x8 RGB LED Matrix with PWM

texts:
I've got this nice RGB LED Matrix. My goal is to use several of them to create a 16x16 color display. Unfortunately, the display is common cathode.

From experiments driving a single LED with 8-bit PWM, I've noticed that there's a visible difference between colors at the lower (dim) end of the scale. In other words, increasing the brightness gradually from 1 to 16 will not be smooth but perceived as choppy. Increasing the PWM resolution to 16 bit resulted in perfectly smooth transitions.

I've found several LED drivers with 16-bit PWM, like the TLC5943. Unfortunately, the ones I've found are all current sinking, meaning they will only work with common anode types of LED matrices.

Are there any current sourcing LED drivers with 16-bit PWM?
If not, is there any way to use a current sinking LED driver to drive a common cathode LED matrix?


texts: KY-040 rotary middle push button switch is unreliable

texts:
I have the following rotary encoder with a built in push switch:

http://henrysbench.capnfatz.com/henrys-bench/arduino-sensors-and-input/keyes-ky-040-arduino-rotary-encoder-user-manual/

I connect the switch pin to a regular digital input pin, putting it into input mode and looking for when does the pin go LOW (that is the pushed in state). However this is unreliable, sometimes even turning the rotary encoder triggers the switch input. Any idea how to fix this?


texts: I need a tachometer for a motorcycle that 'fires' the ignition every cycle (360 degrees).  Tachs are cheap for 4 cylinder applications (fire twice per cycle, every 180 degrees) but very expensive for motorcycles.  If I could double the frequency of the pulses from the ignition, it would appear to be a 4 cylinder ignition, and I could use an inexpensive automobile tach (which have a 4-6-8 cylinder setting).  I see circuits for doubling a fixed frequency, but the ignition frequency is pretty continuously varying.  Any ideas?


texts: Capacitor Shorting in transformer circuit

texts:
I built the circuit shown in the link with 240v

https://www.instructables.com/id/Variable-voltage-ignition-coil-power-supply/

It did not work (produceing no spark), as I believe my capacitor was much too low of a value (around 5nf).  Anyway, The capacitor was made from tin-foil like the one below

https://www.instructables.com/id/Homebrew-High-Voltage-Capacitors-on-the-Cheap/

I then made another capacitor in the same way, though forgot to include the space at the end between the tinfoil.  Because of this, the capacitor short circuited.  This caused the light dimmer to go up in a puff of smoke.  I know it was stupid and i'm done with that circuit now, but nonetheless I am still wondering why I got no spark.  Even as the circuit had virtually no capacitance, the ignition coil produced no spark.  This makes me think maybe the fault in the original circuit was not the capacitor?  Also, does anyone know why this caused the light dimmer to die?


texts: Is it safe to leave floating the low voltage supply of a logic level shifter?

texts:
I need to interface two devices, one runs at 5V and the other at 3.3V. In order to safely interface them, I'm using a simple logic level shifter (LLS) of this kind:

It's a pretty straightforward circuit design, I have used it before, and I understand it reasonably well.

However, in this application the low voltage supply (LV=3.3V) will be provided by the 3.3V device, which will be switched off for long periods of time. OTOH, the high voltage supply (HV=5V) will be provided by the 5V device, which will be switched on at all times .

Thus, LV will be left floating (or weakly pulled-down, at most) often, with HV at 5V at the same time. Is it safe to do that, given the LLS design above? If not, what design changes would you suggest?

Thank you!

Enric

Additional info:

1) The 5V device can't provide a 3.3V supply line.

2) I'd like to avoid as much as possible any solution based on adding active components like, say, a 3.3V regulator. :)


texts: Activating a circuit with a change in resistance

texts:
I am trying to solve a work related issue. Long story short, I have a circuit that monitors the resistance between two electrodes. When an object passes by these electrodes, the resistance reduces drastically, the circuit then measures this and activates another circuit.
I want to replicate this, mainly due to a couple factors, one being that the circuit doesn't work properly due to some external issues but also to provide a temporary solution till we get a fix!
I read somewhere on here that it can be done with a microcontroller, but no further explanation was given. I've got a lot of electrical experience but less so in electronics or programming, so some heavy advice and guidance or even something to reference so that I can learn more, would be greatly appreciated! I figured I'd post this to try and learn at the very least!
EDIT: (at the request of some comments I read)
I don't have specific values as I don't actually know them, I only really know the principle of operation which is, really quite difficult to explain, the above is as simple as I can make it with my current level of knowledge! I'm sorry!


texts:
I saw the following non-ideal transformer in my textbook as an exercise. Find the equations for VA and VB. Then, find the required frequency of V1 with all elements such that the transformer is resonant if k = 0.

I tried to find the voltage equations for both points A and B:

$$ v_A (jw) =  jwi_A(jw) L_1 + jwi_B(jw) k \sqrt{L_1 L_2} $$
$$ v_B (jw) =  jwi_A(jw) k \sqrt{L_1 L_2} + jwi_B(jw) L_2 $$

Are my equations correct? Also, I believe that resonance is reached when the impedances all cancel out but I am not sure how to apply it here.


texts: Can Lithium Ion Batteries be used to generate heat for a RC Hot Air Balloon? Any particular heat-generating device?

texts:
First the background: OK - this is a personal project that I've always been interested in trying but never got around to it - a remote controlled hot air balloon.

Sadly I am not technically-inclined and I'd appreciate your guidance. :)

I am aware that the lift generated to make such a balloon airborne is that the air inside the balloon is warmer and therefore less dense than the air outside the balloon.

I have seen oil or petrol burners - even a candle being used to this effect - but would really like to be able to regulate the lift (hopefully direction also) in a responsive fashion.

This is why I am interested in a small electric heater of sorts to heat the surrounding air and generate lift - and also a small fan to quickly draw heat out of the balloon to decrease lift. Not too quickly as I don't want to see it go into an uncontrollable descent. :)

The questions:

Could one or more Lithium Ion batteries produce enough energy to generate sufficient heat for this purpose?
What kind of heat generating device would probably efficiently convert energy into heat?
Any foreseen complications?


texts: I think my XBee XSC is broken. Am I missing something?

texts:
I have two XBee XSC 9600-baud chips, and I've been trying to make sure I know how to use them before integrating them into my project. Other people have used these same boards successfully, so they definitely worked at some point, but of course that also means they could have been broken at some point.

The test setup I have is one Xbee attached to a DF Robot Mega IO Expansion Shield attached to an Arduino MEGA 2560 and the other on a DF Robot XBee USB Adapter connected to a laptop. The shield has a space specifically for an XBee, with the DI/DO of the XBee connected to the TX/RX1 of the Arduino (thus, a minicom terminal for the Arduino is also effectively a terminal for the XBee).

My extremely simple testing program for the Arduino just outputs a couple bytes every half-second or so:

#include <Arduino.h>

void setup() {
    Serial.begin(9600);
}

void loop() {
    delay(500);
    Serial.println(millis());
}

Also, just to make it clear, I have reset both chips (several times) to factory default by grounding the reset pins, as suggested by a myriad of Google results. The results stay the same.

Now to the actual problem: it doesn't work. :)

More specifically, the data sent from the Arduino and its XBee is echoed by the adapter's XBee as nulls, or, if I swap the XBees, as nulls interspersed with the occasional letter (note the program only ever sends numerical digits).

Also, of the two, only one successfully connects to X-CTU (I try both of them separately with the USB board), and the same one is the only one of the pair that responds to the +++ command mode activation.

Basically, my conclusion is that one of them is permanently broken. However, I am sufficiently inexperienced with this and the chips are sufficiently not cheap that I wanted to ask if anyone saw anything I missed. Do I really have a broken XBee, or am I just missing something?
x


texts: how to deal with ACK and DATA one after the other in I2C efr32fg14

texts:
in I2C We have the IF register to catch the ACK from the slave ,
And we have I2C0->RXDATA to catch the recieved data .
But as shown in the diagram bellow i cant code
Pseudo code:
check if ACK was recieved
wait a little and catch the input data with I2C0->RXDATA.
what is the method of handling two types of data intended for different registers coming one after the other?
Thanks.


texts: How can I safely test how a power supply handles abnormal situations?

texts:
I have a bunch of chinese 5V power supplies. The seller indicates that the power supplies have input protection, output protection, over-voltage protection and short circuit protection. That's all great, but I would like to know that this is the case for sure, instead of trusting the seller when leaving those power supplies running 24-7 unattended. Essentially, I want to see what happens if (1) I short circuit 5V and GND, and if I put more load than specified.

The devices have a bunch of capacitors, two transistors, an inductor, a fuse, the transformer itself and a lot of resistors. I suppose, therefore, that there are two potential risks:

A resistor, a transistor or a transformer could heat too much and burn.
A capacitor could explode.

Therefore, I suppose that during testing:

I should keep the power supply in a location where, if a fire starts, I could either put it down with a fire extinguisher or let it burn without being able to damage the surroundings.
I should wear safety glasses and keep myself at a safe distance from the device (given that it has a casing, a small capacitor exploding shouldn't cause too much trouble anyway).
Plug it to a power source which would turn off in a case of a short circuit, such as an UPS device (which is very well built, and so would be protected against any short circuit).

Are there other things I should be careful about?


texts: How do I drive a MOSFET when I have an 11.1v power-supply and an arduino

texts:
I am trying to use a irlb3034 as a switch to power an airsoft motor and control it with an arduino. I am using a diode between the source and the drain and a 2.2k resistor between the gate and the source. Do you have any idea how I can control the mosfet with the arduino? Many thanks,
Thomas


texts:
I want to switch ON and OFF an incandescent bulb using MCU. Please suggest an electric switch (like relay or something) for 220V 50Hz AC line which can be used here. I would prefer something very cheap to keep the total project cost minimum.

EDIT: Don't limit this to incandescent bulb. The solution should be applicable to every daily life electrical appliances.


texts: Start Delta Motor Starter, at higher ampere in Delta Configuration

texts:
We are using 3 Phase Six Wire out standard ABB foot mount motor of 25HP.

We are using star-delta starter with delay of about 30 second from star to delta.

We are seeing around 40 Ampere when machine starts in star, but that amperes jumps to 130 ampere when the starter switched to delta, which trips the whole circuit in six to ten seconds.

How do I diagnose such behavior ? As I understand, the ampere should be reduce when it is used in delta configuration.

Thanks.


texts:
I am trying to create a battery model in LTSpice. The battery model is comprised of a voltage source and a series resistance. However, I need the voltage source to change as the amount of charge in the battery changes (the differential of the charge = current out of the battery). In addition, the resistance needs to be a function of the current.

Can someone tell me how to do this LTSpice? The voltage sources I see are constants or sines or pulses. I cannot seem to make them a function of something (in my case the charge). Similarly for the resistance.


texts:
When I try to compile some code with macro definition at the following definition
# define _SPEED_FACTOR0 0.9 //or any float value

I get the error

floating constant in preprocessor expression

I am using avr-gcc (version 4.8.2)
here is the full compilation command and the error

avr-gcc -g -Os -mmcu=atmega644p -c test_sens_mot.c ../utils/sources/*.c -I../utils/includes
In file included from ../utils/sources/motors.c:1:0:
../utils/sources/motors.c: In function ‘go’:
../utils/includes/global.h:14:25: error: floating constant in preprocessor expression
# define _SPEED_FACTOR0 0.9 //only on timer 0

I am interested in avoiding this, and still using macros and float values.
thanks!


texts:
After performing some tests on a small sized solar panel, I have been able to determine that the panel outputs on average, around 6v (Open source voltage) 300mA (Short circuit current) with no load. Testing with variable loads the solar panel only managed to output around 5v 5mA.

In order to drive the circuit at the solar panels load, I need a current of up to 2A. Seeing as the increase is so high, is this at all possible using something like a current amplifier?

Alternatively, I can switch out the solar panel being used for a 'solar battery bank', the one I have is a solar panel mounted on a 15000mA battery. From here I can drive the circuit, although,  ideally the output voltage should vary depending on the panels output rather than the battery. In this scenario I could use a potentiometer to vary the voltage. But I'd rather just amplify the current or the original panel of possible.


texts: Amplifier overheating - how to find out if A671 PNP transistor broken?

texts:
I have a beautiful old Wega V 3840-2 amplifier. However, it has suddenly given out. I have some basic tools (soldering tools + multimeter: I'm a mechanical engineer, so I'm afraid I don't have my own oscilloscope), so I was wondering if I could somehow nurse it back to life.

The problem is that while listening to some music, the right audio channel suddenly gave out, and is instead playing a nice and soft 100 Hz hum, regardless of any volume or input. At the same time, I can feel one of the right channel main amplifying transistors heats up significantly within a few seconds, despite being attached to a massive heat sink. So, I know have two scenarios: either the 'hot' transistor broke down, or something upstream of the transistor is. The latter scenario is supported by the fact that sometimes, after a few seconds the transistor springs back to life with a slight crackle on the speakers. This would suggest a broken capacitor somewhere long the way, as far as I know.

My question is how do I determine where the problem lies: in the transistor or upstream?

Some additional details: the main amplifying stage seems to consist of a two-stage amplifier: a C1061 and A671 (PNP) transistor. The latter transistor is the one that heats up significantly. No other components seam to heat up. No components have visual indications of damage.


texts: Can you control a 12V Solenoid Valve using motor dev kit MCLV-2?

texts:
The MCLV-2 is a motor driver development board, of 24 volt and up to 15Amp (in total).
Aside driving a motor, I'm also interested in testing to see if these circuitries are suitable to run a 12 volt valve

Where would you connect a valve? Is it one of the motor pins? (pin 3-5 on connector J7)
for more information see MCLV-2 Dev Kit User Guide, pg22

And the more important question, although this is dedicated for 24 volts output. Can I use a 12 volt valve instead? (it's cheaper for the intended application)

The dc output rating, on pg. 43 claims its voltage output is  min: 0, typical: 24, max: 48
Is there an additional circuit I ought to have prior to sending the signal to the valve?

The motor signals are processed by this high and low driver chip

Now if the motor driver really is assuming a position feedback, then can I get away with using a proportional flow-rate controller for feedback?


texts: ADV7180 Breakout Board - critique sought

texts:
I plan to make a breakout board for Analog Devices's ADV7180 analogue video decoder IC. I wonder if someone would be kind enough to look over my schematic and board layout and let me know if I'm making any basic mistakes before I attempt to have the board made. Ultimately I hope to connect this to an FPGA and do some image processing before connecting to another breakout board with an ADV7391 encoder.

Some of the questions I'm uncertain about:

This device has a 27 MHz data clock and parallel port. Can I use 2.54 mm pinheaders or do I need something more suited to high speed data?
Is it safe to route the clock line over 2 data lines as I have done or do I need to take those 2 lines right up and around?
Where there are multiple pins for one supply do I need decoupling capacitors on each pin or is it OK to have decoupling capacitors on one pin then a trace to the other pin?

Any comments or feedback will be much appreciated.


texts: Do electrons actually flow when a voltage is applied?

texts:
It's said in books that a circuit is a closed path and thus that electrons come back to the source. If that's the case, what would happen when there were an earth fault in a circuit? How would the electrons return to their source?

Do the electrons actually move out of their atoms or do they just vibrate and transfer the energy that way when we apply a voltage?


texts: How does a "bulk connected to input voltage" mos work?

texts:
This is the circuit I am supposed to analyze, but I don't understand at transistor level, what does a MOS do when its gate is grounded and its bulk is the input terminal! I mean bulk is tied to Vdd or GND for latchup problems, but when it is connected to Vin, it means it is positive in half period and negative in the other half period of ac voltage Vin...
and if you have a simpler circuit that helps to understand the such an implementation, please share.


texts: Is it possible to sketch a bode plot for a discrete-time transfer function?

texts:
For a regular s-domain transfer function, there are simple rules you can use to draw an asymptotic bode graph, basically by taking a slope of +/-20dB per decade and a phase shift of +/-90 degree for each pole/zero.

Is it possible to do the same for a z-domain transfer function?

I'm explicitly not looking to plot the exact transfer using Scipy/Matlab, but a pen-and-paper approach that gives intuition.

Basically, if I have an s-domain TF, it's fairly easy to have an intuition of the gain, phase, and corresponding stability margins. For a discrete system, I have close to no intuition about them at all.


texts: Hotwiring a Bluetooth speaker into a Bluetooth receiver

texts:
New here. So I have this mini Bluetooth speaker I bought a few years ago. Fast forward to now, and I've upgraded from it. Was going through a junk box and found it again, and wondered if I could just cut the wires to the speakers and resolder them to a headphone jack, to create a Bluetooth receiver for my non-bluetooth headset. It should be easy, I just am worried about one thing: the preamp is designed for speaker volumes, not headphones volumes. It is a mini speaker, and it's maximum volume is only a fraction of my newer speaker, but even still I'd rather not run the risk of blowing my headphones. I tried searching online but all I could find was people hotwiring Bluetooth headsets instead of Bluetooth speakers.
Should I be worried about this? Should I slap a resistor onto the ground? If so, how much resistance should I use?


texts: Air Circulation inside waterproof IP67 enclosure

texts:
We are using an SHT15 sensor + Arduino to measure relative humidity. The electronics is supposed to operate in a very high Relative humidity (~ 70 - 80) and wet conditions. To protect the electronics we have placed it inside an IP67 enclosure.

However if we seal the box with sensor inside then we are not measuring the humidity of environment. Also, there will be pressure buildup inside the box. we need some kind of vent / membrane filter that will let sensors do accurate measurements by allowing air circulation yet protect the circuit from moisture and dirt damage.

Any idea on how this is done in Industry?


texts: Detecting object passing through gateway

texts: Hoping this is the right place for this.  Honestly not even sure what to call it.  Essentially I need to find a way to detect an object flying through a physical portal/gateway/doorway.  I do not care where the object goes through or direction just that it did.  I'm looking to detect ping-pong ball.


texts: Drive piezoelectric speaker with low power MCU

texts:
I have several piezoelectric crystal speakers connected to a TI MSP430 series MCU.

All speakers share a common PWM driven MCU pin and each one use a distinct MCU pin to select them. If only one of those select pins is driven low or high and the others are in open state, one distinct speaker can output the audio waveform delivered by the PWM pin. The peak-to-peak PWM amplitude is 3V this way, as the select pins can't be driven by the PWM frequency too.

Now I need to raise the volume level of the audio output.

I tried to use an integrated amplifier, however the options are scarce as the circuit should be battery powered for years, and only amplifiers with uA standby consumption are usable. I tried some, but they are meant for analog input and can't cope with the PWM drive, thus producing a massive noise floor.

What else options are there? It is possible to use some IC providing an balanced PWM drive (eg. dual H bridge to provide 6V peak-to-peak) which operate with one-digit uA standby power? Or is there any discrete circuit with equally low static consumption?


texts: 150 A 12 - 16 V DC Short Circuit Protection

texts:
I am powering a ROV from a 4S LiPo battery (12.0 V minimum, 16.8 V maximum). The resistance of the battery is 36 mΩ, so that a maximum current of 470 A can flow through a short-circuit. In order to avoid risk of fire, I would like to implement short-circuit protection. The machine draws a peak current of 100 A (with a safety factor of 1.2 applied). Therefore the short-circuit protection device must trip at a current between 100 A and 470 A. I have been unable to find fuses that are rated at 12 V and a suitable Amperage. I have found the following product, intended for caravans and boats:

https://www.amazon.co.uk/Carviya-Waterproof-Manual-Circuit-Breaker/dp/B074RDSDB9?ref_=fsclp_pl_dp_5&th=1

But I am unable to find a data sheet that confirms its specifications and timing. Could anyone please advise me whether a fuse or alternative circuit breaker for this application exists, and if so, if it would be sufficient to avoid damage to the vehicle?


texts: Microcap BJT amplifier DC and AC analysis

texts: I am using to simulate DC and AC amplifiers of 2n3904 but it does not match with my theoretical calculations. My simple circuit is in attachment. Normally IB  must be 28,12 uA but it seems 14.9 uA. Also for Ac analysis Vout/Vin should be about -268 but regarding to simulation it is about -180. Could you please help me to solve this problem.


texts: What is the importance of peak factor and form factor?

texts: I get that form factor and peak factor are suppose to be ratios involving the RMS, maximum and average values of current or voltage for AC circuits, but I don't get specifically why those ratios are important that they need a special name. Is there any explanation or usage that shows importance to why the quantities for those ratios are selected and placed that way?


texts:
I want to use a TMP36 temperature sensor, so I thought to transfer the signal through an RJ45 cable. (Is that equal to a cat5 cable? I just used an old ethernet cable)

When I use the sensor next to the MCU (an Arduino) with some common jumper wires, I read a value of about 25oC.

25oC equals to 25*10 + 500 = 750mV

When I use the sensor a few meters away from the MCU and transfer the signal with an RJ45 cable, I get readings as low as 3oC.

3oC equals to 3*10 + 500 = 530mV

I use an RJ45 cable (8 wires inside) about 1.8m (6ft) long with terminals like these: https://www.sparkfun.com/products/716

I wonder how a voltage drop of about 200mV occures in less than 2 meters of cable? On the same cable (different wires) I transfer the digital signal of a DS18B20 temperature sensor as well as the signal of a DHT humidity sensor, and both seem to work fine.

Is this voltage drop reasonable? If so why? In any case what kind of cable should I use in order to transfer a signal for just a few meters?

Any thoughts would be appreciated.


texts:
Since it is holidays in my place, I started working on a project that I have seen in Instructables; with the help of my Arduino Mega I am displaying the output signal.
These are the results using a red LED in order to recover the oxygen values:

The circuit I am using:

The capacitor I found in my house is 620nF so not 500nF as in the schematic.
The experiment was done in the dark; I had no light except the one coming from the red LED.
I am not really sure what I have done and why I am not getting a proper signal.
The code in Arduino contains 1 line :
Serial.println(analogRead(A0)*5/1023.0);

Thanks a lot for your kind help.


texts: How does data travel correctly over the wire?

texts:
I understand that through varying voltage, data can be transmitted as "high" and "low". What I don't wrap my head around is how the receiving end "dissect" the frame.

I know there is a concept of frame, lets say the receiving end will always receive 8 bits at a time as one frame and begin the next frame for the next 8 bits.

1111 0000 -> one frame

But what if one bit is lost? Won't that create a domino effect for the rest of running time since frame will be offset by one bit and everything after will not be correct.

How does this get enforced on bit level?


texts: How to predict and compensate for the dynamic and static resistive torque due to losses in a motor

texts:
I will have external torques acting upon an axle to which a motor is connected. I want my motor control system to fairly precisely compensate for most of the torque that the motor imposes on the axle itself due to things like motor frictional losses, induced eddy currents, etc.

In other words I'd like it to appear from outside as if the motor doesn't exist. If one were to spin the axle with their hand the axle should continue spinning at that rate until externally stopped, and you should have to do no more work to stop it than you would if the motor weren't present (ideally).

My motor will need to operate around 10W and -200 to 200RPM. Ultimately this system will be used to modify the stiffness of a mechanical torsional spring without adding damping.

What considerations do I have for motor type selection/design if I want to:

mimimize the needed loss compensation torque
simplify the control system

?

I assume brushless non-geared motors are superior from a friction perspective, however I understand permanent magnet motors have significant eddy current losses and also suffer from "cogging" which may complicate control.

Additionally:

What methods exist for predicting/estimating the magnitude of these torques from commonly available motor specs?
Which motor losses are typically constant and which vary with temperature / velocity / other factors?


texts: Does a led determine itself current load?

texts: If I use a power source rated at 2.5v and 1 amps for power a standard red led , what should happen to led? Does it get burn for the high current value or not?


texts: Charging 6 NiMH batteries in series via solar

texts:
I'm currently working on a project in which a Atmega328 is powered by 6AA NiMH batteries in series (7.5v, 2000MaH). It is in sleep mode most of the time, except to turn a servo a couple times a day, for a couple of seconds (Hence the need for the high voltage).

I have a solar panel at 12V and 1.8W, so maximum of 150mA. After doing a lot of research, and looking at this post: Charging NiMH batteries with 1W solar panel, charge controller needed? .
The maximum output for my solar panel is within the c/10 -> c/40 range that is safe for the NiMH batteries to be charged at.

My question is, none of the resources I could find explicitly say if what I am attempting is OK for multiple cells like I have.. Due to the remote nature of my device, charging each cell individually, or using a LiPo, is not an option.

Thank you very much.

EDIT: Below is a PCB design for this circuit. According to @BruceAbbott The voltage of the panel would be fine, but since my servo can only handle a max of 8v, would the batteries still be able to lower to voltage to not damage my servo?

I believe the reason it is safe is due to how the current and voltage is controlled from a solar panel, for example, this IV curve (NOT the panel i'm using, just an example.)

This should ensure that the voltage never exceeds the dangerous limit?


texts: IC that allows two dc voltages to switch to one of them as output

texts:
I am unable to find any IC that would allow me to have 2 DC inputs (5v/12v coming from the PC psu) and have one of them as output (being either 5v out or 12v out). This is for power to a PC Fan that should, at the far end when using a 140mm case fan, would pull 4.2 to 6W. So around ~400mA...

I figured that a DPST switch would work but I'm not quite sure that is what I need for this?

An illustration of what I am looking for the IC to do:

Being hooked to a microcontroller (PIC), I would be able to switch from the default voltage (that being 5vdc) to the 12vdc and, if needed, back to 5vdc.

Anyone know of an IC that would work like this for my needed purpose? It would also be nice if the IC had 4 outputs (2 inputs) so that I wouldn't have to have so many of them on my PCB. I will have 8 4pin connectors so that would be a total of 8 outputs that I would need.

So something like this?


texts: pure continuous analogue 96 Hertz signal

texts:
I work with autistic children.  I need to produce a tactile input using pure analogue sound of 96 Hertz through a transducer.

The fifties  signal generator I got on e-bay does not put out enough signal strength to run the transducers. I need the signal to be pure analogue continuous and and the volume to be adjustable.

How do I generate a signal of 96Hz with a low source impedance?


texts: Full-wave controlled bridge rectifier and the RMS voltage derivation?

texts:
I have a question that reads:

  A full-wave controlled bridge rectifier is considered, shown below. Vs = 230V. Load is represented by \$i_o = 10\$ A. Frequency is 50 Hz and the delay angle is 45\$^{\circ}\$.

  (a) Sketch \$V_{o(avg)}\$, \$V_{SCR1}\$ and \$i_s\$

  (b) Derive the formula for calculating the average value and RMS value of the output voltage

Do I assume that this FWB rectifier has an RL load or an R load?

I am assuming that there is a purely resistive load:

So, they look roughly like this

  (a)

(apologies for paint)

  (b)

$$V_{o(avg)} = \frac{1}{\pi} \int_\alpha^\pi V_m \sin{\omega t} \text{ d} \omega t
= \frac{V_m}{\pi}\left[-\cos{\omega t}\right]_\alpha ^\pi = \boxed{(1+\sin{\alpha}) \frac{V_m}{\pi}}$$

and RMS:

$$V_{rms} = \sqrt{\frac{2}{\pi}\int_\alpha^\pi V_m^2 \sin^2{\omega t}\text{ d}\omega t }$$

Then, I think I just use \$\sin^2{\omega t}=\frac{1-\cos{2\omega t}}{2}\$ to contiune the integration. Is this right, or am I making things too complicated?


texts: How to calculate PCB track width on proteus?

texts: The current in my circuit is 60A and voltage is 36V. How wide should the tracks on my PCB be?


texts: What is Atmel's 2x5 ICSP connector called?

texts:
I'm looking for a male connector that fits in the left female connector shown in the image. My goal is to break each lead out to holes on a breadboard. What is that kind of 2x5 connector called?

Searching for ICSP connectors doesn't help me.


texts:
A component burnt up on my remote control receiver and I want to identify it.

Thank you


texts: I'm trying to find out if there is any way to control the CC lines on a USB-C from an android app.  I need to signal to my embedded gadget some event, instigated from an android app.  I can't find any details on the phy layer of USB for android.  any suggestions?


texts: Looking to use an Op-Amp to scale a high-voltage system to a low voltage system

texts: I am looking to scale a voltage of range 30V-120V to a 9V-14V range. I am looking into using an Op-Amp and have found that ideal Op-Amps use a system that cannot take a varying 3rd input as a constant to the proportion. Any help as to what I should do?


texts: Interpreting touch screen data (I2C, FT5306)

texts:
Edit: sussed it, largely to help below. It turns out, screen X/Y do not have to correlate to touch sensor X/Y and, even more strangely,
  the touch resolution does not necessarily match screen resolution! The
  latter was really borking things up due to a fudge in the old screen
  that was being replaced having higher touch resolution than screen.

Sorry in advance, this is long.  I am very experience embedded engineer, done some basic LCD stuff before, but never a touch screen.

I am trying to update a system to use a new capacitive touch screen LCD for which the touch interface was previously SPI and is now I2C.

I should stress, I am successfully driving the screen via the RGB parallel interface - that bit has not changed. I have got the I2C interface up and running and when the screen is pressed I am getting the interrupt from the screen, able to read X1 and Y1 registers quite happily and I can see the values changing as I press different parts of the screen.

The datasheet [for this MI0430H1T-9] says it is 480 x 272 and when I read this touch data back I am getting minimum readings of about 33,9 and maximum of 464, 235. I assume the bezel is preventing me touching the very edges of the screen.

Now, the first issue is that I would expect the X to be reading from 0-480 and the Y from 0 to 272. However, X and Y seem to be the opposite way round to what I would expect.

I am reading registers 3 through to 6 inclusive. Datasheet says 3 and 4 are X position (12 bits plus event flags) and 5 and 6 contain Y position.

What I seem to get though is X data in registers 5 and 6. So, when I touch bottom left of the screen (the long side of the screen and therefore 480 pixels in length), registers 5 and 6 are changing, whereas registers 3 and 4 stay with approximately the same values as I move along the length of the screen.

On top of this, the bottom of the screen gives larger touch values and the top of the screen smaller touch values.

To summarise: bottom left of the screen I would expect to be 0,0, but gives me a touch reading of 259,33, top right gives me 39,458.

So, am I misunderstanding how these things work? The image from the datasheet below: Is that saying that, actually, Y touch data is 1-480?


texts: What does a black band at the end of a resistor mean?

texts:
I have a burned out big blueish gray resistor (probably a 1/2 or 1 watt) that I'm trying to find the value of but there is a mysterious black band at the end of the resistor where the tolerance band would be but obviously the tolerance/failure rate/temperature band cannot be black.  What does it mean?

4.6mm x 15.5mm

I have confirmed colors:

Brown
Black
Gold
Gold
Black

So I think it's safe to say it's a 1 ohm, 5% tolerance.  But what is that last black band!? It's driving me insane.


texts:
I have always assumed superconductors and ideal conductors as the same thing, but recently I found out that they are not.
I tried to look up their differences on the internet, but I got only mixed up explanations.
Can someone tell me their key differences and similarities with proper definitions? (Because the one that I found on the internet were rather similar)
Also, do the ideal conductors follow Ohm's law? I have a feeling that they should but since they have R=0 ,I don't know if that will workout well.


texts: How much current is used with a μC GPIO input and pullup resistor?

texts:
I'm trying to understand power budgets a bit better and I have a question regarding pullups. I have a input to a microcontroller that needs to be logic high at all times. The micro goes to sleep now and again, so the internal pullup isn't an option. Looks like so (wow that's big).

simulate this circuit – Schematic created using CircuitLab

I'm dealing with a low power, battery-operated system here (2 AA batteries), so every bit of power savings counts. My question is how to figure out how much current this draws. If I just look at V = IR, we're talking 30μA, which is actually a lot for this application.

What I don't really understand is how to factor in the microcontroller. I'm assuming there's something I need to factor in from the datasheet, but I don't know which elements are relevant.

The 100k resistor is from a reference design, but is there anything stopping me from putting a much bigger resistor to cut down on current draw?

These are probably basic questions, but I'm a software guy out of his element here, so bear with me.

Leakage

Based on some comments, it looks like leakage current is the microcontroller spec I should be interested in. Below is what I found in the datasheet. Is 3 nA the magic number?


texts: Minimal USB-SIE code example for PIC16F1454 and question about windows driver

texts:
Im new to PIC microcontrollers. Im looking for minimal USB-SIE (Serial Interface Engine) code example for PIC16F1454.

I was browsing Microchip forum, but there are examples with so many details...

Questions:

Where I can find send and receive byte example with schematic?

Do I need to install Windows driver for USB-SIE, or it will work natively?


texts: How can computer parts suffer if the computer isn't protected by an UPS?

texts:
In datacenters it's common to use Uninterruptible power supply (UPS) to protect the computers. They are used for several reasons, but one is that electronics possibly can suffer from the power grid if the power isn't "filtered".

Is it only the power supply unit of the computer that can suffer or can the computer parts also suffer? And how can they suffer? Does an Uninterruptible power supply work differently to an Power supply unit (PSU) or is the PSU already protecting the computer parts from the power grid?


texts: Second order active filter design using differentiator

texts: Just like a two integrator loop biquad circuit for designing the second order filter is it possible to use two differentiators? What are the problems faced in doing so?Thanks.


texts: Why does my lithium flashlight battery voltage lowers as the charge lowers but not my power tools battery?

texts:
I started poking things with my multimeter and it's interesting. I have a lithium battery in my flashlight and as the charge lowers the shown voltage on my multi meter lowers. But my Milwaukee battery don't. The power indicator on the battery shows halfway but they still read 18v.

I'm a total newbie to so why I don't know this.


texts: Find cutoff frequency of a common emmitter amplifier

texts:
simulate this circuit – Schematic created using CircuitLab

I need to find the cutoff frequency of this common emmitter amplifier. Is it possible to simulate a bode plot?


texts: Need help choosing options for 12V supply from a Lithium-Ion battery

texts:
There are lots of Class D audio amplifier modules for 12V use that are both readily available and inexpensive, intended for automotive use (hence the 12V rating). I would like to use one of these, rated at about 20 Watts max into a 4 ohm speaker load, as part of a portable  "practice" guitar amp, and I'd like to power it with a Lithium-ION or LI-Polymer cell pack. The problem is, all the modules I've looked at have a maximum supply limit of about 14.5V and worse, their sound quality starts to diminish at about 10.5V. So the problem, of course, is that a 3 cell Lithium pack is going to output between about 9.6V (3.2 x 3) and 12.6V (4.2 x 6) over the bulk of its charge range. So with this choice, the sound will begin to suffer long before the pack has exhausted its useful charge. I don't need precision voltage regulation, but I DO need to at least do a little better then a raw 3 cell solution.

I'm not sure what options I can consider here and could use some advise. I suppose I could add another cell and look into a buck regulator circuit, with the disadvantage of adding more bulk to the battery pack, and losing some efficiency to the regulator. Maybe there is a boost regulator I could look into for the original 3 cell approach, but it would have be nearly bypassed at full charge, and of course be able to efficiently supply about 2.2 amps (assuming 100% efficiency of the class D amp). Does anyone have any thoughts, or maybe could recommend other options I've not considered here?

Addendum: Here's a link to one possible inexpensive solution. Based on answers indicating a boost regulator might be my best choice, I started poking around for a ready made module, and I'm finding this one all over e-bay. So I'm just passing this info along for anyone else in the same boat. It seems that with a boost regulator, excess voltage is passed through, so if adjusted to 12V and the input is 12.6, then the output will be 12.6. But thats not a problem for me, and if it was I could simply adjust to 12.6, or even 13V. At 150 watts, this one might be overkill, but they are not as huge as they look in the picture (65mm long). Of course this particular seller may go away. But there seem to be many suppliers, and for around $3 USD, its hard not to get a few just to experiment with. Here's a screen shot in case the link stops working. They seem to be pretty easy to find at this point.


texts: What type of connector is this 3-pin socket marked "DC24V" on a printer?

texts: The device in question is a printer, I've never seen such a connector before...


texts:
I have different 4.5v small LED circuits (from 100mA up to 350mA consumption, with some 555 ICs) that I'd like to power using a small regulated USB wall charger (4.95V output, 0.8A).

As per my understanding (I'm new to electronics...) I can calculate the proper resistor for each circuit knowing the current. However I'd like a solution that can sustain 4.5V regardless of the current (within the limits above).

I've been reading about voltage dividers and zener diodes, however I'm not sure about the best approach for this small drop. What would be the the best way?

Update: these are independent small lighting circuits that I've build for small models, powered by 3 1.5v batteries. The problem I'm experiencing now is that the voltage of the batteries drops in time, dependent on the type (rechargeable, etc.) and brand. For example, because 3x1.5v = 4.5v, I've used some LEDs with fV 2.1 in series with a small resistor, to make a more efficient use of the drained current. However in time the batteries V drops to 3.8v, below the minimum level the LEDs need, affecting their brightness (and a new set of batteries is 4.8V!). In hindsight, maybe I should have considered a regulated power supply from the start, instead of trying to compensate for the variable V in the batteries during their lifetime... I might post a new question about this topic, but feel free to comment on this too :)


texts:
I have a designed circuit board that has a problem with its start up sequences. The problem is that the voltage ramps up (could be as low as from 0V to 5V) so slowly that the chip won't physically turn on.
I want to add an independent circuit board that will act as a bridge to solve that problem. The circuit will collect the voltage from that slowly ramping voltage and once it hits 5V it will have a switch to instantly release the 5V.
The flow will be :

[some input voltage] --> [voltage regulator]--->[some detection
circuit that know when it hit 5V mark] ----> [release the voltage]

I have no idea how to design the detection circuit.
Edit:
This is the voltage regulator I'm using (TOS54302.)
The chip is a pMDDL2450 2.4GHz data link RF module.


texts: System Generator: Problems with CORDIC block at getting the bitstream file

texts:
I don´t get to get the bitstream file. I have several errors when I try to generate the bitstream file.
The error

I have this error message from the file called xflow.results:

  ERROR:Par:228 - At least one timing constraint is impossible to meet because component delays alone exceed the
    constraint.  A physical timing constraint summary follows. This summary will show a MINIMUM net delay for the paths.
    The "Actual" delays listed in this summary are the UNROUTED delays with a 100 ps timing budget for each route, NOT
    the achieved timing.  Any constraint in the summary showing a failure ("*" in the first column) has a constraint that
    is too tight.  These constraints must be relaxed before PAR can continue.

  Please use the Timing Analyzer (GUI) or TRCE (command line) with the Mapped NCD and PCF files to identify the
    problem paths.  For more information about the Timing Analyzer, consult the Xilinx Timing Analyzer Reference manual;
    for more information on TRCE, consult the Xilinx Development System Reference Guide "TRACE" chapter.

This is strange to me because I have never had a constraint problem before.

What could I do to avoid constraint problems in System Generator?

The link for my .mdl file:
https://www.dropbox.com/s/h15ns3p55wlbuc2/singledivider_exampleconceptlatencyandsimtime.mdl

The link for my xflow. file:
 https://www.dropbox.com/s/odqoakbrs21ngbx/xflow.results


texts: General directions for a timer circuit which will not use microcontroller and which can measure several hours needed

texts:
Some background info first:
In my country, price of electricity depends among other things on the time of the day when energy is used. Because of that, many people tend to turn on big energy consumers after midnight, when electricity is cheaper. One of my friends needs a new laundry washing machine, so I went browsing with her. We noticed that many new machines have a delayed start option which would be very useful because it would be possible to fill the machine and program it and it would start working by itself during cheaper time. I don't think that it would be too complicated to make a circuit which will start a washing machine after X amount of time.

More relevant part:
After examining my washing machine, I noticed that machine itself is started by a normally off pushbutton. I'm thinking that the button could be replaced by a transistor or some sort of normally off relay. Anyway that's not (yet) the problematic part for me.

The question itself:
How would I design a circuit which would wait for several hours and then "push" a button without using microcontrollers? I know that a microcontroller is the most elegant solution, but I'd rather skip collecting necessary gear for working with them at this time. Discrete logic gates, flip-flops or anything else which doesn't need a programmer is acceptable for me.

My first idea is to create or find prefabricated some sort of counter which would be connected to a slow oscillator. The oscillator would have very low frequency (say 2Hz if possible) and the counter would send signals to a device which would respond when counter reaches a certain number (say after 18 000 seconds).

I was thinking about using 74LS162/3 counters. In 74LS162's datasheet under minimum frequency it says 25MHz if I'm reading it right, so I guess that it doesn't fit my needs, but 74LS163 has 0 as minimal frequency so it looks like a logical choice to me.

As for the oscillator, the slowest crystal I could find is 32 768 KHz which is too fast for me. I thought about using capacitor and coil to make my own oscillator. Some (maybe too) basic calculations tell me that L*C needs to be 1.989*10^-2. What capacitor/coil combination would be good for that?

I didn't think too much about power supply, but I'd either use "wall-wart" adapter or check the insides of the washing machine for any available power sources.

The last part of my question are vibrations. Are there any special considerations for circuits which are going to vibrate? I was thinking of using one of those solderable  protoboards for basic circuit board.

I know that a book can be written for every point, but at this moment I'm just looking for some rough ideas.


texts: LTspice - using save/load bias with a parameter sweep

texts:
I have a circuit which has some hard time converging in a DC simulation.
The circuit does converge nicely in a transient simulation when skipping initial condition calculation.

Therefore, I've ran the transient simulation to get the operating point and saved it with the .savebias statement.
Afterward I load the operating point in the next simulations with the .loadbias statement.

It all works fine and well, until I add a parameter sweep (.step param) in which case the .savebias statement only saves the last sweep value.

Does a solution for this exists ? How can I save the operating point for each value of the swept param separately and load separately ?

I've tried to save the file with the swept parameter value in the file name but to no avail (.savebias tran_bias{stp}.txt).

EDIT:
I have managed to save the operating point (rather manually but it's ok for now since I only have 4 values in the sweep) using the undocumented "step" parameter for .savebias

.savebias transient_bias_250R.txt internal time = 500u step=0
.savebias transient_bias_500R.txt internal time = 500u step=1
.savebias transient_bias_1k.txt internal time = 500u step=2
.savebias transient_bias_2k.txt internal time = 500u step=3

The question of how I can load the corresponding file to the corresponding sweep with .loadbias remains.


texts:
I am interfacing with GSM SIM900. I wrote a program so that I can read the SMS in SIM900. I have made a function to transmit and receive. Whenever msg comes, GSM responds with +CMT along with slot number.I am trying to extract that slot number which is in digits, but I am getting garbage values

Here is the code:

while(1)
{
    if (serial_Rx() != NULL) // SOMETHING PRESENT TO BE READ
    {
        serial_Tx("done"); // print done
        PORTC = 0x01; // turn on led
        for (int i=0;i<=14;i++)
        {
            data[i] = serial_Rx(); //storing received in data

            if(isdigit(data[i]))
            {
                serial_Tx("enter");
                PORTC = 0x02;
                data1[i] = data[i];
                serial_Tx(data1[i]);
            }
        }
    }
}

Transmit and receive funstions:

void serial_Tx(char *str)
{
    for (unsigned int i=0;str[i]!=0;i++)
    {
        UDR=str[i];
        while(!(UCSRA&(1<<UDRE)));
    }
}

char serial_Rx()
{
    //Wait untill a data is available
    while(!(UCSRA & (1<<RXC)))
    {
         //Do nothing
    }

    //Now USART has got data from host and is available is buffer
    return UDR;
}

void uart_put(char data)
{
    UDR=data;
    while(!(UCSRA&(1<<UDRE)));
}

Hyperterminal:


texts: How to use same 'input' for two circuits

texts:
First of all, please excuse my complete lack of knowledge in electronics :)

Let's start with a little bit of context. I am trying to modify a machine that already uses a photo-interrupter to measure distance and speed. My goal is to be able to 'read' the state of the photo-interrupter while letting the original circuit work as intended.

Here is the original circuit, simplified to the extreme. Basically, 'Input' is directly fed to a PIC micro-controller. To be completely honest, I haven't been able to figure out much more by staring at its PCB...

My first thought was to just plug both circuits inputs to the collector pin of the photo-interrupter. I would then power the photo transistor by either power source (both 3.3V) and connect grounds. My circuit's 'input' is an input pit of a micro-controller as well.

Another possibility I thought of: using a emitter follower circuit so that, if I understand correctly, both circuits would be able to draw current from their respective power sources. Only issue I have is the voltage drop due to the emitter follower.

My question:

Experimentally, both solutions seem to more or less work, but given my lack of knowledge in the field, I would very much appreciate any comment on what is the 'right' solution.

Should I completely isolate both circuits ? With an optocoupler, for example.

What are the shortcomings of my simplified solutions ?

Thanks !


texts:
Can exposure to plasma or energy from Tesla home windings damage the body's cells?
More generally, will the plasma or energy from the Tesla coil ionize?


texts:
I have a datasheet for a part (TPS6735IDR) that shows application circuit examples where polarised capacitors are connected the wrong way around (positive terminal to ground). I thought this would cause them to blow up? Is the datasheet correct or have they made a mistake? Datasheet provided below:
https://www.ti.com/lit/ds/symlink/tps6735.pdf?HQS=dis-mous-null-mousermode-dsf-pf-null-wwe&ts=1621909192241&ref_url=https%253A%252F%252Fau.mouser.com%252F
The circuit that I mentioned is on page 12 (figure 15, application circuit).


texts: Circuit for converting motor tacho-sensor sine wave output to 5V TTL for MCU

texts:
I'm trying to measure the speed of a washing machine motor. The motor has a speedometer attached to it, which generates a sine wave with frequency equal to rotation frequency of the motor. I'm attaching the image of the sensor output signal below:

I'm trying to convert the signal to a 0-5V TTL signal for a MCU to measure the frequency. What is the best approach ?


texts: BSD style Open Source alternatives to CMSIS?

texts:
Since the licenses on CMSIS is unclear when it comes to open source,
it is probably a violation to include the CMSIS in a open source project regardless if it using a GPL or BSD style license.

Is there any CMSIS alternative out there for the Cortex M based MCU:s out there that is compatible with a BSD or Apache2.0 license?

Or does anyone know if it is ok to include the CMSIS in a open source project?

Thanks


texts:
Prototyping with real components is very time consuming.
In order to save time, I have been looking for a digital circuit simulator, compatible with the MSP430, with no success.
How do professionals deal with prototyping? If they prototype at all.


texts: SR Flip-flop with 2 npn transistors - initial state

texts:
I built a SR flip-flop circuit according to this schematic with two NPN transistors:

I read that the initial state of such a flip-flop is undefined. I observed that in my test circuit it's always the green LED that's powered initially, even if I exchange the red and the green LED.

How can the initial state of such a flip-flop be set?


texts: What is this inductor looking (RF) component?

texts:
This PCB antenna circuitry supposedly is able to transmit on both 406MHz and 121.5 MHz. I can clearly see a micro-strip printed antenna.

Facts: Dual-band 406MHz, 121.5MHz antenna

My Assumptions:
1. 1/4 wave monopole dual-band antenna

Questions:
1. What is that inductor looking thing?
2. How can they transmit 121.5 MHz with such a small antenna?
3. What is the point of the zig-zaged strips? Filter? add length?

FYI
121.5MHz:   Wave length is 8.0988 ft, 1/4 Wave is 2.0247 ft
406MHz:     Wave length is 2.4236 ft, 1/4 Wave is 0.6059 ft


texts:
Is it necessary to enable the interrupt for a given event source in order for the event to fire, or is it only necessary to select the source from the event system?

To clarify, I am asking about the Xmega Event System, not the interrupt system.


texts: Comparing voltages bigger than V+ on LM311

texts: I want to use an LM311 comparator to compare my 12V battery voltage to some reference I have, but I want it to output 5V so I can read it with my microcontroller. Due to this, I'd think I have to set the V+ pin to 5V. If I do this, can I still input 12V to it?


texts: How to achieve 57 PWM outputs most easily and cheaply

texts:
I need to light up 19 RGB LED strips, which it seems would require 19*3=57 PWM outs and 57 transistors.  The transistors aren't an issue, but of course the 57 PWM's is.  Most micro controllers simply don't have that many.

How can I do this more simply?  Is there some kind of device I can get that would let me just pass data to it, perhaps over I2C, and it would control many PWMs? Is there another solution I haven't considered?  Maybe whatever is used to control those 8x8 RGB LED dot matrixes?

Any help would be greatly appreciated.  Thank you!


texts: Need to purchase a Serial port that can be soldered to a motherboard

texts: All I can find are adapters and gender changers. Where can I find one with actual leads I can solder?


texts: What does voltage connector's voltage rating mean? AC-rms or AC-peak voltage?

texts: As mentioned in the datasheet below, what does voltage rating "300VAC, DCmax" mean? Does it mean 300Vac-rms 300VDC or 300Vp 300VDC?


texts: Is off grid solar setup limited by battery charging current?

texts:
This question is strictly regarding off grid solar power setup, using PV panel, MPPT Charge controller, battery and an inverter to convert DC to AC.
Am I limited by the input charging current a lead acid battery can take?
Consider a 12V setup, where I am charging a 100AH C10 lead acid battery. Now, as per my understanding and please correct me if I'm wrong here, I should be charging the battery with 10A current.
If I'm charging at a little more than 12V, say 13.5V, my power input from charge controller to battery is

13.5*10 = 135W

That kind of limits the PV panel I can add to system to somewhere around 180-200W, considering the losses, in ample daylight condition. That is one medium size panel.
So, what do I do? May be I should put two batteries in parallel or series.
Lets consider two 100AH C10 lead acid batteries in parallel.  Now I can bump up input current from charge controller to battery bank to 20A. So, my input can be increased to 13.5*20=260W. It will be the same if I connect my batteries in series.
The way it seems, I am limited to using one medium sized panel per 100AH battery bank.
The charge controller I'm using is a PCM60X that supports 12/24/48V charging. At 48V, it can support upto 3.2KW. I was just wondering, how many batteries I will have to purchase to use that 3.2KW.
Of course I can simultaneously put load to the system, drawing out power during day time, while charging the battery. But I cannot keep on calibrating my charge controller for maximum charging current output for that.
Now, there is another parameter, that says maximum charging current should not be more than 0.3C, which will be around 33A for the 100AH battery. This is what I don't understand. What is the current current I should be charging my battery with? If I can go upto 33A, then it gives me a lot of head room and I can configure my MPPT charge controller accordingly.
One last question, what changes with respect to charging current if I switch to a Lithium Ferro Phosphate battery rated 100AH?


texts: How to implement serial-to-fiber optic Ethernet with WIZnet W5500?

texts:
I'm using W5500 to implement a serial to Ethernet converter, but I need to transmit over fiber optic cables. I will have a TX cable and a RX cable.

How can this be done since the output of W5500 is differential? Can you suggest a schematic?

Thank you!


texts: How to convert raw ADC value into voltage in volts in software?

texts:
Let's say I have a microcontroller with an ADC and my goal is to measure instantaneous values of the line to line voltage of the three phase grid 400 V/50 Hz.
I have a voltage instrument transformer with the following nameplate data: 400V/6V. Secondary winding of that transformer is connected directly to the 16 bit ADC which has bipolar channels +/-10V.
As far as the conversion from the raw data read from the ADC into the voltage in volts I have following idea how to do that in C++ software:
    uint16_t raw_value
    float voltage

    if (raw_value & 0x8000) {
          // negative number in 2's complement
          voltage = (static_cast<float>(raw_value) - 65536) / 32768 * 666.66;
    } else {
          // positive number in 2's complement
          voltage = static_cast<float>(raw_value) / 32768 * 666.66;
    }

As far as the value 666.66 it is a channel norm i.e. voltage at the primary side of the transformer corresponding to the full scale value of the ADC i.e. 10V. I have calculated this value based on following \$6\,V \sim 400\,V\$ i.e. \$10\,V \sim 10\cdot\frac{400}{6} = 666.66\,V\$. Basically this value specifies the maximum measurable amplitude (with given transformer and adc) of the line to line voltage.
Can someone tell me whether my approach to converting raw ADC data into voltage in volts is correct (namely in respect to the channel norm)?


texts: Does the op-amp output depend on the difference in input?

texts:
If there's two different input voltages, does the op-amp amplify the difference between them. Or is it only the differential op-amp that does this ?
I'm confused!! .. I remember a question where the output voltage was 0 because the two input voltages were the same, but is that always true ?! But isn't the voltages of the two inputs the same anyway in the ideal op-amp ?!


texts: PCI card electromechanical specification

texts:
I am making an old PCI (5V) form factor card for a product, and am having a hard time finding any sort of reliable drawing showing the official dimensions of the gold fingers, key cutouts, and their relationship to the PCI mounting bracket.

Was there an official PCI specification released that I just am unable to find on the internet?  Is there some other resource that has these?  I am trying to avoid the mistakes that would come about from manually measuring PCI cards I have in house.


texts: Do Karnaugh maps use a base ten numbering system??


texts: Analysis of Branch misprediction in MIPS 32 bit architecture

texts:
I am confused about what happens when we use a Bimodal branch predictor in the MIPS architecture shown in the image below.

I am considering the case where there is already a branch delay slot implemented and it uses a 1024 entries BTB and a branch predictor with a 2-bit saturating counter which gives the direction as taken or not taken.

My thinking is as follows:

Case 1 - Conditional branch is fetched.Checks for an entry in BTB. If there is an entry, then,a target address is predicted from BTB and the branch direction is taken, but at the execute stage we compare the predicted target address with the actual target address, if they don't match then at the fetch stage we kill the fetched instruction and, then we get the correct target address as follows at the fetch stage:

if(misprediction)
PC value = correct target address

Case 2 - Conditional branch is fetched.There is no entry in BTB. So the branch is resolved only at the execute stage.

Case 3 - Unconditional branch is fetched. Branch direction is always taken and an entry is found in BTB, then the target address is predicted from the BTB. And  at the execute stage we compare the predicted target address with the actual target address, if they don't match then at the fetch stage we kill the fetched instruction and, then we get the correct target address as follows at the fetch stage:

if(misprediction)
PC value = correct target address

Is this correct?


texts: Why fast inner current loop and slow outer loop of DC-DC converter

texts:
Let say we have a DC-DC converter  operates with double loop control (inner and outer) , and with switching frequency of Fs= 20000 Hz.
Please ,if you could answer the two following questions:

1- Usually, the inner current loop bandwidth is chosen  based on the relation of  Fs/10 , = 2000 Hz in this case Way?

2- in a two loop control of DC-DC converter such as : boost converter , always the bandwidth of inner current loop is faster or higher than the outer loop .why?
Some paper mentioned that , The outer control loop bandwidth can be calculated as = inner loop bandwidth/10 = 200 Hz in this case Why?


texts: Design a clipper circuit using 1N4148 general purpose diodes and a R = 1 kΩ to clip input signal voltages that are above 5.7 V or less than −0.7 V. Below is my schematic in which Vo<=Vdo + 5V and Vo> =-Vdo. Vdo=0.7V. My question is if this circuit follows the specs.


texts: Does water actually damage or only temporarily disable electronics until drying out?

texts:
Does water leave any damage after drying out?

If it does, where and how exactly does it? How can it be repaired?


texts: Multiple feedback low-pass filter design

texts:
I'm trying to design second order multiple feedback low-pass filter with cut-off frequency at 1500 Hz and Chebyshev approximation.

Transfer function for this scheme is defined as:

Where:

And condition for real values of resistors:

However using Matlab and cheby1 function I get extremely high values of coefficients and as a result high values of resistors and capacitors.

hertz = 1500; % passband in hertz
rad_s = hertz*2*pi; % convert to rad/s
order = 2;
ripple = 3; % dB

[b, a] = cheby1(order, ripple, rad_s, 's');

% Extract coefficients for computing sheme values
a1 = a(2);
b1 = a(3);
H0 = -b(3);
fprintf('Coefficients:\n\ta1=%d\n\tb1=%d\n\tH0=%d\r\n', a1, b1, H0);

% Condition for capacitors
KCmin = (4*b1*(1-H0))/(a1^2);
fprintf('Capacitors condition:\n\tC2 / C1 >= %d\r\n', KCmin);

% Choose satisfying capasitors
C2 = 10^(-3); % F
C1 = 10^(-12); % F
fprintf('Chosen capacitors:\n\tC1=%d\n\tC2=%d\n\tCk=%d\r\n', C1, C2, C2/C1);

R2 = (a1*C2 - sqrt((a1^2)*(C2^2) - 4*C1*C2*b1*(1-H0))) / (2*hertz*C1*C2);
R1 = -R2 / H0;
R3 = b1 / ((hertz^2)*C1*C2*R2);

fprintf('Resistors:\n\t%d\n\t%d\n\t%d\n', R1, R2, R3);

And output is:

Coefficients:
    a1=6.078036e+03
    b1=6.288448e+07
    H0=-4.451880e+07

Capacitors condition:
    C2 / C1 >= 3.031241e+08

Chosen capacitors:
    C1=1.000000e-12
    C2=1.000000e-03
    Ck=1000000000

Resistors:
    7.518520e+03
    3.347155e+11
    8.349974e+04

Also I noticed that whatever ripple I chose condition C2/C1 was always of 10^8 order.

What am I doing wrong?

UPDATE

I believe I know what the problem is: given equations are in normalized form and I need coefficients for normalized form too. However MATLAB gives coefficients which are totally ready to be used. Therefore as I understand I have to remove w from the equations but it has not helped me in some reason.

Also I found normalized coefficients in my textbook:

The last column is normalized coefficients for 2d order 3dB Chebyshev filter. But I can't understand where from I have to take H0.


texts: How can I tell what kind of fan controller to use?

texts:
I have an HP SAN storage array that has 2 fans on the back. They run at full speed all of the time, and I'd like to slow them down based on the temperature of the hard drives in the array.

The fans don't have any good exterior markings (other then 12V), so in the name of science, I sacrificed one of the pair.

There are 6 wires:

M+
M-
PROG
TACH
ENB
IDENT

I get that M+ and M- are for power and that TACH is probably to measure the speed of the fan, but any idea what the other 3 are? And based on those connection names, any idea on the right way to control the fan speed?


texts: Some doubs regarding AC/negative voltages in an audio signal

texts:
I know that audio signals are AC signals (negative/positive voltage).

Assume a typical Fuzz (guitar pedal) effect circuit below. It seems signals stay between 0 and 9 V (9V is the power/battery voltage).

Also, when I look at some through an oscilloscope however, the GND is considered 0 V, and the voltage goes from 0 V to some mV/V, only positive. I used for this a line level signal (not guitar audio output, since I don't have a guitar myself).

So I'm a bit confused about the 'negative/AC' voltage. Can someone clear that up?


texts: Detect position of walkers along a path using IR transceivers

texts:
I am working on a project that the position of people walking along a path needs to be known. I'm a hobbyist so I don't know what options I may have.

I want to use IR sender and receivers to detect the position of people. I need to use around 20-25 sensors (one every 50cm). The easiest solution that may come to mind is to connect each IR receiver to one pin of my Arduino, but it requires too many pins and also huge amount of wires. To use less pins and wire I thought I could use an arrangement like analog keyboard, similar to the following image, keys representing IR sensors.

But this way only one input can be detected. Is there any way to detect multiple inputs using only a few wires?


texts: unfamiliar gain equation of differential amplifier

texts:
I am examining op amps and I found this pdf very helpful: http://www.aicdesign.org/SCNOTES/2010notes/Lect2UP230_(100327).pdf

In this tutorial,  the op amp circuit topology is given as this:

and gains of stages of the op amp are given like this:

First time I see an equation like this. I thought the (DC)gain of the first stage is: \$gm_{2} * r_{ds2} // r_{ds4}\$

it seems really wrong to me. Can anyone explain why the gain is represented that way in this tutorial?


texts: Does computer memory record the zero binary state?

texts:
It's been two years since I started reading about electronics and computer circuits. I fell in love with the homemade computers and the possibility of building one by myself.
You will see: When somebody explains computer memory, says "There is, and there isn't" "There's Voltage (1) or there isn't voltage (0)"

Is there a way computers record the zero state? (If it's with different voltages, how do they recognize it)

For example, if I want to create a serial paper tape I'm going to put a hole where there's a one, and I'm not going to do so when there's a zero. But my computer will not recognize that "lack of hole" as a zero, and when reading:

If the original signal is: 1010

Then in the tape it's: 1(Nothing)1(Nothing)

Wich turns out on the final data as: 11 (That is, not correct)

I know that computers use something like timing or control signals whether must be data or not. Can someone explain me that?

Thanks by now.

PD: I don't know if it's the best forum. But since my question is about the electronic way computers read and write data, I decided to post here. Don't kill me, please T.T!!


texts: Why is it an advantage that carbon brushes have 'high resistance'?

texts:
I recently heard that in a universal motor (and I'm presuming regular DC motors too) they use "high resistance carbon brushes", and I can't seem to find anywhere that explains why they need to use "high resistance" brushes.  Wouldn't it be the lower the resistance the better? The only thing I could find was this on Wikipedia.

  For certain types of electric motors or generators to function, the coils of the rotor must be connected to complete an electrical circuit. Originally this was accomplished by affixing a copper or brass commutator or 'slip ring to the shaft, with springs pressing braided copper wire 'brushes' onto the rings which conduct the current. Such brushes provided poor commutation as they moved from one commutator segment to the next. The cure was the introduction of 'high resistance brushes' made from graphite (sometimes with added copper). Although the resistance was of the order of tens of milliohms, they were high resistance enough to provide a gradual shift of current from one commutator segment to the next. The term brush remains in use. Since the brushes wear out, they can be replaced in products intended to allow maintenance.

Based off that, my question would be: Why is it important that there be a gradual shift of current from one commutator segment to the next? How is the achieved by having slight resistance in the brush, and how does that solve the initial problem shown in italics?


texts: We have on the collector of the first transistor is a resistor at 1000 ohms , could you tell us what function this resistor performs in this place and how to argue that it is at 1000 ohms


texts: How does voltage and current affect speed and torque of a motor?

texts:
I have a motor attached to a foam wheel (made of insulation material). The wheel is VERY light, yet the motor I am using cannot handle the torque required to run it, resulting in the motor creating a burning smell. This is an 18V motor that I connected to a 12V 2.2 A supply. If I lower the current further, wouldn't the speed decrease along with the torque? Or is voltage related to speed and torque related to current? I am not sure if this motor can handle the load, but I want to know if there is anything I can do to give it a chance.

I know this question has been asked, but it was about a brushless motor. This is a brushed motor, so it might work differently.


texts: Capacitor changing output voltage from 12v to 20v

texts:
I have a transformer with two output coils I have wired them together in series and used the connection between them as 0v and used the other two leads in a diode bridge rectifier. Without any filter caps, I get +12v on one rail and -12v on the other. However when I add in any kind of cap for filtering my voltage jumps up to 20v.

The parts I am using are largely salvaged; but the only part that I have little to no info on is the transformer. It takes US AC voltage, (110-120) but I don't really know what it's intended output is.

I am very much in the learning stage with this stuff so odds are I have made a dumb mistake, but hey, that's why my parts are salvaged. No cost, none lost. Am I right?

EDIT: To clarify I am going for a dual power supply. With 0v and +/-Voltage. I would prefer +/-12v because 20 volts pushes the limit of some of my other external components, but I can change things if needed.


texts: Improving battery life: BLE device with a 100uF capacitor

texts:
I have a BLE beacon and I was wondering if adding a capacitor in parallel with the coin cell battery would help with the battery life by smoothing out the peaks. The scenario shown in the chart is the BLE advertising event (every 1s). So I first added a 10uF then also a 100uF capacitor in parallel and took a trace of the power profile. The two series shown is with a 10uF capacitor (orange line) and the other series with both 10uF+100uF capacitors (blue line). Looking at the charts, I have two questions:

For the 100uF series, why is there a large spike at the start of the advertising event ? I expected the larger capacitor to help smooth out the initial peak of the advertising event not make it worse. (there's a bit of CPU work before the main spike which is smoothed out but that should not deplete the capacitor). Instead, it looks like its charging at the same time and I suspect there needs to be some way to limit the draw of the capacitor. I tried adding in various resistors but that just converges to not having a capacitor in the first place.
It does not look like adding in the 100uF is helping at all, are there ways to make it help and not hurt or is it better to not have it ?

Thanks for the replies. Turns out to be buggy UI software. I reran the tests with different s/w and got results more inline with what you would expect.


texts: How to distinguish independent capacitors in an n-order circuit?

texts:
As in the image above, the capacitors are said to be dependent, so it is a first-order circuit.
How do I tell if two capacitors in such circuit are dependent or independent so it is first-order but not second-order circuit?


texts:
I do not understand "The circuit on the right is a feedback amplifier with loop gain T. Since all time constants in that loop are of the same order of magnitude, they create a system with several poles"

How do I derive the feedback loop gain T = (gm1)*(Rin) ?

Could anyone point me to some maths reference / equations ? Razavi book does not mention about the circuit on the right though.

Note: the current mirror on the right is a 4T Wilson current mirror https://en.wikipedia.org/wiki/Wilson_current_mirror#A_Four-Transistor_Improved_Mirror

Let me start with 3T Wilson mirror in BJT implementation.

  A feedback path is thus formed that regulates IC3 so that it is nearly
  equal to the input current, reducing the systematic gain error caused
  by finite βF.

systematic gain error due to finite βF ?


texts: The 74LVC1G07 is open-drain, but I don't find anything in the datasheet that tells whether or not it can handle 12v on the output ("Y") pin.


texts:
I want to get full list of supported AT commands and other undocumented codes for some cell phone. I found that using strings command (on linux or win alternative) I can get all ASCII or UTF constant strings from firmware binary file, but it is a junk.
I don't have any JTAG hardware.
Maybe I should get fullflash from the device and look for some interrup routines.

Is there any other way to get these info?


texts:
As I understand it, DC motors have Kv values because their speed is determined by the applied voltage. AC motors don't have Kv values because their speed is determined by the frequency of the AC input.

The structure of a brushless DC motor (BLDC) is essentially similar to that of a permanent-magnet synchronous motor (PMSM). The main difference is the input voltage, which produces a different BEMF (trapezoidal for BLDC, sinusoidal for PMSM). So I've been wondering why BLDCs have Kv and PMSMs don't.

My theory is that BLDCs have Kv values because their speed is increased by increasing voltage, and not by changing the input voltage more quickly. PMSMs don't have Kv values because their speed is increased by increasing the frequency. Does this sound accurate? Or am I completely mistaken?


texts: Why are relatively powerful chips used for simple tasks like playing a song?

texts:
In a book my Michio Kaku (called Physics of the Future) he makes the claim that a chip in a birthday card that sings a song is more powerful than all the computers the allied had in 1945.

Now, I don't say I believe this claim, but my question is: Why use a relatively powerful chip for a simple task like this? Or am I underestimating the task of playing a song when opened?


texts:
It seems that the voltage over ethernet ranges from 2 to 3 volts. How much current typically runs through the wires? I tried Googling with no success.

I ask this because I'm looking for components that are able to switch on and off an ethernet connection.


texts: Raspberry Pi 3 GPIO Input Offset Current Specs?

texts:
I'm using a Raspberry Pi connected to a custom breakout board.
I'm reading in low power signals from an analog opto-isolator and was wondering if there are any specifications for the GPIO pins such as \$V_{IH}, V_{IL}, I_L\$? I'm trying to get the most gain I can from the isolator without adding additional hardware, which means having a large value pull-up resistor.

simulate this circuit – Schematic created using CircuitLab

I have found for the PI it seems documentation is sparse...

If there is no documentation that anyone knows of, would the illustrated method below be considered reasonable for \$\pm\$5% measurements? I would take the measurement over a few temperature ranges (~0C, ~20C, ~40C).

simulate this circuit


texts: RF Splitter/Combiner with vectors in phase and antiphase - Where does the power go if they cancel?

texts:
Updated

I have a RF splitter/combiner. I am focusing on the black and red vectors. (Picture attached)

When the black vector of 0.25V and 0 phase enters the box, it will split. 1/sqrt(2)*0.25V  at 0 phase (half power split and no phase change) will go to port 1 and 1/sqrt(2)*0.25V  90 degree phase to port 2 (half power split and phase change)
When the red vector of 1/sqrt(2)*0.25V and 90 phase enters the box, it will split. 1/sqrt(2)*0.25V at 90 phase (half power split and no phase change) will go to port 2 and 1/sqrt(2)*0.25V with 180 phase at port 1 (half power split and phase change)

This means at port 1, we have perfect cancellation. A lot of the signal has gone. Also at port 2, we have perfect addition that leads to 0.35V. Lost 0.15V. In reality we get 0.5V output at port 2, what has gone on in this hybrid splitter/combiner that vector maths cannot show because half the signal is gone?

Please help


texts: Calculating battery percentage after voltage drops

texts:
I would like to display a battery percentage based on the remaining charge in the battery. I do not know if there is a better way of doing it other than measuring the voltage across the batteries.

How do i accommodate the sudden voltage drop of loads that are switched on. For example assuming a single lipo battery with a 100% at 4.2 volts and a 0% at 3.5volts. With the logic circuits total resistance, the voltage will drop a little bit by lets say 0.05 volts, which is then read i can display the battery is at 94%. seems straight forward. Now if we add lets say a high power motor and upon turning it on (lets ignore the voltage drop over time) the battery voltage will drop by lets say 0.25 volts(due to added resistance) which mean that my microcontroller will read 3.95 volts or 64% (assuming linear voltage curve which is NEVER the case in batteries). But if we turned the motor back to off the voltage drop of the battery will go back to only 0.05 so i have to display 94% again.

I do not like displaying battery percentage that is going up and down, it will lead to confusion. Also i know that proper battery indicators do not go up and down, so i can conclude that there is something they have done to accommodate switched loads.


texts: Dynamo phone charging leads to discharging

texts:
I am trying to make my bicycle dynamo charge my phone.

Currently, I've got dynamo (outputs 6V AC), connected to a rectifier, then capacitor (2200 microfarad), regulator (outputs 5V), capacitor (2200 microfarad), and usb extension cord to which I plug my phone.

simulate this circuit – Schematic created using CircuitLab

The diagram is wrong

Regulator:

On the output I get stable ~5.2 V

When I start pedalling, my phone begins to (agressively/quickly) discharge. Even with the turned off phone, ~5 min of pedalling discharges the phone by 30-35%.
Having said that, the charging icon is ON on the phone, so it detects the current

Phone model: LG Nexus 4

What may be the problem?

Tested on bunch of lamps. All work fine

P.S. my background is not in electrical engineering


texts: Question regarding dimension when creating an EAGLE Footprint

texts: Hi so i was trying to create a footprint based on this dimension. But i'm not quite sure what these two numbers mean exactly? Are they MAX/MIN? Which one should i use? Thank you!


texts: How to remove pin name from Eagle Device Page? [See Image]

texts: How to remove those pin name from Eagle Device Page?


texts: What is the difference between EMC testing (Electromagnetic compatibility) and EMI testing (Electromagnetic interference)


texts: I built a copper plate coil, 100 mm by 0.2 mm, 5 turns, 4 cm in diameter. How to determine its approximate inductance value based on its dimensions? Conductor cross-section is 20 mm square, it should be able to withstand a current of 100A (or more if it provides good cooling) without significant heating, even at high frequency. I'm going to use it to build an induction "furnace".


texts: Extremely Long Prototyping Board for LED Strip

texts: I'm interested in building very long led lighting strip. Does anyone know where to get a long, thin prototyping/matrix board(if they even exist)? I can't think of a good approach for mounting/soldering two dozen leds(each with its own resistor) in parallel, spaced 2" apart. Thanks!


texts: What is the use of zigzag pattern on PCB board

texts:
I found this on old CPU motherboard circuit and find its interesting.

What is the purpose of that pattern? is it only for aesthetic or is there something else? I only seen the same pattern on bluetooth module rf antenna.


texts: Switch quickly between sets of layers in eagle

texts:
Is there a way in eagle to quickly switch between sets of layers? e.g. all top layers, all bottom layers, both top and bottom.

Currently, when I want to see only the top layers, I have to click / unselect, Bottom, bPlace, bOrigins, bNames, bValues, bCream, bDocu.


texts: Voltage protection of PNP Open-Collector Pull-Down Resistor Circuit

texts:
Circuit
Consider the following U-Shaped Micro Photoelectric Sensor Panasonic PM-T54P with two PNP Open-Collector Transistor outputs:

I chose the supply voltage to be 12V DC. In the place of the two loads I want to place two voltage meters (to be more precise the NI 9401), which can endure a maximum voltage of 5V DC.
After some calculations, I came up with the following first schematic for Output 1 (the one for output 2 is identical, so I leave it out):

simulate this circuit – Schematic created using CircuitLab
Some explanations:

The connection to ground at the pull-down resistor R_GND is supposed to prevent a floating input into the NI 9401.
It should be possible to get a switch into the schematic between V_A and V_In, which physically opens or closes the connection, but I did not know how to do this.
The resistance R_NI is supposed to limit the current into the NI 9401 to less than 250uA in case the circuit is compromised and the resistors R_A and R_GND are bridged, so that R_NI alone has to deal with the full 12V of V_A.

Questions

Do I really need the connection to ground at R_GND? Can one tell from the internal circuit on the I/O circuit diagram if e.g. Output 1 will float or will have 0V if the transistor Tr1 is non-conducting?

Let's assume that V_A rises due to a control error of the user up to 30V, but I still want exactly my 12V at V_In.
Could I accomplish this task with a 12V Zener-Diode between V_A and V_In as shown in the circuit below?

Finally I want an additional protection for V_Out, which should be capped at exactly 4.7V independently of what happens before it.
Could I accomplish this task with a 4.7V Zener-Diode between R_NI and V_Out as shown in the circuit below?

This is my draft for both question 2 and 3:

simulate this circuit
And here is the result for a DC Sweep of V_In between V_In = 0V and V_In = 30V. It seems to be OK, right?

Update
Now it states here that the input impedance of the NI 9401 is 47kOhm, so I tried to create a new schematic accordingly, based on the remarks from Bruce Abbott and rioraxe. Would that be correct?

simulate this circuit
Here's the result: