texts:
I've made a circuit with 74HC109 JK flip flops. The purpose is to catch a pulse from two signals and for about 20 seconds keep the stored value (of which pulse came first). My problem is I need to reset the circuit, both at power up and later on. Unfortunately I don't know how to pull the /CLR lines without wrecking the /Q lines outputs. Grounding them when they are high, I suppose would cause the to draw a lot of current? Is it possible to solve by make a open collector coupling between the /Q and /CLR?

simulate this circuit – Schematic created using CircuitLab


texts: Is LM3914 protected from reverse voltage?

texts: I think I accidentally applied reverse voltage (+12V to pin 2) to LM3914 in simple 10LED circuit and now only LED1 lights up. Is my LM3914 burned?


texts:
I'm wanting to use one of the Arduino's PWM output to control a high-powered LED. I can't remember the exact specifications, but it was considerably more current than the ATMega328 can provide.

I realise that this would usually be achieved with the use of a transistor, and a resistor to current-control the LED. However, I'm not wanting the LED to become less bright as the battery voltage sags, and therefore I'm wanting to use a constant current source instead of the resistor.

My first thought was to use an LM317. What I'm wanting to know, though, is if it can respond at the 64KHz it would need to?

Alternatively, could I use a simple MOSFET to achieve the same thing cheaper and simpler? (Then I wouldn't need a transistor nor constant current source, as the MOSFET would do both of these)

Thanks,
Rob.


texts: How to wire a single input for two separate chargers e-bike

texts:
I'm currently designing my own e-moped for university (named ‘enduro 器’); I am currently going through the wiring and I am in need of some assistance.

(refer to the image above) I want to be able to switch between the two onboard chargers with a 3-way switch. One is 5A, the other, 10A. Could you please advise the best way to do this? Ideally, I would hop off my bike, flip the switch to whatever charger I want (faster or slower) and then plug it in via a single/shared plug into the wall.


texts: 24V H-Bridge DC motor, why voltage drop to 3v if motor connected

texts:
I want to drive a DC motor using an L298N H-Bridge Driver IC. I'm using the schematic from this website:

The motor is 24 V with about 7.5 ohm impedance (thus, it draws about 3.2 A). I'm using a 24V power supply, rated 10A max.

If the motor is not connected, the voltage (measured either at Vin or motor terminal) is 24V, but once the load (motor) is connected, the voltage drops to 3V.

I've tried the logic input when load is disconnected, they work well as expected (measured as 24V or -24V at motor terminals according to logic input being fed).

Can you enlighten me about what's happening with this circuit?

P.S.: I'm using 2N3906 2N3904 for transistors, 1N5822 for flyback diodes. From schematic above I've also added a 10uF / 25V decoupling capacitor between Vin and GND.


texts: Connecting LED to RO pin of RS485 Transceiver

texts: I am using this RS485 transceiver in a circuit of mine and I'd like to place a tiny 0805 LED in series with a 1k resistor coming off of the RO (receiving) pin.  I'm hoping this would result in flashing of the LED.  However, since I don't have a ton of experience with RS485 transceivers, I'm not sure this will work.  Will it cause any issues with communication?  Will it look right? Thanks.


texts:
Overview:
I am currently working on a project that requires a 24v alternator, which is powered by a mower engine.
This engine in particular runs around 3,000 RPM, and does not exceed 3,200 RPM (based on a few quick tests with a cheap tach).
The main reason for this question is that I am trying to understand the power output relationship between the alternator and engine.
Example:
I did a bit of research and see that alternators, which conform to ISO 8854, are rated as IL/IRA VTV. Where IL is the idle amperage output, IR is the rated amperage output, and VT is the test voltage.
However, when looking at alternators online, these metrics are often left out, which leads me to believe I may be incorrectly interpreting their meaning.
For example, and as reference to the questions below, take this Delco 10SI (1102916), which is rated for 40A @ 6,000 RPM.
Questions:
If you know the engine runs at 3,000 RPM, with a max of 3,200 RPM; Do you gear your alternator pulley in such a way that maps the running engine RPM (3,000) to the alternators rated RPM (6,000) to provide the 40A regularly? Or, will pushing 40A continuously burn the alternator out? In other words, if the measurements provided for the alternator are based on 6K RPM, is that peak (highest RPM the alternator should see)? or average (average running RPM)?
If it is peak RPM, can you just linearly extrapolate and say @ 3,000 RPM the alternator will provide half the current (20A)?
Background:
From an application standpoint, the 24v alternator will be used to charge 2 12v 55Ah (wired in series @ 24v). The expected engine run-time is around 1 hour. The goal being to charge the batteries, as the mower engine is running, for that hour duration.


texts: Type-III Compensator design for Half-Bridge DC-DC converter control

texts: Can anybody guide/share some technical documents which can help me to design type-III compensator for DC-DC Half-bridge?


texts: Synchronous vs Asynchronous Counters for Periodic Phenomena

texts:
Suppose that we have a synchronous 4bit counter A that counts from 0 to 9 synchronized with a clock signal CP. We put an AND gate such that the signal Y = Q3*Q0 is 1 when we count a decade. The signal Y is now driven to both another counter B that counts decades and the RESET pin of counter A.

My question is the following:

  Which option is better, namely a synchronous or an asynchronous
  counter, to use for counter B in order to count these periodic
  phenomena (a decade occurs always after 10 pulses)?


texts:
I want to calculate the amplification of the following amplifier.

I used the re model.

I do the calculation this way..

So, in my case:

So according to my calculation the amplification factor is 39.4.

Here's the problem.
When the input signal has amplitude of 0.01v, the output wave swings from 3.54v to 2.01v
Thus an amplification of (3.54 - 2.01)/0.01 = 153 (not even near what I have calculated.)

What am I doing wrong?

Ps:re value is multiplied by 2, because, I think with an Ie of only 0.48mA, the junction is in the knee region, where the resistance is more.


texts: I can't flash my new ATMega328p with PL2303 USB-TTL converter

texts:
I've soldered my ATMega328p-au to a SMD to DIP board, and I've connected pins like this:

USB | ATMega
RX ---> TX
TX ---> RX
5v ----> 5v
GND -> GND

and GND --> button --> RESET

My USB-TTL converter doesn't have a DTR pin. But, I tried programming my Arduino UNO with it. I hold RESET pin on my Arduino UNO, click upload and release the button. It works.

When I do the same with ATMega, avrdude / Arduino IDE gives me this output:

~$ sudo avrdude -c arduino -p atmega328p -P /dev/ttyUSB0 -U flash:w:blink.hex

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
...
avrdude: stk500_recv(): programmer is not
avrdude: stk500_getsync() attempt 10 of 10: not in sync: resp=0x00

avrdude done.  Thank you.

Same error with -c avrisp and on Arduino IDE.
1) Do I need something special for first time, like burning a bootloader? I read that I can flash it without burning bootloader, so I don't think that's the case.
2) Also I saw a lot of people using crystal and capacitor for flashing. Is it necessary? Because I don't have crystal.
3) If I can flash it without a bootloader and without a crystal, what am I doing wrong?

Thanks!

Edit:
It appears I needed a ISP programmer. Even though I tried it with ISP programmer it did not work. I connected a 16MHz crystal and I successfully programmed it!


texts: Why is negative voltage bias important for my photo diode?

texts:
I have (in the example circuit) a photo diode with the following data sheet: http://www.ibsg-st-petersburg.com/datasheet/PD/PD24-01-HS.pdf.

Now I was wondering (after there is no data about it in the data sheet): Why is it important how high the negative voltage bias is (except for determining the dark current)? Where does the negative voltage drop come from, and how do I calculate it?

In the circuit I have the resistor R1 with the resistance 1 kOhm, the diode D1 with a voltage drop of approximately 0.7 V, the diode D2 with resistance of approximately 70 kOhm (according to the data sheet) and R2 with "low resistance". Then I get a voltage drop of approximately 2.9 V over the diode. Is the calculation correct, or did I forget something?


texts: Automatic power off circuit for battery charger

texts:
I'd like to ask you a question about my circuit to automatically turn off battery charger. It works now fine except when voltage is close to the switch of treshold, coil of relay sounds noisy so I know that I need some histeresis but have now idea how to implement it there.

Thank you]1


texts:
OK this was one of my assignment question and i am baffled doing it. I am trying to get nodal voltage for this circuit since morning but its no help.

Please help me get nodal voltage for the following circuit where V1= 25 and V2= 7.


texts:
I am trying to connect an ESP8266 Wifi Module on a Pro Mini Atmega328 5V 16M
Full Specs Here - Specs

The Atmega328 pro mini outputs 5v on the vcc pin while the ESP8266 can handle max 3.3v.
How much resistance do i need to make the voltage drop so that i don't damage the module?

Tried Calculating with Ohms law R=V/I
R=5-3.3/250mA=6.8 ohm

When i use that resistor the voltage doesn't even come within the 3.3v spectrum
What am i doing wrong?


texts: How to test power output of an 8.5kW generator?

texts:
I found a very cheap 8.5 kW AC generator which works on gasoline. Produces 220 V, 380 V and 12 V as output. Some people online say is fake and it can't have 8.5 kW, that it actually has 2 kW and the label is wrong. The seller assures me that he run a 7 kW industrial welder with it and works fine. The seller is also incentivized to lie or exaggerate.

I plan to go and test this generator myself. Trouble is, it's unwieldy to carry all this loads with me required for reaching a 8.5 kW consumption or close to that. I have a 2.3 kW motor, the motor is heavy, requires me to cut something like a tree trunk to know for sure, I have a big room heater rated for 2 kW but i only have 1. So basically i need to take my 3 angle grinders, my motor, my room heater, and maybe 2 other hair driers, move them 200 km away, then put them under load, just to test this :)) Sounds like a big complicated mess. And if I go there and ask the seller to bring all this devices to generate so much load, that's something he might not be supper happy about. I would like this to depend on me.

Is there a better way to add a lot of load?

What is that simple test one can do with ease and find out how good is a random generator?

Then I've been thinking about electrolysis. I can simply drill 2 plates of steel 20 cm by 20 cm, put them in a plastic water container, and let electrolysis draw power while the generator runs. Then using a multi-meter I can check the amperage. The voltage meter already exists on the generator.

Is this something which is likely to work? How big the electrolysis plates need to be for this to draw 8.5 kW of power?
Is there some other easy way to do this?


texts: Circuit Diagram Conventions: wiring a MOSFET gate to "CE"?

texts:
As can be seen in the "Typical Application" circuit of the first page of this datasheet, the gate of an n-type MOSFET (named Q3) has been wired to "CE".

I cannot decide what this means as CE is not a net referred to elsewhere on the diagram. My first thought was "common emitter", but that terminology isn't applicable to MOSFETs, nor would I know what that would imply in this case. Is the diagram indicating the gate should be shorted with the source? Or is something else entirely?


texts: How to interface with LCD display - HYeLCD, HC20216NYU

texts:
I am trying to drive a small (20x2) LCD screen from a Parallax Propeller board/chip.  Can't find a decent manual anywhere.  This is the LCD:

http://www.jameco.com/1/1/24982-hc20216nyu-lyvo-20-2-black-yellow-parallel-lcd-display-green-backlight.html

On that page there is a PDF which gives the pinouts:

http://www.jameco.com/Jameco/Products/ProdDS/2155372.pdf

...which is better than nothing.

But I can't find anything about what kind of data I'm supposed to push over those data pins, frequency/timing, and some detail about what the other pins do.

I've googled quite a bit.

EDIT: After a bit more googling (with the proper wording - tks @Joe Hass), it seems like a lot of the same parts are used in these things (e.g. Samsung S6A0069), so I'm thinking one of this propeller object might work with it: http://obex.parallax.com/object/337


texts:
I am looking for photos of MCUs / Arduinos and the like which have been used in difficult/dirty/challenging environments but still work.

If anyone can point me towards any pics like this, I'd appreciate it.


texts: Possible to imitate a wolf's howling with a simple electronic circuit?

texts:
I would love to build a small circuit board that outputs something that sounds similar to a wolf howl to a small speaker. With "simple", I mean I would prefer if I could use simple components such as capacitors, resistors, coils and transistors etc rather than micro-controllers.

Is it possible to get close to a howling wolf without using a µC to playback a sample?


texts: I've got a 2N3904 hooked up to a pin on a NodeMCU Board (3.3V logic).  I am trying to short the button contacts on a fan remote to trigger the speed and such, however, when I pull the base high (3.3V) or low, nothing happens.  The only way I can get the remote to send a signal is if I "manually" short the collector and the emitter.  I have attached a schematic below for reference.  I'm thinking it's the incorrect resistor value....


texts: Spurious signals around LO feedthrough in HP 8591A spectrum analyzer?

texts:
I am troubleshooting my HP 8591A spectrum analyzer. It is fully functioning, except for these spurious signals around the 0 Hz feedthrough. This noise is only within 15 MHz of DC.

Where should I look for the possible fault? I have checked every single signal path, test point, and everything is within the specs specified in the service manual.


texts:
Given this integrator circuit:

And with Vin being a pulse wave which changes alternatively from 0V to 5V with a frequence of 100KHz, I need to find out the value of Vout after a large number of cycles.

I would like to get a hint on this problem, my intention is to calculate the Vout after each charge/discharge cycle using the formula V(t) = Vo*(1-e^(t/(R*C))) (charge) and V(t) = Vo*(e^(t/(R*C))) (discharge) for a large number of cycles using a computer program which does the calculations but I don't know how to take into account the remaining Voltage from the previous cycles in the charging formula.


texts: How do you pick component values for a debouncing filter?

texts:
I bought an incremental/quadrature rotary encoder for a project I'm working on.

The specs: https://www.bourns.com/docs/Product-Datasheets/PEC12R.pdf

They provide a diagram of a suggested filter circuit for debouncing the contacts on the encoder.

Here is the diagram from the PDF as an image:

I'm not an electrical engineer, but I get the basic idea of an RC based filter. The resistor values make sense: They pull the switch up to logic 1 value while limiting the current drawn from the 5V rail. How do you select a capacitor value for such a circuit? Do you measure the maximum rate-of-change for the square wave pulses you'd get from this switch, round up a little for safety, and then design a low pass filter that blocks signals at higher frequencies? Do you identify the frequency of the jitter and design a filter that filters that?

The project is built using an Arduino microcontroller and a digital input. I have written an interrupt service routine (ISR) that detects a falling edge on one of the inputs of the encoder, and then compares the value to the value of the other input to determine rotation direction.

I'm not sure how much hysteresis an Arduino digital input line has. The whole arrangement would probably work better with a Schmitt trigger in it, but I don't have a lot of room left on my project board for a DIP package, and don't have the skills for surface mount soldering.

(I'm beginning to think the digital input on the Arduino can't handle the slow-changing signals from the filtered output of the encoder and that I will need to add a Schmitt trigger.)


texts: Calculating voltage gain for AC analysis

texts:
Why do we connect load resistance to the output of re model while calculating voltage gain

This image shows calculation of voltage gain for common base configuration of NPN transistor


texts: Creating a SPDT 'transistor' solution for MIDI

texts:
In my previous question MIDI Both as Input or Output  the advice was to use a CD4053 to make a SPDT switch (multiples). However, I was thinking how it could be done with transistors. Not that I want to 'implement' this, but just out of curiosity if I understand the principle behind it.

I made a schema (sorry for my handwriting and no app used):

Actually only the upper part (above the orange/white line is of importance).

The idea is to have one single MIDI connector (pins 4 and 5 are used, 3 always to GND).

To select between MIDI In or Out:

Signal from Arduino for MIDI In (enabled, HIGH) or MIDI Out (Enabled, LOW)
When HIGH, the first and third resistor (from left to right) are getting voltage on their base, meaning a circuit is made from pin 4 and 5 from the MIDI connector, to the pin 4, MIDI In 'functionality' and pin 5, MIDI In 'functionality' (depicted as the round MIDI In circles)
Because of the inverter, the second and fourth (from left to right) the transistors will not have voltage on their base, so will not do anything.
When LOW, the first and third transistors will have no power on their base, while the second and third have.

Would this circuitry work? I know a CD4053 will be much easier, but it's just for trying in the future where I might need only one SPDT and a CD4053 is too much.


texts:
Can anyone tell me as to how I should write behavioral description for a latch in VHDL? Since it's level-sensitive, will the below line of code represent a latch?

if clk='1' then Q<=D;
end if;


texts: Can a 12V AGM battery be damaged by too light a load and relying exclusively on a 10.5V low voltage cutoff?

texts:
A problem I have with 12V power inverters is that they are set to give a warning beep and/or shutoff at about 10.5V (1.75V per AGM cell).  This is supposed to protect the battery from overdischarging, and thus help it to have a longer service life.  However, the effectiveness of this protection is load dependent.  For example, if I put a very heavy load on a 12V battery such that it would hit 10.5V under load very quickly, that battery would likely "spring back" quickly to 12.0V or even higher when the load is removed, thus the 10.5V low voltage cutoff is effective in that scenario.  However, imagine I put a very light load on a battery (such as a small parasitic load) and takes 100 or more hours to get the battery down to 10.5V.  Now we have a BIG problem!  The load is so light that once removed, the battery will NOT spring back to 12V or even any voltage close to that.  If we are lucky it will be maybe 11V with no load but that is way below 50% SoC!  That battery will be discharged WAY too much!  So it seems the 10.5V low voltage cutoff is assuming at least a moderate load such as enough to get the 12V battery down to 10.5V in perhaps 20 hours or less.

So to me it seems very dangerous to the battery's health if the load is very light and the entire setup is not monitored carefully.  For example, someone has a small 0.25A load in their car (that happens to have an AGM battery under the hood), and they don't drive that car for a week so the load has been draining for 168 hours so that would be about 42 Ah drained from the battery.

So am I correct in saying that small loads on a battery can be more detrimental to the battery's health than large loads for the reason I explained here?  If so, why do inverter manufacturers set the protection at 10.5V and not consider the load?  For a light load, it should be more like 11.5V for protection.  Is it too difficult and/or expensive to do a load dependent low voltage cutoff so they just "cut corners" and set it at 10.5V assuming a "reasonable" (20 hour max) load down to 10.5V?

I suppose "worst case" might be turning on an inverter with NO load on it (other than the inverter itself), and relying on the 10.5V (or something close to that) low voltage cutoff when using an AGM battery for example.


texts: Charging Li-Ion 4S with TP4056 (DC isolation)

texts:
I want to power a "suitcase boombox" amp using 4 Li-Ion 18650's. To charge these batteries I'm thinking TP4056, because they're small cheap and have nice charging features.

From what I have read so far that even at first glance having multiple TP4056's with their own DC-DC isolation seems weird, it's alledgedly not a bad way to mitigate some of the battery balancing downsides.

Two questions:

Are there any pitfalls of this approach? Apart from DC-DC isolation (see next question)?

As discussed on the internet and here on EE, to charge the batteries using multiple TP4056's, one needs isolation. Commonly mentioned is the isolated 0505S DC-DC converter. Big downside is that it's only rated for 1W. To get most out of the charging process you'd want more like 5W.

I'm not finding any cheap/small/simple DC-DC buck converters, but I do see some AC/DC 220VAC>5VDC converters that claim to have isolation, such as this one:
https://www.aliexpress.com/item/AC-DC-5V-700mA-3-5W-Power-Supply-Buck-Converter-Step-Down-Module-for-Arduino/32451069599.html (or will this burn down the house?)

Do these AC-DC converters provide the required isolation (or how to tell?)


texts: Capacitors in series for higher voltage applications

texts:
From the second circuit below, the red area is a startup network. The App Note states:

My question is, if I have three capacitors in series because my application reaches 1100V, then the bus voltage is divided by three. Now I don't have a middle point, but two middle points. Is it okay if I connect my startup transistor in the second point, like this?


texts: Output 48MHz system clock on a GPIO pin other than MCO pin on STM32F030

texts: I want to output the max 48MHz clock signal of STM32F030 to drive another subcircuit. The problem is the chip STM32F030F4P6 (TSSOP-20 package) I prefer to use a GPIO because the MCU doesn't have the MCO pin (PA8). Is there a way around?


texts:
I am new to electronics, so please bear with me. I have next task to do:

I have programmed Arudino Mega 2560 to provide some arbitrary digital signals on predefined pins. This is to provide some kind of simulation that will bring signals to ICP DAS device DIs, so that it can count them. This simulation works, pins do change their state from HIGH to LOW and vice versa. ICP DAS DIs require +10+VDC, and will draw no more than 20mA current.

Logically, I need some NO switch that will allow +12VDC to ICP DAS Input when Arduino output is HIGH. I have been advised to buy a logic-level MOSFTET. By looking at the examples on internet, P-channel MOSFET is always used to switch the positive DC terminal for load, and N-channel MOSFET is always used to switch the ground (0VDC) for load.

For this reason I have bought p-channel tsm3401cx> I connected Arduino output to pin 1, +12VDC to pin 2, and pin3 to my voltmeter. When I measure voltage from arduino, I can see that it periodically jumps to 5VDC, and returns to 0V. When I connect transistor, as soon as I bring signal to source, no matter if signal on gate is LOW or HIGH, switch closes immediately. I have come to understanding that this is because of the difference between in polarity between the gate and the source (Vgs), which is always larger than the gate threshold.

So, how can I achieve what I need (switch +12VDC by +5VDC signal)? What kind of transistor do I need?

Edit:

Transistor output should be connected to ICP DAS digital input:

Contact: Wet Contact
Sink/Source (NPN/PNP): Sink/Source
On Voltage Level+10 VDC ~ +50 VDC
Off Voltage Level+4 VDC
Max.Input Impedance10 kΩ


texts: What is the connector on lenovo ideapad miix board called?

texts:
The connector on board of keyboard of lenovo ideapad miix 300-10iby tablet.

Male part:

Female part:


texts:
Questions

What do the "revisions" mean in the processor documentation at the ARM Information Center?
Do they refer to silicon processor core design revisions, documentation revisions, or something else?
What do the r and p stand for?

Please include a citation(s) if you can.
Example
The Cortex-M3 documentation includes the following subsections:

Revision: r2p1
Revision: r2p0
Revision: r1p1


texts: LTspice: Is there any way to access .measure results from within a subcircuit?

texts:
I have a subcircuit in my LTspice schematic.  It appears as a schematic block.  Within the subcircuit's schematic there is a .MEASURE statement.  How can I view the results of this .MEASURE statement after running a simulation?

Normally, if I put a .MEASURE statement in my top level LTspice schematic I can view the results in the SPICE Error Log located under the view menu.

For example, if I put this on my schematic as a spice directive:

.MEASURE testvalue PARAM 7*7

The following line appears in the Error Log after running a simulation:

testvalue: 7*7=49

However, if that same .MEASURE statement is on a subcircuit's schematic, then it does not appear in the Error Log.  Does anyone know how to view this data?


texts:
There are 2 systems,A and B. Communication between them is via Uart.

As part of periodic health check for CAN Bus, its possible to do a loopback and check the status of the CAN transceiver and the bus(in addition to those taken care of the CAN spec itself like error counters).

Similarly, if my choice is UART for communication, is there any method i can ensure that the Tx and Rx lines are functioning properly without System A having to send a msg to System B and asking System B to retransmit back the same data received by it? I want to make the Health test by each system independent of the other.


texts:
I'm not into electronic so this is why I ask people who know.

I have an opportunity to buy a 5,000 mAh LiPo charger but I will use it to charge up to 14.8V 8,000 mAh batteries.

Will it charge the battery or should I buy a stronger charger?
Can it damage the battery?

The charger is a LiPo RC charger (ECO SIX) and the batteries are zippy 8000 mah 4 cells 14,8v thanks again

RM:mAh figures edited  - originally wrongly said 5 mAh ad 8 mAh


texts: What is the right order for 16bit data on 8bit 8080 data bus

texts:
I'm trying to create a program to drive a TFT LCD with an ILI9486 in 8bit but I don't know if I must send the configuration data and commands MSB or LSB first.

The color data for the pixels in 16bits mode seems to be MSB first.


texts: Calculate output voltage and current of a boost converter

texts:
If I have two AA rechargeable battery (1.2 V, 2000 mAh) connected in series, and I then connect it to a boost converter (DC to DC converter) so that the output voltage is 5V, what is the maximum current I can get? Can you please show how to calculate this?

Just to give you a bit more info, I have one of these so called "mobile boosters" which can charge your phone from 2 AA batteries. At the back, there is a small label saying that the maximum output is 5 V @ 500 mA . However when I plug it to my Blackberry, I turn on the engineering screen, I can see that the charging current is 1250 mA which is what I normally get when I use the wall charger. When I plug it to a computer, the charging current become 500 mA which makes sense as USB2 port can supply up to 500 mA. What I don't get is why does it say 1250 mA when the source can only supply 500 mA. So is the Blackberry gives out false information or the mobile booster actually deliver more than 500 mA?

Please try to keep the answer simple, don't get too technical, I'm not that great with physics :D


texts: Determine the Zero-State Response and Zero-Input Response

texts:
simulate this circuit – Schematic created using CircuitLab

For t > 0 I have determined the transfer function:

$$ \hat{H}(s)=\frac{\hat{Y}(s)}{\hat{F}(s)}= \frac{s}{s^{2}+s+1} $$

Now I need to find the zero-state response for t > 0 if: $$ f(t)=e^{3t} $$

And the zero-input response for t > 0 if: $$ y(0^{-})=1V \ , \ i(0^{-})=0 $$

Are the ZSR and ZIR related to h(t) or would it be i(t)? I know that for ZIR F(s)=0. But what piece of this problem is the response?


texts: How to estimate ripple current for PWM loads?

texts:
I'm buying some caps for a PCB which I'm designing, and I'm not quite sure how to estimate the ripple current they need to be.

This PCB is intended to switch about ~15A from 12V to 24V at ~100kHz.

The PSU for it is a switching aluminum box, usually rated at 30A. (The PSU already has some huge caps in it and even if I run the PCB without caps everything runs ok).

In all other instances of this design I've just put 2~8 220uF 35V caps in parallel at the board and never had any problems, I'd just like to have a second opinion.


texts:
What is the best way to provide rechargable power for an arduino based portable device? So far I've found the following options:

1: Use removable batteries and include an external charger with my device. Probably the cheapest option, but not very elegant and many users will probably find it annoying having to constantly take out the battiers to charge them.

2: Package this pack inside my device: https://www.sparkfun.com/products/11358 . Not exactly cheap, maybe too big for me, and it would look wierd with a USB cable going out of my device and then back in. Likewise the user would have to disconnect this USB cable and then insert an external USB cable for charging. Not pretty.

3: Use a LiPo battery and put this charger inside my device: https://www.sparkfun.com/products/10401 . However as I understand it this only charges LiPo batteries and can't be used to power an arduino. There is also this board https://www.sparkfun.com/products/10161 , but I'm not sure if I understand how to wire everything.

What I want is having my device function like a cellphone in terms of charging: it should run on an internal battery and for charging the user should simply have to connect a cable from a charger. My power needs aren't very high; just a small 3x3cm LCD, a bluetooth module, an arduino and some other minor stuff.

Is a "battery management IC" what I'm looking for? It is mentioned in this question: how to implement an integrated rechargable battery in my project? . What kind of wiring do I need to add this to my device?


texts: Is NRTL approval required for the sub components I purchase and assemble into a final product in order to sell the product in USA?

texts: I manufacture a lighting product made up of components I purchase and then assemble into a housing and heat sinks that my company manufactures. The components I assemble include an electrical driver/ transformer and high intensity LED chips. Must the components I purchase and use each be independently NRTL approved. Currently the driver/transformer is already UL approved but the high intensity LED chips have no stamping that indicates such although they are manufactured by Epistar a major Tiawanese producer of high intensity LEDs. Am I right to assume that I will have no requirement to have my LED chip supplier individually have NRTL approval. Will testing focus solely on my end product with no requirement of me to have my supplier get independent approval?


texts: What is this thermal adhesive? (heat transfer compound)

texts:
Well generally I I encounter this thermal adhesive. for example in inverter (brand: allen bradley). But it is different from I've seen before. It is very solid and generally using at very strange places, such as between 2 capacitors or at leads of a mosfet or top of capacitors block. Also it is very hard the repair a circuit, if that glue was used. Actually I cant find this stuff at store or web and I didnt understand why people use this?

this mine used. It is very liqued.


texts: Fritzing unrouted connections with Autoroute

texts:
Why does Fritzing's Autoroute leave unrouted connections?

Is there any way to tell it to route every connection?


texts:
I have a joystick that is connected to an arcade board. I would like to “listen” for movement on the joystick using a Raspberry Pi or similar. The joystick runs on 12V, and I would be using the Raspberry Pi’s 3.3v GPIO.

Would a relay in series with the joystick signal wire be appropriate for this? If so would a fly back diode be recommended too?
This is the relay board that I was looking at (12V):
https://s.click.aliexpress.com/e/j9MIN2Y

Are there any precautions that I should take to avoid adversely affecting the existing system?

Thanks!


texts:
This has been bothering me for while. I am sure there is an easy explanation behind this, but I need some insight. Current is flow of electrons, and electrons flow, when there is a potential difference.

So here I have my first question: If I connect a battery + to another battery -, why doesn't it discharge into itself, as I create a connection between high and low potential regions? I read that it is because there is no closed loop.

But then I have another question - when lightning strikes, where is the loop? It just discharges into another cloud! Also, when I walk on a carpet, get charges accumulated on my body, and then touch someone, there is a spark. Is there a loop, and if there is, where is it?

And one more: If I touch 220V line and put my foot on the ground, I die, but if there is a loop, it should have very high resistance, shouldn't it?


texts: Is it possible to use a potentiometer as a DP3T style control?

texts:
I'll try to be specific:

I have an audio application that has 3 inputs and 1 output.  The classic answer would be to use a DP3T to switch between the inputs.  However, I would like to have a continuously variable output, one that blends as you sweep a potentiometer.

Say for instance if the pot was fully clockwise it would give you the signal X, at the midway point, the signal Y, and counterclockwise the signal Z, but between noon and clockwise you would also get a blend of XY.  X and Z would never blend, just meet with Y towards the middle of the pot throw.  Is this something that can be done with one pot and VCAs, or a one pot mixer?  I'd like to stay away from multiple gang pots, unless that is the only answer because my application requires vertical PCB mount and conformity of potentiometers.

Thanks!


texts:
I'm designing a headphone amplifier, and I'd like it to be compatible with both 32 ohm and 600 ohm headphones. Therefore, I figured I could introduce a switch which allows the user to change the gain of the stage depending on the type of headphones they are. This would work by breaking or making a connection to a resistor in the feedback loop. In the image below, this switch would be between R6 and R8.

However, I'm not sure if this is overkill or if it could introduce any issues in sound quality/noise. Therefore, I considered just setting the amplifier to high gain and accepting that the volume control (implemented in the diagram as R7/R10) would not be able to travel the full distance for lower impedance headphones.

I wanted to get some feedback from someone more experienced than me - is this overkill? Am I worried about nothing? Is there a better way to implement this? Any feedback is appreciated!


texts: LED Sequence control using decoder/Simultaneous decoder channels

texts:
I'm working on a project that is used to monitor how many parts I have left in my cupboard of bits.

There are 5 separate parts whose level I want to monitor, each part will have 3 LEDs to display the stock level. I'm planning to use bi colour LEDs (L-59EGW-CA) in the following configuration:

I will be using 15 LEDs in total (3 per part x 5 parts). I'm planning to drive the circuit from an ATMEGA328P (Arduino UNO) and will have an Up/Down increment pushbutton for each part (5 up, 5 down in total)

I started to design a circuit for the system and came up with the following (Please bear in mind this is just a representation of the circuit, I'm aware there is not enough outputs etc.)

Datasheets:

ULN2803A
CD74HC4514

The ATMEGA328P goes through the decoder to the transistor array which switches the LED on. Now this would be good, if I only had 1 part. I've realised that because I have 5 parts I can't have multiple channels on the decoder on simultaneously. For example, in my diagram I want both the LEDs to be on, however they're for different parts so I can't just common the cathodes together.

After a long introduction here's my actual question:

1. Is it possible to have multiple outputs of the decoder on simultaneously?

I was thinking that if in the arduino code I kept switching between the decoder channels (and allowing for prop delay) then I could light the LEDs however they'd be dimmer due to a PWM type effect

2. After my input pushbuttons I have 10 digital pins left over for the 5 different parts. Is there another way to do the LED sequence using only 2 pins?

I've had a go using just 2 pins, I had to change to using a common cathode bi colour LED as opposed to a common anode and it uses 3 chips and a diode. It also means that I can only have 1 flashing red LED rather than 3.

Would this work, and is there a simpler way of doing this?

If you think I'm being a complete tool and that there's a better way then let me know

Sorry for the massive wall of text guys.

I am not using just 3 LEDs I've stated in the question that I'm using 15 and that the schematics are a representation as to not clog it all up


texts: How do I get a lower/higher voltage from a cuk converter?

texts:
By definition, "The Ćuk converter is a type of DC/DC converter that has an output voltage magnitude that is either greater than or less than the input voltage magnitude"

So I was wondering how I can get:
a) An output voltage lower than input voltage
b) An output voltage higher than input voltage

Also, for a Cuk converter, is it possible to easily switch between low and high output voltage configurations, without changing the entire circuit?


texts:
Ok, let's suppose we want to explain the resonant frequency of an LC circuit.
By kirchoff laws is not so difficult ending to the equation:

By using the Wolfram alpha engine I end up with the following solution:

( I used k = 1/LC ) so I guess the result is correct, a part for the constant part that I can't explain intuitively. I suppose there should be some explanation that drop one of the constant to 0, but I really can't figure it out why. So the question:
Is there a simple explanation on how to choose the correct constant values in the result?


texts: DC blocking capacitor in opamp feedback loop - does this count as the "signal path"?

texts:
I'm a bit new to electronics, so this may be a dumb question, though I hope not.

I'm working on a pre-amp circuit which can drive several TDA7492 boards from a single source (I've found they don't enjoy all being connected directly to some sources)

The preamp is a single supply design, with a gentle gain to boost the 1.25v line level from my Pi to "professional" +4dB level (These boards can take up to 3.6v peak-peak) to maximise the signal, followed by the amps themselves and a unity-gain stage to supply an isolated aux-out for my friend's poweramp.

It works nicely in PartSim, though I haven't decided exactly on some of the component values for the gain:
http://partsim.com/simulator/#38256

/Edit: Added a much simplified schematic:

The coupling caps will be polyester, and I've arranged so that I can use low values, which are within budget.  Higher value polys get expensive very quickly.  I've had all the expected issues with version 1.0 of the amp where I very mistakenly used Tantalums.  I understand now why these are very bad - inductance and ESR.

My problem is with C1 in the circuit.  What C1 does is block DC and thus sets the DC gain to unity, which keeps the DC offset at 1/2 supply whatever AC gain is applied.  Without this, the gain pushes the offset up and can clip the waveform.

I need the feedback resistance to be low overall, as I've read that this is good for low distortion - I assume the distortion would be due to thermal noise in the feedback circuit.  This means I need a high value cap here so that the filtering effect of R1+R2 & C1 doesn't lower the gain in the audio range.  The best I can achieve is the 220uF you see here which drops the output by 10% between 20 and 50Hz.  I can live with this.

But my problem is understanding whether C1 is in the signal path.  I can see arguments both ways - the signal doesn't really flow through it, so probably not.  But if I used an electrolytic here and it didn't pass the signal cleanly, would this in fact create distortion before the capacitor and pass the noise in to the inverting input, either affecting the gain or even amplifying the distortion?

If I can use an electrolytic, that's great.  If I can't, I've got a problem with a high enough value poly cap being extremely expensive (But perhaps I can compromise here - can anyone suggest a more appropriate, inexpensive capacitor type?)

Thanks very much in advance! :-)

-Oli


texts:
I would like to find transfer function between input signal \$U_1\$ and output signal \$U_2\$. So, I know how to find the transfer function of each op-amp, for example,

1 transfer function: $$\frac{v_o}{v_i} = -\frac{R_3}{R_1}\frac{1}{1+R_3C_3 s}$$
2 transfer function: $$\frac{v_o}{v_i} = -\frac{1}{C_4 s R_4}$$
3 transfer function: $$\frac{v_o}{v_i} = \frac{R_2}{2R}$$

Is that correct way to find $$G(s)=\frac{U_2}{U_1}$$? How can I do it?


texts: Impedance in a multi-frequency AC signal?

texts:
Consider a full-wave rectified voltage \$V=V|\sin(\omega t)|\$ being supplied to a capacitance \$C\$ and a load \$R\$ in parallel. The voltage across the capacitor is the voltage across the resistance. To find that voltage we need the current. To represent the supplied (rectified voltage) I used a Fourier series (only the real part represents the actual physical solution) and got an output which is a superposition of 3 different frequency AC (\$\omega=2,4,6\$) and a DC \$2/\pi\$. To solve for the current I need \$Z\$ so that \$I=V/Z\$. In normal cases, \$Z_c=\dfrac{1}{i\omega C}\$, but with multiple frequencies, I am unsure what to use?

How can I get a function for the variation of voltage across the
 capacitor?


texts: Energy Harvesting, Equivalent Capacitance of Battery Formula

texts:
So I was reading through TI's datasheet for their BQ25505 here, and came across the following:

  8.1.2 Storage Element Selection

  In order for the charge management circuitry to protect the storage element from over-charging or discharging,
  the storage element must be connected to VBAT pin and the system load tied to the VSTOR pin. Many types of
  elements can be used, such as capacitors, super capacitors or various battery chemistries. A storage element
  with 100uF equivalent capacitance is required to filter the pulse currents of the PFM switching charger. The
  equivalent capacitance of a battery can be computed as:

  $$C_{EQ} = \frac{2 \ \cdot \ mAHr_{BAT(CHRGD)} \ \cdot \ 3600s/Hr}{V _{BAT(CHRGD)}}$$

I was looking for a bit of enlightenment for this formula.

Assuming a few things, (according to a battery datasheet here) I should have

\$mAHr_{BAT(CHRGD)} = 2,000\$

and

\$V _{BAT(CHRGD)} = 4.2\$

First off, am I correct in assuming \$V_{BAT(CHRGD)}\$ is 4.2V and not the nominal 3.7V?

Secondly, what is this \$C_{EQ}\$ formula giving me back? Why is this \$C_{EQ}\$?

If I get 3,428,571 it doesn't mean anything to me, hence my questions.


texts:
I am using a TMP36 and an Arduino (like shown in the diagram below) to measure temperature.
The temperature sensor sensor is changing values abruptly.  It looks like there is an error.
Can you please tell me if this is normal or not?
For the information I soldered  additional wires to theTMP36 so that I can attach it somewhere next to a metal (but avoided short circuiting it.) I don't know if that changes anything in the reading.

The  code looks like this:
int sensorPin = 0;
void setup()
{
  Serial.begin(9600);
  }

void loop()

{
 int reading = analogRead(sensorPin);
 float voltage = reading * 5.0;
 float calculated = voltage /= 1024.0;
 float temperature = (voltage - 0.5) * 100 ;

 Serial.print("voltage is "); Serial.println(voltage);
 Serial.print("calculated is "); Serial.println(calculated);
 Serial.print("temperature is "); Serial.print(temperature) ;Serial.println(" degrees C");
 Serial.println("");

 delay(1000);
}

The result looks like this:


texts: Is "limitation on the peak sinusoidal input" Vsig max? and if it is, what difference does it being "max" make and how do I get it?


texts: MM5451 (LED Driver) basics - trouble lighting LEDs

texts:
I'm using an mbed micro controller to switch on all channels on the mm5451 LED driver. I have wired accordingly with 5v PSU, 1k resistor on pin 19 for brightness control (have varied this with no results), data/clock, LEDs with negative to the mm5451 (and positive to +5v inc resistors).

I've got a very basic loop that sends out a string of pulses (35 + start bit) which should switch on all channels, but I'm not getting any light.

#include "mbed.h"

DigitalOut dat(p22);
DigitalOut clk(p21);

int main() {
    while(1) {
        wait_ms(500);
        for(int i = 1;i < 37; i++){
            dat = 1;
            wait_us(20);
            clk = 1;
            wait_us(90);
            clk = 0;
            wait_us(20);
            dat = 0;
            wait_us(10);
        }
    }
}

Datasheets:

mm5451: DATASHEET mm5451

mbed: NXP LPC1768

Here's an image of the output pulses:

Hopefully the chip isn't broken and I'm just making a really stupid error.
Looking forward to the obvious answer!


texts: How to bond PCB and metal for high power RF boards

texts:
I want to bond a PCB (2 layer & 0.6mm thickness) to a metal (copper & 4mm thickness.) Could anyone help me with the process of bonding it? There is a power amplifier that has to be soldered with the metal and also to the PCB.
I found a few options, but still unaware of implementation part.
Like thermally & electrically conductive adhesive (TECA) like coolspan from Rogers.
Is there any other way to bond the metal and PCB?
Like soldering (sweat soldering/sandwich soldering?


texts: How to map a truth table to ternary logical functions?

texts:
Please be kind. I have a thorny and important question from a different field of engineering whose answer may be fairly well-known in electrical engineering. I asked a similar question on StackOverflow

Suppose I have a truth table of 5 inputs and 1 output. I used the Espresso algorithm (e.g., Logic Friday) to minimize the table and write some efficient VHDL. Everything works fine.

Instead of minimizing and mapping the truth-table to NAND gates, I would like to map to arbitrary ternary logical function. I'm not interested in multi-valued logic, but in logical functions that have 3 input variables. There are 256 of these functions, and 3-in NAND is just one of them. Not all of these 256 functions may be interesting: some reduce to their 2 input variable siblings.

Question: how can you map a truth-table (e.g., with 7 inputs) to any of these 3-in functions. A tool that does something similar would be great, but a method on how to simplify to arbitrary ternary functions would be best.

Background: modern CPUs can do arbitrary ternary logic operations on 512-bit registers (e.g., instruction vpternlog), but due to complexity, compilers leave it to the programmer, who is somewhat clueless on how to optimize this.


texts:
I need to implement a circuit to generate two short (2usec) pulses, one positive and other negative (+-16V and 4A) to SET/RESET a magnetic sensor, HMC1001. Here the design proposed on the datasheet:

First I made a simulation on www.circuitlab.com, here my schematic:

The output is not even near 16V and 4A... I don't have the expertise to evaluate what's wrong on this circuit. Any help will be welcome.


texts: Cicuit to keep power supplied (12V DC) for a few seconds after power is cut?

texts:
Ok I'm just starting to learn electronics and here is what I got.  I have a water pump that drains until water has lowered to a certain level (I don't want the pump running dry, the pump sits in the water).  I am using a relay and a float switch to shut the pump off when the water drains to a certain level.  The 110v AC pump is connected normally open (I believe) so the switch cuts the 12v DC coil power when level is reached, thereby cutting the pump.  The problem is that when the water reaches that level the float switch is rapidly moving open and closed during every ripple in the water, so the pump is constantly on, off, on, off for about a half hr to hr until it pumps enough water out with every tiny squirt of water during the short on phase until the ripples don't raise the switch high enough.

My solution was to put a 2000uF capacitor in parallel with the coil on the relay.  This keeps power applied for about a second after the switch is opened.  It seemed to be working at first, but eventually the float switch would get stuck closed, therefore the pump would stay on indefinitely.  Also, the switch stays stuck closed when I disconnect it from the circuit.  I verified this with a multimeter.  I could flick the switch with my finger and it would unstick.  I don't know exactly how the switch is made, possibly a reed switch cause the floater must have a magnet to work I guess.  The switch is supposed to handle up to 100V so I am assuming its a current problem maybe?

Max Switch Voltage : 100V DC;Max Switch Current : 0.5A;Max Breakdown Voltage : 220V DC;Max Carry Current : 1.0A

Here are my questions:

1) Why is the switch getting stuck closed? Do I need to use a resistor or something?

2) What am I doing wrong or could do better?  Is there a better solution?

Here is the float switch I am using
http://www.amazon.com/gp/product/B005NFWWLW/ref=oh_details_o05_s00_i00?ie=UTF8&psc=1


texts: Average current from a 4V lead acid battery

texts:
I am using three 4V rechargeable lead acid batteries in series as a power source for an embedded system. The logic system taps out 8V which is fed into an LM7805 and the 12V is used as input to an L293D for powering 2 geared DC motors. However, the system resets intermittently. The batteries used are these :

The system draws out around 30ma without the motors running. With the motors on, the current tops out at 150ma(no load on the motors). Can the batteries provide this amount of current continuously? Am I overstressing them?


texts: What kind of filter/filters are being used in this feedback loop?

texts:
simulate this circuit – Schematic created using CircuitLab

I am having trouble understanding the feedback loop for this gain stage for a guitar distortion pedal. I am completely new to electronics. I tried looking for similar looking RC filter topology and have found none. I though at first that it might be a twin t notch filter, but it isn't that one.

Based on what I have read, \$C_4\$ is used for power supply decoupling. What would be the correct formula for its frequency cutoff?

$$
{1\over 2\pi R_6C_4}
$$

or

$$
{1\over 2\pi R_{ps}C_4}; R_{ps} = (R_3+R_4+R_6)
$$

What is the function of \$C_2\$? How do I simplify the feedback loop resistance only, without the filter for the power supply decoupling? Sorry if I am doing it all wrong. Any pointers would be greatly appreciated. Thank you.


texts: Is there such a different phase control relay?

texts:
PROBLEM

The standard phase control relay is output from any phase. However, there will be no output when that phase is gone.

PROPOSAL

When any phase is gone, the switch of the phase distribution circuit will connect the other phase to the output. The following picture is intended to give an idea.

Is there such a sold phase control relay? Or do I design it myself? Thank you.


texts: BLDC/BLAC controller motor voltage reverse protection

texts:
I am currently designing a BLDC controller and keep running into a power safety issue:
I have added a smart diode reverse protection controller to my design with its transistor between the fuse and the bulk capacitance (4 x 220uF elcap bank).
This was done to protect all downstream components (and the polarized capacitors especially) from reverse polarity events.
Now obviously this poses a big problem during regenerative braking since the IC (LM5050) interrupts the supply line and makes the micro think an undervoltage event occured (which it momentarily did, since the power to the motor was cut).

What is a good way to mitigate/solve this issue and how does this get solved by real electronics designers?
Thanks!

simulate this circuit – Schematic created using CircuitLab


texts:
As we all know, the cross technology interference is a critical problem. CTI means that different communication technologies operate on the same spectrum (e.g., 2.4GHz), and this would lead to the critical interference problem. There are lots of works study the interference on ZigBee[1].

Now, I have the question that
"What is the type of the wifi interference to ZigBee? Multiplicative or additive?".

Because of the different interfering type, the different filtering methods would be utilized. [2]

[1]Understanding the Impact of Cross Technology Interference on IEEE 802.15.4
[2]https://www.quora.com/What-is-the-difference-between-additive-and-multiplicative-noise


texts: How many bits are addressed through one CAS command in DRAM?

texts: From what I understand one column and row pairing corresponds to 64 bits from the DRAM chip, but this makes me think that one would then incur the CAS Latency (~18 clock cycles in DDR4) for EVERY transfer. I feel like this is obviously not the case or else DRAM would be severely limited by the CAS delay and not the available bandwidth. Thanks for the help!


texts: My servo wont turn when accepting commands from an arduino

texts:
I'm trying to turn a servo with my arduino when it receives commands from a serial input, in this case my keyboard. I have already done this with motors and it works fine but when I try with my servo it doesn't move at all. So far I have this written

#include <SoftwareServo.h>

SoftwareServo myservo;
int movemotor;

void setup() {
  Serial.begin(9600);
  myservo.attach (10);
  myservo.write(90);
}

void loop() {
  movemotor = Serial.read();

  if (movemotor = 111) {
     for (int pos = 90; pos >=0; pos--) {
       myservo.write(pos);
       delay(15);
    }
  }

  else if (movemotor = 99) {
     for (int pos = 90; pos <= 180; pos++) {
       myservo.write(pos);
       delay(15);
    }
  }
}

I'm powering the servo externally with a 9 volt battery and have made sure to connect its ground to that of the arduino but can't see anything else I did wrong. Any help would be greatly appreciated.


texts: Can't Search for specific value at RAM - verilog

texts:
My module has search for specific value at RAM and then return its location address.
when I wrote a test bench, I see that the module didn't work correctly! always the output value is "don't care". Although I have initialized the memory.

Search module>>>

module Search (
    clk,
    rst,
    SearchData,
    FindAddress,
         StopSearch
);
input           clk;
input           rst;
input[7:0]      SearchData;
output reg [1:0]   FindAddress;
output reg StopSearch;
integer i,x;

wire read_rq;
reg [1:0] nxt_address;
reg [2:0] ii;
initial
begin nxt_address=0;i=0; ii=0; end

wire[7:0] read_data_inx;

D0_RAM1 D0(
    .clk(clk),
    .rst(rst),
    .read_rq(read_rq),
    .write_rq(0),
    .rw_address(nxt_address),
    .write_data(0),
    .read_data(read_data_inx)
);
always @(posedge clk )
begin
        for ( x =0 ;x <4;x=x+1) begin
                if (read_data_inx == SearchData)  begin //master i has priority
                        FindAddress <= nxt_address;
                        StopSearch <=1;
      end

                nxt_address <= nxt_address+1;
        end

end

the RAM module:

module D0_RAM1(
    clk,
    rst,
    read_rq,
    write_rq,
    rw_address,
    write_data,
    read_data
);
input           clk;
input           rst;
input           read_rq;
input           write_rq;
input[1:0]      rw_address; //2 bit
input[7:0]      write_data;
output[7:0]     read_data;

reg[7:0]     read_data;
reg[3:0] count_;
integer out, i;

// Declare memory 2^2 x8 bits
// 2^2 = 4
reg [7:0] memory_ram_d [3:0];
reg [7:0] memory_ram_q [3:0];
initial
begin
count_=0;
        for (i=0;i<4; i=i+1) begin
        memory_ram_q[i] <= i;
                  memory_ram_d[i] <=i;
                  count_=count_+1;
                  end
end

---> Any ideas?

Thanks.


texts:
I currently have a project that has integrated sensors to monitor human health and related biomarkers, my domain is human-performance so giving athletes the tools to get better at their respective game.
I have recently begun trying to gather information regarding bioimpedance in order to implement this in my embedded project. For a prototype I am using the STM32 series ( blue pill chip ) to package a sensorframe of values ( o2, pulse, gyro & acc data, temperature ) now I really want to add bioimpedance to this device - heres what I think I know so far anyways

We need to emit an electric current over a multi-channel ( I want to calculate bone density, muscle mass, fat mass)

We need an emitter and a receiver

there needs to be two connected components by a wire that connect the two devices that complete the circuit

My questions are this, what frequency do I need to use to calculate my targets?


texts: Purpose for Shunt Resistor on Opto Isolator Input?

texts:
I was looking at a BeagleBone Black Cape and became curious on an input circuit to the BeagleBone GPIO (used for a NPN proximity sensor).  Upon further reverse designing, I notice a // 220Ω shunt resistor (R1) with the LED.  I have a basic understanding on diodes/LEDs (current limiting series Rs for LEDs) but I cannot understand the purpose for R1. So I cal'd the currents thru R1, R2 and the LED but after looking at the datasheet (PS2802) at the "forward current vs. forward voltage I am not sure if my cal'd currents are correct.

In short, the series current limiting R2 (1.2kΩ) I understand it's main purpose and how to calculate it's value but the shunt R1 (220Ω) purpose is confusing me.

My original question was just going to ask.  What is the purpose for R1?

But now, my secondary question is (in general).  Are my current values correct?

I hope I can become enlightened;-)

simulate this circuit – Schematic created using CircuitLab


texts: GSM Module + RS485 transceiver possible?

texts: I was wondering if someone could confirm if it is feasible to interface a GSM module for example SIM900, SIM900, Quectel's M95 or Neoway's N10 , maybe if we use the RS232 interface with HW the flow control pins RTS/DTR to the MAX485 or equivalent to talk to a master RS485 node ? or do i need to use a microcontroller to handle that job ?


texts:
I'm starting a new project in my Electrical Engineering degree at my university and I need help.

Overall, my project is about a mini robot that collects data and sends it (via wireless communication) to the main control unit from a distance of about 100 meters.

It's main specification demands are: small, lightweight, use an STM32 microcontroller for the mini robot and it is preferred that the data that is sent from the mini robot to the main control unit will be secure as possible.

Here is where I need help. I have 2 options for the wireless communication: Bluetooth and RF.

I know that RF has a larger distance communication capabilities, but I'm afraid that the RF module weight will be heavier than the Bluetooth module.

My questions are:

What are the main differences between RF communication and Bluetooth communication (weight, dimensions, power demands, communication distance, data transfer speed and secure data transfer)?
What communication method do you recommend me to use (with respect to my project demands)? RF or Bluetooth?

Thank you for your help.


texts: How to estimate the power consumption of a motor when running at low load

texts:
I am trying to calculate the electrical power cost-saving of reducing the amount of time a machine runs idle (when the motor is running unloaded).

From the meter data, the amps when idling is about 20% of full-load amps.

So, the real power consumption (for 3-phase motor) is given by:

power_consumption = voltage*fla*0.01*full_load_amps*np.sqrt(3)*power_factor

(where fla = 20)

But I also know the PF will be very low (24% we think) so does this mean that the power consumption is also not that high and therefore there is very little saving?

Intuitively I suspect not, since motor efficiency will be very low power will be being lost somewhere, maybe in the distribution system.

How do I estimate the actual power cost (at the utility meter) of this idling machine?


texts:
I recently got a Technics turntable and the belt that came with it is super crappy and makes the platter hickup when it passes by the seam on the belt.  This is not audible, but it got me thinking about ways that I could control the speed of the platter.

Since it is a technics table it has a little strobe and markings to looks at which are awesome, but "totally the 70s".  Along with replacing the belt I started thinking about adding some 21st century technology to my turntable.

Adding an Arduino equipped with a light sensor and a speed controller.
New brushless motor
New belt :)

My goal would be to use the light sensor with the markings that the strobe method currently utilizes to give the Arduino a reading of the speed.  With that information I would apply a PID algorithm to control the motor that is spinning the platter.

My question is: would this work?  And please tell my why this would be a bad idea if not.


texts: Measuring a negative input on unipolar supply ADC

texts:
Electrocardiograms ("EKG") measure the PQRST waves in a heart beat. In the sequence, Q and S are negative.

Given that, could anyone please explain how differential signals can be fed to an ADC which is connected to unipolar supply (say 3.3 V with respect to ground)?

How can the negative part of the input signal be detected even if the device is referenced to ground?


texts: How to properly discharge a high voltage capacitor?

texts:
I have recently blown a capacitor on my home made emp. I have got the perfect replacement which is an electrolytic capacitor, 330v, 140 micro farads.

I have charged it but I want to learn how to safely discharge a high voltage capacitor.

I was going to short the capacitor but my friend said that high voltage capacitors can blow when you short them.

I don't have any resistors that I can discharge with.

Any ideas? Or can you short the capacitor without it blowing?


texts:
In low voltage applications, it is assumed that both voltage & current carries information instead of energy.

So how is it possible to transform the information carried in the form of Voltage to Current without altering it and vice versa?

I’ve heard there are are many voltage to current & current to voltage converters. My question is that Aren’t current & voltage relative to each other, with voltage comes current & in current we can have voltage? Both exist at the same time & without one another is impossible.

if so then what do you mean by Voltage to current & current to voltage conversion?
How is it possible to transform them from one form to another?

for eg: If one of the terminal of 1k resistor is connected to 5V source & another to Input pin of any IC let’s say then:

What is the Voltage & current at the input pin of that IC?


texts: Use a PWM or other controller for 24V/500W application

texts:
I've been gaining understanding about using PWM for a motor speed controller. I'm developing a project (go kart) that uses a 24V DC starter motor and I want to build a motor speed controller that is somewhat rudimentary/simple.

Is it possible to utilize Arduino technology or some kind of PWM connected to a relay that switches the power supply on and off to the motor at the cycle speed that will act as a 'throttle'?

Or, is there a rudimentary means of controlling the motor speed in 4 or 5 stages (less elegant but equally as effective...)?

Any links to other resources or advice is greatly appreciated.


texts: using RC delay to trigger output enable pin of tri-state gate

texts:
The attached image is a circuit using a rc-delayed (reset) signal to control a tristate gate (U855C).
After MPU_RESET is asserted, C852 starts charging. Gate U855D is always enabled. When the capacitor is chaged to roughly above 70% of Gate's VCC (1.8V), Gate D ouputs high and Gate C is disabled.
My question is, could I just connect RC to Gate C's OE_N pin directly, bypassing Gate D?
Theorectically, Gate C should be disabled when voltage at OE_N pin (pin 10) reaches about 30% of VCC (0.54V for 1.8V VCC), I can just tune the RC value to have a larger time constant.
Is there any pitfall to do this? The purpose is to save a gate for other usage.


texts: Is an unlocked PLL an open-loop clock? And is a locked PLL a closed-loop clock?

texts:
What is the difference between an open-loop clock and a closed-loop clock?

Is a PLL with an oscillator lock a closed loop clock? Is a PLL without an oscillator lock an open-loop clock?


texts: Where can I find PCB templates for add on boards

texts:
I want to design some add on boards that will use Mikroe Click Board (TM), Pmod interface and Arduino Interface. The work shall be done in Altium Designer.
Do there exist any PCB templates that I can use as starting point with the connector and silk screen already in place?


texts: Counter glitching? Instability? Can't get a trigger lock on the scope, what might that be?

texts:
I have a 4 MHz clock and 4 x 74LS161 4-bit counters hooked up to get a 16 bit counter. It's all done how I have done it many times, synchronous with clock going into all the counters and RCO of previous stage hooked to ENT of the next.

It's not the first time I'm using the '161 counter. But maybe the first time I'm using it in 16 bit configuration. What's happening is at the higher stages, e.g., chip 3 bit 2 (of 0 to 3), i.e., bit 10, the output starts to wiggle horizontally on the analog scope and I can't get a stable triggering.

This happens not if I just have the counter count with outputs without load, but it happens when I connect the output to the 74LS652 bus transceiver / registers. This is the same setup that I ran successfully with 74HC393 and 74HC4040, and the transceiver output enable on the input side is disabled fixed so I know I don't get output contention here.
I am also pretty sure my power is plenty of 5V and clean. It's breadboard, but I am fairly neat working with breadboard and I have had very good results with my setup. Only now that I moved to the 74LS161 counter (which I actually knew better than the 4040) suddenly I get this wiggle problem. And it's not in the fast lower stages, it is in the higher stages, bit 10 to 15 getting worse as we go up.
What could cause this and how can I debug this (with only an analog scope, no digital waveform capture device.)


texts: Gas engine on a robot: Is is possible? Is it a good idea?

texts:
For a college project, a group of us are trying to design a remote controlled snowblower. We want to go with a battery and a gas engine basically like a car. Our logic for this was batteries wouldn't last long enough without being too large/heavy/costly and an electric cord would probably get tangled and cut and might not be long enough.

We have some MechEs working on the mechanics of the thing but us EEs got stuck with the drivetrain and control side.

I've worked with robotics before (FIRST FRC in highschool and other college stuff) but I've never touched a gas engine of any sort. I'm having a little trouble with finding information on this topic and I expect its because I'm just not searching for the right things.

I'm wondering if anyone here has worked on systems like this in the past and can offer advice on where to start, any important things to consider or just general comments on the project.

Thank you!


texts: Am I having an impedance issue in a cable between two devices? And if so, How can I resolve the issue?

texts:
I have two devices, device 1 and Device 2. The devices are approximately 60 feet apart connected to each other through a long cable. They communicate with each other at 2400bps synchronous serial using the single clock source. Device A needs a clock for input and output clocking.  The current design has an "In Cable" loopback of the clock as shown below to provide both needed clocks.

Sometimes it was noticed that Data In of device A would not receive data.  When this situation occurred, device 1 could check the incoming RX clock (Which should be at 2400bps) and it would be at a value that was not 2400bps.  It would usually be a multiple or more of the original 2400bps clock.  Values such as 4800, 7200 and other values have been seen at Device 1.  Th obvious reason that data was was not coming into device 1 is that the clock was invalid for the Data (which was clocked at 2400bps).

If I try to put an O-Scope up to the clock signal into deice 1 to see what it looks like, it immediately clears up and is seen as 2400bps.

We have 20+ data paths with this configuration.  Some work and some do not.  Swapping cables may make bad paths work, or might make them not work.  Using cables known to work between two different device might cause the path not to work. All cables are professionally made and I do not think it is a cable issue.  It is unpredictable what device/cable set will work or not.

I am not an EE but have been researching this issue and I think there could be some impedance issue at device 2. The clock signal could be reflected back and forth between device 1 and 2, ultimately the RX clock IN on Device A giving improper clock signaling, and thus no Data in at Device 1.

I have read that some resistor or capacitor added in the path can cut back this issue, but I am not an EE so I am not sure if a) this is an impedance issue and b)where would I put a circuit to fix it. Someone has mentioned an inline 22.5ohm resistor to start.  Someone else has mentioned anything <100ohms.  At this point, I can not tell you the output impedance of device A. it is an old component and is currently undocumented.


texts: Why does the voltage value on the RESET pin of my microprocessor not go high?

texts:
I am facing an issue that I do not understand.
I am using a STM32F030K6T6 microcontroller with a capacitor X7R 0603 100nF 10% 50V connected to the ground, whose the value corresponds to the preconization specified in the datasheet as follows:

Most of the time, I do not have any problem. But on really few boards, the microprocessor stays blocked in reset mode because the voltage of the NRESET pin which stays quite low, around 470mV. There is nothing more connected on NRSET signal: only the microprocessor, the SWD connector (without any plugged-connector) and the capacitor.
Do you have any explanation? Could it be because of ESD? A broken capacitor series ? (I have measured its resistance with the ohmmeter to check if there is a short circuit, but it's greater than 1Meg Ohm) Or an issue of capacitor charge/discharge?


texts:
I have experience with selecting low end PICs, but haven't had to select a controller for DSP before. Initially I thought about the dsPIC line, but the only reason for this because I am comfortable with the microchip line.

So, what options do I have to select from? How can I decide what is best for me? Are there in general differences between lines? Example, the MSP430 line is good for very low power, are there any similar type of things for the DSP lines?

For my specific project I am going to have 3 sets of SPI from ADCs that are 24bit at about 400KHz, but I am find with broad description on how to find the proper platform.


texts:
I have never designed a laser device, but I have tried to read extensively on them.  I'm aware of the different classes of lasers, and the dangers associated with them.  For instance, I know about the requirement for an interlock that shuts down the emitter whenever the case is opened.  I know class 2 lasers must be visible so that they instigate the "blink reflex".  I know the diodes need a lot of protection, from overvoltage, overcurrent, ESD, and so forth.  They need regulated current and closed-loop feedback to maintain constant optical power.

My questions are:

1) Is it really as simple as grabbing a laser drive chip and a three-terminal diode from digikey and hooking them up according to the datasheet?  Should the laser drive chip be able to handle all protection mechanisms necessary, or is there typically another device that's needed to handle some other form of protection?

2) Is there a central regulatory body that does any testing to determine what class of laser you have, and whether your product follows all the necessary regulations?

3) Are there any known issues using lasers with 1mm core plastic optical fiber?  I know that POF has very different transmission windows vs. glass fiber, and I know that one of these optimal windows is 650nm.  Would the beam stay narrow inside the fiber, or would it begin to disperse?  Would it still be coherent and collimated after going through, say, 15 meters of POF?

For additional application information, know that I don't actually need coherent or collimated light (in terms of safety it's probably better if it wasn't coherent or collimated).  Rather, what I need is a very powerful bulk light source (1 mW or better).  The light source must be able to turn on and off, but it doesn't need to be modulated and the source itself will not encode any information.  Thus, if there is perhaps some other device that can provide 1 mW into POF I will be very willing to investigate it, but at this point I am investigating the laser approach, because it seems like most LEDs aren't even capable of 500 uW.


texts:
What are some reasonably reliable ways of detecting that a water pump (electrical motor based) is "dry running", i.e. no water is passing through the pump either because there is no water available at the inlet, or due to "air-block" ?

I'd prefer mechanisms that are least intrusive, i.e. ideally - do not require re-plumbing. However, if all practical mechanisms involves some plumbing work, then it might as well.

An indication regarding possible cost of sensors, installation skill required, would be very useful.


texts: Design own Buck-Boost converter - Some questions

texts:
For a project of mine I would like to design my own buck-boost converter because the fixed solutions are more expensive and a bit to big for my preferences.
Vin is 12VDC - 24VDC regulated to 12VDC with ~8A max. If I take the designs from TI or RS it doesnt seem that complicated. Only a big inductance, some FETS and some capacitors.
Now what I am curious about is:
Does it need a heatsink ? If I look at predesigned once they always have big heatsinks.
If I dont want to use SMD but through hole, what kind of capacitors do I need to use ? The Datasheet or design guidelines say ceramic but in the predesigned I see electrolytic capacitors ?


texts: Can't find definitions of model irfs4010

texts:
I'm trying to run on the LTSpice the circuit below. It's the circuit of a Boost-Converter.
When I try to run, LTSpice shows the message "M1: Can't find definition of model irfs4010".
Sorry if i'm not being clear in the ask, I have no experience and I can't give more details, however if anyone can help me, i'll be grateful.


texts:
Imagine a pulse train around 80Hz. Using two DAQ at the same time I sample this pulse with 5000Hz and 10000Hz. I get slightly different pulse widths in each case. I use an algorithm which detects rising edges and find each pulse widths.

Do you think sampling freq. have effect on detecting pulse widths in this case?


texts: Arduino analogread: neighbor pin noise on ADC even with big delay

texts:
I'm reading two analog input values (light sensors, with pull-down resistors) on an Arduino MEGA 2560.

One pin is supposed to report the value of 0, while another pin is supposed to report a value of ~800. I know this for sure, because if my sketch reads ONLY 1 of these pins, that's the results I get.

If I try to read both values in a loop, then the first pin seems to be influenced by the second pin in it's reading, and is higher than 0. I know it's good practice to either call the analogRead() command twice or to put a tiny delay between switching analog-input-pin-reads to give the ADC a chance to stabilize. But, even if I call analogRead() twice AND give it a delay-value of 1 sec (!!) the first pin still gives me higher reading than it should.

  loop only reading pin 1:
  pin 1 = 0

  loop reading pin 1+2, no delay between calls:
  pin 1 = 20, pin 2 = ~800

  loop reading pin 1+2, calling analogRead twice:
  pin 1 = 6, pin 2 = ~800

  loop reading pin 1+2, with delay(1000):
  pin 1 = 6, pin 2 = ~800

Trying to understand what's going on ...

Here's the simplest code to test this

int sensor[2];

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

void loop() {
  for (int i = 0; i < 2; i++) {
    analogRead(i); // read pin twice and ignore first result
    sensor[i] = analogRead(i);
    delay(1000);  // give long delay to let ADC stabilize
  }

  Serial.println(sensor[0]);
  Serial.println(sensor[1]);
}

Here's a simplified schematic showing how 1 sensor (TEMT6000 photo transistor) is connected to the analog pin. It has a pull-down resistor to avoid random floating values in case no sensor is connected. The pull-down resistor is so high (220K) to allow for low-light readings. Sensor cables run in parallel with cables feeding an LED. I've included it, just in case. But, note, in all tests listed above, the LED was not turned on.

Now multiply that setup by 8. As I have 8 sensor units connected to 8 analog pins.


texts: STM32F103 ARM - Modifying Clock At Runtime - FLASH Latency

texts:
I am having b it of confusion regarding changing the clock tree of an STM32F103 Cortex M3 at runtime and I am hoping someone can help me with it.

I am using a development board which has a 8Mhz HSE on board. As per the defaylt configuration of STM SPL stm32f10x_system.c file, PLL (derived from HSE) is selected as the SYSCLK source on boot.

I would like to use PLL as the source (derived from HSI). From what I have understood, the main steps are

Enable HSI. Wait for it to be ready
Set HSI as SYSCLK source. Set HCLK, PCLK1 & PCLK2 accordingly
Disable PLL. Change it's source to HSI and set multiplier
Enable PLL. Wait for PLL to be ready
Set PLL as SYSCLK source. set HCLK, PCLK1 & PCLK2 accordingly

As per above I wrote my routine called when main() starts

//TURN ON HSI AND SET IT AS SYSCLK SRC
RCC_HSICmd(ENABLE);
while(RCC_GetFlagStatus(RCC_FLAG_HSIRDY) == RESET){};

//SET HSI AS SYSCLK SRC. CONFIGURE HCLK, PCLK1 & PCLK2
RCC_SYSCLKConfig(RCC_SYSCLKSource_HSI);
RCC_HCLKConfig(RCC_SYSCLK_Div1);
RCC_PCLK1Config(RCC_HCLK_Div1);
RCC_PCLK2Config(RCC_HCLK_Div1);

//DISABLE PLL
RCC_PLLCmd(DISABLE);

//CHANGE PLL SRC AND MULTIPLIER
RCC_PLLConfig(RCC_PLLSource_HSI_Div2, RCC_PLLMul_16);

//ENABLE PLL
//WAIT FOR IT TO BE READY
//SET SYSCLK SRC AS PLLCLK
RCC_PLLCmd(ENABLE);
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET){};
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

//SET HCLK = SYSCLK = 64MHZ
RCC_HCLKConfig(RCC_SYSCLK_Div1);

//SET PCLK2 = HCLK = 64MHZ
RCC_PCLK2Config(RCC_HCLK_Div1);

//SET PCLK1 = HCLK/2 = 32MHZ
RCC_PCLK1Config(RCC_HCLK_Div2);

This works just fine. Then I realized that I would need to change the FLASH latency as well as per my clock

So I did this

//SETUP THE SYSTEM CLOCK AS BELOW
//CLOCK SRC = 8MHZ HSI + PLL
//SYSCLK = 64MHZ
//HCLK = SYSCLK = 64MHZ
//PCLK2 = HCLK = 64MHZ
//PCLK1 = HCLK = 32MHZ

//TURN ON HSI AND SET IT AS SYSCLK SRC
RCC_HSICmd(ENABLE);
while(RCC_GetFlagStatus(RCC_FLAG_HSIRDY) == RESET){};

//SET HSI AS SYSCLK SRC. CONFIGURE HCLK, PCLK1 & PCLK2
RCC_SYSCLKConfig(RCC_SYSCLKSource_HSI);
RCC_HCLKConfig(RCC_SYSCLK_Div1);
RCC_PCLK1Config(RCC_HCLK_Div1);
RCC_PCLK2Config(RCC_HCLK_Div1);

//SET THE FLASH LATENCY AS PER OUR CLOCK
//FASTER THE CLOCK, MORE LATENCY THE FLASH NEEDS
//000 Zero wait state, if 0  MHz < SYSCLK <= 24 MHz
//001 One wait state, if  24 MHz < SYSCLK <= 48 MHz
//010 Two wait states, if 48 MHz < SYSCLK <= 72 MHz */
FLASH_SetLatency(FLASH_Latency_0);

//DISABLE PLL
RCC_PLLCmd(DISABLE);

//CHANGE PLL SRC AND MULTIPLIER
RCC_PLLConfig(RCC_PLLSource_HSI_Div2, RCC_PLLMul_16);

//ENABLE PLL
//WAIT FOR IT TO BE READY
//SET SYSCLK SRC AS PLLCLK
RCC_PLLCmd(ENABLE);
while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET){};
RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

FLASH_SetLatency(FLASH_Latency_2);

//SET HCLK = SYSCLK = 64MHZ
RCC_HCLKConfig(RCC_SYSCLK_Div1);

//SET PCLK2 = HCLK = 64MHZ
RCC_PCLK2Config(RCC_HCLK_Div1);

//SET PCLK1 = HCLK/2 = 32MHZ
RCC_PCLK1Config(RCC_HCLK_Div2);

This also works. So my questions are

Is setting flash latency optional? since in my case it worked even without it.
When exactly do you call the FLASH_SetLatency function with the new wait state? Before setting the new clock or right after?


texts: Practical understanding of "tapping" into vehicle 12V battery / fusebox for power

texts:
Disclaimer: I did "tap in" and hooked things to my battery (on my car) many moons ago and did it without really thinking what am I doing, and I was probably doing it in a very hack/ghetto way, but it all worked. Now I'm looking into tapping into this pictured circuit on my bike, and I want to actually understand what happens when I turn the key and fuel pump primes up.
On the fuse box on the bike, first fuse from the top is headlight fuse, which seems like only fuse I can tap into to be able to hook few small devices into the circuit, and all of them being switched only when the key is turned.
I highlighted the headlight bulbs, the first fuse line, and it seems it all goes to relay. May I ask how does a sequence actually go, from turning the key, if we had to slow motion explain how the current flows in that moment, from 12V battery, does it go to the fuse first and then primes the relay that closes the headlight bulb?
I wasn't aware that non-flashing items (like main headlights) are hooked on relay, this is security feature I presume?
I am trying to understand this fully because I plan on running one bulb via Arduino, so it would mean I have to circumvent the current wiring?


texts:
I'm having some problems solving the voltages across the capacitors in the following circuit:

Because it is a parallel circuit, we know the voltage across C3 must be 6V.

But how can you figure out the voltage across C1 and C2? Does C1 store all the energy and leave C2 with no voltage? Or is it proportional?

I tried solving it in CircuitLab, and it calculates 6V across C1 and 0V across C2...


texts:
I want to put in series 2 74hc595N . I made the schematic from here:

When I send a value the first register sends it also to the second one. I have same value on both. I change them (master/slave) but the result is the same. What I am doing wrong because several days ago I made it and it worked.... I can't figure it out.


texts:
Looking for some feedback on this RF feedline and antenna area. Starting from the MCU pins, we have:

Murata RF connector with integrated switch (MM81302600) - for inserting the VNA and tuning the PI network
PI network
Extra in-series 0402 footprint (C14/C15) to route the signal to J3 (UFL connector), in case I want to use an external antenna instead of the one on the PCB.
Chip antenna: 2450AT42A100

Looking forward to any feedback you might have!


texts: What is the minimum C rating for li-ion battery cells? I am trying to charge 3.7V 10Ah battery pack with small 0.3W solar cell. I used LTC3105 DC/DC boost converter to boost voltage of solar cell to 4.2V. I could not find any online documentation or thread for this. I know it is safe to charge with lower C rating. My question is will my battery even gets charged with such small current?


texts: If you add the output of a half-wave rectifier to a full wave rectifier, what can you expect as your output? Moreover, how would you actually implement this in a circuit? Do you just have the output of the half-wave rectifier connected to the input of the full-wave?


texts: What (if any) is the leakage current through a NPN (C-E)?

texts:
So I have a circuit where  I need the current consumption to be low. Therefore I am using a 10M\$\Omega\$ resistor to 'pull-up' the pin on a chip which will need to be switched between high and ground (by high I mean the supply voltage which is ~3V).

In order to pull this pin down to ground when necessary I have a BJT (BC847C) which will be triggered by a microcontroller in order to bring this pin down to ground. The problem is, this doesn't seem to be working. Therefore I am wondering if there is any leakage current through the collector and emitter junction of the NPN which would be creating a voltage drop over the 10M\$\Omega\$?

The circuit really needs to be low power (in the tens of \$\mu\$A's) hence the need for large resistors as it will be on all the time (there are two switches that are being controlled by this set up and I need to switch between them)


texts: Understanding computer organisation and architecture

texts:
What are some of the user friendly books for "computer organisation and architechture" which are best for self study. Such a text that one can grasps the big picture, and understandhow various things are fitting with each other.

Topics include: machine instructions and addressing modes, ALU and data path , cpu control design, memory interface, I/o interface (interrupt and DMA mode), instruction pipelining, cache and main memory.

Thanks


texts:
I am trying to measure the state of a switch on a vending machine motor (model # BC-D27/28). It has a micro switch on it that has a lead going from COM1 to NC2 when engaged and COM1 to NO3 when disengaged.

There seems to be a 18 mV state when the switch is engaged that drops to zero when it is disengaged.

The machine is wired only to the + and - terminals of the module.

Ultimately I would like to control an array of these with an Arduino or Raspberry Pi.

How can I measure the state of the motor's switch to know when to disengage the motor?


texts: How to control 12V from 5V using transistor?

texts: i have used BC547 Transistor to stepup from 4.6v but I can't able to draw above 5v from collector, I have given input of 4.6v to base and emitter to ground and collector to output load. but load doesn't activate. Can anyone help me out from this problem?


texts: Using multiple current sense resistors in parallel to handle a high current measurement with cheaper resistors

texts:
I am measuring the current going to a motor using current sense resistors; however, in order to get a resistor that can handle the proper power, the price goes up way too much.  My question is, can I use multiple lower power rated resistors in parallel to measure the same current value?  In other words if I need 10W single resistor, I would break that up into five 2W resistors in parallel with the same value.

They would all have to be the same resistance value/tolerance and the power margin would need to overcome the tolerance of the resistance.  Seems mathematically fine, but wanted to see if there are any gotchas here?


texts:
Please be kind as I am fairly new to electronics. Anyways, from what I read on multiple forums the rules are fairly straight forward, but I am puzzled as to why my led burnt out. So I connected the led with the resister and a 9V battery. My resister is 470 ohms. Led is 20 mAH with a 2v drop I think. Anyways, it was working fine with resister on breadboard going from the positive end of the led and then other end of resister going to the power (+) side of the breadboard. Then I went to see how I can make it different but still follow the same rules for my big project, which is multiple leds on an ugly sweater. Anyways, when I went to have a wire go from the positive end of the led to the power side of the breadboard and then placing the resister (both ends) on the power side of the breadboard, it burnt out my led for some reason. I want to know why this matters as it seems like it is still the exact same circuit. Also, as a side question, I can have as many leds as I want going to the resister but I lose time it will run on a single 9v battery right?

Good:

Bad:


texts:
I keep running into ESD ratings in datasheets but I have no idea what they mean, for example in LM385 datasheet it says:

What does this mean for an electronic engineer or a hobbyist like me? can someone help me understand these points please:

What is the normal and maximum human body static voltages and what cause it to increase?
What does the value 500V mean? is it safe to touch it with hand for example?
How can I tell what's my ESD voltage at a given time?


texts:
I am relatively new to electronics and circuits. I'm modifying an alarm clock to have a battery backup. I've found a few circuits that show how to build a battery backup circuit and it makes a lot of sense to me. A few of these circuits allow the battery to be trickle charged though and I'm not clear on how these work. Here's one:

V3 is the main power. V2 is the battery. If V3 is on, power goes through the resister and back into the battery (the resister value is arbitrary, I just haven't figured out what it should be). The power doesn't go through the D2 diode because it's reverse biased. But why doesn't the power go from the battery, V2, through the resister and to the load as well? And when V3 is out and the battery is powering the load, which path does it take? Does it go through the D2 diode or the resister? Apologies if this seems like a stupid question. I've been doing my best to learn this, but I can't find answers to these particular questions. Thanks for the help!


texts: 7 position switch, only one position active at a time?

texts:
I am wiring a 6 channel camera switcher (http://www.brandmotion.com/360-vision/blind-spot/6-way-video-switcher-9002-6118.html)

And in addition to the automatic triggers (there are 6 trigger wires, when one receives 12v, it switches to that camera) I want to add a manual switch. I've looked and looked for a 7PST (I think thats the term) ideally in a push button format (7 individual buttons) but I cannot find anything.

So my question is either 1) do these switches exist? or 2) How can I wire 7 individual switches so that only 1 circuit/switch can be putting out 12v at a single point in time?


texts: Modular 18650 battery pack - using differnet chemistries?

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I have been building an 18650 based battery pack for our new motor home and have run into a few snags that I cannot find answers for. Some issues have been addressed on this site but I am going to list them aswell for good merit.

Pack Specifications
18650 cells that are used but tested for mAh (2200+) and internal resistance  (200mOhm or less)
20 - 18650 cells per module
6 - modules in parallel per battery
2-12 batteries total
So each battery pack is 20p6s

Each battery has BMS
Each cell is fused
All modules in all batteries have very similar cells as to not become unbalanced.

Two batteries are currently connected to a charger/inverter and have stayed remarkably balanced. Teating each module regularly has shown difference of no more than ~.1 volts

Questions
1. I recently acquired a few hundred 18650 cells of different chemistry. Can I use them all in the same modules?

Specifically I have used all low amp >5 laptop cells (lithium cobalt) and this new batch is high amp <10 vape cells (lithium magnesium)
I have found no information on this subject and would love to get some in site

I am soon adding two more batteries (with individual BMS) identical to the current two. Is there a limit to how many batteries I can use in parallel like this?

If anyone is interested i will also soon be releasing a DIY guide on how to build this style pack. It's all modular so testing for low voltage or failed cells is easy and replacing them is just as easy.

Thanks
-Wabalooba


texts: Normally closed input GPIO power consumption

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While an ARM MCU is in deep-sleep mode it has to wake up from a normally closed input. (Driven by a reed switch.)

I use 2 methods:

common to ground, input pin internally pulled-up and falling edge wakes the MCU.
common to Vcc,  input pin internally pulled-down and rising edge wakes the MCU.

Both works fine but it raises power consumption at about 100 μΑ.

Is there a solution with an IC that consumes zero power ?


texts: Calculating voltage spike of an inductor

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Suppose there is a circuit like this where the inductor has no resistance

In this circuit, if Switch 1 is initially closed, then there is

10/100 = 0.1 A

of current flowing through the inductor.

Then, if Switch 1 is instantly opened and Switch 2 is instantly closed, the inductor discharges through the resistor.

However, I have read that since the current through the inductor cannot instantly change, that must mean the instantaneous current flowing through the inductor after Switch 2 is closed must be the same as before.

Am I correct when I calculate the instantaneous voltage across the resistor the moment after Switch 2 is closed as

V = I * R

V = 0.1 * 10000 = 1000V?

Also, does this mean that the instantaneous voltage has nothing to do with the inductance of the inductor?


texts: Way to show that the current through a Darlington pair is determined by the emitter resistor

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I have the following circuit:

simulate this circuit – Schematic created using CircuitLab

Is there a way to show that the current through \$\text{R}_1\$ is given by \$\text{V}_\text{i}/\text{R}_2\$?


texts: Is it possible to store flyback voltage in capacitors?

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I recently put together a circuit that I use to control an electrical motor. I use an Arduino's PWM through darlington-pair transistors to control the speed of the motor. During construction of this circuit I was advised to use a flyback-diode to block flyback voltage spikes created during the collapse of the motor's magnetic field to prevent a spike from damaging parts of the circuit.

Would it be possible to somehow harness this spike of voltage and store it in a capacitor? I am a hobbyist and know enough to put together some basic DC circuits, so I'm not super well versed in the capabilities of different components.

I figured if this was possible, I would somehow have that short burst of energy the capacitor(s?) store then applied to the motor when a sudden increase in RPMs is needed.

Any thoughts, ideas or reference material on how to store flyback voltage in a capacitor? Or am I just coming up with silly ideas I don't understand? ;)


texts: Manually calculated -3dB cut off frequency differs from the simulated value

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I have been trying to do experiments with a differential BJT pair.
As the output resistance for the common emitter configuration is R_c (1k), instead of finding the capacitance, I attached a 1pF capacitor. I wanted to find the cut-off frequency of this circuit instead of the one without it.
This is expected to be similar to a single pole system.
My theoretical bandwidth is 1/RC but from the simulation I got about 26MHz.
Is the variation due to the capacitance or some mistake I made while calculating?


texts: How to place a plated slot on a mechanical layer in Proteus 8 PCB Layout

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I need rectangular PTHs on a board that mounts to three tabs which serve as structural support as well as electrical termination (the enclosure and tabs are out of my control). I followed the advice in an answer to a very similar question. Here is my setup for the padstack:

I've been advised that slots should not be on the same layer as the board edge in the gerber, so when exporting I overlay the edge on Mech 1 and I select Mech 2 as the Slotting/Routing Layer. See below:

From this, I would expect that the board edge would be on Mech 1, the slots would be on Mech 2, and the vias would be on Drill. What I found on inspecting the gerber was the board edge on Mech 1, nothing on Mech 2, and vias + slots on Drill.
Mech 1:

Mech 2:

Drill:

I would be happy to discover I've made some mistake in my creation of the padstack, but I suspect I'm doing something incorrect in exporting the gerber/excellon files.


texts: What are the AC characteristics of a battery?

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I'm planning on building a single cell AA NiMH battery charger and in the process I decided that I must also build a battery simulator to help me debug the charger. In my research, the best simulator circuit I came across was the one described in the Linear Technologies Application Note 58, Appendix B (page 35), which relevant part of its schematic is below.

In the circuit description, the AN says:

  R10 and C5 simulate the AC characteristics of the battery.

Well, I have no idea what that means. I did search the net for a description but couldn't find anything useful.

So, my questions are:

What exactly are the AC characteristics of a battery?
Are there AC characteristics that are particular to NiMH cells?
Out of curiosity, what happens if I don't add those components to my simulator?


texts:
I have a 2s lipo baterry pack I would like to charge with a multi-purpose battery charger I use quite often for bigger balanced pack.
That one (see picture) does not have a balance wiring harness and has only 3 wires and from other post of this site i understand the white one is a temperature control.

Should I connect the white to ground before charging? With a resistor?