texts: How to trace a wire hidden behind plywood wall?

texts: I have multiple electrical lines running behind my plywood wall. Unfortunately, some wires got lost behind the wall and the electrician is unable to trace them. Now the wire which I want to trace has its one end in sight. I want to find the other end. Many other wires may criss-cross this wire inside the wall which doesn't concern me. Is there a simple way to find the other end? There are some detectors available in the market which cost many thousand rupees. I want to avoid purchasing them.


texts: Audio amplifier bridge tied load (BTL) output as analog signal to MCU

texts:
I am trying to find a way to amplify the signal from an electret microphone & feed it as an analog signal to a microprocessor to drive LEDs based on sound. If I look at the amplifier ICs they all have differential + and differential - BTL outputs.
Like this:

In this case which output should I be feeding into the analog pin of the MCU?


texts: Sensitivity (or responsitivity?) of an electrochemical sensor - Definition

texts:
I read a paper about an electrochemical sensor where there is the term sensitivity expressed in ampere. What is its definition? I found a IUPAC definition here, but the units are ampere/watt or volt/watt.

I read also the description of the tag sensitivity (or responsitivity), but online I didn't find this definition about a sensor which works in amperometric condition. I'm looking for a definition where there are also the possible units of measurement.

Thank you for your time.


texts: Push-pull output stage and driving circuit function

texts:
simulate this circuit – Schematic created using CircuitLab
Hello, what is the exact purpose of the C3 and C4 capacitors, two diodes and R3 and R4 resistors in this circuit used to drive the output stage. The input signal is a 1kHz square wave with 5.2V on and 0V off provided from an opamp. Vref is 6V.
Thank you


texts: Usability of a deeply discharged Li-ion batteries

texts:
I have a question about Li-ion batteries.

About three years back I bought two Sony VTC 5 batteries for my vape. They are rated as 2500 mAh 30 A.

But I quit smoking about a year ago and I left these batteries inside of my vaporizer. They were nearly discharged, so that was mistake number one I suppose, but I didn't give it a second thought at that time.

Recently I found that these batteries are still in the vape and I realised that I can use them in a project, because they are quite powerful and not that cheap to simply dispose of them and buy a pair of different ones. I measured them and they had only about 0.2 V, so I thought that they are dead. However I still tried to hook them up to a Li-ion charging module, which indeed recharged them to 4.15 V. I thought that maybe they'll undergo quick self discharge, as I've previously experienced with some old NiMH batteries. But they still do have 4.15 V and they are still powerful enough to run some high-current demanding applications.

But the unresolved question I still have is this: How has this over a year long deep discharge state influenced its capacity? I know that I cannot expect 2500 mAh, but I really don't have enough experience to make any sensible guess. I also don't possess any kind of a capacity meter, so a precise measurement of the actual value is not possible.

So do you have any kind of an estimate of the capacity left in the batteries? 75%? 50%? even less? You know, if there is still more than 1200 mAh, these batteries are more or less useful for me, but less than that is not worth it in the application I intend them to use in.


texts: How to Minimally Communicate with an ADS131E04 ADC via SPI

texts:
I have bought a few ADCs from http://www.ti.com/product/ADS131E04 and I cannot get hear from them via the SPI.

I am putting the ADC in a TQFP socket and I connect the PWDN, RESET, SCLK, CS, DIN, and DOUT signals to the respective pins of an Arduino Due microcontroler (3.3V). I am also powering via DVDD and grounding via DGND. This should be enough for me to read a register so I can see that the SPI communication with the ADC is working. Unfortunately I don't hear back from the chip. The SPI read register request is sent to the ADC but the chip does not reply back. I have tried almost everything, including manually generating the SPI waveform. I am checking everything with a scope and a logic analyzer. I simply don't know how to get this working.

Edit 1: Thanks to everybody for giving suggestions. Today I have redone all wiring and I made sure that the power-up is fine. I measured VCAP1 and it gets to approx. 1.3V, so the analogue power-up is OK. I checked all CLK and SCLK requirements and they seem fine. This is a screenshot of the logic analyzer:


texts: What is wrong with my inverted pendulum?

texts:
I have been making an inverted pendulum using LQR. Here's a list of my hardware:

Microcontroller:  Microchip WiFIRE (PIC 32)
Motor Control:    L298N
Encoders (2x):    US Digital shaft encoders (4095 counts)
DC Motor:         Faulhaber Coreless DC motor (2338S006)
Gearbox:          Faulhaber Planetary (3.71:1)

I am using Simulink to program the PIC32. So far I have verified that the encoders for the cart and pendulum are generating the correct measurements. The system 'wants' to behave, but is unwilling to 'push through' to keep the pendulum upright: if there is a positive error on the pendulum angle, the cart does not most fast enough to accelerate the pendulum in the opposite direction and get underneath it (it's being lazy). Attached is a screenshot of my Simulink model.

I have tried messing around with my Q matrix for the LQR but I'm convinced there is something missing in my modeling of the system. Here is an image of the MatLab code I used to simulate the dynamics

I understand this is a very open question but if this behavior sounds familiar to any of you I would really like to get some input on where to look next, I feel like I am stuck and have been really excited to get this up and running.

Thanks

Update: Tim, good point. Here is an image of my equations of motion.


texts: I took a old webcam from a laptop and connected it over usb, it does not work

texts:
The camera has 5 pins: 5v, D-, D+, GND and powerC.

I dont know where to plug power c in.

Can someone help me please, the camera is CNF9138_A1 By Chicony


texts: Passive network with more than Unity gain

texts: Can a passive network have a transfer function of more than Unity gain for some frequencies? Can you give an example? Thanks.


texts:
Can I have about 4 to 5 seconds backup by 1F 5.5V Super Capacitor?

Power supply output voltage: 5v 600mA
I need 5v 0.5A for my system.

I want to use it as ups for only 4 to 5 seconds so I wasn't thinking about using batteries. should I change to any other capacitor?
If it's not possible by capacitor then how can I do it?

A Schematic would be amazing. Thankq


texts: Why is the current for \$i(t)\$ \$5mA\$, not \$5e^{-\frac{t}{0.8m}}\$ mA?

texts:
Close the switch of  the circuit, and  it is in the steady state. We open the switch at \$t=t_1\$ suddenly.  What is the value of \$i(t_1)\$?

simulate this circuit – Schematic created using CircuitLab

The solution for this is as below:

\$V_{R2}=120\times \frac{2}{4+2}=40V\$, so \$i(t)=\frac{40}{6k+2k}=5mA\$

I understand the formula above, when  \$C_1\$ is most fully charged,\$C_1\$ will become like an open circuit, so \$V_{C1}=V_{R2}=40V\$

However, I found here that the formula  of discharge current  from the capacitor is:

\$i_c=\frac{V}{R}e^{-\frac{t}{RC}}=\frac{40}{8k}e^{-\frac{t}{8k \times 100\mu}}=5e^{-\frac{t}{0.8}} \$ mA.

I know we can see "almost fully" charged as a voltage source, just like the formula from the solution, but I think my method should be right, too.
  Why is the answer for \$i(t)\$ \$5mA\$, not \$5e^{-\frac{t}{0.8m}}\$ mA?


texts: Small variable width fonts for LCD display

texts: I'm looking for a small variable width font that can be used on small LCD screens (in this case a 128x64 pixel screen). I'd like it to have a height of 8 pixels or less, so that the characters will be displayed on one line of the screen. I've tried using programs such as "The Dot Factory" and "GLCD Font Creator", but it seems they are ill-suited for such small fonts.


texts: What's this amplifier filter configuration?

texts:
I've come across an audio amplifier circuit that contains this following configuration:

I recognize R1,C1, and R3 to be part of a first order high pass filter, but I'm not sure what C2 and R2 are for. Does it filter high frequencies?


texts: Steps to replace a 10k ohm pot with a 10 ohm pot

texts: I was about to build an all-in-one board for a retropie computer inside a gameboy advance sp shell, when I found this board that already was made and shared by someone else. I have a different potentiometer for the audio circuit only that I would like to use because it is the oem volume slider. The guy says everything else works and here are the eagle files of the creators project:


texts:
This answer led to the conclusion that it is unclear what the meaning of the frequency listed by crystal manufacturers actually means.

Given this graph on page 79 of this ECS Crystals Application Note

there seems to be three obvious possibilities:

fs - the series resonant frequency

fa - the antiresonant frequency

fL - some value in the area of usual parallel resonance

In the case of fL the frequency specification itself would depend on load capacitance (see Figure E in this application note).

Here are some typical datasheets that turn up on the manufacturer's websites:

Datasheet
Part Numbering Guide

They seem to leave the meaning of the frequency ambiguous.

So, my question is this:

What is the meaning of the nominal frequency specified by manufacturers of crystals?


texts: Maximum Supply Voltage Output by Transformer - Sanity Check

texts:
First off, I am not an electrical engineer by trade, or even by education.  Pretty much everything I know about EE is self-taught, and I know enough to make a hobby out of it, but may be missing basic, core concepts.

I have found an article on how to build an audio amplifier, linked here.  I am confused by one of the calculations it presents, under the heading "Find the Maximum Supply Voltage Output By a Transformer" (the link takes you directly there).  Here is an excerpt:

  Keep in mind that a transformer’s voltage rating only tells you it’s AC voltage output. The DC voltage will be higher after the bridge rectifier diodes on your power supply convert the AC voltage to DC.

The article then goes on to include 1.41 in its calculations, which I recognize as how to deal with peak vs. RMS measurements, I understand where that's coming from, but my question is: is that at all necessary?

Is AC in general by-default expressed in RMS values?  Is the "120VAC" here in the US actually closer to 170V peak-to-peak?  I was under the impression that all AC expressions where peak-to-peak, and that if a transformer was outputting 25VAC on its secondary, then a full bridge rectifier (and capacitors for smoothing) was just going to output something close to 25V DC.  Is that not correct?

Am I missing something else that would be blatantly obvious to an officially-educated engineer?


texts: Best way to power an ESP8266 (3,3V) from AA batteries with LDO

texts:
My latest project uses an ESP8266 (ESP-01) to transfer data when a button is pressed. The ESP is always connected to the AP. No deep sleep. Right now I am powering it with an USB-charger which is directly connected to an AMS1117 LDO to regulate the voltage to 3,3V. This works fine so far.

Now I need to power the ESP with AA Nimh rechargeable batteries. I thought of putting 4 AA in a battery tray which should result in nearly ~5V. Because of the high quiescent current (>1mA) of the AMS1117 I am searching for a 'better' LDO. I see a lot of projects using the MCP1700 LDO in combination with the ESP. This LDO has a very low quiescent current (<2 µA), but the datasheet says the max output current is 200mA, from what I've read the ESP can have peaks up to 250+ mA. Isn't this a problem? I also found the MCP1825s which has an output current up to 500mA, but a higher quietscent current of <120µA.

1) Which LDO should I use to have a stable but power saving setup?

2) How can I calculate the time this setup will work until the batteries voltage drops below their minimum? Using 4 AA (each 1900 mAh) starting at about 5V until 3,6V. 3,6V because the dropout of the LDO is about 0,3V and the ESP needs 3,3V. Assuming an average current draw of about 100mA. Is it just simple 1900mAh/(100mA+LDO current) = ~19h ? How fast will the voltage drop from 5V to 3,6V?

3) Which caps should I use for decoupling the LDO? Just the ones suggested in the datasheet? Is it important if the capacitors are ceramic or electrolytic?


texts: Why only 500VAC rating for this Y-capacitor?

texts:
I’ve been looking through a reference designs for an off-line flyback converters (this one by Texas Instruments and this one by Linear Technology).  Both of them have a Y-capacitor between primary and secondary for EMI suppression.  Like this, for example:

from Fig.2 here

So far, so good.

Common UL standards (UL8750, UL1310) require dielectric strength between primary and secondary of 1kVAC plus twice AC line voltage.  That adds up-to about 1.5kVAC.
In these reference designs, the Y-capacitors in question  are rated for 500VAC (datasheet) and 250VAC (datasheet).  Doesn’t this undermine the UL requirement for the dielectric strength between primary and secondary?

One of these capacitors has this paragraph in the datasheet:

  Dielectric strength between leads
  Component test: 4000 VAC, 50 Hz, 2 s
  As repeated test admissible only once with: 3600 VAC, 50 Hz, 2 s
  Random sampling test (destructive test): 4000 VAC, 50 Hz, 60 s

Much higher voltage ratings.  Does that take care of dielectric strength required by UL standards?

Interestingly, I also couldn’t find Y-capacitors with 1.5kVAC to 2kVAC rating (on DigiKey and Mouser).


texts: Arduino/Atmega328: check if PIN is shorted to GND

texts:
In a project with an Atmega328 running at 8 MHz and powered from 3.3 V, I need to check if a 2-pin jumper is permanently inserted.

So, the schematic is:

and the board is:

I cannot figure it...

Is it really simple as:

1) Configure the PIN as INPUT_PULLUP?

2) Check if PIN is HIGH then is connected and do stuff?

3) Do I need external resistor (and what value) or is it sufficient the INTERNAL_PULLUP?

4) Can I leave the PIN shorted to GND for a massive amount of time, let's say for 1 year? This ATmega will be on "forever"

pseudocode, to understand:

void setup() {

  pinMode(PIN_CHECK , INPUT_PULLUP);

}

void loop() {

   // at first post, I did put this HIGH, but I was wrong.
   // the check need to be for LOW, when connected
   if ( PIN_CHECK == LOW ) {

     Serial.println("The user has placed the jumper, the pin is shorted to GND!");

   }

}

Thank you to all


texts: 1bit Full Adder Cell in IC not working as supposed?

texts:
I got an adder cell, which in IC mirror layout is this:

EDIT: Transistor-level, standard adder circuit:

Which I actually made in IC like this:

It's not working as it should! I labelled it same as in the first figure, so the labels themselves are ok, but the signals are like this:

As you can see, the sum signal S is working as it should, but the carry output is buggy. Not only that, the COUT and notCOUT are not opposite, so sth is definitely wrong. I throuroughly examined the circuit, but can't find where I made a mistake.

Can anyone spot the error? THANKS!!


texts: Constructing a reactive lighting system?

texts:
I've recently written a Matlab script to develop/simulate PWM output for RGB lights based on sampled audio input. I made this script with plans to actually construct a device that can run the algorithm and thus control RGB lights.

A brief explanation of the script (I'll post it below as well) is  as follows.

Filter the incoming signal into 3 bands of low, mid, and high range frequencies.
Creates frames of  0.05 seconds in length (I think) to hold RGB values for
the duration based upon the 3 filtered signals. Low = Blue, Mid = Green, High = Red.
Use a peak ("bump") detector of sorts on the original sampled signal to look for volume increases in the song. The areas of high volume are recorded.
Add Bumps to frames. To be honest, I'm not sure I like the way I implemented this and may change it in the future although I'm still trying to figure out a better way. I intend the "bumps" to change the color FROM the background color (created from the 3 filtered ranges) and then have the "bump" color fade to the background color until the next "bump" occurs.
Draws a bunch of squares and displays an image to (hopefully correctly) simulate the colors and duration the lights will produce. Each column of color should represent an "interval" length (I have it to 0.05 seconds) of color. With this I should be able to visualize the expected output of the LED?

That's a quick overview of the script I want to implement in hardware. I'm honestly not sure it'll work but I have no way of knowing at the moment.

I have very little experience with actually working with hardware and am lost and have a few questions. I plan to get the analog signal from devices such as a phone audio jack.

In the Matlab script I've decided to sample at CD quality 44.1 kHz, but I'm not sure how to achieve this in hardware. Some have suggested a dedicated ADC which I agree may be a good idea, but I'm not sure how to shop for one. I'm not sure if I would need to sample at 16 bits for my purpose? What are some ADCs that could work for this purpose?

If I have a dedicated ADC I will need a way to transfer the information to another device. What is a good method to do this? I will want to perform filtering on the sampled signal as well as some data analysis to determine the value of 3 PWM output pins at a given time.

On the topic of filtering, since I am starting with an analog signal would it be easier to filter it before sampling with an ADC or digitally? I'm leaning towards digitally but I have no idea how to implement digital filters on a microcontroller.

I am also concerned about the speed and memory size of the microcontroller required to process the data. Assuming I can figure out how to interface an ADC with a microcontroller for processing, I would need to digitally fitler the signal into 3 bands as well as preserve the unfiltered signal for analysis. I also need to be able to keep an average of the last few thousand samples at a time (is an averaging filter a good way to do this? or a simple total_value/samples_taken a better implementation?) In my current design, I plan to update the PWM values for the LEDs every 0.05 seconds. What sort of microcontrollers would be able to accomplish these tasks as well as interface with an ADC?

Overall I'm looking for hardware that can perform the above operations, and I'm not sure what will work or where to start looking? Thanks in advance for any help.

MATLAB Script (pastebin link)


texts: Possiblity of Using Transistor as Resistor

texts:
I would like to know it if is posible to use NMOS transistor to act as a resistor with a sinusoidal power supply ?

The circuit I have is very simple; it consists of a 20Vpp-sinusoidal source connected to a resistor (100 M to 700 M Ohm) then to ground. However, I want to replace the resistor with an NMOS transistor such that the circuit behaves in a similar manner.

So, would it be possible to do that without a DC source? Given that I can design my own NMOS transistor with any parameters values I need, such as Vth, mobility, W/L,...etc

I know for a fact that if the transistor is to act as a resistor it must be in the triode region where VGS > Vth & VDS < VGS - Vth, but I am not sure if it is going to work with no DC biasing source.


texts: Eagle is placing thermal reliefs around small SMT IC pins - how do I edit them?

texts:
I'm using Eagle for a PCB project. Referring to the image below , you can see that Eagle insists on placing thermal reliefs on IC pins that have been grounded. The problem with this is that the they will actually allow for more thermal dissipation by having added these 'spokes'.

Is there any method for editing these thermal reliefs such that adjacent pins are not directly connected to one another? Essentially, how do I remove the thermal relief 'spokes' such that there is only one that is grounded.

How do I edit the thermal reliefs around pins?


texts:
I want to turn on LEDs 0, 1 and 2 when pinc1, pinc2 and pinc3 are triggered. Also, I want to use a pin change interrupt.

Problem: only LED 1 is on.

This is my code and I am using atmega328p and Proteus for simulation:

#include <avr/io.h>
#include <avr/interrupt.h>

volatile uint8_t bemf = 0 ;
ISR(PCINT1_vect)
{

if (PINC & 00000010){bemf=1;}
if (PINC & 00000100){bemf=2;}
if (PINC & 00001000){bemf=3;}

}

int main(void)
{

DDRD = 0xFF ;
PORTD = 0x00;
PCMSK1 |= 1<<PCINT10 | 1<<PCINT11 | 1<<PCINT9 ; // pinc1 pinc2 and pinc3
PCICR |= 1<<PCIE1 ;
sei();

while (1)
{

  if (bemf==1){PORTD= 1<<PIND0;}  // TURN ON LED 0
  if (bemf==2){PORTD= 1<<PIND1;}  // TURN ON LED 1
  if (bemf==3){PORTD= 1<<PIND3;}  // TURN ON LED 2

}
}


texts:
I wanted figure out what is wrong with my led setup.

I have 78 leds in series connected to a mean well elg-150-c500b data sheet

The leds are a few different colors they range vf 3.6v to 3.8v and max amps 700mA to 1000mA (all are 3W leds on a star heatsink).

Whenever I plug in the driver all the leds light up for a second then several leds blow, about 20 or so from the right of the panel dimly light up.

Leds that blow up (all same colors warm white):

1st run: 3, 78

2nd run: 2, 3, 5, 78

3rd run: 1, 3, 6

The leds that blow are to the right of the panel (where my incoming +/- connections are).

What I have tried so far:

Tested each led connections to ensure they are not leaking to the
shared heat sink.
Added a 100k resistor as per the driver datasheet.
Tested each led is working using a 6v 550mA power supply.
Made sure the led polarity is correct on each led connection.
Tested the driver using 3 leds on my workbench, drew about 12.8v; the leds dimly lit up due to not having enough load (this is to be expected as driver needs 150v to function as it is cc).
Checked heat of heat sink was cold as normal after run.

Some things to note

The driver is case grounded and is connected to the shared heat sink via screws.
When testing each led connection, some leds extremely dimly lit up when one prong of the mm was touching the heat sink and the other the led connection.
On the 1st run I had a multi meter connected and noticed it sent the full 315v through the system.
The leds are connected to the shared heat sink using thermal adhesive.

I would like to know what can I further do to troubleshoot this problem and find a solution?

Also if one or more of the led connections are touching the shared heat sink could this cause the issue?

Edit.
The other question is also mine, I wanted to delete it and re-ask the question in a more readable and informative matter.


texts: Determine the robustness of a controller

texts:
How do I determine whether a PID controller I've designed is stable?

How do I determine its stability due to the transfer function it's being applied to, and how well it rejects disturbance and noise?


texts: Confusion in block diagram of open loop and close loop control system?

texts:
I am studying Modern Control Systems, 11th edition, by Dorf and Bishop.
On page 221 it first shows in fig4.7 open loop control system(the writer names it as open loop) and on page 222 close loop control system is shown in fig 4.9

Snapshots of both images are attached

I wonder why the writer is calling fig4.7 as open loop despite the fact that it contains feedback path with gain block Kb


texts: Difference between THD equation and design circuit current

texts: Why does the summation of design circuit current equation (Ib) start with 1 while for calculating THD the summation starts with 2?


texts:
I require an opamp-based circuit that calculates the expression OUT = A - max(B, 2V), as shown here:

There are no strict requirements on the shape or exact position of the transition, however in the linear region (B > 2.5V), the curve should be precise.

Below is a circuit for a regular difference calculator (OUT = A - B); is there a simple way to modify this in order to achieve the desired effect? I was thinking of employing a diode to achieve the nonlinear effect, but I'm at loss on exactly how to proceed.

simulate this circuit – Schematic created using CircuitLab

I'm using a rail-to-rail output, over-the-rail input amplifier, and have no requirements on the input/output impedance of the circuit. I have all sorts of positive reference voltages and supply rails available, should those be necessary.

Application info

I need this circuit as the feedback loop of a switching + linear voltage regulator; A must be about B + 0.8V to compensate the linear regulator's drop, so feedback = A - B would suffice.
However, the linear regulator requires at least 1.4V to run, thus the max(B, 2V) requirement.

simulate this circuit


texts: Can I extend the life of a solenoid by reducing its supply voltage?

texts:
Say that I have a 12VDC 2A rated solenoid, but I test the lowest voltage that my solenoid operates reliably for my specific application. Could I just operate the solenoid at this lower voltage to extend the life of the coils?
This question came up because I received a 12VDC (2A) solenoid valve before receiving the power supply, so I tested it with a lower rated power supply and read 8VDC and 1.7A during operation. Then I installed the 12V supply and during operation it reads 11V 2A (what it's rated for).
But that got me thinking, this solenoid gets really hot. Wouldn't it be happier operating it at a lower voltage if it works just fine?


texts: Why can we bias MOSFET with current source?

texts: My question is: If I have properly set VGS to prevent MOS from turning off, then if we biase a MOSFET with a constant current source, how can we conclude that it is working at saturation region? How large should this current be? How come that it will automatically work in saturation region? Why not triode region?


texts: 6 x TEC1-12706 in series cannot reach desired amperage, why?

texts:
]I have 6 EC1-12706 in series connected to a variable DC Power Supply (rated with maximum 30V and 10A). I set the power supply to 30V and 1.50A.
My problem is that the DC Power Supply when the output is enabled keeps the voltage to 30V but the ampere goes down to 1.29A.
Why does the power supply cannot provide the 1.5A desired?
My calculus is that in series the 30V should be divided by 6 (5V each TEC) and the amp distributed among the 6 equally.
Schematic:

Photo:

EC1-12706 DataSheet:
https://datasheetspdf.com/pdf-file/634368/HB/TEC1-12706/1
DC Power Supply:
https://www.amazon.com/gp/product/B07Y5XVTQL/
Testing data:
I tested with a single EC1-12706 unit. I set the variable DC Power Supply to 12V and 5A, the power supply says (and the multimeter) says: 12V, 2.4A (cannot reach 5A, hence it seems that the 1.98ohms of the spec sheet is wrong?
Inside:


texts: Long times ago I bought on the ebay a cheap rs232->usb converter, today I wanted to use but I realized that I don't have the pinout. This is the converter how can I figure it out the pinouts, does anybody has experience with this?


texts:
Searching over the Internet for high power DC12V 100A-200A relay (to switch power on power shortage automatically from power adapter to battery) I have not found any device that is more powerful then this 30A module.
May be there is a way to adapt car relays for this purpose? Or may be any other product you can suggest?
Thank you.


texts: What is the underlying mechanism behind Wi-Fi getting slower with greater distance?

texts:
It's common knowledge that the further you go from a Wi-Fi network point, the slower the network over Wi-Fi gets. But why would this be the case? Radio signals propagate at essentially the speed of light, and so from signal propagation alone distance shouldn't be a factor for any reasonable range (thousands of km/miles).

My theory is that any time a network packet is sent, there's a probability that it will either not arrive at the location, will arrive with corrupted data, or will arrive in the wrong order, and this probability increases with increasing distance, forcing the TCP layer to cause packets to be sent and resent. This sending and resending process does take a quantifiable amount of time. Not enough that a single packet will provide any noticeable delay, but enough that if one in three packets needs to be resent, and then all the packets put back in the correct order at the other end, extra time will be taken. But that's just my theory. What's the real answer?


texts: What type of eye protection should you use with a battery tab welder?

texts:
There are a ton of youtube videos and websites about how to make a DIY battery tab welder - however none of them seem to have any information on what type of eye protection to use.

I know that some people making small tac welds with regular welders will line things up and then just look away or close their eyes while pulling the trigger - is that what's supposed to be done here as well?

I know that the big welding helmets have auto darkening adjustments but it takes a small period of time for the adjustment to happen - perhaps the battery weld would be so quick that it would not be worth using a helmet for this?

Below is an excerpt from Jim's Blog showing one of the upgrades he made to his version of the welder. It also shows him using the welder but he does not appear to be using any helmet or goggles.


texts:
I am planning to build an electronic fencing scoring apparatus for training purposes in our club (so no FIE certification required, it's a pure hobby project).

For hit indication, I want to use a bunch of colored LEDs in a grid (probably 9-25). However, I have no idea how bright those LEDs need to be. Being for fencing, I have the following use case:

Well lit indoor environment (a gym hall)
distance of 5-10m
wide viewing angle (routinely viewed from ~60°)
colors are red, green and white

Are there guidelines or a rule of thumb for the luminous intensity I should use?

Does the necessary luminous intensity change when using multiple LEDs in a grid, or can I just add up the intensities of all LEDs?

As this is the first project where I use LEDs for more than just small status indicators that don't have to be visible from far away, I'm a bit clueless. Even an order of magnitude estimate would be a help.


texts: ESP8266 wont send or receive returns busy s . .

texts:
I'm attempting to make a fermentation temperature controller with the ESP8266 sending data to and from my local webserver. I'm testing the esp with the arudino serial monitor and an ftdi board. I have my timeout in Apache setting to 300 and don't know why I'm getting the 408 error code. I can't find where or how to set the request headers that it mentions in the error log. Please help I'm way to many days into this project with no return so far.

Here is the output for esp and the webserver log

ESP8266:

AT+CIPSTART="TCP","192.168.2.14",80

CONNECT

OK
AT+CIPSEND=44

OK
> GET /fermControl/update.php?temp=62 HTTP/1.1 \r\n

busy s...

Recv 44 bytes

SEND OK
AT+CIPCLOSE

CLOSED

OK

Apache Access.log:

192.168.2.176 - - [23/Jun/2015:14:51:38 -0700] "-" 408 0 "-" "-"
192.168.2.176 - - [23/Jun/2015:14:52:04 -0700] "-" 408 0 "-" "-"

Apache Error.log

[Tue Jun 23 14:32:54 2015] [info] [client 192.168.2.176] Request header read timeout
[Tue Jun 23 14:36:43 2015] [info] [client 192.168.2.176] Request header read timeout
[Tue Jun 23 14:38:37 2015] [info] [client 192.168.2.176] Request header read timeout
[Tue Jun 23 14:51:38 2015] [info] [client 192.168.2.176] Request header read timeout
[Tue Jun 23 14:52:04 2015] [info] [client 192.168.2.176] Request header read timeout


texts: Choosing the right transformer to replace batteries?

texts:
I have an idea for a hack I'd like to build, but I need some help figuring out the right transformer. Let me know if there's a better place to post this sort of request.

I have some exterior LED path lights that work on 4 C-Cell batteries each.  There are 6 of them, so having to replace the batteries is relatively expensive and a bit of a pain. Looking at the lights, I see that I could easily solder wires to the battery contacts and replace the batteries with a transformer.  I could run a low voltage wire indoors to a transformer and never have to worry about batteries again.  My problem is that I'm not sure what transformer to get.

I did some simple math but I have no electronics background, so I would appreciate getting guidance from folks that have more knowledge about this stuff.

Here's what I know:

Each light takes 4 C-cell batteries in line. That is they are stacked one on top of the other with positive terminal touching negative.  I think that means I'd need to add the voltages together meaning 4 x 1.5V = 6V required.

I have no idea how much power each light draws (specs don't say anywhere) and the math I did doesn't seem to make sense. I know that alkaline batteries are normally rated for about 8000 mAh.  The manufacturer of the light claims that the lights last about 50 hours before needing the batteries replaced.  8000 / 50 = 160 mAh draw.  That seems really low to me.  Is 160 mAh a reasonable amount for an LED light (supposedly 80 lumens output if that helps)?

So if I multiply that out 6 * 160 = 960 mAh required.  I want to be able to add a few lights so let's double that (so just under 2A).

Does that mean I need a 6V transformer that can do 2 amps?  That seems really low to me, so I'm hoping someone with electronics knowledge can provide some help figuring out what I really need.

Any guidance or nudges in the right direction would be greatly appreciated.

Thanks.


texts: My capacitor does not do what I expect it to do

texts:
Fixed: The capacitor was defective. It works well with a different one.
I’m new to electronics and need your help.
I built a circuit similar to this one (see comment for the exact components):

I expect the LED to remain on for a short time when I release the button, my capacitor discharging and providing current to the base, keeping the transistor open.
It does not. What am I doing wrong?
Adding some pictures of my actual circuit:


texts: Dynamic Range Compressor Pedal Operation

texts:
A Dynamic Range Compressor works by "clamping" an incoming signal. Above a certain input threshold, the gain of the device is reduced to a lower level. This has the effect of making quieter sounds louder and louder sounds quieter. The circuit below is a realization of this concept applied to a guitar signal.
As I understand it, the circuit works as follows: The input signal is fed to an OTA which is set at a particular level. The output from here is then sent to a series of transistors which put out a voltage inversely proportional to the magnitude of the OTA's output. This is then fed back into the OTA's bias pin via a variable resistor. The higher the signal's magnitude - the lower the current into Iabc. It is this feedback loop that can be described as compression.
That, at least, is the gist of it. I would like to know specifically, how Q2, Q4, and Q6 work towards this end. Having looked at it for a while I would wager that Q2 operates as a phase splitter whose outputs are summed together by Q4 and Q6 in conjunction with R12. However, I fail to understand how this would vary with the signals magnitude given that a wave plus it's inverse( sin(x) + -1*sin(x) ) is 0. Anyone willing to steer me in the right direction?


texts: Counting number of push button press by external interrupt

texts:
It's a requirement that I should count the number of button press by external or any other interrupt.

So when I use the external interrupt to increment the counter by 1, it sometimes is crease by 2 or 3 due to debounce. Can anyone tell me how to count accurately in this case?

void Handle_PB() // my ISR called by pushbutton press falling edge
{
    pb++;
    if(pb>3)
    {  num1=1;
    }
    if(pb>4)
    {  num2=1;
       pb=0;
    }
}

pb is the pushbutton counter. and num1 and num2 are flags.

So after 4 times pushbutton press I want to do some other task. Simerly after  5 times pushbutton press I want to do another task. so Important is to count an exact number of a button press.
I know the debounce principle. But where can I put this debounce delay code as it is interrupt driven?


texts: Using high resistance resistor greater than 10M possibly does not work with 555 Timer

texts:
I am trying to create a 20 minute timer for 20-20-20 Rule with some bunch of resistors and capacitors available with me.

I am using a 10M reistor here in place of R1 and some 10K/20K in place of R2.

Since i want a beep of a second or two as up signal so i used Not gate at output and then added a small active buzzer.

It seems like it is working for small resistor value and not for over 1M as some comment i found here. Is this really true?
And isn't it possible the output to be low for more time and up for small time so i can avoid Not gate.

Any ideas are appreciated.

I can definitely change the capacitor value but want to know about Resistor limit on these cheap 555 timers.


texts:
I am using PIC18F67K40 With mikroC. I need Configuration settings for this particular chip

I have referred to the EVM of PIC18F67K40 for designing of my custom board.

Edit: I am using external through hole crystal 16MHZ on my custom board.I programmed chip with a small LED blinking program and it is working. I dumped another code but its not working on the chip. Hence i am suspecting the configuration bit settings.
I have set following on the configuration bit settings:

Oscillator selection: HS
Low Voltage programming:Enabled
MCLR PIN:ENABLED

Do I need to set any other bits?


texts:
I'm using a PCF 8591 ADC for the sake of the photo resistor on it - here.

The project doesn't seem too complicated for a software engineer like myself but I seem to need some help. I'm using an ESP01 to talk to the PCF8591 via i2c which is working fine as far as I can tell. I am also using the ESP01 to switch it on only when I need it (to conserve power). Currently it's going to a basic small NPN transistor. When I switch the ADC from the transistor it seems to have a max value of 127 for the onboard photo resistor BUT if I power it directly via my 3.7v battery, it has a full range up to 255.

Why does it max out? Is there a better way to do this?


texts: JESD78D - pin clamping voltage and current

texts:
I'm studying the JEDEC Standard No. 78D and on one of its notes it says: "The pin clamping voltage for positive I-test is given by Vclamp = Vmax + 0.5(Vmax-Vmin) with an upper limit of 1.5Vmax..."

What does it mean with "pin clamping voltage"?

In another part of the text it states: "The current clamp for the supply group is set according to the total nominal supply current of the group. The clamp current for the Jth supply group is the greater of a or b..."

What does "current clamp" mean?


texts: How to determine operating mode of BJT transistor?

texts:
In the lab, I worked with this circuit:

I varied RL over a range of values and measured VC and VE. Then I got the IC values and plotted the results down below:

I am very confused as to how to know what mode my transistor is working in. Also, I do not understand why both plots look so different. Did I get the wrong data?


texts: I'd like to start out that this is my first ever electronics project. I built a 5v power supply from here, using a 7805 5v linear regulator. the only problem is that it is outputting 4v instead of 5v. I want to move on and mount an atmega328 chip, but I'm not sure if I might damage it on accident. Is it safe to go ahead?


texts: What's the name of a timeout relay which won't re-trigger if it times out?

texts:
I would like to replace the relay which triggers a water pump, with a relay which times out after, say, 10 minutes. And if it times out, it stays locked out until reset.

Needs to be 230v AC on both sides of the relay.

If it doesn't time out, the next time it's triggered it should come on normally.

I've spoken to everyone from RS to Farnell, and they have everything but that device. Making me wonder if I was using the wrong terminology.

I've got about 10cm by 12cm space to replace the standard relay currently inside the box (an ancient RS 348-403).

Thank you

(I noticed that the question warns me that "The question you're asking appears subjective and is likely to be closed". It either exists as a thing, in which case it has a particular name it's known by (eg: "no-retriggering timeout relay"), or it doesn't. I'm asking a question in the vein of "what's the name of the device which reduces voltage". Note that the question is clearly "what is the name of", rather than "what do you call" - the latter would indeed be subjective!)


texts: Barn Door tracker motor battery selection

texts:
I am planning to build hinge based barn door tracker, as in the attached picture

Its a simple meachanism for astrophotography aid, camera is mounted on one plate and other plate is connected via hinge in one side and lead screw and a stepper motor on other to rotate the lead screw and move the plates apart from each other at constant speed.
The weight to be moved including camera and plate would be roughly between 2kg to 4kg (depending on what lens i use on camera)
Speed required to move at is 0.25 degree angle shift in 1 minute (between two plates) , yes its very low speed but i need to move it constantly every second in a smaller steps, roughly 0.0041 degree/sec.
I am planning to use NEMA17 stepper motor with 4.4 Kg/cm capacity (see link for details specification)
link here.
I found that the required driver/shield would be A4988, see spec here
The lead screw i am planning to use is here
Everything will be controlled by Arduino Uno3
based on this configuration my understanding/guess is that i require 12v Battery which can supply current between 2 to 3Amps. meaning a lead-acid battery, something similar to this
My questions are.

Can i use smaller battery or supply directly via powerbank to the above mentioned configuration? or what can be changed in the config (motor/driver) to achieve same req with lower size battery (9v) or powerbank (if its at all possible)

If my load (weight) is less than 3kg, is it possible that i use different driver module for e.g EasyDriver4  (in case low current is required)? what is here the relation between weight on plate, voltage and current motor requires?

Can i use lower capacity motor since my required speed is very very low.

suggest alternate config (i am looking for cheap and smaller size alternatives)

Any help would be greatly appreciated.


texts: I want to know that since in bjt's saturation state base and collector junction is forward bias why we take saturation voltage (Vce) as 0.2 Volts? Base and collecor junction is PN so voltage must be 0.7.What is the reason behind this ?


texts:
SE,
I am trying to replicate the F-shape microstrip antenna design shown in:
https://www.researchgate.net/publication/330747527_Dual-Band_Monopole_Antenna_for_RFID_Applications
in Keysight's ADS,
I have set up the substrate and layout to mirror the values used in the paper. The layout is terminated with a 50 ohm pin which represents the SMA 50 ohm connector in the paper.

I should expect an S11 plot as shown below:
but when I simulate it in ADS, I get

I don't understand why my S11 plot is different if I used the same values and followed the paper
verbatim.


texts:
I have been going through a container of old electronics and discovered a set of ten DIP-14 ICs labelled "268."  I have searched this number as well as the additional unique number on each chip, but have had no luck identifying them.

Does anyone in this community recognize this chip?
Might someone have a data-sheet on hand?

Thank you


texts:
I recently came across a block diagram of a state variable filter on one of my reference books which looks like this:

I am not sure about the negative sign going into the summing point from the side of Vin. In my limited experience with control systems I have not encountered this and do not understand what it implies.

Without taking into consideration the negative sign of Vin, the transfer function I came up with is:

My question is not whether the transfer function is correct, but simply what effect does the negative sign next to Vin mean and how it affects the transfer function above.
Thanks!


texts: Assessing and reducing EMI from PWM LED lighting

texts:
I need to run 50 individually dimmable LED fixtures on a pair of wires 30m long. Total load will be about 6A at 48V DC. I have to get power and control down a single pair, and AFAIK there are basically two options:

Add an encoded high frequency carrier to the DC, as used in data over mains applications.
Use an H-bridge to supply power as square wave AC, and modulate it with PWM or FSK to encode the data.

I'm leaning towards option 2 as it will be cheaper, and also option 1 has the potential for lots of noise problems in the data with 50 PWM driven fixtures on the line.
Ideally I'd be sending data at 25kbit/s, but I think I could get away with 2.5kbit/s.

I don't need to pass any approvals, but I don't want to be causing problems with radiated interference. I don't know where to start when it comes to estimating or measuring the interference this setup will cause. Is a 30m cable carrying 6A switched at 2.5kHz (or 25kHz) a complete non starter?


texts:
I have designed a circuit which powers up multiple components or electric modules from a source voltage of 12V. This circuit powers 1 micro controller (PSOC 5LP, rated voltage 12V), 3 stepper motors (rated voltage 12V, current 1A), 2 Servos (rated max voltage 6V), a laser module (rated 12V and required current of 2A) and a few LEDs and IR modules (rated voltage 5V). All these components are connected in a parallel network. The LED modules are supplied with regulated 5V from the source 12V.
Now my question is, since all the components other than the laser require less than 2A of current, will supplying a maximum current of 2A and 12V form the source to this parallel network damage my circuitry and other components like the micro controllers or other LED modules?

Thank you so much, cheers


texts: How can I calculate current(I) when I don't know voltage drop

texts:
So everyone knows Ohms law (\$I=\frac{V}{R}\$)  .

Let's say I have a 9V battery and a LED. Furthermore the LED only needs 1.9v so the voltage drop of my resistor would be: \$9-1.9 = 7.1\mathrm{V}\$

I have a 1k resistor (1000 ohms) so now to calculate current we have to plug it all in...

$$I=\frac{7.1}{1000} = 0.0071\mathrm{A}\space\space (7.1\mathrm{mA})$$

But what if I change my mind and I don't want my 1k resistor to drop 7.1V but 7.2V instead, so now it would look like this:

$$I=\frac{7.2}{1000} = 0.0072\mathrm{A}\space\space (7.2\mathrm{mA})$$

And now this is the part where I get confused. Because I can't control the voltage drop of my resistor so it can either be 7.2V or 7.1V. But I don't know which one is the right one.

I could say I want my 1k resistor to drop only 1v so then again:

$$I=\frac{1}{1000} = 0.001\mathrm{A}\space\space (1\mathrm{mA})$$

So and if I don't know what my voltage drop is then I don't know current either. So can someone explain this to me?


texts: Designing state machine for Jk FF Counter

texts:
The counter is supposed to go from 1>3>4>7>6 and use JK flip flops.

While filling out the state table I'm a bit confused about what to do with invalid states. Since I think this is 3 bits and should use 3 FFs I have columns for present state, next state, and FF inputs: A B C An Bn Cn Ja Ka Jb Kb Jc Kc. I just wrote invalid for the next states that aren't included in the state diagram, but what do I do for the FF inputs, are these invalid too or don't cares? And if invalid, does that count as a zero when solving for their equations using kmaps? Any help is appreciated, thanks.


texts: Cut-off frequency, gain and quality factor calculation of complex 2nd order low pass filter

texts:
I'm building a full analog chorus-effect pedal. My schematic is based on that of a Rockman X100 headphone amp, designed by Tom Sholz. In this schematic, there is a 2nd order low pass filter that looks like a variant of a Sallen-Key low pass filter, but I have never come across a topology like this.
Can someone help me to derive the formulas for calculating the frequency, gain and quality factor?

link to the original schematic: https://www.dropbox.com/s/3kii0qlqiwtoosj/rockman-x100-and-soloist-schems.pdf?dl=0
It starts on page 2 underneath the 'Stereo Chorus' title.


texts: ARM STM32 simulator like proteous and some good book to start with?

texts: I want to get my hand dirty with ARM programming. I have 8051/PIC16F/PIC18F programing experience. I searched about ARM and find STM32 series cheap. But before buying i want to get handy with it via some kind of simulator similar to proteous from labcenter.com. I searched about it but could not find any thing useful. Could some one please refer me to some good simulation based development environment for ARM preferably STM32 series. Thanks


texts:
Please help me solve this star delta problem:

My attempt:

What to do next to solve this completely?


texts: How to calculate the resistance to heat a resistor to a specific temperature

texts: Let's say I'm planning to buy some length of Kanthal-A1 wire. To power it, I have a 120 volt, maximum 20 amp power supply (my wall outlet). That part is okay. The problem is, I want it to be able to reach a certain temperature (1200 c), but the only thing I can control is the resistance! How can I figure out the max temp it'll be able to reach by only controlling the resistance?


texts: PIC18 - problems getting inline assembler routine to work

texts:
(EDIT: Added C18 disassembly code)

I need to optimize a function written in C for a PIC18f4585.  I am using C18 to compile.

The function I am trying to re-write in assembly is:

void readResetTimers (void)
{
   register unsigned char tmr0_temp;
   register unsigned char tmr1_temp;

   tmr0_temp = TMR0L;
   TMR0L = 0;
   tmr1_temp = TMR1L;
   TMR1L = 0;

   tmr0_value = tmr0_temp;
   tmr1_value = tmr1_temp;
}

I thought that I could instead use assembly code to load the value of each registers into variables tmr0_value & tmr1_value as they are declared in the global namespace, however my system doesn't work when I substitute the following code in:

void readResetTimers (void)
{
_asm
    MOVF    TMR0L, 0, 1
    MOVWF   tmr0_value, 1
    CLRF    TMR0L,0

    MOVF    TMR1L, 0, 1
    MOVWF   tmr1_value, 1
    CLRF    TMR1L,0
_endasm
}

Any ideas would be appreciated,
Cheers.

 void readResetTimers (void)
  04D4    CFD9     MOVFF 0xfd9, 0xfe6
  04D6    FFE6     NOP
  04D8    CFE1     MOVFF 0xfe1, 0xfd9
  04DA    FFD9     NOP
  04DC    0E02     MOVLW 0x2
  04DE    26E1     ADDWF 0xfe1, F, ACCESS
405:               {
406:                  register unsigned char tmr0_temp;
407:                  register unsigned char tmr1_temp;
408:
409:                  /* Read the two timers into CPU registers and reset them
410:                   * as quickly as absolutely possible.
411:                   */
412:
413:                  tmr0_temp = TMR0L;
  04E0    50D6     MOVF 0xfd6, W, ACCESS
  04E2    6EDF     MOVWF 0xfdf, ACCESS
414:                  TMR0L = 0;
  04E4    6AD6     CLRF 0xfd6, ACCESS
415:                  tmr1_temp = TMR1L;
  04E6    0E01     MOVLW 0x1
  04E8    CFCE     MOVFF 0xfce, 0xfdb
  04EA    FFDB     NOP
416:                  TMR1L = 0;
  04EC    6ACE     CLRF 0xfce, ACCESS
417:
418:                  tmr0_value = tmr0_temp;
  04EE    CFDF     MOVFF 0xfdf, 0xe4
  04F0    F0E4     NOP
419:                  tmr1_value = tmr1_temp;
  04F2    CFDB     MOVFF 0xfdb, 0xe5
  04F4    F0E5     NOP
431:
432:               }


texts: RaspberryPi: Load cells and HX711 amplifier

texts:
I've created an app that will read 10 weighing scales at the same time with separate values but since some wires are like 1 meter long, I get so much noises in the values.

I just wanna know if what's the best way to minimize the noises?
Which is better? HX711 near the Raspberry Pi or HX711 near the load cells?


texts: Powering an LED with transistor in saturation mode

texts:
I currently try to design my first transistor circuit to switch an LED on and off. So I came up with this circuit diagram:

I have to use the following components:

PN2222A NPN BJT
IR LED TSAL 6200

What I need to figure out are the values of R1 and R2. So first I picked a desired current of 70mA from the 5V source to GND. According to the LED datasheet, 70mA of current induces a voltage drop of 1.3V. Figure 11 of the transistor datasheet shows that the saturation voltage at 70mA is roughly 0.06V.
Now we can calculate R2 using Ohm's Law:

$$R2 = \frac{5V - V_{D1} - V_{CE(sat)}}{I_{C}} = \frac{5V - 1.3V - 0.06V}{0.07A} = 52\Omega$$

In order to get the base current \$I_{B}\$, I looked for DC current gain in the datasheet. The lowest value is \$\beta = 10\$ as shown in Figure 11. Therefore

$$I_{B} = \frac{I_{C}}{\beta} = \frac{0.07A}{10} = 7mA$$

Which is definitely a problem. I don't want to draw more than 2mA from the logic source as it can possibly be damaged. To stay on the safe side, I need to find a way to increase the lowest possible value of \$\beta\$ to reduce the base current.

Is this the way to go? And if yes, how would I accomplish an increase of \$\beta\$ ?

Please don't tell me to buy other transistors with higher DC current gain, although I will definitely do that later.


texts: I am using a 12V,600 rpm PMDC motor. When I start the motor, it takes a little bit of time to reach its max speed due its inertia. My requirement for a specific task is that the motor should reach the max speed as early as possible. I am using 11.1V,30C ,8000 mAh Li-Po battery. Is there any way to achieve it without changing the motor. Can I use capacitor bank to supply the transient currents for overcoming inertia quickly. Please don't downvote.


texts: Derivation of resistance of coaxial cable

texts:
I've read the derivation for coaxial cables taken from this website.
https://physics.bu.edu/~duffy/semester2/c09_resistance_calc.html

The thing is, I can't seem to understand it but I do know that it did explain it completely. Maybe someone else reading would understand it. I just want to ask if someone could explain it in more detail? Like you can totally use the same variables and derivation as shown in the picture, just explain it differently. That way, I can look back on the source and kind of get what is happening from the more detailed explanations.
What I am familiar with is the basic formula for resistance,
\$ R = \frac {ρL}{A} \$
Based on the information, my face value thought on how the variables were represented are:

Resistance - R -> dR
Resistivity - ρ -> ρ
Length - L -> dr
Cross Section Area - A -> 2πrL

Well I think it's wrong somewhere. I think the dr is suppose to be associated with the cross section area. So I would appreciate it if the analogs from the original formula could be explained. I can take over the solving from there, since I am familiar with integral formulas and the dr/r definitely results to the answer having a natural logarithm. a is the lower limit, the radius of the cable and b is the upper limit which is the radius of the cable including the insulation.


texts: How can I determine a maximum run length for CANbus?

texts:
I'm using CANbus to communicate between two circuit boards. 120 ohm termination resistors on either end. Transceivers are MCP2561 and ISO1050. Bit rate is in the hundreds of kilobits/second. Medium is four-conductor 22AWG twisted cable, with the other two conductors carrying 9V and signal/power common. I'm not concerned about voltage drop on the power lines, only about signal integrity.

Is there a means by which one might go about estimating the maximum run length of a configuration like this? I don't need an answer down to inches; an order-of-magnitude answer is close enough for my purposes. But I haven't any idea where to start.


texts: Do constant current LED drivers consume significant current when all outputs are disabled?

texts:
I'm trying to understand the datasheets for several shift-register constant-current LED drivers, such as TLC59281, TLC5916, CAT4016, IS31FL3726.
All of them have something similar to this in their electrical characteristics:

In this example the "BLANK" pin is an ENable pin. Am I reading it correctly that it will consume 1mA even when disabled?
Or does the Vout = 1 imply that it would not consume current if Vout were 0V? Or is the only way to have a very low power mode would be to put the whole thing in front of a big mosfet?
example datasheet: https://www.ti.com/lit/ds/symlink/tlc59281.pdf


texts: What causes a varistor to have low resistance when connected to a board?

texts:
I was inspecting the control board on a non functioning opener motor, there are no visible blown out components. No skid marks. I went to testing conductivity on the fuse component, good across there. After some googling, I saw you can test varistors via checking for infinite resistance. So I tapped all of them, one (10D431K) was reading low. I pulled it off the board and hit it with the leads of my mulitmieter, but then it read ok like the rest. I had a spare, I soldered back in and I got the same low reading from a new one.
Some backstory
The opener is fairly new one so I was trying to save it, or make an attempt before replacing. I had the panel replaced in my house, there was some 'creative workarounds' done by the previous owner so I don't quite know what happened when power went back to the garage, but nothing worked and it took some extra steps by the electrician to complete the job. It sounds as if ~250V (not 240V) went over the line. The lights and air compressor still function. The door opener, not so much. Verified good power to the board on the internal jumper.
TLDR
What causes a 10D431K MOV to show low resistance on a board, but infinite while not attached? What else should I be testing? Why is it the only one that gives me a reading when the rest show nothing? Down/upstream capacitor?
Note: I'm a curious amateur at best Have soldering iron/multimeter, will travel.
Edit - judging by the comments, I am further out of my depth than I realize. I'll try to clarify.


texts: Differential ADC where input goes below ground rail?

texts:
I've been reading up on differential ADCs but haven't quite wrapped my head around them. I'm a hobbyist with no real training, you see.

I'm wondering, is it possible to use a differential ADC with +5/0 supply and an input signal where the negative input is below 0V? I'm wondering if I just have to keep the signal difference within 5V (like +/-2.5V) or if the signal must be between the supply rails of the ADC?


texts: Should I expect 28 dBi gain if I design properly 2x2 microstrip patch antenna array in which an element has 7 dBi gain? Or expectations should be 10-11 dBi?


texts: Can ST L3GD20 Gyro's Low pass filter be disabled?

texts: I am fairly new to hardware and datasheets and looking at the datasheet of ST's L3GD20 Gyro I know that the high pass filter's frequency can be chosen, but it can also be disabled at all. I cannot understand whether the embedded low pass filter can be disabled too?


texts: Detect Twist-Opened Bottle Cap on Arduino

texts:
I'm building a smart bottle cap. Every time it's twist-open it records a long timestamp to local storage. When user opens a smartphone app it syncs data from storage to phone via bluetooth LE. It is powered by button cell.

What would be the best low-power cost-effective way to detect when cap is twist-open? I have the following sensors: http://amzn.com/B00CBDUD60

I was considering:

Potentiometer
Rotate Encode
Hall Sensor
Tilt/Mercury Sensor

EDIT: Thanks for the inputs! I've actually had the same discussion on arduino.cc forum, and people had reached the same consensus: a simple tactile/pushbutton attached to the inner "roof" of the cap, and covered with a waterproof lid. Here's a sketch: http://goo.gl/MdxIGZ


texts: T-Feedback Circuit Vo/Vi (Why is my approach wrong)?

texts:
Here's what I did. I know it's wrong but I cannot figure out why.

Let \$V_s\$ be the voltage at the node between R2, R3 and R4.

From the ground to \$V_o\$ terminal there is a voltage \$V_o\$ which
is divided over R3 and R4 in such a manner: \$V_s=\frac{V_o R4}{R3+R4}\$

Is this correct?

From the ground to \$V_i\$ terminal there is a voltage \$-V_i\$ which
is divided over R1, R2 and R4 in such a manner: \$V_s=\frac{-V_i R4}{R1+R2+R4}\$

Is this correct?

Now equating the above two equations one gets the wrong answer for \$\frac{V_o}{V_i}\$. The correct approach uses a Thevenin simplification.

I understand the Thevenin approach but what am I doing wrong here?


texts: Is it ok to take out the ICs/components from oven immediately after baking hours? Or is there a standard cool down temperature before opening of the oven after baking?


texts: Creating two branches with similar current using capacitors/resistors

texts:
I am studying for my midterm practical and I am stuck on a basic question. Below is a circuit that will help explain (made in Multisim).

So, we are given this basic structure. All components must stay in their given locations, but their values may change ,but the currents in each individual branch comes out dramatically different when using a Single Frequency Analysis. I assumed C1 = 1.7uF and C2 = 4.7uF because my professor told me that I needed to make assumptions for some values.

My work:

X represents impedance.

$$X_{C_1}=  \frac1{2πfC_1}=\frac1{2*π*60*1.7*10^{-6} }=1560.34Ω $$

$$X_{C_2}=  \frac{1}{2πfC_2 }=\frac1{2*π*60*4.7*10^{-6}}=564.38Ω $$

$$X_{C_1} = X_{C_2} + R_2 $$
$$ R_2 = X_{C_1} - X_{C_2}$$
$$ R_2 = 995.96Ω$$

However, the circuit demonstrates a minimal current difference when R2 is around 1500Ω. What factors am I not including?


texts:
I am using a SAS expander IC. In the datasheet, it is given to use a 150 MHz LVPECL clock with specifications as attached in the snapshot.

Can somebody please explain how to use common mode & differential specifications while choosing a LVPECL clock.


texts: Identifying diode like symbol with two lines going into the "triangle", used in a H-bridge

texts:
I have a question about a special circuit symbol:

The component is a switch of a H-bridge. I checked a few symbol lists like here or here - but I can't find the right component. What is the meaning / component of this symbol?

This is the full schematic:


texts: Is voltage a delta? Can it always be treated as a potential difference from a reference point?

texts:
I've always considered voltage to be absolute, i.e. something that is there or is not there. However, the more I think about it, it seems to be more like a delta.

For example, let's say we have a supply that lists its pins as (A) -50V and (B) 0V. If we treat pin (A) as "ground", i.e. as if it were 0V, can we treat pin (B) as +50V?

Another example might be that pin (A) is +10V, and pin B is +25V, so the potential difference is +15V. Can we treat this the same way as if it were 0V and +15V?


texts: Dance Dance Revolution Floor Sensor -- How Does It Work?

texts:
I'm attempting to build my own dance pad, and after researching a lot of DIY solutions, I decided to see what the original arcade machines use. They use 16 of these sensors per stage --

My question is, how do these sensors work? Are there switches impregnated in the rubber/silicone?

These sensors could be proprietary, but there may be something else out there that works similarly.

Buying 16 of these is cost-prohibitive, so if I can get away with casting some membrane tactile switches in silicone I certainly will.

If nobody knows, I will order one, dissect it, and post results here.


texts:
In systems where there is back-emf induced to oppose the applied voltage, or to change it in cases of power converters, is there a direct way to cancel back-emf or harness it back?

The simplest way to cancel back-emf to me is to increase the supplied voltage from the supply, but is there another way?

Another complicated idea to me, might be an inductor, but what if the back-emf was quite high? Use multiple inductors?

Just wanted to know the possibility.


texts: Auto-Transformer: how to understand the following diagram?

texts:
I have a question about the CW Auto-Transfomer that I will be using.

The wiring diagram is above. As you can see, the equitment takes 277/240/208/120V as input. But on its specification sheets, it never specify the output voltage. Can I assume that regardless of input level, the output voltage (which supplies to the cap and the lamp) will always be the same?


texts: Can capacitor charge to higher voltage than source provides?

texts:
Hi I played with some basic circuits in lushprojects.com simulator and came up with this one that surprised me - when the capacitor C1 is charged for the first time by pressing the SW1 switch the oscilloscope in the simulator displays that its final charge as 8.36V - well above the 5V source voltage.

My question hence is - is it just an inaccuracy in the simulator, perhaps caused by a missing resistor in the charging loop, or can the capacitor in fact charge to a higher voltage then the source?

Thanks!

simulate this circuit – Schematic created using CircuitLab


texts: Could we remove the resistor in parallel with voltage source or in series with current source?

texts: Although this question have been asked. But I want to ask again. I still doubt about it. It is written in "Electric Circuits (9th Edition) by  James W. Nilsson, Susan Riedel". And if we remove it, I think it'd change the power in circuit. I'm confused now.


texts:
Am I calculating total input capacitance or gate capacitance or none of the above? And are my calculations even correct to begin with. The point of this is that I want to know what gate capacitance im dealing with to properly chose a gate resistor to give me the rise time I need, more or less.

So I have the following circuit using the old IRF540

simulate this circuit – Schematic created using CircuitLab

I am probing the gate directly and get the following readings:

I am loosing 500 mV somewhere but anyways:

My voltage at 1 time constant is:
(This is where the dashed vertical line is)

So measuring the time from 0 V (solid vertical line) to the 1 time constant line (dashed) you can see is about 530 ns. So my time constant is 530 ns and the gate resistor is 100 ohm then:

Is my logic correct that this is my input capacitance? And given will this vary if I have same Vds but a Vgs that is NOT equal to Vds?

Extra points: Where are my 500 mV?


texts: Getting a specific voltage output depending on the difference of two voltages

texts:
Can someone please help me come up with a circuit with the following specification? I need to find out the difference of two voltages (can be done using an op-amp). Then, if the difference is negative, I want an output as -1V, if the difference is positive, I want +1V, and if the difference is zero, I want 0V.

I'm trying to build the backpropagation of a neural network using components like opamps etc.
The weight update is given by w_o+ (a*(desired_output - observed output)* input to a neuron). Most of these can be done using multipliers and adders. However I'm not sure as to how can the part (desired output - observed output) be implemented. I know that it can either be 0, 1 or -1


texts: Wrong way usb connexion to MCP73831 lipo charger

texts:
I have a problem with my mcp73831 lipo charger; i have a connection with two neodym magnet connected to usb in one side and my circuit with the MCP73.. in the other side.

There is no problem when i respect the connexion polarity (5v from usb -> to 5v mcp73831 and Gnd from usb -> to Gnd mcp73831).

But, when i change the polarity, the mcp73831 burned... and i was wondering why this IC is not protected from wrong polarity connection ..

So, i want to add a diode with low drop voltage connected to 5v from mcp73831, in forward-biased mode.

I add two circuits to better understand the problem.

Without diode:

And with diode :

Am I allowed to put a diode between the MCP73, would the voltage drop of the diode be too much?


texts: How to ground a vintage device that was powered without a ground?

texts:
This is a follow-up to Is there a mathematical relationship between the battery AH rating, and that of the transformer in the charger

Since that post I've uncovered a vintage battery charger (Manufacturer: Philips Model: PK-5000) in the old house itself. The device looks good, albeit it has probably not seen service in easily 3 decades ... or so; certainly not since I was a little boy.

It has a 2-point supply (without a ground point); what should be done to ground the device so it may be powered by a proper 3-point plug?


texts: Which temperature transducer has these characteristics?

texts:
The resistance temperature characteristics of a temperature transducer is show in the figure below,

The transducer in question is which of the following?
A) Nickel RTD
B) NTC thermistor
C) Platinum RTD
D) PTC thermistor

Note this question is from the 2000 GATE question paper on the Instrumentation subject.

My attempt at a solution

It does not look like Nickel or Platinum RTD,

Can't be NTC since the slope is positive.

I thought it must be the PTC since it has a "critical temperature" after which Resistance shoots up, but switching PTC thermistors have a slightly negative temperature coefficient up to the point of minimum resistance. While the graph shows a positive slope until the "jump off" temperature.


texts: Does an antenna violate the principal of a circuit having a return path?

texts: Seems weird that an antenna has no return path. Also, what about capacitive coupling. How are these circuits?


texts: How does actually the resonance phenomenon help to receive AM signals in a receiver?


texts: Can an FPGA design be mostly (or completely) asynchronous?

texts:
We had a very short FPGA/Verilog course at university (5 years ago), and we always used clocks everywhere.

I am now starting out with FPGAs again as a hobby, and I can't help but wonder about those clocks. Are they absolutely required, or can an FPGA-based design be completely asynchronous? Can one build a complex bunch of logic and have stuff ripple through it as fast as it can?

I realise that there are a whole lot of gotchas with this, like knowing when the signal has propagated through all parts of the circuit and the output has stabilised. That's beside the point. It's not that I want to actually build a design that's entirely asynchronous, but just to improve my understanding of the capabilities.

To my beginner eye, it appears that the only construct that absolutely requires a clock is a reg, and my understanding is that a typical FPGA (say, a Cyclone II) will have its flip-flops pre-wired to specific clock signals. Is this correct? Are there any other implicit clocks like this and can they typically be manually driven by the design?


texts: How can I tell charge-only USB cables from USB data cables?

texts:
Like most computer hobbyists and programmers, I've amassed boxes of USB cables to connect USB, Micro-USB, and Mini-USB to chargers, computers, and gadgets. These cables are a mix of phone charger cables, and cables that came with external hard drives, bike lights, GPS units, and other miscellaneous gadgets. The problem is, they all look the same, just plain black cables.

How can I tell if one of these cables is a charge-only USB cable instead of a USB data cable? Ideally, I would love to rely on some visual clue, but I have a multimeter I could use to test the cables with if I knew a good approach to this.

My goal is to label these cables so I can resolve this ambiguity so when I reach in to my box of cables, I know which cable to use for charging my phone and which one to use to synchronise my GPS with my computer.


texts: Capacitance to digital converter for moisture measurement

texts:
I'm currently working on a irrigation system for which I would like to build a low cost soil moisture sensor. I would like to measure the moisture levels of a given environment based on a capacitance.

So far I was unable to find a differential capacitance sensor (see fig.I)

I had a look at multiple touch sensors controller/button controller/you name it. They all had a ground plane and did not measure in differential mode. Does anybody know a differential capacitance sensor suitable for my purposes.

Note: Due to volume restrictions in my design, I am unable to use a sensor with a ground plane per measurement plane. Also, due to flexibility in the design (see fig. II) I can adjust the copper tube to match the capacity range of the sensor and can therefor not specify such a range.

Note 2: The copper tube inside the plastic tube should function as measurement pads. (see fig. II)


texts:
I'm learning how to program a PIC10F220. I'm using a PICkit 3 programmer and running physical experiments, as well as running the simulator in MPLABX.

One thing I want to do is set the proper level for a port output latch before the tristate (TRIS) switches to output mode. This diagram suggests that it should be possible, and that the input and output paths are separable:

I've written this chunk of assembly:

    ; !GPWU=0: enable wakeup on pin change
    ; !GPPU=0: enable weak pullup on GP0,1,3
    ; T0CS=0: timer 0 internally clocked
    ; T0SE=0: ignored
    ; PSA=0: prescaler assigned to timer 0
    ; PS=111: 1:256 prescaler
    movlw b'111'
    option

    ; ANS1=0: GP1 digital
    ; ANS0=1: GP0 analog in
    ; CHS=00: channel GP0/AN0
    ; GO=0: not converting yet
    ; ADON=1: ADC is enabled
    movlw b'01000001'
    movwf ADCON0

    ; We can write to the GP2 latch even if it's still in input mode;
    ; this ensures no glitch between clearing TRIS and sending the GP2 output.
    ; (but this doesn't work in the simulator)
    btfsc GPIO, GP1  ; Check GP1 status (negative logic)
    goto gp1_off
gp1_on:            ; if it's clear, port 1 is on
    bsf GPIO, GP2  ; turn GP2 on
    goto gp2_done
gp1_off:           ; if it's set, port 1 is off
    bcf GPIO, GP2  ; turn GP2 off
gp2_done:

    movlw b'1011'  ; only GP2 output, others input
    tris GPIO

As in the comments - in real life this works, but in the MPLABX simulator attempted modifications to GP2 have no effect. Why would this be? Have they failed to model the write latch as being functional even when the corresponding TRIS bit is still high (input)?

This seems pertinent:

  BIDIRECTIONAL I/O PORTS

  Some instructions operate internally as read followed
  by write operations. The BCF and BSF instructions, for
  example, read the entire port into the CPU, execute the
  bit operation and re-write the result. Caution must be
  used when these instructions are applied to a port
  where one or more pins are used as input/outputs. For
  example, a BSF operation on bit 2 of GPIO will cause
  all eight bits of GPIO to be read into the CPU, bit 2 to
  be set and the GPIO value to be written to the output
  latches. If another bit of GPIO is used as a bidirectional
  I/O pin (say bit 0) and it is defined as an input at this
  time, the input signal present on the pin itself would be
  read into the CPU and rewritten to the data latch of this
  particular pin, overwriting the previous content. As long
  as the pin stays in the Input mode, no problem occurs.
  However, if bit 0 is switched into Output mode later on,
  the content of the data latch may now be unknown.


texts: MCU selection for developing a baby monitor

texts:
I'm developing a project which involves a device (stationary, connected to mains) making some simple calculations and processing, and then sending an alarm (a simple message to trigger a vibration motor) to one or more devices worn as bracelets .

I began developing with a Texas Instruments CC2530 SoC (2.4GHz, 802.15.4), but I'm facing some issues, mainly related to the range of communication, which is, due to a relatively low output power (4.5dBm at max), very short.
The devices must work inside a home environment, but I don't know how much TX power I would need in such a situation.

Since the RF communication is fairly simple, is it a good to develop such a system using 2.4GHz and a protocol like SimpliciTI or even ZigBee?

What would be other ways to design a system with these specifications? (very simple communication, long indoor range)

I was thinking of the 900MHz band, which is supposed to have a longer range, since communication speed is not crucial to me.

Any ideas for a practical solution?

Thanks,


texts: Current Generalized Immittance Converter (CGIC) Nodal Analysis

texts:
Below shows the current generalized immittance converter. I am trying to derive the transfer function (V3/Vin) of the said filter but I am getting problems in obtaining the voltages at some of the nodes.

These are the equations at the nodes I managed to obtain;

Node V1: (V3-V1)Y2 + (0-V1)Y6 + (Vin-V1)Y5 = 0

Node V2: (V4-V2)Y4 + (Vin-V2)Y7 + (0-V2)Y8 = 0

Node V3: (V1-V3)Y2 = 0

Node V4: (V2-V4)Y4 = 0

Node Vin: (V1-Vin)Y5 + (V2-Vin)Y7 = 0

I realized when I worked down with these equations I was not able to get the correct transfer function so I know some of the voltages into the nodes above are wrong. Can anyone help at least guide me to get the correct equations at each of the nodes so I can work out the transfer function. Any and all help will be greatly appreciated. Thank you.


texts: Powering electronics with a low-cost thermoelectric generator?

texts:
When I replaced my water heater, the installer was telling me how cool the Bradford White unit I got was because the electronics are powered by the same heat used to heat the water in the tank.  I thought it was a cool idea, but didn't give it much more thought after that, until now.

Are there good resources for designing circuits that can be powered with heat?  I couldn't find any information on Bradford White's website, but google turned up this one article about how MIT is researching the use of body heat to power electronics.  I think it's pretty fascinating and would like to play with the concepts, if possible.  I assume that if MIT is currently working on it, then it's way past the ability of my pea brain to put something together, but hopefully someone here can prove me wrong.  :)

EDIT -- I should have thought of Peltiers immediately, but it just occurred to me.  I haven't ever tried applying a heat differential to one and measuring the voltage, but it's worth a shot.

EDIT -- I had to revise the title for this question.  I found a thermoelectric generator, and if its price is any indication, this technology is insanely expensive.  Does anyone know of an inexpensive way to implement powered circuits with a temperature differential?


texts: Can the wire of a high voltage power line be used as the primary coil of an air cored transformer?

texts:
Back in the 90's I heard this story of a guy who in the 70-80's lived remotely near the power lines and that he was very good in electrical engineering and that he had free electricity by using the power line as a primary of an air cored transformer.

Besides the utter danger of going anywhere near the power lines I find it unlikely that having the second coil at a safe distance (which might be at least 10 meter) still can make this arrangement act like an air-cored transformer.

Is this theoretically possible or is it just a myth?

Disclaimer !!!

This question is for pure scientific/theoretical/possibilities curiosity.

Messing with the high voltage power line and its proximity is very dangerous, potentially lethal and most certainly illegal.


texts: Relationship between Transformer Weight and Cooling Method

texts:
Recently I was studying that for 3 Transformer each of 100 MVA, 500 kV/132 kV transformer, three different cooling methods are being used:

For first one we use Force Oil cooled
Second uses Self-oil cooled
3rd one uses Forced air cooled
The content said that forced oil cooled transformer is heavier than force air cooled and self-oil cooled is the lightest one. Why is it so?


texts: Detect presence of multiple (200-300) RFID tags on a single surface

texts:
I'm working on a project where I want to detect presence of multiple (200-300) RFID tags on a specific surface. I have a general understanding of electronics, but no experience with antennas and RFID.

The surface would typically be a 20x20cm-30x30cm flat antenna on a table connected to a raspberry pi, and I would like to somehow get access to a list / array of the ID's for all RFID tags present on top of the antenna.

For example; Les say I tag 300 Lego pieces with RFID tags and use 250 of them to build a 30cm high structure on top of my antenna, then I would like to access the ID's of the 250 pieces I've used in an application on my raspberry pi.

Is this doable with reasonably affordable components? Any suggestions to what sort of antenna I should be looking for, and where I can get one?


texts:
I'm trying to control a device using a digital potentiometer (AD5245S). In my application I can't tie the low-ref of the potentiometer and ground, so I'm using an I2C optical isolator (ISO1541) to isolate digital potentiometer and power isolated circuit using potentiometer lo-ref and hi-ref.

Cirquit works fine, but I see noise on the wiper when any device is communicating using I2C. I was thinking that connecting SDA pullup to potentiometer low reference somehow messes the results (like connecting a resistor in parallel to potentiometer). Or maybe I just have digital noise, because I haven't added bypass capacitors to devices. Can you see what can cause this behaviour?


texts: What are low cost circuit and PCB design software?

texts:
Do you know of any freeware or low cost circuit / PCB design software?

I know a few which I have listed below but I was wondering if there were more of its kind. Please mention the good features and issues you've faced with the software.


texts:
This oscillator provides clock to an FPGA which powers the ultrahdmi mod for an N64 (https://www.retrorgb.com/ultrahdmi.html).
It's clearly marked
A03ZZ
1414
Clock output is diametrically opposite pin 1, it's a 4 pin device, it takes a 3.3V supply. Dimensions are nominally 3.2mm by 2.5mm
When I scope it with my limited equipment I get a weak ~75MHz signal (50mv p-p), but that could be junk from a number of sources.

The story behind this: it came to me with a glitch where it would lose on screen display functionality over time. Careful application of compressed air suggested the oscillator was the culprit, so I tapped it with the soldering iron on all 4 corners - now the device simply doesn't work. I've since fixed the bridge between the land and the exposed leadframe to no avail. I'd  like to try replacing this part with something as close as possible, but if we fail to identify it SMD oscillators are cheap enough that I'll buy a spread of spectrum and try em all if I have to.


texts: Bus arbiter that can handle multiple concurrent requests vhdl

texts:
I am working through a weird problem. We are pin constrained on our FPGA and need to control a common bus. This was all fine and good as all the software was sequential, but now some requests will be coming in at the same time for devices, but will now have to be put into a queue.

How should I take care of making sure that everything gets shoved into a FIFO without priority and without dropping data? I've got the outer design complete for controlling everything up until the bottle-neck where everything gets shoved into the pipe before being granted access to our "bus". Some requests will take a long time to come in, but will do so concurrently from an FPGA whereas software commands will come in sequentially, but less predictably. If I don't care about the order in which I grant access to the "bus", what is the best way to pipe all of this information into a single FIFO under the assumption that some commands will be coming in at the same time without knowing how many there will be? I would like to avoid having to request/ack/grant if possible as I would like all of this to be taken care of by a single component that just receives a bunch of data and takes care of the complexity. What is the easiest way to accomplish this?


texts:
So this is the cicuit for a 1h0257j VolksWagen polo vacum pump for central lock. I got it for practice since it was replaced.
The question the problematic part seems to be a burned soldering, it is just a bridge but since the water damage made it more and more isolated and at the end gave in. So, how do i liquidate the burnt solder? Tryed heating it but it didn't do anything and can't heat it further without damaging the board itself.
On a side note i removed the legs of the connector since most some of it was burnt too (mainly the power suply slots) but i can't seem to be able to soak up the damaged solder, i used striped (new and clean) cooper wire. I tryed to add some flux thats what the shiny part is, the burnt part around the already liquified solder are just the is oxid i could't remove from it with alcohol and brush on the first run.


texts: Standing Wave ratio vs frequency in power transmission lines?

texts: What is the relationship between Voltage Standing Wave Ratio (VSWR) and frequency in context of transmission lines?


texts: Link footprint to schematic KiCad (version 4.02)

texts:
I can't seem to figure out how to link footprints I created to their schematic counterparts.

I created the schematics in the schematic library editor then connected them up in Eeschema just fine, but after creating a new footprint in the PCB footprint editor, I saved as a footprint in a new library, went back to the Eeschema window clicked >Preferences>Component Libraries>Add>path/newlibrary.pretty but my new footprint doesn't appear in the list of Component library files in that window, or in the list when I right click on a schematic component > Edit component> Footprint> Select.

I have tried to follow the steps in both of these, but they both appear to be using previous versions of the software. Does it have something to do with the .pretty folder, I don't see that mentioned in either of these.

https://www.youtube.com/watch?v=aVNMJVaRf6M

http://mithatkonar.com/wiki/doku.php/kicad/footprint_management

Thanks in advance, I am sure its something small since this is my first time using the program but I have been stuck on this for days and keep coming back to it.


texts: Import DXF defined padstacks in to Allegro/Orcad PCB

texts:
I'm using Orcad PCB Professional 17.4-2019 S017
I've got a symbol with some funky pads on it, one the padstack editor cannot generate.
Here's where I'm trying to get to. Green is mask boundary, blue is top etch, Grey is paste, red is package boundary, white is silk, purple is construction lines.
Note the goofy pads on the corners.

I know you can create a new flash symbol drawing and import a DXF in to it, save the flash, and use that in the Padstack editor. That is going to be more painful than I think it ought to be. The pads are more than rotationally different from each other.
Anyway, what I would like to do is design the symbol in Orcad PCB Pro such that the symbol is close to the real design, export a DXF, modify the problematic pads in AutoCAD, and bring the DXF back in, and export the new modified padstacks.
The section in the manual called "DXF Bi-Directional Interface" makes me think such a thing is possible. There is even a "PADSTACK" block section in the DXF file.
I made the following symbol in Allegro to get me close.

Export the above symbol in DXF using the following settings:

And using the attached CNV file (At the bottom).
And when I just reimport the DXF file unchanged, using the following settings:

I Receive the following error:

And the symbol drawing appears broken.
I would love some tips or help.
Incase the CNV file didnt' attach, here's the text of it (forgive the formatting):
#This is the Layer Conversion File used for
#importing DXF data into Allegro/APD.

#CLASS!            SUBCLASS!                           DXF_LAYER!

COMPONENT VALUE!
                   SILKSCREEN_TOP!                     CV_SILKSCREEN_TOP!
                   ASSEMBLY_TOP!                       CV_ASSEMBLY_TOP!

DEVICE TYPE!
                   SILKSCREEN_TOP!                     DT_SILKSCREEN_TOP!
                   ASSEMBLY_TOP!                       DT_ASSEMBLY_TOP!

ETCH!
                   TOP!                                ET_TOP!

PACKAGE GEOMETRY!
                   SOLDERMASK_TOP!                     PG_SOLDERMASK_TOP!
                   BODY_CENTER!                        PG_BODY_CENTER!
                   SILKSCREEN_TOP!                     PG_SILKSCREEN_TOP!
                   PIN_NUMBER!                         PG_PIN_NUMBER!
                   PLACE_BOUND_TOP!                    PG_PLACE_BOUND_TOP!
                   ASSEMBLY_TOP!                       PG_ASSEMBLY_TOP!

PIN!
                   TOP!                                PIN_TOP!
                   BOTTOM!                             PIN_BOTTOM!
                   FILMMASKBOTTOM!                     PIN_FILMMASKBOTTOM!
                   FILMMASKTOP!                        PIN_FILMMASKTOP!
                   PASTEMASK_BOTTOM!                   PIN_PASTEMASK_BOTTOM!
                   PASTEMASK_TOP!                      PIN_PASTEMASK_TOP!
                   SOLDERMASK_BOTTOM!                  PIN_SOLDERMASK_BOTTOM!
                   SOLDERMASK_TOP!                     PIN_SOLDERMASK_TOP!

REF DES!
                   SILKSCREEN_TOP!                     RD_SILKSCREEN_TOP!
                   ASSEMBLY_TOP!                       RD_ASSEMBLY_TOP!

#END

Thanks!


texts: how to filter out noise while measuring voltage across H bridge?

texts: I am using a 3 ohm resistor in series with H bridge driver to detect stall current. When it stalls the current shoots upto 200 mA causing a drop of 0.6 V. I am measuring voltage across the H bridge so, I will sense a voltage of VDD - 0.6, based on which I can decide that the motor is stalled and I can stop driving the motor. My question is will the voltage across the bridge will be very noisy. I am giving the voltage input to ADC of the micro controller directly. Is it manageable in software itself to filter out the noise?


texts:
I am looking for a suitable solution for my challenge:
I want to run a 12 V water valve (0.5 A current) with Li-ion 3.7 V - 4.2 V batteries while being able to charge these from a 5 V solar panel (or USB).
Two solutions came to my mind:

Connect the batteries in parallel (resulting in a 3.7 V), boost to 12 V to run the valve and charge with an ordinary 1S charger.
Connect in series (3S coming at ~12 V) and somehow boost from 5 V to 3S charging voltage and charge with a BMS+Battery charger the 3S pack.

I would love your suggestions on what is the best approach to this problem (energy efficiency, product availability)


texts: System recommendation smart citizen measuring noise and air quality

texts:
I really much like the idea of citizen science movement. After researching a couple of projects and tinkering around with Arduino (ESP8266) and Raspberry Pi I was not sure what to use. Especially the sensors seemed a really complex topic.
Then I came across the following projects and found them fascinating:

Smart Citizen - Barcelona based project measuring light, noise, temp., humidity, PM etc.
sensor.community - Stuttgart based project focusing on PM and noise
safecast - Tokyo based project focusing on radiation and PM

Considering the above platforms and the option to build something from scratch, what would you recommend? My focus so far is on noise and air quality, which I want to measure over time - more  may follow.
Any recommendations and hints into other directions would be really much appreciated!


texts: Ideal voltage regulator for power amplifiers

texts:
I'm working on a dual rail power supply that will provide DC current for 4 power amplifiers.

Two of them require 20V and the other two 25 - 50V. All 4 draw a maximum of 2.5A of current, hence my transformer is 24+24V, 10A. Currently I have the output of the transformer to a rectifier bridge and on each rail 10.000µf capacitors, resulting in 35V.

My question is: how I drop this voltage to 20V, allowing a maximum of 5A of current to flow through? I've read about shunt regulators but it seems I would need a very large resistor and zener for this amount of current.

Are there other options? Which is the most suited for this case?


texts: Separate CAN messages having same ID in function of data content

texts:
I am working with some temperature and pressure sensors. These sensors send the messages to a receiver connected with Dewesoft Sirius. In this way I can read the CAN messages on my laptop.
The problem is that every sensors send messages with the same ID identifier so I have an unique channel for every sensors. The ID of the sensors is in the message content together with other informations as temperature and pressure. So I would like to create different channels for every sensors I have in order to read each sensor informations in specific channel and create separate plot for every sensor.
Is there a way to do this? Thanks to all.


texts: Why can't resistors be used to connect cathode pins to GND instead of segment pins to VDD with a 7-segment display?

texts:
When using a common cathode 7-segment display, is there a reason that two resistors can't be used to connect the two cathode pins to GND instead of using seven resistors to connect the seven anode pins to VDD?

I'm assuming there's a good reason, because I haven't been able to find any schematics that do it this way, but I'm unsure of why this would not work?


texts:
I am having some problems designing a HV DC DC converter. I have 12v input. The device that needs such high voltages is a UVTRON sensor from Hamamatsu. The devices need a supply voltage of 325V to 400V (+-25V). The datasheet can be found here. Because it is unsure which sensor we will be using we need to easily change from one to another, soldering is allowed. In the final design it will be fixed.

The required power is very low, and as such designs I find floating on the web are not always great for this application because of safety.

My current approach is using a transformer (750311468 from Wurth Elektronik for example) and using a mosfet + controller (which I already have) to convert the DC signal to a square wave. However with such high voltages I am unsure if the approach I am taking is right. Also the dangers involved makes this a big risk. I do not want the transformer unleash all of it's current in a saturated state on a person.

I also looked at the Cockcroft–Walton topology but in simulations it seems impossible to get the voltage accurate enough.

Do you guys know of topologies which give me a voltage between 300V and 400V and are "safe" to use in this application?


texts: Effects of 200R (199R) instead of 220R in this circuit

texts: I'm building a MIDI in circuit, and I found out my batch of 220R resistors are actually 199R... Can this cause problems/have negative effects for using in a MIDI In/Thru circuit ?


texts: Adding a volume control for headphones, driven by microcontroller

texts:
I'm currently driving a pair of earbuds with this circuit:

P0 is directly connected to a 3.3V microcontroller pin, which is using PWM to drive it.

I "stole" this filter circuit from the upper left corner of this schematic.  I modified it slightly, since I am driving stereo headphones from a single mono input.

The problem I'm running into is that the sound is really loud.  I would like to add a volume control.  I've read through How to make my own volume control for headphones?, but my situation is slightly different:

I don't have an amplifier.
The signal I'm starting with is 3.3V, rather than 1V.

My questions are:

Should I put the potentiometer before or after the filter?  Or does it not matter?
Should I use a 1K pot, as mentioned in the other question, or does my situation require a different value of pot?  More importantly, how do I calculate this value?  (The other question doesn't explain how the value 1K was chosen.)

Thanks!


texts: Where do I lookup values for building a USB HID descriptor?

texts:
I'm trying to educate myself a bit on creating a USB HID descriptor in C for a PIC32 USB project I want to attempt.

I've downloaded the HID Usage Tables document from http://www.usb.org/developers/hidpage/ and trying to figure out where the actual values are indicated for different elements in the HID descriptor.

Let me explain with an excerpt from the sample I'm looking at:

ROM struct{BYTE report[HID_RPT01_SIZE];}hid_rpt01={{
  0x05,0x01,        // USAGE_PAGE (Generic Desktop)
  0x09,0x05,        // USAGE (Game Pad)
  0xA1,0x01,        // COLLECTION (Application)
  0x15,0x00,        //   LOGICAL_MINIMUM(0)
  0x25,0x01,        //   LOGICAL_MAXIMUM(1)
  0x35,0x00,        //   PHYSICAL_MINIMUM(0)
  0x45,0x01,        //   PHYSICAL_MAXIMUM(1)
  // ...

From the above example, it is clear that the BYTE array is constituted of key/value pairs, if I may call it that. For example the 2nd line: 0x05,0x01 indicates the key 0x05, which is the Usage Page, and 0x01 is the value indicating Generic Desktop

I'm trying to figure out where these values are indicated in the HID Usage Table PDF document. For instance, I can find no reference that

USAGE_PAGE == 0x05

and for example

COLLECTION == 0xA1

I tried searching the PDF for 0xA1, no result. The only way I am able to find out what the values are, is by either looking at the comments of the example, or by using the USB Descriptor Tool from the link above.

I'm just wondering, am I totally daft for missing this key/value reference documentation?

There are loads of examples online, like for example the following link: http://www.frank-zhao.com/cache/hid_tutorial_1.php

But even this references loads of string values like END_COLLECTION == 0xc0

Where do I find the reference for these values? What am I missing?


texts: Solenoid flyback considerations in this pFET/nFET inversion circuit

texts:
I am trying to combine FETs, where logic permits, to reduce the size of a pcb. Is it poor practice to have the pFET's gate and nFET's drain shared by an inductive load that will usually be grounded through the same nFET? The voltage polarity and the Vg requirements against Vs of the pFET make me want to assume it seems feasible, but just want to be sure. Should the snubber diode be specified with a reverse breakdown as low as possible so as to at all protect the limitations of Vgs on the pFET, or will the snubber fully ensure no transients?

Thanks