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  1. foTONICS

    Isolated Grounds

    Hey all, So I'm putting together this circuit to test a prototype board and I'm unsure if connecting the grounds on each side of an isolated DC/DC converter is a bad idea. So here is a brief explanation of my circuit: 1. I will be powering this device from a 12V supply 2. The rotary encoder...
  2. foTONICS

    noisy differential signal

    Hey everyone, I was probing a signal at work and noticed that it was very noisy, also that this noise had a very pronounced sinusoidal shape to it. Each spike in the noise is on an either rising or falling edge. This particular signal is the (+) half, RS422. Is it possible that the larger...
  3. foTONICS

    slew rates, rise time, and EMI

    So lately I've been diving (a little blindly) into EMI, ways to contain it, and the different components and/or layout of a PCB that contributes to EMI. Yesterday I came across some articles that mention how the rise/fall time of high speed digital signals can contribute to EMI so it's best to...
  4. foTONICS

    ph4148 vs 1n4148

    Hey everyone, I have a power supply that's busted and I've traced it down to a couple diodes. One is a zener that I was able to identify but the other one I'm not too sure of. There is PH4148 written on it but when I google that I just keep getting redirected to 1N4148 high speed switching...
  5. foTONICS

    Is it my transformer or rectifier?

    Hey everyone, I have a power amplifier that has not been working lately, more accurately it shorts hot and neutral together when I turn it on via the mechanical switch on the front of the unit.I used a multimeter to trace the problem to either the transformer or bridge rectifier. transformer...
  6. foTONICS

    reed switches

    I was just wondering, Since reed switches operate on magnetic fields, can they be used as a fail safe of sorts? Like with transformers or beside a conductor to see if too much current is going through it
  7. foTONICS

    large power amplifier

    I don't really have a question about this, I just figured people may be interested in this large transformer I found inside a power amplifier I have here at work Actually I do have a question. The high wattage resistors across each of the caps, that's to slowly dissipate any left over energy...
  8. foTONICS

    etching my first pcb's

    Hey all, I've always wanted to give etching a shot and recently I've started acquiring all the necessary stuff to do so. It's a little hard being that I don't have a lot of room in my apartment and I doubt the wife wants containers full of ferric chloride on the kitchen table but there's always...
  9. foTONICS

    eagleCAD DRC

    Hey everyone, I'm a newby when it comes to laying out PCB's and have run in to a limitation of sorts, was wondering if anyone had any insight. I have an automotive relay that I'm trying to stick on my board and two of the pins have pads that are overlapping, see the bottom left of "pad...
  10. foTONICS

    FPGA circuit design prerequisites

    Hey all, Just wondering. I've always been interested in FPGA design, VHDL, and programming microcontrollers with C. I'm wondering if I have the right background to possibly do freelance FPGA work in the future. I went to school for electronics engineering technologist (3 year program). I work...
  11. foTONICS

    questionable RS-232

    I was probing an RS-232 connection at work and came across this waveform. At first it looked okay but as I zoomed in I noticed there were no nice clean transitions, is it normally this rounded or is this waveform being distorted by something?
  12. foTONICS

    Using Vref as the input to comparator module

    I have a PIC16f627a uController and I want to use the comparator module. One input to this comparator will be a signal from a sensor and the other input will be from the Vref pin on the uController itself. The datasheet mentions that when using the Vref pin I should use a buffer (like a 741...
  13. foTONICS

    attempting to fix my broken laptop charger

    So I have an Acer laptop with your typical charger (120VAC in/ 19VDC out) that connects the laptop to the wall. This morning it stopped working. Using a multimeter I tested the connection between the wall and charger and got 120VAC. Then I checked the end that goes into the laptop and got...
  14. foTONICS

    C vs C++ with uControllers

    Hey all, I love programming uControllers and for the most part I use C. The other day while chatting with a friend he asked me if I program in C or C++. Now I have to admit I didn't know the difference between the two. I did some research and from what I found C in a top-down approach and is...
  15. foTONICS

    sniffing with a sniffer

    Hey guys, So in my particular line of work we sometimes need to send out equipment for emissions (RF emissions, not exhaust) testing. We borrowed a spectrum analyser but do not have the appropriate loop antennas so we decided to make our own. One of the engineers gave me a little back theory...
  16. foTONICS

    NRF24L01

    Hey everyone, I've got this NRF24L01 RF wireless transceiver. datasheet -The pin in question is the IRQ which is an active low interrupt pin. -I'm interfacing it with a PIC16f627a uController -The IRQ pin will connect to the PIC's interrupt on change pin (PORTB), when the NRF receives...
  17. foTONICS

    Will this work?

    So I have this 12V 20A SPST toggle switch that has a built in LED. Now when I first bought this thing I was under the assumption that the LED only turns on when the switch is in it's 'ON' position, but after looking at the datasheet some more I realized that it's always on, regardless of switch...
  18. foTONICS

    bit shifting

    so I know that: 6 << 1 will shift 0110 to become 1100. so I have this variable "sPORTA.port" that I will load with data, shift it, then store the data into PORTA. So I want to shift bits one at a time so I tried: sPORTA.port << 1 but that doesn't do anything, so I tried...
  19. foTONICS

    static electricity

    So I'm sitting at my cubicle and I need to work on something, problem is I don't have a connection for my anti-static wristband so I just figured I would connect to the case of my PC. Now I wasn't 100% positive if the case to a PC is grounded so I googled it and came upon this response from...
  20. foTONICS

    lighting a 7 segment LED

    Hey all, I'm writing some code that counts the number of times an interrupt has occurred then displays it on the 7-segment display. When it comes to lighting each individual segment (a,b,c,d,e,f,g) is it normal practice to light all of them at once or in sequence? I ask because I've noticed...
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