Recent content by foTONICS

  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

    yes they're twisted. The rate is 200Hz and the distance is only about 10 inches or so
  3. foTONICS

    noisy differential signal

    Checked out the datasheet and they mention terminating it with a 120Ω resistor at the RS422 receiver input, I terminated it with the closest I had, 100Ω, and that took away almost all the ringing: But this brings up something that I read the other day concerning transmission line termination...
  4. foTONICS

    noisy differential signal

    Once I get to it I'll snap a picture and show you, just finishing up some more important stuff
  5. foTONICS

    noisy differential signal

    I tested a waveform of similar voltage levels, frequency, and it's also differential and it looks fine:
  6. foTONICS

    noisy differential signal

    Would this 100Ω be across the two differential signals + and - or from the half I'm measuring and ground?
  7. foTONICS

    noisy differential signal

    Yes, Lecroy waverunner6050a I've noted the ringing at 43MHz on the rising edge and 49MHz on the falling edge: Wikipedia mentioned having a sample rate greater than twice the fundamental frequency, in this case 43MHz and 49MHz, does this sound appropriate? ( Wikipedia isn't too too trusted )...
  8. 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...
  9. foTONICS

    slew rates, rise time, and EMI

    I've noticed on some PCB's that a line of vias extend around the perimeter of the board, going down to what I assume to be the grounding layer. If this helps EMI why don't I see it more often? Is it a last ditch effort to contain EMI?
  10. foTONICS

    slew rates, rise time, and EMI

    So designers play a balancing game between keeping EMI low and having fast data transfer rates?
  11. 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...
  12. foTONICS

    Is it my transformer or rectifier?

    I did mention quite a few times when the electrical contractor was here that the P.A. needed it's own dedicated circuit as per the crazy inrush. The first person I talked with wasn't the one who did the work so there may have been something lost in communication to the electrician who actually...
  13. foTONICS

    Is it my transformer or rectifier?

    a very poorly written chinese to english operations manual You're right in your assumption that it's connected to the rectifier. There are four of these total http://cdn.rcmart.com/images/hcg_33000.jpg 33000MFD 100VDC
  14. foTONICS

    Is it my transformer or rectifier?

    Hey Minder/dorke, The electrician swapped out the breaker for a 30A, I turned on the unit, and after a dim of the overhead lights the beast roared to life.....all this work and it turns out just to be inrush which makes me a little irritated that I spent so much time disassembling stuff. At...
  15. 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...
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