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  1. KrisBlueNZ

    High voltage pad is too near other pads?

    I agree. Xenon flash tube designs I've seen all have a short well-insulated wire running directly from the transformer to the trigger electrode. The trigger voltage shouldn't be connected anywhere on the PCB.
  2. KrisBlueNZ

    Theoretical Problem

    Yes, the question is short on details. Simplest answer seems to be two zeners reverse-connected in series between the voltage and the 0V reference. The zener that clips the positive excursions needs to be around 9.3V (10V minus the forward voltage of the other zener) and has its cathode towards...
  3. KrisBlueNZ

    Pink noise generator circuit mod

    I think we'll have to go the way I described. Here's an updated schematic. The extra components are RC (220R), DC (1N914) and RP (100K), and SW1 and K1. SW1 is any SPST switch, i.e. a single set of contacts that closes when you want the noise to start up, and opens when you want the noise to...
  4. KrisBlueNZ

    Pink noise generator circuit mod

    Yes. That one needs a current limiting resistor for the blue LED illuminator. Assuming you want to power the illuminator from 15V and operate it at 20 mA (fairly bright), the resistor needs to be R = V / I = (15 - 2.8) / 0.02 = 12.2 / 0.02 = 610 ohms, nearest preferred value is 620 ohms. (the...
  5. KrisBlueNZ

    Pink noise generator circuit mod

    I think you should get the relay that I linked to. I don't think there will be a problem with pops and I think it's a tidy way to disconnect the circuit's output from the amp input when the circuit is powered off. They're only USD 1.80 each. Edit: And a 120 ohm resistor and a 1N914 diode for...
  6. KrisBlueNZ

    Pink noise generator circuit mod

    Pops occur when there is a DC voltage across the contacts before they close. For example if I put the contacts between the coupling capacitor and the 100K resistor to ground. In this situation, if the contacts are open, the coupling capacitor doesn't charge up, because there's no DC path to...
  7. KrisBlueNZ

    Pink noise generator circuit mod

    BobK, mixing the signals together is not the answer, because when the noise generator circuit is not powered, its output will interfere with the signal coming from another source. The junctions in the op-amp's output stage will not be biased, because the op-amp has no power, but they will...
  8. KrisBlueNZ

    record movements in my sleep

    Have you considered ultrasonic (Doppler effect)? Or if you're really keen, an infra-red light and camera with movement detection on the video signal. But I'd go for ultrasonic personally.
  9. KrisBlueNZ

    Pink noise generator circuit mod

    Sure, you can switch the power to the noise generator on and off, but: 1. The pushbutton switch you linked to is a momentary pushbutton. It conducts WHILE you HOLD it in. It's not a push-on, push-off switch. So you would have to hold it in to keep the noise generator going! You need one like...
  10. KrisBlueNZ

    Pink noise generator circuit mod

    Yes that's fine. The pushbutton you linked to is fine but put a 1K resistor in series with it to limit the peak current - it's only rated for 100 mA. I would just use a couple of wires that you can touch together. That's a lot cheaper than a pushbutton! The 100K pots are to set the output...
  11. KrisBlueNZ

    Problems substituting a relay

    That's right, if you use a bridge, the common rail of the circuit is guaranteed to be live. My point is that the circuit should already be isolated for safety reasons, because it must be considered to be potentially live, because it is galvanically connected to the mains. NOTHING ELSE should be...
  12. KrisBlueNZ

    Problems substituting a relay

    You're not supposed to rely on that. Any circuit that is galvanically connected to the mains (whether to Phase, Neutral, or bridge rectified mains) must be considered to be potentially live and must be isolated. Also, reducing the value of the shunt resistor across the series LED will make...
  13. KrisBlueNZ

    Problems substituting a relay

    No, not at all. And I am quite capable of posting barbed comments too. As you say, it's a disagreement about design considerations. I did find weaknesses in the design, and I should have thought about it more before I posted my initial response. On the internet, it's surprisingly easy for...
  14. KrisBlueNZ

    Pink noise generator circuit mod

    Google "stripboard layout". There are several packages, including a web-based one. You could also do it on paper. RS Components have a few N-channel JFETs too. Their best bet is the J310G which is a TO-92 part. MMBFJ309LT1G looks suitable but is SMT. Other ones I found on the RS Components site...
  15. KrisBlueNZ

    Pink noise generator circuit mod

    No, not at all. It was a fair question. I am aware, myself, that people in my kind of work would normally use simulators. I never used them at my previous job, and there were times when using one would have picked up mistakes and saved time. Recently I tried the free simulator at a site called...
  16. KrisBlueNZ

    Pink noise generator circuit mod

    No I haven't simulated or prototyped the circuit! I have reasonable confidence in my ability to design a circuit like this, and I have designed similar but not identical circuits. I actually have very little experience with simulators. I have traditionally tested low-frequency circuits like...
  17. KrisBlueNZ

    Pink noise generator circuit mod

    No problem. The time durations are controlled by RT and RR but are also affected by QA's gate characteristics, which vary significantly from one device to the next, so the best way to get them how you want them is by experimentation using trimpots, at least initially. To reduce the quiet time...
  18. KrisBlueNZ

    Pink noise generator circuit mod

    Here's an updated schematic and a circuit description. Let me know what you think. Circuit description: The low-volume signal from T1 in the pink noise generator enters through CA and RA and is amplified by op-amp UA and fed to the speaker amplifier. RA and the drain-source resistance of QA...
  19. KrisBlueNZ

    Pink noise generator circuit mod

    Here's a first draft of a schematic. It's turned out a bit more complicated than I expected. Have a look and see if you want to have a go at building it. I'm sure you could, but you may want to start with something simpler to get the hang of things if you haven't done electronic construction...
  20. KrisBlueNZ

    Pink noise generator circuit mod

    Those speakers have an internal DSP-based processor for the active crossover (it is bi-amped - separate power ampifiers for the two speaker drivers), which also does compression, so it should be very difficult to overload it with too much input signal. It would be preferable to operate it below...
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