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  1. KrisBlueNZ

    LM3524 PWM pin 10 shutdown voltage

    0.7 volts is suspiciously close to the base-emitter forward voltage of the two transistors connected to that pin. You asked what voltage "is needed" on that pin, and I suggested 2~5V. My meaning was that if you want to shut it down, applying 2~5V to that pin will do that. I did not mean to say...
  2. KrisBlueNZ

    High frequency PWM dimming of LEDs?

    Are you sure the LED module doesn't actually make contact with the wires inside the insulation, like an insulation displacement connector?
  3. KrisBlueNZ

    LM3524 PWM pin 10 shutdown voltage

    Hmm, I see what you mean. The data sheet isn't very helpful. It does show the internal circuitry though, and based on that, and the suggested current of 1 mA into pin 10 to shut the device down, a voltage between +2V and +5V on pin 10 will shut it down.
  4. KrisBlueNZ

    Sorting things out with a small circuit

    No, the iPhone and other USB devices include a charge current regulator that limits the current drawn from the USB port. Find the charger that was supplied with the iPhone and other USB device and see what current it's rated at. Often they're about 1A. Your 5V regulator only needs to be able to...
  5. KrisBlueNZ

    Comparator inputs

    Thanks for those answers. I'm afraid I'm still not sure what you want, but here's what I have so far. I'm not sure whether this circuit will do everything you want. Have a look at the description and let me know. I haven't worked with current transformers before, so if you use this circuit...
  6. KrisBlueNZ

    High frequency PWM dimming of LEDs?

    Oh, so you HAVE built it. You answered one of my questions by accident LOL. What kind of problem do you think an irregular waveform would cause? I don't think it will make any difference to the LEDs; they'll only draw current on the positive peaks of the waveform anyway.
  7. KrisBlueNZ

    High frequency PWM dimming of LEDs?

    Sounds like you're trying to reverse-engineer a system that you don't have direct access to, and don't know much about. Every guess you make is potentially a reason why your version won't work. Good luck; you'll need it!
  8. KrisBlueNZ

    Component help

    The data sheet I have doesn't mention 80 mA anywhere. It says the BuckPuck is available in four maximum current ratings of 350 mA, 500 mA, 700 mA and 1A. The actual output current can be controlled in several ways. It should be easy to set the maximum output current to 900 mA, then control the...
  9. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    No; resistors are not polarised.
  10. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    The value isn't critical at all. 18k, 20k or 22k is fine. 1% metal film is best. 1/4 watt or higher.
  11. KrisBlueNZ

    Comparator inputs

    I'm not totally clear on what you want to do. I've mostly designed something that MAY do everything you want. It would be best if I describe it to you, and you tell me whether it's right or not. I'll do that tomorrow. Your last post was very helpful but I still need one other piece of...
  12. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    I'll describe how to add the resistor. The resistor is a cylindrical thing with a wire coming out each end. (Don't get a surface mount (SMT) resistor!) Cut one wire to about 1/4" long and solder it to pad D. Now you need to solder the other lead to pads B and C (both of them). Try to make a tidy...
  13. KrisBlueNZ

    Component help

    Check out another thread here: https://www.electronicspoint.com/interfacing-microprocessor-and-buckpuck-led-driver-t256123.html In the first post there's a link to a switched-mode constant-current LED driver called a "buckpuck" that might be just what you want.
  14. KrisBlueNZ

    High frequency PWM dimming of LEDs?

    I'm no expert on this subject, but I think your approach has several serious problems. I don't see how you can use a twisted pair of wires (with equal currents flowing in opposite directions) as the primary of an inductive coupling system. The whole idea of twisted pairs is to reduce...
  15. KrisBlueNZ

    Hissing in ATX power supply.

    LOL :-) Be grateful that it's just the fan. Much simpler to diagnose and replace! Edit: BTW, my post wasn't clever. That's exactly what freeze spray is used for, in the electronics field. It wasn't my idea!
  16. KrisBlueNZ

    Hissing in ATX power supply.

    Sometimes a good bash ("percussive maintenance") will stop the fan from making a noise... for a while. Also, changing the angle will do this - try propping the back or front of the machine up slightly so it's not completely level. Generally I think the problem will reappear with time.
  17. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    Yes, but I don't think it would fit into those holes. Also, trimpots have a "linear law" and volume controls have "logarithmic law" (because the ear's response is logarithmic). If you use a linear trimpot as a volume control, you'll find that over most of the range, the volume doesn't change...
  18. KrisBlueNZ

    OEG Relay Problem

    Like Steve said, you should just replace the relay instead of trying to fix it. Digikey and Mouser have information on that relay, but don't have any in stock. It's probably obsolete. But you can download the data sheet for it, and search those sites (Digikey and Mouser, perhaps Newark) for...
  19. KrisBlueNZ

    Comparator inputs

    That's a good design. It uses a few tricks so minimise components and simplify the circuit that make it a bit hard to explain though. The first op-amp operates in the "inverting amplifier" configuration (Google or Wikipedia it), with a gain of about 200 (100k / 470). Its input is the left hand...
  20. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    OK, nice work. Good clear pictures and descriptions and information there. It looks like pin A connects to a tap part-way along the carbon track in the pot. It would be intended for a "loudness compensation" connection, but as you say, it's not connected to anything on the PCB, so you don't...
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