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  1. KrisBlueNZ

    +/- voltage to ADC

    You may be able to avoid op-amps altogether. V1 represents your source signal (±10V). V2 is your 5V power supply. R1~R3 do the rescaling and offsetting so that the full input range is mapped to 0~5V. You can change the resistor values as long as you keep them in the same proportions. ADCs...
  2. KrisBlueNZ

    Fine temperature control (Triac + temperature sensor)

    Yes that's right. We're talking about a heating load, not a light bulb, so it's fine to switch it ON and OFF with a cycle time measured in seconds.
  3. KrisBlueNZ

    Variable voltage dropper for speed control of tattoo machine

    I really don't think there's a problem. I'm awake at random times. Folks get immediate replies from me at all times of the day or night. I'm trying to make people wonder if I'm super-human :-)
  4. KrisBlueNZ

    Component suppliers

    I don't know why that would be a problem. Mine works OK with tantalums over 10 µF. I was meaning, do you have any suggestions for changes to the "component suppliers" resource?
  5. KrisBlueNZ

    KLH R3000 Stereo Receiver wont turn on.

    By replacing it and seeing what happens!
  6. KrisBlueNZ

    Fine temperature control (Triac + temperature sensor)

    Right. You'll need a more complicated control circuit, I think. Assuming that the control circuitry is a separate transformer-powered circuit, you will probably want to use an optocoupler to drive the gate of the triac - something like the MOC306x series. These include a zero crossing detector...
  7. KrisBlueNZ

    Component suppliers

    Looks like it's a jazzed-up version of the one I just got: http://www.ebay.com/itm/281235252022. It uses an ATMEGA328. Designed by a guy in Germany who specifically says it's free for non-commercial use... which is why folks are selling it on eBay at a profit! Do you have any suggestions for...
  8. KrisBlueNZ

    KLH R3000 Stereo Receiver wont turn on.

    I don't know. It may not be the only problem. There's one way to find out though.
  9. KrisBlueNZ

    Variable voltage dropper for speed control of tattoo machine

    You mean the emitter is close to 0V? What internal resistance did you assume for the battery when you did that simulation?
  10. KrisBlueNZ

    Putting LEDs In My Drums

    Yeah, you won't get enough energy from any normal microphone to light an LED. But you can amplify the signal from a ribbon or dynamic microphone and use that signal to control an LED or an LED strip.
  11. KrisBlueNZ

    KLH R3000 Stereo Receiver wont turn on.

    Then I would assume the failure of the original supercapacitor was not caused by an external problem, and install a replacement.
  12. KrisBlueNZ

    KLH R3000 Stereo Receiver wont turn on.

    OK. Now do you think it might be a good idea to buy a supercapacitor and install it? You may want to check the voltage across the supercapacitor position to make sure there's no other fault in the circuitry. If the voltage is greater than 5V that would explain why the original one failed, and...
  13. KrisBlueNZ

    Variable voltage dropper for speed control of tattoo machine

    I don't know what you mean. Can you define the path this current will take? That won't be a problem unless the battery can supply dozens of amps. And a resistor in series with the base wouldn't help unless a capacitor is added from the base to 0V to force the transistor to "soft-start" the motor.
  14. KrisBlueNZ

    Chicken Coop Door Opener

    Sorry. The first one was a typo. I've added an edit in the post. You're right. When the door reaches the fully closed position, the magnet activates the switch (which is at the fully closed end of the door travel). The switch closes to 0V and pulls the controller pin low. The controller pin...
  15. KrisBlueNZ

    Fine temperature control (Triac + temperature sensor)

    Why would you want to leave the gate floating? Normally the gate is driven from a low impedance source that's referenced to MT1, which is normally the 0V rail of the circuit. Often there's a low-value resistor, and sometimes also a capacitor, between the gate and 0V as well. The gate normally...
  16. KrisBlueNZ

    Power supply

    OK, that's obviously a different circuit from the schematic you posted. We will need to trace out the design of that board. I'll need to see photos of both sides of the board, in focus and with enough detail to make out the markings on all components and the paths of the copper tracks. It looks...
  17. KrisBlueNZ

    Treadmill dead need to track down parts!!!

    Wondering why specific component is suspected. Unable to read marking due to focus. Thinking bigger picture vs assuming board discoloration indicates failed part.
  18. KrisBlueNZ

    LED TV - power circuit damaged after lightning strike

    Right. And a matching package (TO-220) and polarity (N-channel). Gate-source voltage is unlikely to be important. Aim for one that's not too over-rated for current - high-current MOSFETs switch more slowly.
  19. KrisBlueNZ

    Hardware to play loud MP3 in traffic?

    Yes. According to the battery type comparison at http://en.wikipedia.org/wiki/Comparison_of_battery_types the highest energy per weight is Lithium Polymer.
  20. KrisBlueNZ

    KLH R3000 Stereo Receiver wont turn on.

    You could, but you'd might as well not bother. That's a 47 nF capacitor - one millionth of the capacitance of the supercap. If you're not going to replace the supercap with another supercap, just remove it.
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