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  1. BobK

    Switch Project Help

    I believe the box in the video uses only a DPDT switch, limit switches, a battery and a motor. This project should not need any more than that. Bob
  2. BobK

    thermostat circuit counter

    Okay, I see your point now. They cannot connect to the R and W wires from the thermostat directly. You need access to the other side of the transformer as well. Bob
  3. BobK

    Joule thief

    A sawtooth wave is what you should see. When you put a constant voltage across an inductor the current is rises or falls linearly. Bob
  4. BobK

    8-Pin Dip

    Optocouplers are usually 4 pin. Bob
  5. BobK

    IC Gate Tester Survey

    Yes, yes, yes, yes, no. Most ICs I would be using would be far cheaper to replace than to diagnose. I always buy 3 of anything for a 1-off project, and usually have 2 left over. Bob
  6. BobK

    Voltage Controlled oscillator

    http://www.linear.com/product/LTC6990 Bob
  7. BobK

    Switch Project Help

    You post made me think of this video. I have to build one of these eventually. Bob
  8. BobK

    Connecting Li-ion cells in series

    It seems to me that, as long as the two cells are in the same state of charge when paralleled, then always connected together, it should not cause problems. Connecting a fully discharged cell to a fully charged cell, however, would be a major problem. Bob
  9. BobK

    thermostat circuit counter

    Well, the counter uses 90mA and the hour meter has not indication of the current used. It might work, it might not. For that matter, there might not be enough power for another relay. To do it right, you would need to see how much current the transformer can supply and how much is used by...
  10. BobK

    tinkering electronics for mid-life crisis ?

    If you liked the simplicity of DOS, you might like microcontrollers even better. Imagine being in control from the first instruction that executes when your processor come up. Imagine it coming up in microseconds instead of minutes. It's an entirely new world. My day job is as a compiler...
  11. BobK

    3-5 watt audio amp

    In addition the what Kris said, there is a difference in the type of amplifier you use. A typical old-style amplifier is class AB, which will waste more than 1/2 the energy. A newer style is class D which uses digital logic to control the signal and can be 90% efficient. For battery...
  12. BobK

    Help understanding my new multimeter

    Actualy, having a separate mA connect might be worse. In that case, you would blow the fuse even if you had changed the range to voltage but forgot to move the test lead. BTW: I blow that fuse regularly, I keep spares on hand. Often there is a spare kept inside the meter case. Bob
  13. BobK

    Joule thief

    You cannot calculate di/dt, this is going to depend on the characteristics of the load. With the load being an LED this is not a simple function. The voltage produced as the field in the coil collapses, in this case, will rise to just enough for the LED to conduct the current in the inductor...
  14. BobK

    AC power limiting circuit

    How does a light sensor reject a 40W incandescent that puts out less light than a 10W LED? Sorry, but a light sensor is not the answer. Bob
  15. BobK

    ID please

    You are probably right, dave, ignore what I said. Bob
  16. BobK

    AC power limiting circuit

    The idea is not to keep people in the dark, but to enforce use of high efficiency lighting. Bob
  17. BobK

    ID please

    Despite the VZ designation, they look like 27pF ceramic capacitors to me. Bob
  18. BobK

    Joule thief

    1:19 would mean 1 turn in one of the coils and 19 turns in the other. It looks to me like you have 10 turns for each. Not saying this is wrong, just that you describe it wrongly. Edit: never mind, I now see it is 1:1, 9 turns. Sorry about that! That is the classic Joule Thief circuit and...
  19. BobK

    thermostat circuit counter

    hevans, I wasn't recommending that specific device, it was just to show an example. It turns out there are such meters that operate off 24VAC, which is what he really needs. Bob
  20. BobK

    AC power limiting circuit

    Except that I think he is trying to enforce use of LED or CFG as opposed to incandescent lamps. Bob
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