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  1. BobK

    LM317 2N3055 Variable Circuit Problems

    Depends on what you mean by an ammeter. If the meter is spec'ed to read the range of current you need, you simply put it in series with the output. If you are talking about an analog meter that reads 0-1mA, however, a shunt is needed. Also, there can be a problem if the ammeter is powered...
  2. BobK

    Amplifying current in a sine wave

    Yes. A class D amplifier can handle sinusoidal signals. If the DAC output is 0-5V he most likely has a 2.5V peak signal with 2.5V DC offset, well within the range of a class D amp running off 5V, assuming you remove the DC offset. In fact, if I am right about that, a bridged class AB amp...
  3. BobK

    Amplifying current in a sine wave

    A class D amplifier can get pretty close to 5V peak with 5V power. Bob
  4. BobK

    LM317 2N3055 Variable Circuit Problems

    Okay, that explains it. I am surprised only 2 of the pins were marked. Bob
  5. BobK

    Another find at the Habitat for Humanity Restore

    Ha Ha. I didn't actually buy it. I think they were asking $125. Bob
  6. BobK

    90v/100a DC Power Supply

    Sorry, I tried to but I hurt my back trying to lift it and ended up in the ER. Bob
  7. BobK

    90v/100a DC Power Supply

    Hey, I've got a variac for you that will actually handle what you need: https://www.electronicspoint.com/threads/another-find-at-the-habitat-for-humanity-restore.280397/ Seriously, this is the kind of equipment you would need for that kind of power. Bob
  8. BobK

    LM317 2N3055 Variable Circuit Problems

    There are 4 pins, right? Two marked AC, one marked + and one marked -, right? Bob
  9. BobK

    90v/100a DC Power Supply

    Okay, so 90 x 90 x 30 = 8100W Residential circuits in the U.S. typically max out at 240V 30A which is 7200W. The 120V circuits are typically 120V 15A or 20A which is 1800 or 2400W. Bob
  10. BobK

    90v/100a DC Power Supply

    90V x 100A is 9000W. Where are you getting this power? This is well above the capability of residential wiring. So is this industrial 3-phase power? What voltage? Bob
  11. BobK

    Amplifying current in a sine wave

    Something must be powering the DAC. They do not produce a voltage by themselves. Bob
  12. BobK

    LM317 2N3055 Variable Circuit Problems

    It should not get hot at all when there is no load. Try testing it with the diode test range on your multimeter. With the positive lead to the + pin, each AC pin should read something like 0.6V Same with the negative lead to the - pin. Bob
  13. BobK

    Another find at the Habitat for Humanity Restore

    A good sized variac, with the lovely wife Motricia's foot for size comparison: And some impressive specs: This is from the same place with the old Tectronix scope. Both were from a movie set that was donated. Bob
  14. BobK

    help to calculate frequency of CD40106BC schmitt trigger square oscillator

    In order to get accurate frequencies you will have to use a potentiometer for part of the resistance and tune each oscillator. The only way to get accurate frequencies without tuning is to use a crystal. Bob
  15. BobK

    help to calculate frequency of CD40106BC schmitt trigger square oscillator

    Show us your computation. Bob
  16. BobK

    Advice needed

    When I lived in Phoenix, AZ, where the temp regularly reaches 110F (43C), there were several per year. Bob
  17. BobK

    DIY LED light panel, which voltage regulator to use?

    I did not watch the video, but I looked at the text description. He is using LED strips, which will have a specific voltage needed to operate, typically 12V or 5V. What you need is an mains to 12V (or 5V depending on the strips) converter. There are plenty of these available on Ebay ready...
  18. BobK

    help to calculate frequency of CD40106BC schmitt trigger square oscillator

    I expect that you calculated only half the period. There are two halves (charge and discharge) and that would explain the factor of two in the frequency. Bob
  19. BobK

    Simple millivolt to 5V amplifier module

    Here is what you want to amplify and convert a current to a voltage. https://en.wikipedia.org/wiki/Transimpedance_amplifier Bob
  20. BobK

    Help with invention

    That is for android. For iPhone it is their own language called Objective C. And you have to be an approved developer to get the tools from them (or at least that used to be the case) Or, you can write browser hosted apps for both of them using HTML 5 and Javascript (which is quite different...
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