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  1. BobK

    Keeps blowing circuit module!! :(

    And it can, as long as they don't share a ground. Which is what you found out. Do you have a multimeter? If so, check continuity between the speaker pads and the 3.5mm jack outputs. If they are connected, it is as I have speculated. If none, then who knows? Bob
  2. BobK

    Running 3v and 9v at same time from 6 batteries

    In addition to what others have said: If the servo is not powered, it will have no holding power, so if you expect it to stay in place, there better not be any torque (or at least not enough to move the servo) when the power is off. Bob
  3. BobK

    Keeps blowing circuit module!! :(

    I suspect that the 3.5mm jack is simply connected to the speaker outputs, and is intended for headphones. It would explain everything he has seen. Bob
  4. BobK

    Keeps blowing circuit module!! :(

    Yep, it is a bridged amplifier, that it the only way you get 3W with a 5V supply. So, you cannot connect either of the speaker outputs to ground. Doing so shorts one of the output transistors. Why are you using amplified speakers? Do you need more than the 3W it can supply? Bob
  5. BobK

    Keeps blowing circuit module!! :(

    How about a link to the MP3 module. If it is designed to drive a speaker directly, it may be a bridged amplifier. If so, when you connect this to an amplified speaker, which has a ground, you are shorting the output of the bridged amplifier, since neither side of it is at ground. With...
  6. BobK

    Killing SSR (relays) - Need to understand

    Are you claiming the SSR is burning up when it has cycled off? If so, I think your circuit is the responsible party. Can you show us the exact complete circuit. The previous circuit you published had to be wrong since it connected the AC line voltage to one of the control pins on the SSR (or...
  7. BobK

    Solar powered balloon?

    Why would you have to keep topping it off with hydrogen? Bouancy would need to be controlled, but there are better ways to do this than releasing an replenishing the hydrogen. The first thing that comes to mind for me is to compress / expand some portion of the hydrogen. Bob
  8. BobK

    Clueless Noob - A/C to DC switch

    Replacing the power supply is not going to give you speed control. You need a special circuit and sensors for feedback to do that. Can you give us a link to the so called "speed controller?" Bob
  9. BobK

    need help with an amplifier

    In addition to what LvW says, which I agree with completely, you cannot reasonably drive a 32Ω load with that circuit. You need a push pull output stage. Bob
  10. BobK

    Converter for 115VAC, 60HZ to 230VAC, 50HZ sine wave up to max. 100Watts.

    Ah, I missed the "gas heated" part. Bob
  11. BobK

    IR Switch Trigger in Specific Setup

    Hey, your sketchup guy looks a lot like me (when my hair is not dyed as in my Gomez picture). I've been digitized! Bob
  12. BobK

    Oscilloscope Help

    What is it you are measuring on the scope? The remote will likely draw uAmps when no button is pressed. Bob
  13. BobK

    Op-Amp selection for inverting source signal - Bench PSU build

    To do an experiment on how it would work on dual supplies, you would do the following: Put 2 AA batteries in series by connecting the negative of one to the positive of the other. Now connect the meter with the negative input to the center and the positive to the free positive end of the...
  14. BobK

    Converter for 115VAC, 60HZ to 230VAC, 50HZ sine wave up to max. 100Watts.

    Must be a small water heater if it only requires 100W. Are you sure it requires 50Hz? Typcially, anything that does not involve motors does not really care much about 50 or 60 Hz. Bob
  15. BobK

    Op-Amp selection for inverting source signal - Bench PSU build

    Not necessary. Just switch the leads on the meter. Put the positive lead to ground and the negative lead to V-. Bob
  16. BobK

    simple Calculator

    I think that is what he is asking. :) Given what is out there for basically no money, this not a viable project. Bob
  17. BobK

    Finding the smallest possible actuator, or a new solution. Help massively needed!

    That is pretty challenging. Is it possible to have a flexible wire like the inside of a bicycle brake cable go through your 2x2x6 space with the actuator being larger and somewhere remote? Bob
  18. BobK

    Question about Li-ion batteries

    Nice explanation, except: That should be PRODUCT, not SUM. Bob
  19. BobK

    mosfet, not fully on. losses?

    Don't know where you get 10A at 4V. The characteristic curves start at 4.5V, and it conducts over 20A at that voltage. To find the power loss anywhere on the characteristic curve, find the point on the on curve for Vgs and then multiply the Id by Vds. For example, on the datasheet you linked...
  20. BobK

    Help to solve Operational amplifier

    The RMS voltage is only 10V for a square wave. Power of audio amps is calculated based on a sine wave. With a p-p swing of ±10V, the RMS voltage of a sine wave is 7.07V. Bob
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