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  1. KrisBlueNZ

    Problem with old ceiling fan

    OK so you exchanged transformers and the motor that didn't work properly is still not working properly, so you've concluded that it IS the motor, not the transformer, right? My guess is you should be able to dismantle the motor and clean it out, but you'll need to rely on your own...
  2. KrisBlueNZ

    4047/4066 audio slicer help

    Cool. I think you'll find it's a much better way to control the signal. Yeah you could try it. It will give you a different effect from the A AND B, A OR B, and A ONLY controls, but I don't know whether any of them will be very useful to you in a musical sense. You could use a four-way switch...
  3. KrisBlueNZ

    4047/4066 audio slicer help

    Hi Ben. Re your new design (the first one in your post), it looks OK. I'd suggest adding a bias resistor from the common of the two switches (i.e. pin 5 of U2) to the virtual ground rail. 100k should be fine. This is just to stop that node from floating during the time (if there is any)...
  4. KrisBlueNZ

    Problem with old ceiling fan

    If you have several capacitors, some from fans that work and some from fans that don't, swap them around, to see whether the problem is the capacitors or the motors. In my experience (1 repair so far :-), ceiling fan motors accumulate gunk and/or drift off-centre, either of which makes them...
  5. KrisBlueNZ

    How does this circuit work?

    Yes, you got it.
  6. KrisBlueNZ

    How does this circuit work?

    The micro will be generating a form of PWM signal to control the solid state relay, but it must be synchronised with the phase of the mains voltage, because the instantaneous voltage of an AC signal is continuously varying (according to the sinewave shape), so (for example) a...
  7. KrisBlueNZ

    How do you implement a transformer load with a transistor?

    I HAVE tried to help. Re-read and try to understand post #9 on this thread. And if you like, respond to it. Otherwise... well I guess you'd better try that thronomister then. BTW I know very well what a PLL is. I believe I am well-qualified to judge what is an adequate description of a project...
  8. KrisBlueNZ

    MOSFETs IN SERIES

    OK, 300 Hz is reasonable. The value of the voltage balancing resistors will affect how well the MOSFETs share the total voltage. Lower values will improve the voltage sharing. I can't give you a maximum value. Zener diodes specified for slightly less than the Vds(max) voltage of the MOSFETs...
  9. KrisBlueNZ

    MOSFETs IN SERIES

    OK, and what about the times when it DOES exceed 200 Hz? What's the maximum?
  10. KrisBlueNZ

    Electronic whack-a-mole

    That's cool, Jim! It's interesting to see the similarities and differences between your design and mine. Yours certainly looks a lot tidier! I'm keeping a copy for possible future amusement :-)
  11. KrisBlueNZ

    MOSFETs IN SERIES

    OK, so from Ohm's Law, R=V/I. R=350/0.01 = 35000 ohms. Since there are four resistors in series, each one needs to be at least 8750 ohms. How about 22k each. Power dissipation will be P=V^2/R =(350/4)^2 / 22000 = 7656 / 22000 = 0.35W so they need to be 1W resistors. Total resistance will be 88k...
  12. KrisBlueNZ

    MOSFETs IN SERIES

    Do a Google search. A thorough one. And when you're working with voltages of 500V or more, a transformer (I assume you mean an isolating transformer) may not help you. And a fuse is no use at all - they're there to prevent fires, not electrocution. Yes. D15 across the 12V source isn't needed...
  13. KrisBlueNZ

    MOSFETs IN SERIES

    What else haven't you told us? You'll save time in the long run if you give us a thorough description of what you want to do. Don't try to guess what's important and what isn't. We can make that decision. I saw your comment that "i discovered that when i talk about voltages exceeding 500v...
  14. KrisBlueNZ

    MOSFETs IN SERIES

    Right, that would definitely be a problem. That's why I suggested he uses a diode from his +12V supply to each gate separately, and a zener from gate to source on each MOSFET. I'm still not very confident that the MOSFETs will voltage-share. I would put a resistor arcross each one just to make...
  15. KrisBlueNZ

    How does this circuit work?

    Right. The details of the control logic depend on the characteristics of the motor, and I don't know much about that subject. In any case, the micro needs to know where the mains waveform is "up to", since it's a sinewave and its instantaneous voltage is continuously changing, so it can decide...
  16. KrisBlueNZ

    Electronic whack-a-mole

    Thanks Steve. Although that was probably code for "so you ARE crazy then..." :-)
  17. KrisBlueNZ

    How does this circuit work?

    As I explained earlier, the microcontroller needs a signal that indicates the mains phase, so it knows when to turn the solid state relay on and off to vary the motor speed. This signal has to be taken from the AC voltage, either before or after the transformer. I noticed that the transformer...
  18. KrisBlueNZ

    MOSFETs IN SERIES

    Oh sorry. I foolishly thought that it would be helpful and important to prevent you from blowing up your MOSFETs. Of course, you can just add the zeners later, if you can be bothered. My apologies again, I hadn't guessed that. My crystal ball has been a little cloudy lately. If you make the...
  19. KrisBlueNZ

    How do you implement a transformer load with a transistor?

    Seriously? You don't really know what you're doing, you're asking for expert help, but you KNOW that it doesn't matter what the load is, and you know that there's no need to explain the overall purpose of your design? If you want help, and some kind of useful responses, explain your project in...
  20. KrisBlueNZ

    Electronic whack-a-mole

    Did I spend too much time on that design? Yeah, probably. But it was kinda fun, and exercise for my brain. That's my story and I'm sticking to it ;-)
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