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  1. KrisBlueNZ

    A tip if the "upload a file" button does nothing

    I doubt it! If that bug can affect any application window without the application's knowledge, I doubt there's anything that can be done at the Javascript or Flex level to change the behaviour. BTW I've never seen that problem. But I don't use Show Desktop very much.
  2. KrisBlueNZ

    Water Sensor Switch and Pump

    A small DC pump will draw measurably less current when it's trying to pump air than when it's pumping water. You could use that to detect when there's no more water to suck. You would need to use a pump that will suck water even when it's currently full of air (I guess that's what Gryd3 means by...
  3. KrisBlueNZ

    How to react if the two are connected gyrator?

    All schoolwork belongs in the homework section. I've moved the thread.
  4. KrisBlueNZ

    Massage chair control board help..

    In post #2 I said: The maximum DC voltage you can get from bridge rectifying 115 VAC is about 160V. That's why I suggested a 230V bulb.
  5. KrisBlueNZ

    Using a Varistor to solve a back EMF problem

    Sorry for the delay.
  6. KrisBlueNZ

    Discharge path for buck-boost converter

    It's a buck-boost converter.
  7. KrisBlueNZ

    lm317 sub?

    A 10k resistor gives a LOWER base current than a 680Ω resistor. Ohm's Law says I = V / R, so if voltage is constant, I (current) is proportional to 1 / R, the reciprocal of resistance. Higher resistance means lower current. A 10k resistor can only supply about 2 mA of base current to Q2...
  8. KrisBlueNZ

    Alternatives to pwm power supply

    Yeah. I was just throwing out some terms in case the OP recognised them. Synchronous rectification isn't an alternative to PWM either, but when you're new to the terminology it's easy to get a bit confused.
  9. KrisBlueNZ

    isolation problem

    Hi there and welcome to Electronics Point :-) Thanks for the thorough description of the problem, and the schematics. This REALLY helps. Could you just use a diode between the PWM signal and the relay coil, with a capacitor across the relay coil? When there's ANYTHING happening on the PWM, the...
  10. KrisBlueNZ

    Project Problems! Need guidance.

    According to the schematic, there are four voltage-to-current converters, and the mux only drives one at a time. The other three will be undriven. Their input voltages will be undefined unless you add a resistor to pull them to 0V. You need to add a zero crossing detector that monitors the 20...
  11. KrisBlueNZ

    Using a Varistor to solve a back EMF problem

    Yes, that's probably best, but don't put the diode very far away from the pump. Each time the pump turns off, there will be a heavy current spike in that loop, so its area should be minimised. Yes, but you would have to use the "R" version of the diode if you want to earth the stud. With the...
  12. KrisBlueNZ

    Revised inputs from optocouplers

    Check out this project. It's quite brilliant. I bought one on eBay and it works pretty well. https://translate.google.com/translate?sl=de&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fwww.mikrocontroller.net%2Farticles%2FAVR-Transistortester&edit-text=&act=url
  13. KrisBlueNZ

    Alternatives to pwm power supply

    He might be referring to synchronous rectification I guess, or current mode control?
  14. KrisBlueNZ

    Can I use a resistor as a fuse?

    Can you email Ron a product name and circuit reference so he knows what you're referring to?
  15. KrisBlueNZ

    Using a Varistor to solve a back EMF problem

    Right, well, connect a big diode (rated at AT LEAST 10A) across the pump, with its cathode to the positive side. Something like http://www.digikey.com/product-detail/en/BYV79E-200,127/568-3440-ND/1127193 will do, and you won't need to heatsink it, but the TO-220 package isn't easy to tack onto a...
  16. KrisBlueNZ

    Project Problems! Need guidance.

    Interesting. What op-amp are you using for the output driver in the voltage-to-current converter? What happens to the voltage-to-current converter inputs when not driven by the multiplexer? Do they just float? Do you switch the multiplexer only on zero-crossings of the input signal? Do you...
  17. KrisBlueNZ

    Hi everyone

    Hi again Stu and welcome to Electronics Point :-) It must be amazing living on a houseboat! Kind of like living in a caravan but different!
  18. KrisBlueNZ

    Revised inputs from optocouplers

    Is that important? The relays will take typically 2~3 ms to activate... If that's controlled by the relays, they won't update immediately. The micro will need to wait a few ms to be sure the relays have activated and the inputs are valid. So the outputs are a direct copy of the inputs? In that...
  19. KrisBlueNZ

    Using a Varistor to solve a back EMF problem

    Is the pump AC or DC? If it's DC, just bung a big diode across the relay contacts.
  20. KrisBlueNZ

    Revised inputs from optocouplers

    How does the microcontroller know when these signals from the analogue section are valid and should be actioned? Are they valid immediately on power-up? Or after a short time? Or something else? Is there a time constraint between when the micro reads these states and when it sends the...
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