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  1. Alec_t

    Replacing a faulty SMPS

    It's because voltage is always a potential difference. In this case Vcc is tied to the mains line, but the GND point is floating 5V (or whatever) below Vcc.
  2. Alec_t

    Stabilising wienbridge sine wave using FET

    If you want to upload a file, use the 'Upload a File' button next to the 'Post Reply' button.
  3. Alec_t

    Replacing a faulty SMPS

    It's marked 'GND'. xV is an unknown quantity. Where do you get "5" from? It most likely is 5, because it's the supply voltage to the micro. The capacitor polarity indicates that Vcc is +ve with respect to GND.
  4. Alec_t

    Replacing a faulty SMPS

    So much for my theory ;). In the latest schematic I make TP48 = -12V and TP29 = Vcc = Phase = +xV (+5V?), both voltages referenced to TP31 = GND (common). So GND is floating xV below Phase. I don't see any -5V supply?
  5. Alec_t

    cake water fountain help

    What is the VA/current rating of your fountain and/or existing 33V transformer?
  6. Alec_t

    Replacing a faulty SMPS

    I don't think it should be there. My guess is that someone has created that schematic by reverse-engineering a circuit, but has not done so accurately. I see no reason why low secondary voltages would need to be referenced to the high voltage line. It looks potentially lethal.
  7. Alec_t

    Help with Voltage Transients

    You don't normally need to concern yourself with that for selecting transient suppression diodes.
  8. Alec_t

    Stabilising wienbridge sine wave using FET

    The source should go to ground. Can you post a schematic of your circuit?
  9. Alec_t

    Replacing a faulty SMPS

    I share ramussons's doubts as to the accuracy of the schematic. For safety reasons, don't rely on it. A linear supply should be ok, providing you don't need to draw high current from any of the outputs. Alternatively, SMPS supplies of appropriate voltages are probably cheaply available off the...
  10. Alec_t

    IR carrier frequency

    Optical interferometer?
  11. Alec_t

    Winding coils

    You haven't told us how you do it, so how can we advise on a better way?
  12. Alec_t

    12V power supply

    A car battery.
  13. Alec_t

    Ultrasound Modules

    I can't make any recommendations regarding the transducers, but have a look at this re underwater acoustics.
  14. Alec_t

    cake water fountain help

    The 24V charger may not have enough output current capability to run the pump. If you try to draw too much current the charger may go into self-protect mode and shut down.
  15. Alec_t

    IR carrier frequency

    Measure the wavelength and divide that into the velocity of light.
  16. Alec_t

    cake water fountain help

    If it's designed to be powered by 33V, then it's not surprising it won't work properly with only 24V ;).
  17. Alec_t

    Looking for a 12v 3.5+A MOSFET

    Nice find, 73's.
  18. Alec_t

    Potentiometers not working properly in circuit

    Are you sure you are using the middle pin plus one end pin of the pot?
  19. Alec_t

    Gate automation system - Motors open but do not close.

    If you've eliminated the relays as suspects, then my guess would be that the ULN2003A drives them but is faulty.
  20. Alec_t

    Can anyone help help me with a Gear Ratio?

    I wouldn't. That would be stretching the meaning of 'gearing ratio' somewhat, since the normal definition of 'gear' is a toothed wheel.
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