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  1. KrisBlueNZ

    Analog Switch Help

    A MOSFET behaves very much like a low-value resistor when biased ON. A BJT, even when saturated, doesn't pull its collector all the way down to 0V.
  2. KrisBlueNZ

    Analog Switch Help

    This is the simpler way to do what you want. This is a widely used trick. You only need one regulator, and no analogue switch. When the voltage select line is low, the MOSFET is OFF and the output voltage is set by R105 and R113. Since the ADP171's reference voltage is 0.5V, the output voltage...
  3. KrisBlueNZ

    Analog Switch Help

    What's the part number for U42 and U43?
  4. KrisBlueNZ

    Analog Switch Help

    OK. Yes, I guessed that. If you want a voltage of 0V/1.0V/1.5V there may be an easier way to achieve it, without using U21. If you want to investigate this possibility, post the schematic of the regulator part of the circuit.
  5. KrisBlueNZ

    Powered sub help

    Have a look at the last photo in post #1.
  6. KrisBlueNZ

    Analog Switch Help

    The switch inside U21 is always in one position or the other postion. In other words, A is always connected to either B0 or B1. There is no option for "no connection". U21 is an analogue switch and is not really intended to switch power. How much current are you going to draw from it? If you...
  7. KrisBlueNZ

    Analog Switch Help

    When both regulators are disabled, there is no voltage available on the B0 and B1 inputs of U21 so regardless of which pole is selected, its output cannot supply any voltage. If you want a voltage of 0V/1.0V/1.5V there may be an easier way to achieve it. Post the schematic of the regulator part...
  8. KrisBlueNZ

    Trying to find out the name of a type of component.

    swagguy8, please don't waste our time with irrelevant comments and poor advice. You've made another useless comment on another thread too. We haven't banned anyone for giving bad advice for a long time and I don't want to have to do it again.
  9. KrisBlueNZ

    Powered sub help

    The voltages are marked on the transformer, as others have already said.
  10. KrisBlueNZ

    Trying to find out the name of a type of component.

    A transistor isn't suitable if you want a clean on/off action or stability with temperature.
  11. KrisBlueNZ

    MSP430 measure power consumption

    Great! Is that what you were expecting?
  12. KrisBlueNZ

    a timing circuit

    OK Joseph :-)
  13. KrisBlueNZ

    a timing circuit

    OK, what voltage do you measure across the LED? You've made a mistake. In post #4 you said there was 8.4V from the gate to the source of the MOSFET, and here you say there is 7.27V across the 3.3 kΩ resistor. Those can't both be true unless you've wired the circuit wrong. Double check each...
  14. KrisBlueNZ

    Interference in video switching circuitry

    Yes those voltages are wrong and that could be what's causing the problem. It looks like there is some AC coupling occurring somewhere. Can you repeat the test with an extra step: 1. Disconnect the scope input and connect it to the earth clip so there is no input to the scope. 2. Adjust the...
  15. KrisBlueNZ

    12VDC to 110VAC inverter needed

    Ah, I see it on the photo of how it's supposed to look. Yes, it looks like a centre tap. It goes to the area next to the fan with the big high-current noise suppression choke wound on a blue ring core, which is missing from your unit. It looks like the wires have been cut off pretty close to the...
  16. KrisBlueNZ

    12VDC to 110VAC inverter needed

    LOL well, you could feed mains in the secondary (black wires) and connect some thick wires to the primary (marked with arrows). That'll give you a nice safe low voltage with lots of current, which is good for making big sparks and carving pits into metal, and blowing up certain types of...
  17. KrisBlueNZ

    Trying to find out the name of a type of component.

    OK, so you have a 3V button cell and two low-current LEDs. You want one LED to be ON all the time, and the other one to illuminate only when a thermistor tells you that the temperature is above a certain threshold? I think you need a voltage comparator. Probably one with a built-in voltage...
  18. KrisBlueNZ

    12VDC to 110VAC inverter needed

    No, the transformer doesn't have a centre-tapped primary. You can see there are only two wires. Also there are four MOSFETs which probably implies a full H-bridge drive. There's also a feedback winding - the red and black wires, which disappear into the control board. The drive circuitry...
  19. KrisBlueNZ

    12VDC to 110VAC inverter needed

    That one needs a transformer with a centre-tapped primary and has a square-wave output instead of modified sinewave.
  20. KrisBlueNZ

    12VDC to 110VAC inverter needed

    Ah, I see. I think the circuit you posted in post #4 is not a good design. It's probably only suitable for fairly low power - less than 50W. Its frequency will not be accurate, and it will produce a square wave output, rather than the "modified sine wave" produced by a better drive circuit...
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