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  1. BobK

    mains rectified voltage for christmas lights

    The Chinese XMAS lights I have seen simply use enough LEDs whose forward voltages add up. Not seen one with a capacitor, much less a polarized electrolytic. BTW: you know there are non-polarized electrolytics, right? Bob
  2. BobK

    Resistor Value Identification Help

    But that chart clearly shows the fourth band gold as a multiplier of 0.1 And I have seen other charts that show green as a 0.5% tolerance. Bob
  3. BobK

    Resistor Value Identification Help

    How does one mark a five band resistor of < 100Ω then? Bob
  4. BobK

    Help with a stepper motor IC

    Then reverse one of the coils. Bob
  5. BobK

    Help with a stepper motor IC

    What does the motor do when you attempt to run it? Does it vibrate back and forth instead of turning? Bob
  6. BobK

    help needed with electrical connection please

    The switch should be in the 240 position. If you connected in the 120 position, you probably blew out a lot of electronics by giving them twice the voltage they are expecting. Bob
  7. BobK

    mains rectified voltage for christmas lights

    If you are using it to pass AC, it must be non-polarized. A polarized electrolytic can handle only less than 1V in reverse. Bob
  8. BobK

    Creating 5V DC

    Power Bank. Very high capacity, rechargeable, and a mass market item. edited to add: And the right voltage. Bob
  9. BobK

    mains rectified voltage for christmas lights

    Non-polarized, I hope. Bob
  10. BobK

    More woes driving LEDs via PWM

    Those MOSFETS are not fully turned on at 3.3V. You need to find MOSFETS that have their on state characterized at 3.3V with a low enough Rdson to avoid heating up. Bob
  11. BobK

    More woes driving LEDs via PWM

    If the PI is outputting 3.3V, that might not be enough to turn the MOSFET on completely, resulting in heat. What is the part number of the MOSFET? You need ones with very low threshold voltage, which will turn on completely (or nearly so) at 3.3V. Bob
  12. BobK

    Noob question

    Ah yes, I forgot that they used to have fluorescent backlights. Never had one of those, I went for plasma. Bob
  13. BobK

    Noob question

    I would be very surprised to find any voltage above 500V in an LCD TV. Bob
  14. BobK

    Step Down DC Buck Capacitor Blow up

    Although I agree that this might be the case, that is a piss poor design if it blows the output capacitor when you fail to have a large enough load. Bob
  15. BobK

    24 VAC to 12 VDC

    I get a lot more than that. 24VAC will rectify to 32VDC. You now have 20V to drop in a linear regulator at 80mA which is 1.6W. A smallish heat sink should be enough for that, though. So if it is getting very hot, I agree with your conclusion that something else is wrong. Bob
  16. BobK

    Current control and defence

    Without a schematic, the best I can say is maybe. Bob
  17. BobK

    Making It High Impedance

    Of course you have to make the pin on the micro an output! The pin itself, with no external transistor will pull the input high or low with a reasonable valued pullup, like the 10K I suggested. Bob
  18. BobK

    Good Resource For Learning Bjt Transistors And Amplifier

    You have to go the Wallwart's the only school that teaches the truth about transistors. Bob
  19. BobK

    Good Resource For Learning Bjt Transistors And Amplifier

    It is really a shame that there is this universal conspiracy to put out false information about how transistors work. Bob
  20. BobK

    Making It High Impedance

    You can connect the output enable input directly to your microcontroller output. A pull up of 10K or so will prevent it floating while the micro boots up. After that the micro is completely in control. Bob
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