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  1. BobK

    bridge rectifier circuit putting out wrong voltage

    Or maybe the capacitor is blown in the original circuit. Bob
  2. BobK

    How to identify transformer output

    I meant to connect one of the green wires to one of the white wires. But before you do this, make sure that a green and a white are not already connected by checking the resistance between them (with the transformer not powered.) If you do this, you whould measure either 0V or 21.8V between...
  3. BobK

    need help about pointers

    Have you read K&R or another C primer? This is not a subject easily covered in a forum. Bob
  4. BobK

    Gave it a go, but ultimately I'm too thick.

    Your calculations look correct. And you are using the low end of the Vf, which is the correct way to be safe. If you want to use the 10R resistor, use two 1A or more diodes in series. This will drop and addtional 1.2V or more. Shield your eyes from the LED, it is going to be bright! I...
  5. BobK

    Op amplifier

    The - input will pretty much follow the + input, so there would only be a few millivots (same as the input) across the capacitor to ground. So it should be safe. Bob
  6. BobK

    LED not working on Boss Guitar Effects Pedal (LED does work externally)

    I would think that would be normal behavior. It would take extra circuitry to prevent the unit from being powered when there was no guitar plugged in. Bob
  7. BobK

    need help about pointers

    It would help to know what programming language you are using. Bob
  8. BobK

    How to identify transformer output

    Check first to see of any of the windings are connected together. Most likely they are not. You could then use the two 10.9V windings. Connect one of the leads of each together and measure across the other 2. If you read 21.8V then you have them connected correctly. Otherwise use the other...
  9. BobK

    RGB LED Color Slider

    Since you subject is "digital circuits", wouldn't it be better to do something that involves digital circuits? Bob
  10. BobK

    transistor switch for LED's

    Easiest way is to use a SPDT switch. Common contact to the power, NC contact to the string of LEDs that should be normally on, NO contact to the string of LEDS that should be normally off, with resistor in each string to ground. Bob
  11. BobK

    RGB LED Color Slider

    Don't slide the slider too near to the end with the wire connected, or it will blow out the LED. I would say this is a poor design, and not worthy of a final project. Bob
  12. BobK

    Quad Comparator Help

    That's always a relief. No one wants to talk about hysterectomies, oh, hysteresis, never mind. Bo
  13. BobK

    Solar Panel Project Help

    Those garden lights generally work by charging an NiMH cell enough to run a 20mA LED for maybe 8 hours. Get 4 of them, let them fully charge the NiMH batteries (this will take about 10 sunny days) then put them in series and you might be able to get about a 1/2 a charge on your phone. Bob
  14. BobK

    Digital propeller clock

    Well, it probably is not a DC motor then. Bob
  15. BobK

    traffic light project

    A 4017 is a good choice for making traffic lights. You can find lot's of designs on line. Bob
  16. BobK

    LED Project help, please?

    This tutorial should tell you all you need to know. Or at least enough to ask the right questions. https://www.electronicspoint.com/got-question-driving-leds-t256849.html Bob
  17. BobK

    Which Microcontroller To Use For A Frequency Counter

    Hmm. I guess I am wrong then. I looked at several datasheets, but not that one. The others did not indicate a max clock period when using the built in prescaler. This one indicates 10ns of high and 10 ns of low, whcih means it will handle a 50% duty cycle sqauare wave up to 50MHz. If it is...
  18. BobK

    triigering a cell phonto send amessage

    Trigger it how? Bob
  19. BobK

    Help using TIP42c

    Yep, a resistive divider would work. To handle 24V, assuming the micro is running at 5V, you would need a ratio of about 4 to 1. Bob
  20. BobK

    Which Microcontroller To Use For A Frequency Counter

    I can only speak about PICs. Only the 32-bit PICs would be albe to handle 40MHz directly. To use a smaller PIC you could implement an external prescaler. Bob
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