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  1. BobK

    RS-232 and LED help

    No, what is not helpful is posting schematics that are incorrect and misleading, and ignoring questions designed to help. There was no malice intended in my comment about the overkill on the resistors. I genuinely thought you were complaining about the cost and it was perfectly okay to point...
  2. BobK

    Mosfet bridge safety

    The symbol in the schematic is missing the arrows that tell you whether they are N or P. Bob
  3. BobK

    RS-232 and LED help

    You do not need a .1% resistor, 10% would have been fine. You did not need 1W, 1/4W would have been fine. They should have cost about 10 cents at most. Bob
  4. BobK

    Confused about a DC Motor

    Of course. With the motors I am using they will not run much below 30% duty cycle. There will always be a minimum to start the motor. Bob
  5. BobK

    The art of electronics

    Agree with Adam. Learn the principle. Ignore the specific devices he talks about, they are typically obsolete. Bob
  6. BobK

    RS-232 and LED help

    What Harald said. If you really want to do it right, and light the LED full blast when the UART is transmitting, I would use a 555 as a monostable retriggered by the low state of the TX pin. Then use a constant current driver for the LED. If you only want an indication (not blinding red...
  7. BobK

    Decoding 433.92mhz remote?

    Nope, they come in 14 and 20 pin. Bob
  8. BobK

    Mosfet bridge safety

    Unless he actually has P channel MOSFETS for the high side. In any case, an opamp is still a silly way to drive them. Bob
  9. BobK

    Decoding 433.92mhz remote?

    The 5 pin header has all the right pins for PIC ICSP, so the large chip is most likely a PIC microcontroller. Yep, I just checked the connections and they are correct for a PIC16F88 or other 18-pin PIC. Edit: If you happen to have a PICKIT 2 or 3, you could connect it and see if the chip is...
  10. BobK

    Confused about a DC Motor

    PWM is not the equivalent of using a lower power supply or inserting a resistor because the a higher current is reached during the on portion of the PWM cycle. I can run a motor with a 6V supply and 30% duty cycle, but the same motor will not run on 1.8V. Bob
  11. BobK

    Best op-amp/comparator for audio stuff.

    You said nothing about the input level or the output level, and have given us 3 choices of supply voltage. Not much help, I am afraid. Bob
  12. BobK

    Best op-amp/comparator for audio stuff.

    What is the input signal? What is the output swing? What supply voltages are available? Bob
  13. BobK

    RS-232 and LED help

    So you are using an invisible resistor? Bob
  14. BobK

    A programmable melody generator

    Okay. I have experience only with PICs from Microchip. It is a fairly large investment of time (and a little money) to get started using them this way. Others here are experienced with Arduino and PICAXE which are a little simpler for beginners. If you wanted to go the PIC route, I can help...
  15. BobK

    Easy circuit voltage split(s) using only regulators.

    And by the time you have done that, you might as well have bought a 5V USB charger for less money. Bob
  16. BobK

    RS-232 and LED help

    Does you USB to serial (it is not RS232 if the voltages are as you stated), chip also handle control signals like RTS and DTR? These would be more appropriate to control an LED since they can be set or cleared by software without sending data. Bob
  17. BobK

    Need help on converting 0-5v signal to 0-10v signal

    I have never heard of an opamp with open collector output. Bob
  18. BobK

    Simple Short Range FM Transmitter

    Actually it is not that difficult. A while ago I made a ~100MHz oscillator from a 2n2222 transistor and a coil of 4 turns of wire round around a pencil and a few capacitors and resistors. Feeding a microphone through a cap to base made an FM transmitter that I could broadcast to a nearby...
  19. BobK

    random signal generator

    What about microcontrollers and programming? Bob
  20. BobK

    Use diode to attach multiple circuits

    This is exactly what is illegal. You may not interfere with anyone's ability to receive radio signals. Bob
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