Search results

Search Forums New Posts
  1. BobK

    Digital LED clock

    It is an old PIC microcontroller, and it is one-time programmable. A PIC16F54 would be a flash programmable replacement. Bob
  2. BobK

    7805.. hot. Suggestions?

    Where did you get $15? The part linked in that post is $4.30. Bob
  3. BobK

    Limited Resistance Range on 500ohm Pot

    Glad to hear that you got it working. I second Dave on the 9V battery. What is the current draw of the motor? Even something like 4 AA NiMH batteries would be better, and rechargeable. Bob
  4. BobK

    Which MOSFET do I use?

    I was assuming mV meant up to 1V, so the diode could be a factor if I was correct. On the other hand, I think small signal MOSFETs do not have a body diode, right? I still think an analog switch will do exacly what he wants and is designed for this purpose. Bob
  5. BobK

    Inverting RS232 Signal?

    I am non sure about Arduino (AVR), but on PIC you can set up the serial I/O peripheral for inverted input. Read the datasheet, it might be able to handle it as is. Bob
  6. BobK

    My first go at electronics

    Probably not, I think the flux used for plumbing is different from that used for electronics. Bob
  7. BobK

    Old CRT cathode Tubes

    There are some people on the Microchip forum that have done wonders with that. All you need out of the micro is a few resistors to produce composite video! People have done PAL and NTSC and even VGA. Some really clever coding, using the SPI port get the fast bit rate. Bob
  8. BobK

    Limited Resistance Range on 500ohm Pot

    The circuit is correct with R2 in. There is something else wrong. R1 and R2 form a voltage divider and the regulator will regulate the voltage at their junction at 1.2V. I still say you should check all your connections. Also remove the motor and see if that make a differenence. Maybe...
  9. BobK

    Limited Resistance Range on 500ohm Pot

    What resistor did you short out? I doubt that you have fixed the problem. You may have just created a voltage divider bypassing the regulator. Bob
  10. BobK

    home powered water pump generator.

    Reality really is annoying, isn't it? Bob
  11. BobK

    Geiger counter / radiation meter modification

    If the pulses are of fixed amplitude, a leaky integrator should work to average over time. Bob
  12. BobK

    Limited Resistance Range on 500ohm Pot

    Check your wiring. Something is likely wrong. Check that you have used the pins correctly on the regulator. Use a multitmeter on continuity check to check that all points that should be connected together are, and none that should not be are. Bob
  13. BobK

    Which MOSFET do I use?

    A MOSFET is not useful for AC voltages. They generally have a diode that conducts all the time in the reverse direction. I think what you are looking for is an analog switch. Also, unless you are drawing signficant current at that voltage you want to switch, you would not need a very low Ron...
  14. BobK

    Amplifier Conundrum!

    A voltage divider is not a method for reducing a supply voltage, unless you are drawing a small constant current, which your multivirator is not. To reduce the supply voltage you would want a voltage regulator. Bob
  15. BobK

    using a relay

    I think you would be safe with that relay. You could also measure the voltage across the terminals when open and the current through when you short them thorugh an Ammeter. A transistor might do just as well. Bob
  16. BobK

    Geiger counter / radiation meter modification

    I would think an opamp voltage follower would allow you to tap the signal. Look for an opamp with very low input bias and input offset current. A random microchip one I looked at was 1pA. Bob
  17. BobK

    Few Questions about Sound on Light

    Clearly you have not tried hard enough! :) Bob
  18. BobK

    Raising the current to a circuit without switches

    As a theoretical question: Yes, put a bridge rectifier on both of the voltage sources and connect together the two + outputs and two - outputs. You can now plug in either or both voltage sources with either polarity. The larger one wins. However, if you really are dealing with 1V (which...
  19. BobK

    220v LED DIMMER??

    Wouldn't a triac type dimmer work okay if you took out the smoothing capacitor after the bridge rectifier? Bob
  20. BobK

    Simon Says random generator for PIC 16F84

    You are making this way too complicated. Use a pseudo-random number generator with a long sequence, say 32-bits worth. This will, for all practical purposes never repeat. Store the last number generated in eeprom, and read it on boot up. Bob
Top