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  1. BobK

    Battery question

    More likely, the batteries were shorted. Bob
  2. BobK

    Help pl..!! Automatic Human Sensing Fan

    Why does the IR sensor need to be close to the appliance? Why not anyplace that has a good view of the room? Bob
  3. BobK

    Controlling multiple dimmers from one potentiometer

    Whoops, I missed the fact the it was the power supply that was cutting out. Bob
  4. BobK

    How to convert 6V~3w input to 5V 500mA output (USB)

    Agree with Lapace. The output is too variable to power the gps directly. What happens when you are stopped at a light? You need to power from a battery and use the generator only to recharge the battery. Bob
  5. BobK

    Controlling multiple dimmers from one potentiometer

    I have a theory of why it might fail with what looks like it should be < 8A output. The dimmer is probably actually a PWM device, that is it is turning the voltage on and off rapidly rather than varying the voltage. The filament of a light bulb increases its resistance with increased...
  6. BobK

    Servo control newbie help

    You understand it wrong then. That circuit will set the servo position to any angle by turning the potentiometer. It does not sweep from min to max. I don't think you can do that with a single 555. Bob
  7. BobK

    Voltage regulator for High power LED's

    You cannot regulate both current and voltage. A constant current supply will output whatever voltage is required to maintain the regulated current (within limits). So if you have a constant current supply capable of the max voltage needed, you should be all set. Bob
  8. BobK

    Recommend microcontroller

    And is is only slower than what OP is looking for by a factor of 8. Bob
  9. BobK

    Servo control newbie help

    You could use a one-shot (monostable multivibrator) to make it do only once cycle each time and input goes from low to high. But I would be interested in knowing how you would make the servo sweep from 0 to 180 and back with a single 555 timer? Bob p.s. I would use a PIC. It is trivial...
  10. BobK

    Lights to the beat of music.

    You need at least a diode (to block the negative side of the speaker output) and a resistor to limit the current in series with the LED. But this still won't be satisfactory. As you state, it will only work well at one volume level. You could make the resistor a fixed resistor and a variable...
  11. BobK

    LED Turn signals

    I you are trying to get it blink from 100% to 50%, you could do it like this. Calculate the resistor needed 1/2 the max current. Use two of these in parallel, (which gives you full brightness), but in series with one of them, insert a transistor switch such that it is normally on and gos...
  12. BobK

    Value of an organ

    Go to Ebay and look for completed auctions on the instrument you have. Bob
  13. BobK

    back up battery for mains supply???

    Yes, is it called an Uninterrupable Power Supply, or UPS. Many commercial units are available. http://en.wikipedia.org/wiki/Uninterruptible_power_supply Bob
  14. BobK

    servo operation

    Good choice. I have a PIC low-pin-count demo board sitting on my desk next to me with a servo controlled by the pot on the board. I could send you the code if want as a starting point. Bob
  15. BobK

    Usage of the same timer for 2 modules

    You can run two PWMs off the same timer. Each OC unit has it's own duty cycle register. The only restriction is that that PWM periods are the same, and for your purpose I would think you would want the same period, only the duty cycles would vary. Bob
  16. BobK

    servo operation

    If it is a hobby servo, it requires a series of pulses on the control wire. 1.0 ms is fully CCW and 2.0ms is fully CW. The pulses need to be repeated aout 50 times / second. You cannot control the position with a voltage. The usual angle is 90 degrees, though they will typically go further...
  17. BobK

    Constant Voltage DC & LED's

    The current rating of a power supply is the maximum current it can provide. The amount of current it actually applies depends on the circuit it is powering. If you apply a 5V 1A power supply to a 100 ohm resistor it will supply (by Ohm's law) 50ma. If you apply to same 5V to a 10 ohm...
  18. BobK

    Wireless Remote Question

    Youi could, but you risk it misfiring on occasion. Bob
  19. BobK

    Need help in designing switching/chopping circuit

    Okay, that was far from clear in the OP. Now it makes a lot more sense. Bob
  20. BobK

    Phototransistors

    The obvious factor that you are missing is the range of light intensity that you want the phototransitor to work in. Start this way: Is it direct sunlight compared to shade? It is normal room lighting vs total darkness? i.e. characterize the range you need. Then use google to find a...
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