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  1. BobK

    Component help

    No, you would use a constant current of 900ma if they are in series. Whoops, Kris go there first. Bob
  2. BobK

    help with a small project - precise 1rpm motor & circut

    Agree about the stepper as a better solution, but this might be a bit out of range for a beginner. Bob
  3. BobK

    supply voltage for the sensor

    And don't forget to connect the ground of the 5V supply to that of the DAQ board. Bob
  4. BobK

    Curious about the 4060 integrated circuit

    No, it is only when looking at multiple outputs at the same time and expecting them to be consistent. It has nothing to do with what you are using to look at them. There is no glitch in a single output, the glitch is in the fact that multiple outputs do not all change at the same time. Bob
  5. BobK

    What happens when an Optocoupler or RF isolator fails?

    The optoisolator will have a voltage isolation figure. They are very high. Bob
  6. BobK

    How to wire a LED

    Does it do this with a fresh new battery? Bob
  7. BobK

    What happens when an Optocoupler or RF isolator fails?

    And optocoupler is just and LED and a phototransistor. If the LED is blown out, the output will be permanently off. Bob
  8. BobK

    Battery Operated Light

    The toroid with 2 windings in a Joule Thief is used for 2 purposes: Its primary is the inductor in standard boost converter. The secondary is used for feedback to make the circuit oscillate. Thus, the two functions (oscillator + boost converter) are performed by 1 transistor, which is as...
  9. BobK

    How to wire a LED

    At 70ma you should be getting something like 6 hours out of a 9V battery. Bob
  10. BobK

    Charging circuit 4 AAA NiMh

    It is safe forever as long as you calculate the resistor for charging at 0.05C which is 40 ma. If you are using a 12V DC supply, then take out the diode and capacitor and recalculate the resistor based on 12V instead of the 16 you would get with the circuit I gave you. Bob
  11. BobK

    Charging circuit 4 AAA NiMh

    Here is what the circuit shold look like:
  12. BobK

    Power supply

    Sorry, but you are not going to get anywhere near 1 hour at 160ma. The battery is rated at 150maH a drain of 0.17ma! I doubt that it will produce 160ma at all. Bob
  13. BobK

    Charging circuit 4 AAA NiMh

    \ Why don't you share it with all of us? Bob
  14. BobK

    Charging circuit 4 AAA NiMh

    If you overcharge, you will cause the batteries to vent. NiMH are the most difficult of all the common rechargables to charge correctly. Read what battery university has to say. A trickle charger is the only safe option for a simple charging circuit. The only other option is to use a...
  15. BobK

    PWM circuit

    How about a link to the schematic? Bob
  16. BobK

    Charging circuit 4 AAA NiMh

    A proper NiMH charger has to detect the end of the charge cycle by either detecting a rapid temparature rise or a voltage drop. You can use a trickle charger at 0.05C which will take about 24 hours to fully charge the battery, any other simple charger is going to be bad news. As far as...
  17. BobK

    Component help

    Well, if you can stand 8 pins, there are several 12F parts that have PWM. Bob
  18. BobK

    Impulse DIY fuction for cordless screwdriver power tools

    I probably don't know what I am talking about , but I suspect the impulse mode is more than just turning the motor on and off quickly. I suspect it is increasing the torque by having the motor running, then coupling it to the bit only in short bursts, the inertia of the moving parts gives a...
  19. BobK

    tv head phones

    An FM wireless mike circuit should work fine. You will need to reduce, not aplify the TV output since it will be at a much higher level than a microphone. Bob
  20. BobK

    Audio Modulator Noise

    Okay, I see what you are trying to do. The problem is that the LED only conducts in one direction, so, fed with a sine wave, it is off 1/2 the time (actually more than that because it needs about 2V before it conducts). The on off threshold is the click you are hearing. Does the fucntion...
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