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  1. BobK

    mic and Impedance matching

    Hi and welcome to the forum! Typically, electret microphones have the JFET amplifier built in, and they need a power connection to work. This article shows you how it is connected: http://en.wikipedia.org/wiki/Electret_microphone The output from the capacitor should provide a signal of about...
  2. BobK

    small 2s lipo charger with cutoff

    I take it you want to build the charger into the device. The problem is that your battery needs to be charged to 8.4V and USB is only 5.0V. You will need a boost converter (top up the voltage) and a charging circuit. I doubt that you can find the two combined into a small PCB. If you can...
  3. BobK

    Exchanging data variables?

    Your problem is at step 6. What can you do at that step that allows you to back to step 2 and have the process eventually stop with the correct answer? Bob
  4. BobK

    small 2s lipo charger with cutoff

    No.
  5. BobK

    Exchanging data variables?

    Think of it this way: You have an upper limit and a lower limit on what the secret number could be. Originally these are 0 and 99. Each guess refines your lower and upper limit, depending on whether your guess is high, low or correct. If coded correctly, those two limits and the next guess...
  6. BobK

    555 timer circuit

    How about a schematic? Bob
  7. BobK

    Control 2 wire DC motor with 4 wire controller?

    I am not familiar with that type of controller, so I cannot advise you. Bob
  8. BobK

    Control 2 wire DC motor with 4 wire controller?

    Probably not. How are the 4 outputs labeled? That might be a clue. Bob
  9. BobK

    Help identifying a 5 band resistor

    You do have a point there. If this was indeed a fusable resistor, upping the power rating is not a good idea. Bob
  10. BobK

    Variable resistor question

    Reactance is a generalization of resistance which applies to AC circuits having capacitors and inductors (as well as resistors). It is actually expressed as a complex number because the phase of current and voltage are off by 90 degrees in capacitors and inductors. The phase differs in...
  11. BobK

    Help identifying a 5 band resistor

    It is better to err on the side of higher power rating. If a 1W would fit, I would use it, rather than trying a 1/2 W. Bob
  12. BobK

    Wiring a 7-segment display to a rotary switch

    Easiest way to do it with a bunch of diodes. Each switch position connects power to each of the segments that need to be lighted through a diode. The diodes prevent the connections from other switch positions feeding back to a different one. The exact connection need depend on whether your...
  13. BobK

    Variable resistor question

    It depends on the voltage and current needed for the motor, do you know these? Bob
  14. BobK

    Variable resistor question

    Using a capacitor to control current only works with AC. With AC, a capacitor looks like a resistor that varies with frequency, but, unlike the resistor it will not dissipate any power and therefore not get hot. Bob
  15. BobK

    Changing strobe pattern?

    Yeah, I guess I do sound like a broken record. I just thought this example was a good one for one of the main benefits, the ability to make changes easily in software. Bob
  16. BobK

    Question about dependence of current in a circuit.

    LEDs are a special case where the curve relating voltage and current is very steep. I.e. a small change in voltage can cause a large change in current. Most other devices do not work that way. Additionally, the LED voltage at it's rated current is not very precise, it will vary over several...
  17. BobK

    Changing strobe pattern?

    Yep. There is bit to learn if you have not used microcontrollers, and particularly if you have not done any programming, but the benefits are huge. Bob
  18. BobK

    Power for TYC synch Motor

    My guess would be 100 to 127V AC 50 or 60 Hz. Bob
  19. BobK

    Changing strobe pattern?

    This is why almost every project should be done with a microcontroller. If you had done that, it would be a programming change that would take you about 1 minute. Edit: and it would have taken 1 chip instead of 3. Bob
  20. BobK

    Trying Buck Converter on Pspice

    Did you read my post? Your circuit is not going to work. Bob
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