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  1. BobK

    Wireless power transmission

    Your information is old: http://www.technologyreview.com/news/413957/intels-wireless-power-play/ Bob
  2. BobK

    On-board image processing

    Agree with C.C. I would be looking at a powerful ARM based cpu for this. Bob
  3. BobK

    Looking for a simple circuit for power regulation and led indicator light

    This looks like a classic case of voltage creep. You better hurry up and finish this project before you have to start dealing with dangerously high voltages... bob
  4. BobK

    Transistor amplifier

    Why do bathroom cleaners advertise scubbing bubbles? Bob
  5. BobK

    is there a such thing as a "variable relay"

    But the relay is either on or off. He is talking about a variable control. Bob
  6. BobK

    Transistor amplifier

    Neither the BJT nor the MOSFET is very linear. A good amplifier will rely on negative feedback to make it linear, which can be done with either. Bob
  7. BobK

    dc switching power supply question

    There should be no problem with the power supply being turned off and on daily. How are the LEDs wired? I think it is more likely that you are pushing the current limits of the power supply. If you have a multimeter, measure the current draw. Depending on on how the LEDs are wired, and I am...
  8. BobK

    dc switching power supply question

    He said he had an LED aquarium light. Bob
  9. BobK

    Magnet coil help (turns, gauge, for coilgun)

    I did actually give coil guns a little thought. Must be due to the congitive dissonace of my abhorance for firearms and my secret desire to off those damn squirrels that eat all of our bird seed. I think it would be a fun (and challenging) project. Bob
  10. BobK

    How do I use these PCBs?

    Yep, I keep clipped leads in a tray for future use. My wife keeps asking if they are trash. Bob
  11. BobK

    Magnet coil help (turns, gauge, for coilgun)

    By the way, how were you planning to control the timing of your 100 coils? Bob
  12. BobK

    Magnet coil help (turns, gauge, for coilgun)

    If the current is limited by resistance, nearly all of the energy is going into heat, not into accelerating your projectile. The way an inductor works, is you place a voltage across it, and the current builds at a rate that depends on the voltage and the inductance. The equation is: dI/dt =...
  13. BobK

    Transistor amplifier

    As a microphone preamp, that circuit is probably okay. What are you using for input? Any amplifier will distort when the input times the gain exceeds the voltage that it can output. If you want to make a simple (inefiicient) amplifier that will drive a speaker, do the following: 1...
  14. BobK

    is there a such thing as a "variable relay"

    The method being discussed is a terrible way to control AC power. You need to use the type of circuit an AC dimmer uses, which is a triac. For AC interfaced to a microprocessor you would use am opto-isolated triac. The input can be safely operated from the micro and the output can control...
  15. BobK

    Transistor amplifier

    Which MOSFET? Bob
  16. BobK

    Transistor amplifier

    Your terminology led me to believe you had an NPN bipolar junction transistor. MOSFETs don't have an emitter, collector or base. If you don't know what kind of transistor it is, how can you know which lead is which, there is not standard for pinout. I suggest that you start by getting a known...
  17. BobK

    analoge to PWM with a fixed 10 MHZ frequency

    It means you have something in common with Newt Gingrich. bob
  18. BobK

    How do I use these PCBs?

    You would solder the leads of the components to the pads, and then use fine wire (wire-wrapping wire) to connect the pads of different components (also soldered). Or use bare wire to connect along rows or columns of holes. In my opinion this is not a very good prototyping technique. The...
  19. BobK

    gate driver circuit for mosfet

    It is bypassing the gate resitor during the turn off phase to make it turn off faster. Bob
  20. BobK

    Transistor amplifier

    The resistor would go from the battery + to the base of the transistor. You want it to make the collector 1/2 the battery voltage when there is not input signal. Start with 1K, if the collector voltage goes too low, raise it, if not low enough lower the value of the resistor. This technique...
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