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  1. BobK

    Resonance

    Once again you have not told us what you want to do. You have told us what you think you need (and your statements here are confusing at best). Tell us what you are trying to achieve, not that you need an oscillator in the range of 100KHz to 100GHz (which you surely will not be able to build)...
  2. BobK

    How to connect more LED ?

    Read this: https://www.electronicspoint.com/got-question-driving-leds-t256849.html Bob
  3. BobK

    Transistor, AC amplification

    Add a capacitor between the AC source and the base. Otherwise your DC biasing resistors will simply be overridden by the AC voltage. Bob
  4. BobK

    Dual Polarity high current OF PSU computer

    You can't. The -12V supply is low current. Bob
  5. BobK

    Transistor, AC amplification

    You have two voltages driving the same net, V2 and V3. Also the circuit is not very good even if you decoupled with a capacitor. You need two resistors to bias the base, one to ground and one to V+. And you need a capacitor to couple the input so the base is not absolutely driven by the...
  6. BobK

    Transistor, AC amplification

    I see no circuit here. Bob
  7. BobK

    Replace a pot with a ¿resistor?

    The two pots are for the 2 channels, I presume. Yes, two resistors would always work, hower equal resistance might not be the best. Try temporarily substituting a working pot and measure the two resistors (center pin to each out pin) at the volume you want to set it at. Bob
  8. BobK

    Transistor Mosfet pairs to drive LED cube layers

    SOT 523 1.7 x .98 mm SOT 23 2.9 x 1.3 mm So they are a bit bigger than what you are looking at. Bob
  9. BobK

    selecting motor

    No, I misinterpreted it. I thought you were saying that calling it a motor was slang, and a modern defintiion of motor would not include an internal combustion engine. Bob
  10. BobK

    Help with simple electronics circuit

    The ground symbol indicates a common connection. I.e. all things that connect to a ground are connected together. So the two circuits you show are identical, just represented differently. The symbol you show is actually an earth ground, which means they should be connected to rod driving into...
  11. BobK

    Replace a pot with a ¿resistor?

    A pot can be replaced not by one resistor, but by two. You would attach both to the middle pin of the pot and the other two ends to the two other pins. You could size to two resistors to select any volume level you wanted. The sum of the two resistors should be close the resistance of the...
  12. BobK

    Transistor Mosfet pairs to drive LED cube layers

    What package are they? A SOT-23, which is the most common package for SMT MOSFETS, it really pretty easy to solder by hand with a soldering iron. You just need a very fine conical tip, fine solder wire, some tweezers, and a good magnifier. Of course, you would almost have to have a PCB, but...
  13. BobK

    details about LED displays and VLC

    Pravin, Have you ever heard of an activity known as research? Or an amazing service known as Google? Bob
  14. BobK

    selecting motor

    C.C. Look up the definition of motor on the web. Most of the defs I found included internal combustion engine as an example of a motor. I think motor is the more general term. Boib
  15. BobK

    selecting motor

    Since no one else is answering, I will try. The problem with your post is that it is so vague that it cannot be answered. What is good speed? This might mean anything from walking speed to 100K/hr. What is good torque? At what RPM? Did you know that you can increase torque by...
  16. BobK

    Adding a timer to a siren

    With the switch closed it should remain on indefinitely, then continue for a period after the switch is off again. Isn't that what you want? Bob
  17. BobK

    USB functions with PIC18F4550

    CD or DVD possibly? Bob
  18. BobK

    diy iphone charger efficeny

    Okay, I found the place where the diagrams you posted came from. These resistors on the D+ and D- lines apply only to Apple products, and they set voltages that determine how much current they will pull for charging. If you read it you will find that different values of resistor dividers will...
  19. BobK

    diy iphone charger efficeny

    Efficiency does not mean what you think it means. You might have a charger that charges the phone in one hour but is less efficient than one that charges it in two hours. Efficiency here means (energy put the battery) / (energy used by the charger). Is this what you are asking, or are you...
  20. BobK

    Resonance

    Resonance is not going to have much to do with pulses at the rates you are talking about. Yes, you could build resonant circuits for those low frequencies but it would take them minutes to settle when a signal was received. If you want help, stop asking questions that don't make any sense...
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