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  1. BobK

    Replace variable capacitor with varicap

    You need to couple it to the inductor via a capacitor. And, unless you use a separate isolated supply, you need two capacitors, one on either side of the inductor / varicap. Choose capacitors much larger than the capacitance of the varicap (say 100nF) so that it will not effect the range of...
  2. BobK

    Cleaning Soldering Iron Tips

    I clean my tip on brass (not steel) wool frequently while using it. The tip stay in tip-top shape. Like this one: https://www.amazon.com/dp/B00FZPGDLA/ref=psdc_13837401_t1_B00NS49LPU bob
  3. BobK

    Help with a project idea

    AVR microcontroller, not ARM microprocessor. Bob
  4. BobK

    Beginning electronics, understanding whats actually happening

    I hope I am never insulted by an AK47. Bob
  5. BobK

    Design bass amplifier

    Your post is not clear. Are you using 1 amplifier or 2 for low and high frqeuencies? Bob
  6. BobK

    Help with a project idea

    Arduino is one way you could do it. For a beginner, perhaps the most likely way to succeed. A matrix like Kelly's eye proposed will have the LEDs not at full brightness, since they will be on only a fraction of the time. You can up the current above the continuous max to compensate, but they...
  7. BobK

    MOSFET Circuit Help

    What do you think your MOSFET circuit is doing that would alleviate the problem? Bob
  8. BobK

    Clarification of terms S:N

    Noise is whatever is left when you subtract the signal. (or anything that comes out when I try to play the guitar) Bob
  9. BobK

    DIY Electric Shocking Mouse/Rat Trap

    Peanut butter works better, at least for mice. Bob
  10. BobK

    Airwick Freshmatic Max unit

    I doubt that that is a timing cap. More likely decoupling. All the micros I have used have an internal clock and do not need an external R and C. Can anyone read the markings on the chip? Bob
  11. BobK

    Beginner regulated power supply circuit help

    The formula you are using is for an unregulated supply. Any form of regulation will reduce the ripple. A decent one will reduce it to near zero. Bob
  12. BobK

    Design of constant current source.

    What is the voltage compliance range? I.e. from low to high, how much voltage must it be able to put out. Which is really the same question as what is the range of impedances of the load? How accurate does it have to be. If the voltage is reasonably low, like a few volts, 24V supply + a...
  13. BobK

    How do I make my own musical instrument?

    Sampling is the best method to duplicate realistic sounds. You would need to sample all the sounds of the real instrument at various notes and various forces, and interpolate in between. You best bet might be to buy a sampling synthesizer that allows you to sample new sounds yourself. Bob
  14. BobK

    Boost low volts at a few amps

    What is the speaker impedance? If you are using 8Ω speakers and it is a class D amp, the maximum current will be just under 1A. For 4Ω iw would be 7.5/4 = 1.875A. If it is a class AB amp running from 7.5V, those numbers would be half of that, so, I am assuming class D or bridge tied class AB...
  15. BobK

    Arduino Sound generator wanted

    No, it doesn't. The update is done only at each PWM cycle. If the PWM frequency is 50 KHz, then it is 20us per cycle, which is well within the ability of an 8MHz processor (160 instruction times). There is even sufficient time left over to do other tasks in the meanwhile. If you look at the...
  16. BobK

    Measuring CR123A battery using PIC A/D

    No, you use the battery as the reference, and you measure the internal voltage reference. If you used the internal reference for the ADC reference the battery would read off scale, since it is higher than the internal reference. On at least some PICs, you can select the internal reference as...
  17. BobK

    Multivibrator of varying frequency

    That is explained perfectly well in post #8. Bob
  18. BobK

    Cheap linear actuators

    I built my own kitchen cabinets. One of the reasons is so that there would be no voids. Bob
  19. BobK

    Measuring CR123A battery using PIC A/D

    You will get a different value with divider , but it will be based only on the ratio of the resistors in the divider. What you are doing is like trying to measure the accuracy of a ruler by measuring it with itself. You need another ruler. If your PIC has a votage reference built in, you can...
  20. BobK

    Measuring CR123A battery using PIC A/D

    If the battery is used as the reference and you are measuring the battery with the ADC, you will always get the same reading (1023 assuming 10-bit ADC) Bob
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