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  1. P

    Using external xtal osc with a PIC

    Thanks, M. I haven't got a manual, as such. But looking at Microchip 33023A.PDF section 27.1, I cannot see a reference to EC. How would I describe it in the config file? Sorry for my ignorance but in the past I have only used the internal RC oscillator.
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    Using external xtal osc with a PIC

    I want to use a 20MHz crystal module as an oscillator fed into GPIO 5 of a PIC 12F629. Does that still tie up GPIO 4 pin as the OSC out pin, or can I use it as an input?
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    dc-cdi 12/220 issue

    My mistake. I thought you were referring to pin 5 of the 555.
  4. P

    dc-cdi 12/220 issue

    Pin 5 connects to an internal potential divider and normally sits at 2/3 supply volts. It should not be connected to 12V.
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    Tablet charging problem

    I think the problem is due to a change of impedance between two points.
  6. P

    HUH?????

    With that sort of psychobabble, he would make a successful politician.
  7. P

    The Formula for the Equivalent Resistance of Complex Resistance Network(Circuits)

    I make it 1ohm. Edit: Oops! My mistake.
  8. P

    Should a 555 timer ever get hot?

    The LDR does not control it because you have not connected the THR pin6. pins 2 and 6 should be connected together.
  9. P

    Calculating frequency

    Long ago I was taught a catchy little jingle to remember the formula:- "One over two pie root L C Equals the resonant frequency.".
  10. P

    DPDT switch question

    Sorry, Jim. there was a mistake in my reply. It should have said "In your case where there will be no current as you change over, so only...."
  11. P

    Koford (Slot Car) Bench Power Supply Project

    In my case I needed the full range of voltage available. The 10K is the main control and the 470ohm is a fine control. Yes - but that's no problem.
  12. P

    DPDT switch question

    Switches are rated at a lower DC current than AC because the arc produced by switching DC current can cause excessive heat. Using AC, the arc is self-quenching as the sine wave goes through zero volts so is not sustained. In your case where there will be current as you change over, so only the...
  13. P

    Need help with calculations for a ribbon speaker cable!

    Exactly!
  14. P

    Need help with calculations for a ribbon speaker cable!

    Peter. I have read your postings several times in an effort to understand your reasoning, and these are my views. It appears that you are designing a balanced transmission line between amplifier and speakers. If so, I don’t think you will have much success, for these reasons. Source and load...
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    Koford (Slot Car) Bench Power Supply Project

    You could try adding a small-value pot in series with your external pot to give finer adjustment. I use one of these units as a variable power supply and have removed the internal pot and replaced it with a 10K pot in series with a 470ohm pot, and that gives good results.
  16. P

    radiation pattern of yagi uda antenna is omnidirectional?

    Not sure what you mean by 'X-Y' sense, but horizontal or vertically mounted it will still be highly directional. the only thing that that will give you an Omni directional pattern is a vertical whip or a vertical dipole
  17. P

    radiation pattern of yagi uda antenna is omnidirectional?

    No, a Yagi antenna is directional. The more the directors, the narrower the angle of acceptance.
  18. P

    555 timer circuit

    Yes, that should do the trick.
  19. P

    555 timer circuit

    The time constant would be too low with a 1nF and 1k. There's no need for R2 to be so low. Try changing it to 47K and increase the cap to 10nF if necessary. Edit: I assume you have nothing else connected to pin 3 output that could slow down the fall time?
  20. P

    555 timer circuit

    I have usually found 1nF to be adequate if R2 is around 100k. What is the value of R2 in your circuit?
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