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  1. KrisBlueNZ

    555 simple oscillator not working with small capacitors

    I'm not too sure what you're doing, but... (1) You shouldn't use 300 ohm resistors with a 555. Use 1k at least, as shown on your schematic. (2) A sound card will not record frequencies greater than around 20 kHz. Normally, sound cards sample at 44,100 samples per second, so according to...
  2. KrisBlueNZ

    Need help with motor control

    Hello and welcome to Electronics Point. Unfortunately, my crystal ball is away for repolishing, so you're going to have to post a schematic. Edit: Try connecting them in parallel instead of in series.
  3. KrisBlueNZ

    Newbie needs help with basics

    Hello and welcome to Electronics Point :-) Your circuit looks right to me. Each light will have a second connection (may just be the metal holder) which needs to connect to ground (the chassis). Both lights will be powered from the same wire from the flasher, unless you want them to flash...
  4. KrisBlueNZ

    Use Of Current Source?

    Hi Sarabjot and welcome to Electronics Point. The circuit that you linked to is a source follower. This is the FET/MOSFET equivalent of an emitter follower and is used as a buffer. It is not a current source. There is a link on that page to another page...
  5. KrisBlueNZ

    timer

    Hello Deigh. I think we probably do need a bit more information. You want the unit to be battery powered, and to fit into a matchbox? Have you worked out how you will detect when something is placed on it? A very sensitive switch perhaps? Can you describe the purpose of this thing? That...
  6. KrisBlueNZ

    Forward voltage help!

    OK, well, the LEDs at least seem to have reasonable specifications. They're designed to operate at 750 mA. If you connect three of them in series, which is the best option, you need to feed 750 mA through the series string. The forward voltages add together, so the total voltage across the...
  7. KrisBlueNZ

    Hi, pretty basic question about a simple CMOS TTL circuit

    When the Hazard switch is OFF, you don't want the circuit to do anything, right? And when it's ON, an identical signal comes in on LSIG and RSIG, so you don't need to gate them together; you don't even need both signals. You want your LED to illuminate when SolSIG is at +12V and LSIG (or RSIG...
  8. KrisBlueNZ

    Forward voltage help!

    Hello Simon :-) Welcome to Electronics Point. In addition to what Steve has said... The forward voltage for an LED is the voltage that will be across it when it is running with a particular current through it (current loosely relates to brightness). Usually, the recommended or nominal current...
  9. KrisBlueNZ

    identify an IC

    Yes; microcontrollers in 6-pin SOT-23 packages are available from Atmel and Microchip, and possibly others.
  10. KrisBlueNZ

    need a "translator" for 12 VDC power supply project

    That's a very good video. Making the output voltage of a PC power supply adjustable is not simple. It may not necessarily even be possible. It depends very much on the design of the power supply. This is why Fish suggested using external light bulbs to reduce the voltage to suit your...
  11. KrisBlueNZ

    How do I build a Metal Detector?

    I'm not sure what you mean. Are you saying that the frequency reported by the microcontroller's frequency capture module is varying constantly over a wide range? If so, that could mean that the oscillator is not stable, or that the frequency capture module doesn't work properly or is not being...
  12. KrisBlueNZ

    Split Rail Power Supply

    OK. Turn R6 fully anticlockwise. Connect a voltmeter between points E and F. Don't connect anything to the output rails. Power up the circuit from 12~18V DC. Slowly turn R6 clockwise while watching the meter. The reading will increase. When it reaches 66 mV ±10%, stop turning R6. Leave the...
  13. KrisBlueNZ

    Help With Electret Microphone Project?

    I think you'll find that the electret microphones sound horrible for music. Their frequency response graph will look roughly like a silhouette of the Andes, and putting them in a tube will make things ten times worse. They're also not compatible with standard balanced microphone connection...
  14. KrisBlueNZ

    Astable multivibrator calculations and Multisim

    What do you mean it "worked"? With higher resistances, t(high) in the simulation is a lot closer to the calculated period, and t(low) in the simulation has dropped from being about 10% longer than calculated, to 1.2% longer than calculated, right? If so, that confirms my suspicion that the...
  15. KrisBlueNZ

    capacitor polarity in a phono stage project

    Steve, do you know of any properly tested cases where these differences were detectable by a listener, or are they only measurable?
  16. KrisBlueNZ

    Astable multivibrator calculations and Multisim

    Not exactly. ln(2) is actually closer to 0.693147180559945309417232, according to Windows Calculator! Certainly the value in the data sheet doesn't need to be specified to that accuracy, and I wasn't trying to imply that it should be, although it does look like I was. The issue with the value in...
  17. KrisBlueNZ

    Astable multivibrator calculations and Multisim

    The "correct" formulas are for C charging through R1+R2 towards VCC from 1/3 VCC to 2/3 VCC (output high period), and for C discharging through R2 towards GND from 2/3 VCC to 1/3 VCC (output low period). The time taken for the voltage across the resistor to drop to half its initial value when...
  18. KrisBlueNZ

    Astable multivibrator calculations and Multisim

    I need more information:
  19. KrisBlueNZ

    do you know these resistors?

    No, I don't think using a BC182L instead of a BC182LB (or BC212L instead of a BC212LB) would cause a problem. This is what I suggest. 1. Replace the four black diodes (D1~4) with 1N4006 or 1N4007. They may measure OK but still be faulty. I doubt that the small diode will be damaged but you...
  20. KrisBlueNZ

    Changing the sensitivity of a photo cell

    I can't follow the circuit in that area from those photos. You need to take some better ones. See https://www.electronicspoint.com/take-photos-circuit-boards-t267883.html
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