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  1. KrisBlueNZ

    555 timer HELP

    I know. Your circuit will do that, with some changes. Read my previous reply. If you don't understand something, quote it and ask for clarification.
  2. KrisBlueNZ

    DC Controlled AC Load

    Yes, that SSR you've found looks suitable. If RS have a similar part that has zero-crossing switching, that would be better. Zero-crossing switching means that the switch device will only turn ON or OFF at the instant that the AC mains sinewave crosses 0V, either upwards or downwards. This...
  3. KrisBlueNZ

    DC Controlled AC Load

    Yes, and SCR would be alright on the DC side of the bridge rectifier. The bridge rectifier converts the alternating direction of the AC current into a single direction. The diagram in post #8 is not complete enough for me to say whether it will work or not. You would need some way to generate...
  4. KrisBlueNZ

    Re-ranging (mapping) values in C/C++

    Reducing colour resolution is easy - you just throw away the bottom bit(s) until you get the number of bits you want. For example, if you are converting from 16-bit colour where the value is split into a 5-bit red intensity value, a 5-bit blue intensity value, and a 6-bit green intensity value...
  5. KrisBlueNZ

    555 timer HELP

    As Harald said, the 555's output is normally low, and goes high during the pulse. So you need to remove the PNP transistor, and feed the 555's output to the MOSFET's gate. Usually a small series resistor e.g. 22 ohms is used, to reduce the peak current (the MOSFET's gate has significant...
  6. KrisBlueNZ

    DC Controlled AC Load

    Duke is right, it's valid to connect the AC inputs of a bridge rectifier in series with the load so you can switch the load with a DC device such as an SCR. Dave's design in post #4 will work, with the capacitor replaced by the DC switching device. This is a standard technique. But both sides...
  7. KrisBlueNZ

    LED Flasher help.

    If you want to de-clutter your build, you should take a step back and define exactly what you want to do. The best option to minimise clutter and maximise the ease of making future changes would be to use a microcontroller such as a PIC. A 40-pin device might be able to drive all your LEDs...
  8. KrisBlueNZ

    Need help with a PSU schematic

    That looks good to me. You've got both regulators dropping roughly the same amount of voltage, so they will dissipate roughly the same amount of power, which seems sensible.
  9. KrisBlueNZ

    Automotive headlamp/LED circuit help

    The following thread may be relevant. Start from post #12. https://www.electronicspoint.com/clamp-floating-input-t251881.html
  10. KrisBlueNZ

    Metal detector linking to Pic problem

    If you remove the capacitor from across the search coil, the circuit will oscillate at a much higher frequency than it should. The design frequency is 140 kHz according to the description. The PIC can't sample its analogue input fast enough to capture such a high frequency accurately. You can...
  11. KrisBlueNZ

    Flyback transformers

    The flyback transformer, also called the line output transformer or LOPT ("LOPP-tee"), is driven with a pulsed waveform at the horizontal scan frequency by the line output transistor. (Or MOSFET, I guess). The line output transistor conducts during the visible horizontal scan, as the electron...
  12. KrisBlueNZ

    Need help with a PSU schematic

    Right, only a small one. 0.1 µF or 1 µF and it can act as the output capacitor for the first regulator as well as the input capacitor for the second one. That will also reduce the power dissipation per regulator and might make the difference between heatsinking to the chassis and using...
  13. KrisBlueNZ

    Audio Preamplifier produces glitches (cracks)

    Does the sound come through both channels at the same time?
  14. KrisBlueNZ

    Need help with a PSU schematic

    Right. Well, you have various options. Connect multiple zeners in series to increase the power (two 5W zeners of the same voltage in series are rated 10W). Increase the zener voltage so less current flows. Increase the resistance and/or add a zener in series with the resistor - this will...
  15. KrisBlueNZ

    Need help with a PSU schematic

    That's right. I would put the resistor horizontal, connected closer to the bridge rectifier. That fits more with the way it's used. But that's just a cosmetic thing. Also, 1k is much higher than the values I'm suggesting.
  16. KrisBlueNZ

    Voltage or Amplitude?

    Both. 1 mA is a reasonable collector current for an audio preamplifier with medium-impedance output - it yields a collector resistor of 4k which is typical for an audio preamplifier stage. The 0.7V value comes from the base-emitter voltage of a small-signal bipolar junction transistor with...
  17. KrisBlueNZ

    Need help with a PSU schematic

    Nearly. The voltage to the regulator should come from the smoothing capacitor as well. The series resistor connects between the positive output of the bridge and everything else. Nothing else connects directly to the bridge output.
  18. KrisBlueNZ

    Need help with a PSU schematic

    That's not what I mean either. Connect the resistor between the positive output of the top bridge rectifier and the positive terminal of the smoothing capacitor. Connect the zener across the smoothing capacitor. Or use a higher-voltage zener from the high voltage unregulated rail to 0V. Don't...
  19. KrisBlueNZ

    Need help with a PSU schematic

    Whoa! That schematic is hard to read. But I think you've put the series resistor in series with the zener. My suggestion is to connect it between the positive output of the top bridge rectifier and the smoothing capacitor. You could also connect a resistor in series with the zener, but the other...
  20. KrisBlueNZ

    6 CELL LI-ION 22.2V BATTERY LEVEL MONITOR

    Actually no. Fixing the LM336Z connection probably won't affect anything much. You'll need to readjust the trimpots, but that's all. I really need to know what the LED is doing, with R6 disconnected. Can you run through my steps in post #44 again? Especially steps 5 and 6.
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