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  1. KrisBlueNZ

    Zener diode help

    http://www.micrel.com/_PDF/mic29150.pdf
  2. KrisBlueNZ

    Setting up LED

    If the batteries are connected in series, the voltages add together. If they're connected in parallel, the currents add together. It could be done either way; the fact that the flashlight can be used with only one or two batteries for emergency situations implies that they're in parallel. If...
  3. KrisBlueNZ

    Traffic Light project

    The thing you're making is called a "color organ". Start with a Google image search for color organ schematic, and find the relevant pages from there.
  4. KrisBlueNZ

    Maintaining DC voltage across capacitor with signal?

    Yeah, what Laplace said. And an antenna connected to 2000V DC won't radiate anything... except possibly a bit of corona, a sizzling sound, and a slightly unpleasant smell, if the humidity is high.
  5. KrisBlueNZ

    Choosing an Opto Isolator

    Yes, that general setup will work. You feed +5V into the anode side of the LED, and when you pull the cathode side down to 0V, the LED sees voltage across it, and the SSR is activated. But if there is no resistor in series with the LED, there is nothing to limit the LED current, and things can...
  6. KrisBlueNZ

    Sequential Circuit Timing

    This thread is just wasting our time.
  7. KrisBlueNZ

    Old folks in-home personal alarm system?

    We found a product from Uniden for my mother. It has a "pendant" that you wear around your neck (or on your arm) with a HELP button on it, that works with a Uniden cordless phone base. This is how it works. When she holds the button for a few seconds, it starts the emergency procedure. She can...
  8. KrisBlueNZ

    Help please with transistors

    When you've replaced the transistors you should add a diode across the relay coil to protect Q2 against back EMF. This should have been included in the original design. The relay doesn't have a diode built-in. Here's how to connect it. Just tack it on the underside.
  9. KrisBlueNZ

    Trophy points implementation?

    Trophy points didn't exist until the recent upgrade of the forum software. The subject is under discussion. Make sure you're subscribed to the announcements forum! (The forum that this thread is in.)
  10. KrisBlueNZ

    PC Board Help

    What are you looking for? Software for PCB layout design? A company that can manufacture PCBs? A local electronic component supplier? You can find all of these with a few Google searches.
  11. KrisBlueNZ

    PCB Layout Help

    If you put your scope on the board again, try an experiment. Without moving the ground clip of your scope, remove the scope probe from the point in the circuit where you see the 52 kHz signal and touch it on the ground clip. If you see a similar signal, you can assume that it's just common-mode...
  12. KrisBlueNZ

    What purpose does this capacitor/resistor serve?

    Sounds like a snubber circuit - see https://en.wikipedia.org/wiki/Snubber#RC_snubbers
  13. KrisBlueNZ

    Sequential Circuit Timing

    If you're not talking about counterfeits, what's your evidence?
  14. KrisBlueNZ

    sampling communication lines without interfering the signal

    Yeah, that circuit will affect the signals. Here's what I suggest. This diagram shows four identical inverting buffers, with individually settable input voltage thresholds. Inputs come in at the bottom left. The circuit's 0V rail must be connected to the 0V rail of the camera-flash...
  15. KrisBlueNZ

    PCB Layout Help

    It's going to depend on the higher-frequency components in the 52 kHz signal. A 52 kHz sinewave will have no effect, but a 52 kHz square wave with rise times in the nanosecond range certainly could have an effect. But Olivier's suggestion is the right answer - eliminate the switching noise and...
  16. KrisBlueNZ

    Setting up LED

    That won't work for several reasons. That LED has a forward voltage VF of 3.1V. This means you need to provide 3.1V to it. A single AA cell will only supply 1.5V. There are various ways around this problem, including using three 1.5V cells in series, and a current regulator. That LED requires...
  17. KrisBlueNZ

    sampling communication lines without interfering the signal

    Thanks for the link to that description of the interface and protocol. He says that the circuitry uses a 4V supply, not a 3.3V supply. A logic analyser has high-impedance inputs that won't affect the signals significantly. Is it possible that your circuit is affecting the signals? What are...
  18. KrisBlueNZ

    Microwave Oven technology

    The buzz sound that you hear each time a heating cycle starts is caused by the magnetron filament heating up. During this time, the load on the transformer increases from almost zero to maximum, then it remains at maximum during the heating cycle. This is completely normal and does not mean that...
  19. KrisBlueNZ

    Important capacitor specs ?

    A 100 nF film capacitor will be fine. Film capacitors are not very space-efficient but they perform well.
  20. KrisBlueNZ

    MOSFET Gate Driving Problems

    I agree, a Baker clamp on Q2 in Steve's circuit in post #11 is a good idea if you want Q2 to switch OFF quickly. The Baker clamp would prevent Q2 from saturating, and the associated delay on switch-off; that's what a Baker clamp does. As Steve pointed out, if you use a Baker clamp on Q2, when...
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