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  1. KrisBlueNZ

    Connecting Circuit to 12V Power Supply

    Right, you shouldn't connect either of the outputs to +12V and 0V - that means that the output could short out the 12V power supply, hence the spark you saw. Each output acts as a switch, when you wire to the COM and NO pins. (It doesn't matter which way round.) Each output should be connected...
  2. KrisBlueNZ

    Potentiometer Burnout

    LOL :-) Hey, it looks good! (On the outside, at least...)
  3. KrisBlueNZ

    LED optic sensor circuit

    Yeah, sorry. kpatz put me on the right track. See post #44.
  4. KrisBlueNZ

    LED optic sensor circuit

    Oh, you're right! I thought he was talking about adding the transistor to the photodiode he already had. I've probably really confused him now! Jim (the OP), you could do what I suggest if you go back to using the photodiode, with a separate transistor. You could prove for sure that the...
  5. KrisBlueNZ

    LED optic sensor circuit

    No, the detector is a photodiode and the transistor is just a 2N3904 or similar. It's not just the speed that's the issue. Without a resistor, it may be too sensitive to light and it might never turn off. I agree it'll probably be fine, but now's the chance to do it properly.
  6. KrisBlueNZ

    Potentiometer Burnout

    Wow, what a huge improvement! It's like you've weeded the garden! I think your 74HC4067 has its GND and -EN pins connected to +3.3V! You might want to keep the pushbuttons separate from the analogue stuff - use separate feeds from +3.3V and GND from the Teensy for them, and keep them...
  7. KrisBlueNZ

    LED optic sensor circuit

    Cool! That's great. You don't need to match the 800 mV. The circuit that is monitoring that signal is almost certainly digital; in other words, it has a threshold (that will be somewhere between 1V and 3V, probably) and it only cares whether your voltage is below that threshold or above it. So...
  8. KrisBlueNZ

    IR proximity sensor

    It simply detects changing shadows. As a person moves near the photodiode, the amount of light falling on the photodiode changes. Typically, it will decrease then increase. The change may not be great. But a change is what your circuit needs to detect. It doesn't need to be "calibrated according...
  9. KrisBlueNZ

    LED optic sensor circuit

    OK, that's a pretty clear indication that it's a photodiode. On the first reading you took, where the multimeter displayed 633, your red probe was on the anode and the black probe was on the cathode. Which one of these corresponds to the flat on the skirt at the base of the package? Also, is...
  10. KrisBlueNZ

    How to identify capactiors

    You won't find a 2 µF capacitor these days; the closest is 2.2 µF, but that will be fine. Abbreviating capacitor values like that is done to save space on schematic diagrams. I don't think I've ever seen an actual capacitor marked that way, but I'm sure Olivier is right when he says some...
  11. KrisBlueNZ

    Buying a dimmable power supply

    Yes, I think it will be suitable, as long as the current isn't too high. The voltage you need (38.4~43V) is within the specification (25~54V). The output current is 25% higher than you want (250 mA vs. 200 mA) so you should check that LEDs can handle it. From your description of the it seems...
  12. KrisBlueNZ

    Convert Wireless PIR sensor to use power supply instead of Batteries

    Yes, that looks suitable. 12V at 5A is HEAPS to supply seven devices. At that price, that power supply is probably a cheap Chinese POS that could blow up at any moment, so I hope this is not a critical application. Good luck!
  13. KrisBlueNZ

    Help with power board problem pls

    OK. For the NTC thermistor, Maplin don't have anything suitable. RS Components have one that looks suitable: http://uk.rs-online.com/web/p/thermistors/2117986/ Once you tell us more about the bridge rectifier and the main switching device (on the heatsink) we may be able to suggest suitable...
  14. KrisBlueNZ

    Help with power board problem pls

    Desolder and remove the bridge rectifier and TH901. TH901 is not an MOV, although it looks like it could be one. It's a Microtherm brand NTC (negative temperature coefficient) thermistor. It acts to suppress surge current, not voltage. Measure the TH901 component on resistance range. If it's...
  15. KrisBlueNZ

    LED Flasher help.

    OK... OK! That's probably an important bit of information. Nice work Sherlock :-) Did you work from version 002 of the circuit? The version in post #21, that has the diodes in series with the drain paths from Q1, Q2 and Q3? If not, you'll need to add them. If that doesn't help, you could try...
  16. KrisBlueNZ

    LED optic sensor circuit

    It could cause a problem with slow turn-off, which might possibly mean it would fail to detect the ball if it was falling quickly. But if it's a phototransistor, it definitely should not need an extra transistor. If it's a phototransistor, you should get the behaviour that Rick L describes...
  17. KrisBlueNZ

    Potentiometer Burnout

    Good idea. Can you add a box or a dotted box around them all to indicate that they're part of the same unit?
  18. KrisBlueNZ

    Designing a Time Delayed Relay

    I have one more update for the current version of the design. Updated schematic: A layout suggestion: Paler tracks are on the underside. I think I went a bit overboard on the vias! I'll respond to your other questions soon.
  19. KrisBlueNZ

    LED optic sensor circuit

    You're still using a 10K resistor on the detector? You should be. The 220 ohm, or lower, resistor is only for the LED. Well, maybe we should go back to the theory that the detector is a photodiode, not a phototransistor. You can try connecting it to a separate transistor. Any small-signal NPN...
  20. KrisBlueNZ

    Potentiometer Burnout

    Maybe it's Stephen King's pet rabbit :-) I see. I think it would be useful to show the two potentiometers and the pushbutton inside the rectangle that's marked "JOYSTICK". It's pretty obvious from the pin names, but a diagram wouldn't hurt, if it's possible to do that.
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