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  1. (*steve*)

    Having trouble identifying a diode needed for a repair.

    That chip is a serial input latched driver, so unlikely to be mains voltage, but low voltage rectifier or input protection are a definite possibility
  2. (*steve*)

    Having trouble identifying a diode needed for a repair.

    Yeah, especially if that is a voltage selector switch. Those wires might even come from the incoming mains.
  3. (*steve*)

    Cheapest way to get data from multiple(100s) of sensors?

    This page http://www.thebox.myzen.co.uk/Workshop/LED_Sensing.html describes how a led on its own can act as a light and a light sensor (although not at the same time). If you turn on the LEDs around one that is a sensor, you should be able to determine if there is something in front of that...
  4. (*steve*)

    Cheapest way to get data from multiple(100s) of sensors?

    I've been away from this thread. I was envisaging a linear array, but that was wrong... I wonder if you e thought of using the IR LEDs as the sensor as well as the source of light? I've seen this done with visible LEDs but I cant see why it can't be done with IR LEDs. It might take a little...
  5. (*steve*)

    NPN transistor as switch for LED problem

    And/or maybe a moderate value resistor across the LED so the leakage current does not flow through the LED. The resistance must be such that the leakage current causes a voltage drop significantly less than Vf for the LED
  6. (*steve*)

    LEDs in parallel don't consume sum of individual currents??

    Ok, I'm going to attempt a thought experiment involving public math and an undetermined outcome. Lets see how well I foul it up. (and I'm doing it on a phone, so beware autocratic ions) Lets assume three identical LEDs with a constant dynamic resistance of 0.1V/5mA (20 ohms) for currents...
  7. (*steve*)

    Having trouble identifying a diode needed for a repair.

    Excellent. Is one end connected to the "signal"? If so, where is the other end connected? There are two, are they connected in parallel, inverse parallel, or perhaps in series? Out of interest, if they are undamaged, why the question?
  8. (*steve*)

    Having trouble identifying a diode needed for a repair.

    Where is it used in the circuit?
  9. (*steve*)

    Part required or is another suitable

    It looks to me like it is hard wired to load a particular value, one where most of the bits are the same.
  10. (*steve*)

    Part required or is another suitable

    Perhaps a photo of the board will tell us much more than your drawing.
  11. (*steve*)

    Switching leds

    Dave jones of eevblog did something very similar to change a LED on a soldering iron. If you can find that video, he goes into some detail about various methods. Here it is:
  12. (*steve*)

    transistor equivalents

    The next step, if we get an odd voltage is to trace the circuit and determine the role of the zener -- maybe its not a voltage reference.
  13. (*steve*)

    LEDs in parallel don't consume sum of individual currents??

    Aka "burden voltage". If you have a bench supply with separate sense inputs then you can regulate the voltage at a point other than the output terminals allowing you to cancel out issues caused by the burden voltage, lead resistance, etc.
  14. (*steve*)

    transistor equivalents

    Ok, place the original zeners back into the circuit and measure them again
  15. (*steve*)

    transistor equivalents

    I guess I should also ask the part number of the other zener you replaced. I really hope you didn't use an BZX85c36 here also.
  16. (*steve*)

    transistor equivalents

    The zener BZX85c36 is unlikely to be the correct part. It is a 36 v zener. Can you double check the one you removed. I really hope you still have the parts you removed, otherwise we're in deep do-do
  17. (*steve*)

    LEDs in parallel don't consume sum of individual currents??

    The alternative explanation is that each led has a slightly different forward voltage for a given current. This can also be expressed as them having significant differences in forward current at the same forward voltage. The upshot of this is that placing several LEDs in parallel will cause an...
  18. (*steve*)

    Small DC motor powering another DC motor to generator

    It depends on the type of motor you're using as a generator. But in general, yes you can use the power you're generating, but beware that it may vary significantly based on speed and load. Also remember you'll get significantly less power out of the generator than you put into the motor.
  19. (*steve*)

    Simple 12v 3amp power supply

    You won't get 3A DC unless you use a switch mode regulator. With a linear regulator the max current without overloading the transformer is a little over 2A.
  20. (*steve*)

    Latching circuit with enable/disable latching mode.

    There are many ways to do this, however one relatively simple way may be to use a Schmitt trigger and alter the bias point of your phototransistors' output to be either below the hysteresis range (so it will follow) or within it (so it will latch). The same effect can be achieved by changing...
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