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Thread: Leviton GFCI nuisance tripping and circuit analysis

  1. #171
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    190119-2347 EST

    tersh:

    A typical LED in the forward diode direction, direction in which light is produced, has a voltage drop of 1 to 2 V before current is so high as to destroy the LED. If you were to drive a single LED from 240 and wanted to hold the currnet to about 10 mA, then the series R needs to be greater than 24000 ohms. Further you would need a shunt diode in parallel with the LED, and reverse biased, to conduct when the LED was back biased to prevent excessive peak inverse voltage (PIV) on the LED.

    Q1 --- Any two conductive elements spaced by an insulator form a capacitor. Two adjacent wires form a capacitor, but of a small value. Two wires in a CAT-5 cable have about 15 pfd per foot.

    Q2 --- Longer wires produce greater capacitance. Cutting a wire will reduce capacitance in an otherwise un-modified layout.

    Q3 --- If pins 1, 2, and 3 are shorted together, then the voltage between them is essentially 0. Thus, capacitive coupling to the wires would not put a signal into the chip. If a signal between 123 together and 4 was present, and if the chip was sensitive to this as a signal, then tripping from capacitive coupling could occur. But I think 1,2,3 are some form of differential amplifier input.

    Q4 --- May or may not be a current imbalance. A different time constant for the inverse time function could make a difference between different manufacturers.

    Q5 --- See my first comment before Q1. Your circuit that includes the LED can not be correct as you have drawn it. See my earlier post.

    .

  2. #172
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    Quote Originally Posted by tersh View Post
    I have traced the mistakes about the LED. In the following circuit trace, the LED terminal is clearly labeled N, so it should go to the black which is N, and using continuity test confirms it. It's not really connected to the Hot red line.



    So the circuit diagram is reflecting the corrections:



    What do you think about the above, the LED is not directly connected to the red line, but only the black line.

    I made some measurements. First with a normal working pcb and with one where pin 1 was cut destroying the SCR (it seems without Rset, pin 7 fires with continuously cycle, let's discuss this some other time)

    In the normal pcb with no red led on, pin 5 has ac of 12.2v and dc of 15.4v
    In the fried SCR pcb with red led on, pin 5 has ac of 29v and no dc voltage! why?

    for the working pcb Resistor going to pin 5, the voltage is 119v ac, 94.4 dc
    for the fried SCR pcb, Resistor going to pin 5, the voltage is 115v ac, 95v dc
    (it's almost the same between them)

    for the working pcb, diode going to pin 5, the voltage is 113v ac, 108v dc
    for the fried SCR pcb, diode going to pin 5, the voltage is 113v ac, 90v dc

    for both, the 100ohm going to pin 5 is about 8.4 volts

    for the bad pcb, the 4.7kohm parallel to led measures 10.5v ac, 7.95v dc
    for the good pcb, the 4.7kohm parallel to led measures 13.8 ac, no dc!

    when I mentioned bad pcb (or one with fried SCR), the red led turns on continuously. Never on the good pcb.

    From the above. Any clue what triggers or turn on the red led?? Also note that whenever the red led is on, you can never reset the solenoid. So the reset circuit is connected to whether the red led is one or not.

    (please don't miss my last message about the transient analysis, thanks).
    Btw. The 1 meg ohm resistor is from.collector to ac line red. Not black. I put red in original diagram but when i changed the led leg to black ac line. I moved the 1M ohm to black as well. It should be red..thanks.



    Havent traced a circuit even in college. First time. Sorry.
    Last edited by tersh; Today at 08:40 AM.

  3. #173
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    gar and other electronics experts, above is the clearest diagram so far...

    but note during normal operation, the red led never light up. only during fault. What do you think
    should be in the violet dot so the red led would turn on?

    again the measurements in my message #170

    I made some measurements. First with a normal working pcb and with one where pin 1 was cut destroying the SCR (it seems without Rset, pin 7 fires with continuously cycle, let's discuss this some other time)

    In the normal pcb with no red led on, pin 5 has ac of 12.2v and dc of 15.4v
    In the fried SCR pcb with red led on, pin 5 has ac of 29v and no dc voltage! why?

    for the working pcb Resistor going to pin 5, the voltage is 119v ac, 94.4 dc
    for the fried SCR pcb, Resistor going to pin 5, the voltage is 115v ac, 95v dc
    (it's almost the same between them)

    for the working pcb, diode going to pin 5, the voltage is 113v ac, 108v dc
    for the fried SCR pcb, diode going to pin 5, the voltage is 113v ac, 90v dc

    for both, the 100ohm going to pin 5 is about 8.4 volts

    for the bad pcb, the 4.7kohm parallel to led measures 10.5v ac, 7.95v dc
    for the good pcb, the 4.7kohm parallel to led measures 13.8 ac, no dc!

    when I mentioned bad pcb (or one with fried SCR), the red led turns on continuously. Never on the good pcb.

    From the above. Any clue what triggers or turn on the red led?? Also note that whenever the red led is on, you can never reset the solenoid. So the reset circuit is connected to whether the red led is one or not.

  4. #174
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    A repeat- you need to download and learn to use one of the fea circuit analysis tools such as LTSpice or Orcad student version PSpice.

    Don't expect someone else to analyze incomplete schematics provided piecemeal.

    Include in your model the effects of opening one line of the SP motor that leave one line thru the CTs with a current flowing, compare to the delay times of the trip circuits,

    etc.

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