checking for three phase rotation

Discussion in 'Digital Circuit Design' started by raddom2, Mar 7, 2019.

  1. raddom2

    Thread Starter New Member

    Oct 17, 2018
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    Hello. i am trying to implement this circuit found online. However, I am running into an issue with getting a high and low on the output pin 11 which should cause the LEDs to switch phase checker official.png . Pins 7 and 14 are not included in the schematic i have drawn, but they are being used in real life. Pin 14 (Vdd) will be going to the 12 volts.
     
  2. absf

    AAC Fanatic!

    Dec 29, 2010
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    Are you connecting the emitter of 2n3906 to the negative side of the battery?
     
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  3. raddom2

    Thread Starter New Member

    Oct 17, 2018
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    No to the positive, the negative is to be connected to ground. I have done this in lab but the simulation is an error in that part. Apart from that how would you suggest I get a low and high on the output.
     
  4. absf

    AAC Fanatic!

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    I did a sim in proteus. Though the inputs of U1D are pulsing, the output is a permanent 7.3V DC (not pulsing). As you can see from 2nd picture attached.

    I need more time to find out why or may be other members know why it's so.

    3Ph_rotate_1.PNG 3Ph_rotate_2A.PNG
    Allen
     
  5. absf

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    I checked more closely on the scope and found out that the inputs of U1D are not at 0V level.

    A is at +/- 6V, while B is at +10/-2V level.

    Allen
     
  6. mvas

    Member

    Jun 19, 2017
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    Is your R6 too low ?
    What is the maximum allowed milliamps at output of U1D Pin 11?
    What Phase Rotation does your circuit detect: CW or CCW?
     
    Last edited: Mar 9, 2019
  7. mvas

    Member

    Jun 19, 2017
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    is the Rotation of the Phases A => B => C, from the top, to the bottom?

    What happens if you reverse the Rotation to C => B => A, from the bottom, to the top?
    Now ...
    Will the S-R latch turn ON ( point "B" = HIGH ) when Phase C & Phase B are both ON?
    Then Phase A needs to turn ON ( point "A" = HIGH ) , before Phase B turns off
    With BOTH Point "A" = High and Point "B" = High, then point "C" will be LOW and Q1 will energize ...
    D7 will turn OFF and D8 will turn ON ?

    Also, your R8 may be too a low value
     
    Last edited: Mar 9, 2019
  8. absf

    AAC Fanatic!

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    Yes the phase was from A->B->C as attached...

    3Ph_rotate_1A.PNG
    Your right, R8 was too low. After changing it to 470 ohms, it was able to display a logic high on the logic probe.
    I'll try changing the order of the phase tomorrow as its getting too late now.

    Allen
     
  9. crutschow

    Expert

    Mar 14, 2008
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    (From my post on your thread from another site with the same question).
    Below is my LTspice simulation of the circuit, which appears to work properly.
    V11 (orange trace) pulses low at the line frequency with the shown phase sequence (both LEDs rapidly blinking with D8 brighter).
    An incorrect sequence or a missing phase generates a constant high at V11 (LED D8 constantly ON).

    Note the the CD4011 can't readily drive such a low impedance load, as shown in your circuit, so I modified the LED driver (makes me think the circuit was never built by the circuit's author).

    upload_2019-3-9_14-3-17.png
     
    Last edited: Mar 9, 2019
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  10. raddom2

    Thread Starter New Member

    Oct 17, 2018
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    I appreciate all of the feedback. I have attempted to simulate both circuits to implement your suggestions. However, neither work for me. In the case of adding the 470 ohm resistor, the circuit does not switch to indicate a negative phase. In the case of the latter, only the green led comes on as well. I have included the original author's schematic and @crutschow model which I followed close as possible with what I had in MultiSim. I could not get my graphs to appear singularly on one graph so i will include the voltage of the output pins in separate graphs.

    Original and Volatge plots for lines A,B,C and Output pins 3,4,11
     
  11. raddom2

    Thread Starter New Member

    Oct 17, 2018
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    Have i made any mistakes in my circuit?
     
  12. crutschow

    Expert

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    Which LED is green?
    I see no plots.
    Nothing that I see.
     
  13. raddom2

    Thread Starter New Member

    Oct 17, 2018
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    sorry thought i posted link: https://imgur.com/a/ZhjnaEk
    led 2 is green, led 1 red
     
  14. crutschow

    Expert

    Mar 14, 2008
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    Why not just post them here?
    I don't like going to unknown sites.

    And you need to figure out how to put more than one trace on a plot.
    It's too difficult to follow what's happening by looking at all those different plots.

    Below is my sim with with the loss of Phase A at about 40ms.
    For that condition the green LED stays ON and the Red LED stays off.
    This will happen for any loss of phase or incorrect phase sequence.

    upload_2019-3-18_12-11-23.png
     
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