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 . 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.

 

Are you connecting the emitter of 2n3906 to the negative side of the battery?

 

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.

 

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.


Allen

 

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

 

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 switchView attachment 171800 . 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.

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?

 

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.

View attachment 171922 View attachment 171923
Allen

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

 

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


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

 

(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).

 

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

 

Have i made any mistakes in my circuit?

 

the circuit does not switch to indicate a negative phase. In the case of the latter, only the green led comes on as well.

Which LED is green?

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

I see no plots.

Have i made any mistakes in my circuit?

Nothing that I see.

 

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

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

 

sorry thought i posted link

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.