| Electronics > Beginners |
| Simple phase sequence detector using NAND gate |
| << < (3/4) > >> |
| soldar:
Yes, it should not be difficult to design one. Say the phases are A, B and C and each one generates a short pulse say at the top of the positive half cycle. Pulse from A sets a flip-flop that enables pulse B to light an LED. Pulse C resets the flipflop. If after pulse A comes pulse B it will light the LED. If after pulse A comes pulse C the flip flop will be reset when pulse B comes around and the LED will not light. I think this basic idea would work. |
| Zero999:
The circuit posted at the start of the thread can be easily fixed with the addition of an emitter follower, a base resistor and higher value current limiting resistors. |
| soldar:
I believe the common point of R4, R5, R6 should be also connected to GND. In the diagram it is connected to the Neutral which is not strictly necessary but doesn't hurt either. |
| Zero999:
--- Quote from: soldar on June 17, 2019, 09:47:24 pm ---I believe the common point of R4, R5, R6 should be also connected to GND. In the diagram it is connected to the Neutral which is not strictly necessary but doesn't hurt either. --- End quote --- Yes, you're right. The neutral should be the same as the circuit ground. |
| schmitt trigger:
I found the circuit. see attached. It is essentially identical to the circuit above, but it is optocoupled for safety. Resistor R, is selected for a peak current of 10 mA. As the optocoupler inverts the signal, a second transistor is required. EDIT: OOOOps! I forgot to include the antiparallel diode across the optocoupler input for phase A. |
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