Help on this zero-volt triggered(switched) circuit

Thread Starter


Joined Oct 14, 2007

This is my first post. I am a novice in electronics and would appreciate your expert help.

I am trying to make a circuit that reverses output polarity whenever 0v from the input side is encountered.

The input voltage, which will drive the output device but also acts as a trigger voltage, will be a positive DC and this DC voltage will flutuate in between +50v(peak) and 0v. And my goal is to have this fluctuating DC voltage to "trigger" the reversal of polarity to the output device.

This reversal should occur whenever the input voltage falls down to zero (or very near zero) and the reversal will be continuosly alternating i.e. if the current output polarity is positive-negative then the next time 0v is encountered, will become negative-positive and the next time, positive-negative and the next time negative-positive and so on. And snubber circuit may not be necessary since the voltage at the time of polarity reversal will be zero(or near zero).

What simple IC or circuit or relay or triac or other device this novice is ignorant of will do this? (The max wattage this circuit should handle is about 400w. RMS will be about 200w)

I would so much appreciate if you could help me building this inexpensive but reliable circuit.

Thank you for your time.


Joined May 16, 2005
Any negative-edge-triggered flip-flop would do the trick. Input would have to be conditioned, though, to protect the chip. Try a 4.8V Zener diode in parallel with the i/p, and a resistor in series.