Zenner Diode Clipper: AC Voltage Spikes to 22V?

[Daniel Floyd]

HI.

I am using Piezo Electric as a AC voltage source which gives voltage spikes of around 35V little current because the impedance of the material is verry high, I would like to clip this voltage to 22 Volts i have seen that a 2 x 22V zenner diodes can be used back to back is thie right or will i need a different value zenner for the negative?

also can anybody tell me what rating of diodes i will need?

 

[berkeman]

HI.

I am using Piezo Electric as a AC voltage source which gives voltage spikes of around 35V little current because the impedance of the material is verry high, I would like to clip this voltage to 22 Volts i have seen that a 2 x 22V zenner diodes can be used back to back is thie right or will i need a different value zenner for the negative?

also can anybody tell me what rating of diodes i will need?

Yes, back-to-back or nose-to-nose Zener diodes make an effective bidirectional clamp. Since the source impedance of your source (the piezo) is high, you probably do not need any series resistance.

If you want the clamp voltage to be 22V, you can use either two 20V zeners or two 22V zeners. The forward diode voltage drop adds to the total clamp voltage, obviously.


EDIT -- OH, whoops. You edited your post since the last time I read it. Now instead of resistance, you are asking for what rating of diode to use. Since your currents are small, I would think that a small 400mW rated diode would work.

 

[Daniel Floyd]

Thank you I have ordered some 22v zenner diodes in which I will use tomorrow.

I tried to use this before but this didn't work I assume its because I used a series resistance thus making my over all impedance very high which pretty much stopped my circuit from working. I will simple try using this back to back with no series resistance and see what result I get. Thank you

 

[jim hardy]

Check your zeners when you get them - some zeners use an internal second junction in series for better temperature performance . If you find that yours won't conduct when forward biased to their reverse breakdown voltage, you can use them in parallel rather than in series.

old jim

 

[alphysicist]

I would suggest using a 22V zener diode in parallel with a resistor to create a voltage divider circuit. This will effectively clip the voltage spikes to 22V without the need for two diodes. The resistor value can be calculated using Ohm's law, taking into account the maximum current that the circuit can handle. As for the rating of the diode, it should be able to handle the maximum voltage and current of the circuit. It is always best to choose a diode with a higher rating than what is needed to ensure reliability and safety. Additionally, for the negative voltage spikes, a similar circuit can be created using a negative voltage zener diode. It is important to ensure that the diodes are properly connected in the circuit and that their ratings are suitable for the application.