Voltage spike suppression w/avalanche diode

Thread Starter

BigCircuit3302

Joined Sep 2, 2022
14
Need help with this simple circuit......
Trying to use avalanche diode to shunt any voltage spikes to ground before they enter my device.
Not sure of the diode orientation (cathode to ground or anode to ground)
Your suggestions are appreciated.
Thank you.
 

Attachments

You need to reverse the avalanche diode - but beyond that - your circuit is TOO simple! See my attached Fig. 1 & Fig. 2.

Per my notes on Fig. 1, the three wires going to the diode will short together all three terminals of your regulator. I'm sure you don't want that. And even without that, the two wires going to the relay will short the center and right terminals (E and the regulation circuitry). You probably don't want that, either.

Important question: is the ground symbol connected to the stud (-)? If not, I can't give you a proper circuit. I would need to know how, or if, your regulator and 14.8V are connected to ground.

Assuming ground and the stud (-) are connected together - Fig. 2 shows what I think would be correct. To avoid shorting all three terminals together, you need three avalanche diodes as shown, with the anodes going to common. To avoid shorting the center and right terminals together, you need a double-pole relay with two sets of contacts.

About the avalanche diode, if you don't already know - it is similar to a zener diode but with higher breakdown voltage. It has a reverse breakdown voltage. If the anode is plus, the diode will conduct like a regular diode. If the anode is minus (cathode plus), it will not conduct until the voltage across it exceeds the breakdown voltage. This breakdown is what protects your circuit from high voltage spikes.

Hope this helps.Fig.1.jpgFig.1.jpg
 

Attachments

Thread Starter

BigCircuit3302

Joined Sep 2, 2022
14
You need to reverse the avalanche diode - but beyond that - your circuit is TOO simple! See my attached Fig. 1 & Fig. 2.

Per my notes on Fig. 1, the three wires going to the diode will short together all three terminals of your regulator. I'm sure you don't want that. And even without that, the two wires going to the relay will short the center and right terminals (E and the regulation circuitry). You probably don't want that, either.

Important question: is the ground symbol connected to the stud (-)? If not, I can't give you a proper circuit. I would need to know how, or if, your regulator and 14.8V are connected to ground.

Assuming ground and the stud (-) are connected together - Fig. 2 shows what I think would be correct. To avoid shorting all three terminals together, you need three avalanche diodes as shown, with the anodes going to common. To avoid shorting the center and right terminals together, you need a double-pole relay with two sets of contacts.

About the avalanche diode, if you don't already know - it is similar to a zener diode but with higher breakdown voltage. It has a reverse breakdown voltage. If the anode is plus, the diode will conduct like a regular diode. If the anode is minus (cathode plus), it will not conduct until the voltage across it exceeds the breakdown voltage. This breakdown is what protects your circuit from high voltage spikes.

Hope this helps.View attachment 275621View attachment 275621
Thank you so very much for taking the time to make the corrections in my circuit and helping me..... I will follow your directions and I'm sure it will work as intended.
Thanks again and have a great day.
 
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