quenching diode part number

Dumb question, who want's to play.

What's the correct diode part number for relay coil quenching? I did the search thing and I keep coming up with 1N4004 and 1N4007, but no definitive answer. I'm guessing the 1N4007 is the ideal part number, but 1N4004 can be used also.

Yes, either is fine for relay coils up to 1A.

Generally you need a diode rated (with a PIV) above 400V (for 12V-24V DC relays).

The IN4004 has a 400V PIV & 1N4007 a 1,000V PIV.

Thanks for the reply OldSpark.

Should I be concerned over where I source them, brand, etc.? I'm assuming most are made in China and a diode is a diode as long as it meets the minimun specs for it's rating. Correct?

It shouldn't be a concern. The Chinese are building quite sophisticated & reliable components and since the diode is the most fundamental PN junction required for all semiconductor chips, they should have that well in hand. Of course, the mechanical aspects could be an issue but I haven't had any "cheap" diode problems other than a batch I bought over 30 years ago.

I don't worry about branding (on a component level) tho I do buy thru established companies like our local Jaycar, but I know much of Jaycar's stuff is from Alibaba which AFAIKnow is all Chinese stuff.


Of course many hereon say they never (or rarely?) bother with quenching diodes and they've never had a problem.
That may depend on the driving circuitry... Since most or their circuits are intended to drive relays, they should have their own protection. (Tho I know a few that unbelievably make the user supply the protection!!)
And often - especially for automotive circuitry - inputs & outputs have "rail" limiting - ie, diodes that clamp voltages to the +ve & -ve supply rails - eg, +V +0.7V & -V -0.7V. Not that they necessarily expect inductive spikes of 200V etc.

Then there are those that always play safe, or have experienced blow-ups. (Hi Howard!)
I agree with Howard - it's a great $0.05c (or maybe 20c) assurance. (If only diodes were a simple as 5c to fit!)
But I can't think of anywhere I have used them in my vehicles. Not that I have added my own DIY electronic circuits for ages (which would have that protection anyway), tho I just got a brain-flash that I connected my Alpine's remote-on to a relay (oops? No...)), but then again, that's what it is reasonably expected to connect to, plus of course it's an Alpine.

One nice thing - with a quenching diode, you won't get spike-zapped by a disengaging relay. (Hello again Howard, and a hello to me too!) Nor have that relay cause occasional dash-light flicker.

oldspark wrote:

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It shouldn't be a concern. The Chinese are building quite sophisticated & reliable components and since the diode is the most fundamental PN junction required for all semiconductor chips, they should have that well in hand. Of course, the mechanical aspects could be an issue but I haven't had any "cheap" diode problems other than a batch I bought over 30 years ago.

I don't worry about branding (on a component level) tho I do buy thru established companies like our local Jaycar, but I know much of Jaycar's stuff is from Alibaba which AFAIKnow is all Chinese stuff.


Of course many hereon say they never (or rarely?) bother with quenching diodes and they've never had a problem.
That may depend on the driving circuitry... Since most or their circuits are intended to drive relays, they should have their own protection. (Tho I know a few that unbelievably make the user supply the protection!!)
And often - especially for automotive circuitry - inputs & outputs have "rail" limiting - ie, diodes that clamp voltages to the +ve & -ve supply rails - eg, +V +0.7V & -V -0.7V. Not that they necessarily expect inductive spikes of 200V etc.

Then there are those that always play safe, or have experienced blow-ups. (Hi Howard!)
I agree with Howard - it's a great $0.05c (or maybe 20c) assurance. (If only diodes were a simple as 5c to fit!)
But I can't think of anywhere I have used them in my vehicles. Not that I have added my own DIY electronic circuits for ages (which would have that protection anyway), tho I just got a brain-flash that I connected my Alpine's remote-on to a relay (oops? No...)), but then again, that's what it is reasonably expected to connect to, plus of course it's an Alpine.

One nice thing - with a quenching diode, you won't get spike-zapped by a disengaging relay. (Hello again Howard, and a hello to me too!) Nor have that relay cause occasional dash-light flicker.

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lol I've read several threads debating back-and-forth as to whether they're needed or not. Seems like everyone has their opinion on it. Personally, I guess I'd rather install them and be safe, than not and be sorry I didn't.