Fast snubber circuit for relay coil

[floobydust]

Late here but the zener's required power rating is something to consider as well. 1/2W generally too small for the impulse, good discussion with scope traces https://www.eng-tips.com/viewthread.cfm?qid=426309
Other papers:
TE Coil Suppression Can Reduce Relay Life
TE P&B The application of relay coil suppression with DC relays sourcve of pic 13.5V applied to automotive ISO 55Ω (large 250mA) coil.

[SteveThackery]

Hence the guess work, all in an effort to help them, and simultaneously irritate you it seems.

Now, now, don't be nasty. I've said not one single thing that implies irritation. I simply did my duty to the OP and future readers by pointing out that everything after post #2 is answering the wrong question and will actually have the opposite effect than the OP wants.

I'm puzzled by the reactions to me pointing that out. Instead of "Oh, yeah, you're right about that - we should make it clear to the OP", I get lectured on thread drift followed by some hand-waving around protecting the switching element. Trust me, I'm an expert on thread drift! 😂

Check my posting record - I don't make a habit of posts like this. But on this one occasion I believe my point is worth making. I don't understand the reluctance to acknowledging that.

[Zero999]

Other than that, yep, it won't be faster than a true open circuit, but the skin effect of the armature itself (who knows how it's constructed, maybe it's solid, maybe it's laminated, but there's a cutoff in there whatever the case) will have a minimum decay in some ~ms, so it probably doesn't matter beyond the zener+diode or S-D clamp zener cases, which grant unlimited survival, and well-defined power dissipation limits.

The OP asked a very simple question: will his suggested circuit work to speed up the relay release time. The answer is:

No, it will slow it down.

The thread has wandered off completely, and is going on about back emf spikes. But that is not what the OP was asking about. Every circuit proposed in this thread will leave the relay release time unaffected or will increase it.

The only two people in this thread to get it right are @langwadt and me.

You might be right in theory, but you're wrong in reality, when the switching transistor is destroyed by the back-EMF spike.

Selecting a snubber is a compromise between switching the relay off quickly and not damaging the switching transistor, hence the reluctance to make blanket statements such as no, it will slow it down.

[SteveThackery]

You might be right in theory, but you're wrong in reality, when the switching transistor is destroyed by the back-EMF spike.

I'm not wrong in reality - I have a comprehensive understanding of the issues around switching relays.

Selecting a snubber is a compromise between switching the relay off quickly and not damaging the switching transistor, hence the reluctance to make blanket statements such as no, it will slow it down.

To be clear, I did not advocate not using a snubber. I said all snubber circuits slow down the relay release time, which is not what the OP wanted.  The blanket statement you refer to: "no, it will slow down" is a true statement.

Anyway, I've done my bit. The point is made. Feel free to have the last word - I know you are tempted. 😉😁

[floobydust]

There is always a bunch of information missing about the application, requirements, components etc. making it impossible to give "expert" advice in many threads, especially beginner threads.
You have to be loose and understanding, instead of starting a pissing contest over some tiny detail and "I"m right your wrong!" infantile behaviour.

The "know it alls", "experts" sling mud and shit at people here on EEVblog in a beginner's thread- it derails the thread and the OP flees.
Or maybe this is as good as it gets here, without a Stack Exchange like filtering and ranking system. Other forums are not like this though.

[T3sl4co1l]

I mean, there is no simple process to establish truth.  It can be given on a silver platter, and still not accepted, or internalized.  More often it's the struggle between superfluous or conflicting information, and one must tease the two apart, often making incorrect inferences along the way, but hopefully, in time, establishing a broader web of support that mutually confirms itself.  Other times, it's a struggle to find the information that is out there, gleaming and true, but difficult to access: this is the case whether something is buried in academic journals, libraries, etc., or when some basic input (formatting, support, volunteering) is required, such as on Stack.  Of these two examples, of course, you're far less likely to get an accurate and in-depth explanation from the latter, if any at all; but neither can you let down your critical-reading guard around academic papers.

In any case, if one finds a response confusing, they are welcome to ask again -- or to rephrase their question in a way that better articulates what confusion they are having.  If they aren't capable of that -- unfortunately, there is a certain minimum competency required to learn; hopefully one establishes this early in life, but outside of school, most people aren't interested in hand-holding.  Thus it takes a certain amount of confidence to speak up, and a certain amount of insight, of introspection, to express what exactly it is that one is after.  In other words: the skill of learning itself.  A skill which our schools oh so often actively stifle, so if one finds themselves in this situation -- my sympathies, but wrongs done unto you can still be righted, it can still be learned; find someone willing to mentor you in a subject, perhaps, and be open to new experiences.

Tim

[Zero999]

You might be right in theory, but you're wrong in reality, when the switching transistor is destroyed by the back-EMF spike.

I'm not wrong in reality - I have a comprehensive understanding of the issues around switching relays.

Bear in mind this is the beginner's section and the original poster might not have such a comprehensive understanding.

Selecting a snubber is a compromise between switching the relay off quickly and not damaging the switching transistor, hence the reluctance to make blanket statements such as no, it will slow it down.

To be clear, I did not advocate not using a snubber. I said all snubber circuits slow down the relay release time, which is not what the OP wanted.  The blanket statement you refer to: "no, it will slow down" is a true statement.

I doubt the original poster wanted to blow up their transistor either.

Anyway, I've done my bit. The point is made. Feel free to have the last word - I know you are tempted. 😉😁

All you've done is annoy me and no doubt many others in this thread by saying you and one other person have been the only ones who've posted useful replies.

[SteveThackery]

All you've done is annoy me and no doubt many others in this thread by saying you and one other person have been the only ones who've posted useful replies.

WRONG! And I would thank you NOT to misquote me or misrepresent me.

I said only two of us gave the RIGHT answer. That is NOT saying the other posts aren't useful.

I detest having words put in my mouth. You misquoted what I said - you need to apologise.

[SteveThackery]

I doubt the original poster wanted to blow up their transistor either.

Of course they won't! That's why I made no comment disagreeing with all those posts.  I simply stated that all those solutions actually slow down the release lag of the relay, which is what the OP was asking about. I did NOT disagree with any of them!

Why are you so desperate for me to be in the wrong? Read my posts again and see if you can find ANY false statement or ANY statement disparaging the contributions from anyone else.  I stated a simple FACT which I believe had got lost as the thread developed.

I cannot believe anyone is arguing with me about this. Just read the bloody thread and what I ACTUALLY WROTE.

And don't forget that apology.

[Doctorandus_P]

I am guessing that this relay coil is designed to be operated by a mechanical switch. As a result, at the moment the switch goes open, the full coil current will momentarily be pushed backwards though the diode, and then the current decays rapidly. I guess that they have either chosen a diode that can handle this abuse, or there is an extra diode "anti-parallel" over the LED. Maybe as a separate device, but for mass produced relays, this diode may as well be integrated in the LED itself.

[langwadt]

I am guessing that this relay coil is designed to be operated by a mechanical switch. As a result, at the moment the switch goes open, the full coil current will momentarily be pushed backwards though the diode, and then the current decays rapidly. I guess that they have either chosen a diode that can handle this abuse, or there is an extra diode "anti-parallel" over the LED. Maybe as a separate device, but for mass produced relays, this diode may as well be integrated in the LED itself.

or the LED is actually a dual, I know they exist but more commonly with two different colors 

[Zero999]

All you've done is annoy me and no doubt many others in this thread by saying you and one other person have been the only ones who've posted useful replies.

WRONG! And I would thank you NOT to misquote me or misrepresent me.

I said only two of us gave the RIGHT answer. That is NOT saying the other posts aren't useful.

I detest having words put in my mouth. You misquoted what I said - you need to apologise.

That was my interpretation of the following quotes from you and obviously I'm not the only one, as it would definitely explain the other "nasty" reply you received. If that's not what you meant, then I suggest you consider being more careful about your term of phrase in future.

Totally understand and agree. My concern is specific to this thread. It wasn't clear that post #2 was the answer and everything after that is "shooting the shit".

The correct answer was given in post number 2 by @langwadt. It was completely ignored by everyone, including the OP.

The only two people in this thread to get it right are @langwadt and me.

[SteveThackery]

That was my interpretation of the following quotes from you and obviously I'm not the only one, as it would definitely explain the other "nasty" reply you received. If that's not what you meant, then I suggest you consider being more careful about your term of phrase in future.

@Zero999, you clearly are incapable of admitting that you are in the wrong. Read those three quotes you picked and all three are absolutely reasonable, factually correct, and devoid of any positive or negative emotion. You do realise that the "shooting the shit" phrase was me quoting someone else, don't you?

1/ The OP wanted a way to speed up the release lag of his relay - FACT.

2/ From post #3 onwards, the posts all described how to protect the switching element, without mentioning that all the options make the release lag slower - FACT. (You do agree this is something the OP might like to know, yes? I mean, it is what he was asking about.)

3/ Two people - @langwadt and me - pointed out that the OP's proposed snubber (and all the others proposed in this thread) would lengthen the release lag, not shorten it - FACT. That's what the OP's question was about, so it needs pointing out, don't you think?

I did and said absolutely nothing wrong. My statements were factual and neutral in tone.

Your hostility towards me, plus misrepresenting me, plus refusing to apologise for either, reflects very badly on you, @Zero999. It's a pity you aren't mature enough to recognise and acknowledge that you behaved rudely and inappropriately.

That was my interpretation of the following quotes from you.....

Well, maybe you should stop "interpreting" people's posts and just read them instead. Respond to my words, not your interpretation of them.

And the apology you owe me for misquoting me? No? 😂

[voltsandjolts]

The answer to the OP's question is in post #1 (faster without snubber).
However, that answer is not a solution to the OP's underlying problem.
Hence continuation of the thread, in an attempt to help the OP.
Chill dude.

[SteveThackery]

The answer to the OP's question is in post #1 (faster without snubber).
However, that answer is not a solution to the OP's underlying problem.
Hence continuation of the thread, in an attempt to help the OP.
Chill dude.

I'm totally chill (apart from annoyance at being misrepresented).

To be helpful to the OP, we should have pointed out that the correct answer to his initial question was in post #2. We should also have pointed out that whilst the solutions in the rest of the thread might be relevant to the bigger question, they actually have the opposite effect to what he originally wanted.

I did that. @langwadt did that. Nobody else did.

But instead of receiving an "Oh yes, we should make that clear to the OP", a couple of blowhards with fragile egos couldn't bear having this pointed out to them, so they directed some hate my way and then obfuscated some waffle which strongly suggests they didn't read past the word "snubber" in the thread title.

So where, in all of this, have I put a single step wrong? Where, prior to this message, have I said anything at all disrespectful or impolite? Why are you not telling those sulky colleagues of ours that yes, they probably should have made it clear to the OP?  And that they should give me - the messenger - a break?

Please, before commenting further, carefully read everything that I've written, because I don't believe you have, and try to shelve any adverse expectations you might have picked up about me whilst doing so. You will see that my conduct has been correct, polite and reasonable throughout.

[Phil1977]

But instead of receiving an "Oh yes, we should make that clear to the OP", a couple of blowhards with fragile egos couldn't bear having this pointed out to them, so they directed some hate my way and then obfuscated some waffle which strongly suggests they didn't read past the word "snubber" in the thread title.

What exactly is psychological projection

Calm down, who feels offended by some remarks in the internet should quickly go outside and have some fresh air. And regarding the topic: "Fast snubber circuit" implies from my point of view you want a fast snubber, not no snubber. So the choice is:

- a zener with a voltage that is just low enough to protect the driver
- a diode with resistor
- anything dissipative

[SteveThackery]

Calm down, who feels offended by some remarks in the internet should quickly go outside and have some fresh air.

Trust me, I am blissfully calm except about @Zero999 misquoting me! 😂  Nobody else has said anything offensive to me, so I have no feelings of anything except tranquility. That doesn't stop me from defending myself against angry slurs, obviously, but none of it has any emotion behind it on my part.

Actually the strongest feeling I have is one of puzzlement, to be honest. I'm puzzled by the reaction to my first couple of posts. Instead of "Good point, let's make that clear to the OP" I got lectured on thread drift!  Very weird.

And regarding the topic: "Fast snubber circuit" implies from my point of view you want a fast snubber, not no snubber.

Don't tell me you haven't read the OP's post either!!  He was asking for some means of making his relay release faster. His confusion over what a "snubber" can actually do is typical of a beginner.

(PS: @Zero999 - you misrepresented what I said. That is not acceptable in any forum. Are you big enough to apologise?)

[Simon]

Steve thackery, I am about to not be calm and may do something rash! this is now your thread and argument as you have taken over the thread with nit picking.

[Gyro]

... And regarding the topic: "Fast snubber circuit" implies from my point of view you want a fast snubber, not no snubber. So the choice is:

- a zener with a voltage that is just low enough to protect the driver
- a diode with resistor
- anything dissipative

Precisely.

* Design and sizing are more critical with modern fragile semiconductor drivers, but [Edit:, for instance,] suitably sized RC snubber networks have been used for back-EMF suppression since the year dot.

[Phil1977]

Without any info about the input polarity we can only guess about what the LED is meant for.

Of course, adding a snubber to make switching faster is nonsense. If you need to switch that fast just take a SSR.

[SteveThackery]

Steve thackery, I am about to not be calm and may do something rash! this is now your thread and argument as you have taken over the thread with nit picking.

@Simon - I'm not sure I understand you. Have you properly read all my posts? What about them makes you not be calm?

On a technical level, I'm pleased to see that @Phil1977 is clearly stating what I've been saying all along. Are you not calm with him as well?

Please be explicit about the veiled threat to "do something rash". That way I'll know exactly what is at stake. Thank you.

[SteveThackery]

Without any info about the input polarity we can only guess about what the LED is meant for.

Indeed. My guess is that the symbol in the OP's first post is upside down, such that the +ve feed is at the bottom. It seems very likely that the LED is just meant as a visual indicator of whether the relay is powered or not.  That's actually quite a handy feature.

The only thing counting against that theory is that, without back emf protection, the LED would seem very vulnerable. An earlier post (sorry, off my screen) pointed out that one of the older LED technologies will avalanche under these conditions and recover. It seems unlikely the manufacturer relied on that, though.

I wonder if the relay also includes a flywheel diode/dissipator. Or maybe the data sheet says protection is mandatory (doesn’t seem very likely).

[Zero999]

Well, maybe you should stop "interpreting" people's posts and just read them instead. Respond to my words, not your interpretation of them.

And the apology you owe me for misquoting me? No? 😂

I responded to your words. If you meant something else, then please say so. Otherwise it appears as tough your intention is to troll.

[T3sl4co1l]

Steve: with all due respect;

That you wrote this the other day,

Anyway, I've done my bit. The point is made. Feel free to have the last word - I know you are tempted. 😉😁

And have, subsequently, been wholly unable to let them "have the last word", demonstrates to us that you are not, in fact, "blissfully calm" about this.  But rather, you've been rather annoyed.  Sucked in by the troll.  And thus the trolling reproduces, involuntarily through you.

Leave it be.  Let them take the last word.  Let all see who has the bigger ego.

Tim

[SteveThackery]

I'm going to take the advice of @T3sl4co1l (cool username 😁). This will be my last post in this thread.

@Zero999 has recently written this:

I responded to your words. If you meant something else, then please say so. Otherwise it appears as tough your intention is to troll.

OK, @Zero999, here are my actual words:

The OP asked a very simple question: will his suggested circuit work to speed up the relay release time. The answer is:

No, it will slow it down.

The thread has wandered off completely, and is going on about back emf spikes. But that is not what the OP was asking about. Every circuit proposed in this thread will leave the relay release time unaffected or will increase it.

The only two people in this thread to get it right are @langwadt and me.

@Zero999 then made a big mistake by saying:

All you've done is annoy me and no doubt many others in this thread by saying you and one other person have been the only ones who've posted useful replies.

As you can see, I absolutely did not say that my, and one other's, posts were the only "useful" replies. That is a lie. I said that our posts were the only ones that were right, which is a totally different thing. This lie is what @Zero999 should apologise for.

And what I said is right: every post from #3 onwards fails to warn the OP that the proposed solutions have the opposite effect on release lag than what he was wanting.  I felt it was important to point this out.

In closing, it seems that I do, indeed, occupy the high ground. My intervention was entirely correct at a technical level, and @Phil1977 has supported my position:

Of course, adding a snubber to make switching faster is nonsense.

There is surely no more to be said, except to say how surprised and disappointed I am by the conduct of several individuals, and one individual in particular, on this thread.  Perhaps I expect too much.