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When using a protection diode if it blows it does its job and saves a much more expensive component from getting damaged or destroyed. That's all fine and well but I was wondering about how we then can design this diode to be more easily replaced. Perhaps even by less technically skilled personnel (if possible).

My first idea for this would be to use some equivalent to a fuse holder. I was unable to find anything and I've only seen other similar posts suggest the use of a header which seemed like a bad idea to me.

So my question of course does anyone know of some sort of equivalent fuse holder for use with other components such as diodes?

Hawkeye4040
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  • Depends on the diode package type. – Eugene Sh. Dec 07 '21 at 22:09
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    What do you mean by protection diode? To protect against what? – DKNguyen Dec 07 '21 at 22:12
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    But when the protection diode failed, it already stopped protecting the circuit, and the circuit is now damaged. Would you explain what kind of protection diode you mean where it makes sense to replace a failed diode and expect the rest of the circuit to be OK? I gather if the rest of the circuit is OK the protection diode did nothing else than blow itself up so it is an useless component. – Justme Dec 07 '21 at 22:21
  • you might be able to shoehorn some SMD diodes into one of the "2-SMD" fuse holders (with the matching size), but for the reasons mentioned it's a questionable idea. Also the contacts aren't the same, only on one side for the diodes, all around for 2-SMD fuses. – Pete W Dec 07 '21 at 22:29
  • Specifically to prevent shock when touching electrodes. So obviously this isn't something you'd want to come loose and fall out either but some sort of solderless means to do this so they could be more easily replaced like a fuse would be great. – Hawkeye4040 Dec 07 '21 at 22:46
  • On a side note though I like a lot of the ideas I'm seeing for the TVS application though. That was also another scenario I wanted to consider. – Hawkeye4040 Dec 07 '21 at 22:46
  • Right now it seems like there would be a lot of situations where a device could be thought of as irreparable when a diode that costs under a dollar just needs to be replaced. Pete W's comment is of special consideration too, which is also why I came here to ask because my very best ideas right now for something like this are sketchy at best. – Hawkeye4040 Dec 07 '21 at 22:51
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    If a diode fails when it is supposed to protect a circuit from flyback energy, it suggests the diode is under-rated. Be more specific on the circuit that caused it to fail and make it more robust, rather than focus on ease of repair. – Tony Stewart EE75 Dec 08 '21 at 00:37
  • Okay so just use a diode rated higher than I expect to see as a peak value, right. But say it does blow for some unforeseen reason. We are really to throw away a device over a $0.10 diode. My original question was more is there a solution similar to a fuse holder just so if that happens you can just replace it without having to solder or have any real technical skills, much like replacing the fuse in your car. That was more along the lines of what I was thinking. To clarify, nothing has failed I'm not troubleshooting an existing circuit. I'm trying to address some issues I see in a design. – Hawkeye4040 Dec 08 '21 at 02:39
  • @Hawkeye4040 the trouble is that if you add fuse holders you add another $.20 to every device! If you want a car-fuse style system which is shrouded so users can change it while live without touching electrodes, it probably goes up to a whole dollar. How often are these things failing anyway, within the obsolecense lifetime of the product? – pjc50 Dec 08 '21 at 09:31
  • @pcj50 it's a design that's still being worked on I'm just trying to think outside the box on this one without being too specific about exactly what it is I'm doing. – Hawkeye4040 Dec 08 '21 at 21:34
  • Cost, complexity, and worry of it falling out are certainly cons on the list! – Hawkeye4040 Dec 08 '21 at 21:35

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You could put it on a PCB or mold it into a package, but it might be better to have a more robust design (or less sloppy customers).

One potential issue is that a blown fuse is typically “safe” if removed whereas a shorted TVS that is removed also removes the protection.

Maybe you combine a fuse and TVS into one 3-pin module. Especially since the blown TVS will take out the fuse too.

Spehro Pefhany
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  • I do wish everyone would just be able to solder on a new diode. This is a skill that should be taught to everyone in school in my opinion. – Hawkeye4040 Dec 07 '21 at 22:42
  • The particular usage I had in mind was simply keeping anyone touching an electrode from getting shocked. One-way flow only but how this applies to TVS is also something that'd be great. I like the ideas about redundancy with any form of ESD protection. – Hawkeye4040 Dec 07 '21 at 22:44
  • I do like where this is going though I've been sitting here thinking about this and an approach like that may work in some other situations where there are more components involved I'm definitely not forgetting that one. I feel putting it on a PCB would be too much for the few pieces I'm using here though. Molding it into a package though is a thought but then we're back to it requiring soldering so I might as well just stick with just a diode then. If I'm missing something and there's a solderless way to do it then that may be what I'm looking for here! – Hawkeye4040 Dec 07 '21 at 22:59
  • But if it falls out it's useless so I'm sure that adequately paints a picture of my troubles right there! Otherwise, I probably would've figured this out by now I think, but I'm stuck on it. – Hawkeye4040 Dec 07 '21 at 23:01
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    If you have a replaceable TVS, I would assume the user would remove the blown TVS and operate the equipment without the TVS. Sort of like using a penny to replace a screw-in fuse in the days of yore. – qrk Dec 07 '21 at 23:47
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I'm not sure this is a good idea. I've seen fuse holders become loose and fuses improperly installed. If you do this with a fuse then the equipment simply doesn't work. However, if you improperly install a protection diode the equipment could continue to work under normal conditions...it just would not be protected.

Unless the diode holder would always fail safe you might want to try another approach, such as adding a second level of protection that would fail first. Make the second level protection easy to replace. If the second level protection is always installed and used properly then you save time replacing it, but if not you still have protection.

Elliot Alderson
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  • This is a good point to raise here too. I know it'll be different for different applications to come to think of it. The redundant layer for TVS allowing them to be replaced is a good idea for rugged field designs in my opinion. I definitely don't like the idea of it coming loose and falling out but a solderless solution of some sort would be great as that's really the only way you could expect an end-user to change it. – Hawkeye4040 Dec 07 '21 at 22:41
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Diodes have polarity.
You will need to find something that cannot be plugged in the wrong way. And possibly prevent operation when its unplugged as well.
Header (pin sockets) do not work, since user can put the diode in the wrong way. You would need something 4 pin - one pair to break the power supply and one pair for diode.

Thomas
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  • This doesn't really have relevance to the true question I was asking though. This is going off on a sidebar about the headers. I mentioned that I didn't like that idea in the original post and wanted to avoid sifting through a bunch of answers about that. That was my intent behind mentioning the fact that when I was searching for an answer before posting this I saw nothing but that, justifying me posting about it. – Hawkeye4040 Dec 13 '21 at 06:58
  • Also this really doesn't say anything more than I didn't already say about it with the original post. – Hawkeye4040 Dec 13 '21 at 06:59
  • However I read Your question, I do not see the polarity of diode mentioned, and that is *important* and *not obvious* for untrained personel. All I am saying is - whatever solution you come up with, make absolutely sure it cannot be plugged wrong way in. Diode is not a fuse. – Thomas Dec 13 '21 at 09:56