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Question about industrial(ish) pushbutton LED (self.diy)

submitted 3 months ago by wjrii to c/diy

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So I am working on a project where I want a big dumb red button. I got a light-duty industrial illuminated pushbutton from AliExpress (this one, if you want to know: 22mm 3v-6v, non-locking). It looks like it will be fine to use, but I'm confused about the LED. It seems to work regardless of which orientation, and I briefly tried it without a resistor, and that was fine too.

I'd like it to be fairly bright, but as someone who has blown up his share of through-hole diodes in his day, I would rather not mess up this one, since without the diode light it's sad and dumb, rather than glorious and dumb. :-)

My question is this: is there any standard for these illuminated switches that would make it likely that there is some resistor and diode stuff going on inside the housing, such that this thing is fine to just wire up and use?

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[–] rowinxavier 4 points 3 months ago

In their image it looks like pin 5 is getting positive. I would expect it to work for a short time without a resistor then fail, but if you have a couple you could always sacrifice one with a test.

[–] [email protected] 3 points 3 months ago (1 children)

bigclivedotcom has a few button videos covering elevator and industrial illuminated buttons. I don't think he's done exactly the same as this, but I think no real standard, but they may be cloned off a brand.

Interesting videos to see what's inside the different types. Some use a dual chip back to back parallell led - so that it can light on each half wave of a.c. - or if d.c that'd be either polarity. some have resistors, some have resistors and capacitive dropper (mains rated)

I'd guess the reason for the voltage range is the different resistance included. I don't think you'll really know unless you either measure the current draw, or open it up.

[–] wjrii 1 points 3 months ago

Thanks! I pulled up a few roughly similar, though modular pushbutton videos. I also found an old reddit thread about some significantly nicer Allen Bradley switches, and some general reading about how these sorts of switches are supposed to be deployed, and I'm inclined to think the necessary components are part of the assembly already. I've hooked it up to 3.3v on a USB breadboard power supply, and I'm just going to let it run for an hour. If it doesn't burn/blow out, I'll feel confident enough to use it. It's never going to have more than that on it anyway.