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Redpill me on inductors, /sci/

Anonymous Mon 06 Jul 22:47:06 2020 No.11874895 View Reply Original Report

Quoted By: >>11875231 >>11878140 >>11878248 >>11878480

While putting in a fresh battery I just broke a 3mm x 2mm inductor off a very rare TokyoFlash watch I'd been chasing for years. It drives the piezo that makes the sound effects and there's no way for me to get probes attached to it to tell how many uH it was...

Is there any way to calculate that? The watch is 3v. If not, is it better to start with high uH ones and work down to lower ones or to start with lower uH ones or should I just start in the middle? Can using an incorrect one damage the ICs? It works fine now it just doesn't make the sound which is a huge part of it.

The specific watch, if curious
https://www.youtube.com/watch?v=w_w8y6KFJLY

Anonymous

Anonymous Mon 06 Jul 2020 23:24:45 No.11875006 Report

Quoted By: >>11875016

Just put something about the same size should be fine
Thats what I do when replacing capacitors

Anonymous

Anonymous Mon 06 Jul 2020 23:29:29 No.11875016 Report

Quoted By:

>>11875006
They range from 10uH to 100uH. I already ordered some 100uH ones they were dirt cheap but I'm going to have to wait weeks for them to come from China so I don't know if I should order some other ones or not. I guess I'll just hope that the 100uH ones are correct. What's the worst that could happen right? I just don't really understand induction.

I guess back in the day I put coils on car speakers to pull out the high frequency so probably the worst that might happen is the beeps are a little more raggedy than they might be with a lower uH right?

Now I'm half way convincing myself to just try bridging the pads to see what might happen...

Anonymous

Anonymous Tue 07 Jul 2020 00:30:14 No.11875231 Report

Quoted By: >>11875569

>>11874895
You could probably find a calculator online for a cylindrical inductor of n turns and ferrous core. It could at least give you a place to start.

Anonymous

Anonymous Tue 07 Jul 2020 02:17:15 No.11875569 Report

Quoted By:

>>11875231
I would have to unwind the 3mm x 2mm inductor. If I was doing that I could probably just repair it instead.

Anonymous

Anonymous Tue 07 Jul 2020 15:21:45 No.11877466 Report

Quoted By: >>11877922 >>11878510

Bump? I'm really thinking about just solder bridging those pads. Is the piezo blowing the worst thing that could happen? The other side of the piezo does go back to the pcb not straight to ground, but on the other hand it being disconnected doesn't seem to be effecting anything

Anonymous

Anonymous Tue 07 Jul 2020 17:53:44 No.11877922 Report

Quoted By: >>11878137

>>11877466
Have thought about making a thread on /diy/? Seems to be more tinkerers and people with electronics experience there.

Anonymous

Anonymous Tue 07 Jul 2020 18:56:57 No.11878137 Report

Quoted By:

>>11877922
Will do, thanks

Anonymous

Anonymous Tue 07 Jul 2020 18:57:41 No.11878140 Report

Quoted By:

>>11874895
They store energy in magnetic fields I think.
EE here but not entirely sure.

Anonymous

Anonymous Tue 07 Jul 2020 19:33:45 No.11878248 Report

Quoted By:

>>11874895
you can probably resolder it.

Anonymous

Anonymous Tue 07 Jul 2020 20:37:39 No.11878480 Report

Quoted By:

>>11874895
Look for pictures or videos of people putting in the battery themselves to find the value or call the company and ask them nicely.

Anonymous

Anonymous Tue 07 Jul 2020 20:45:43 No.11878510 Report

Quoted By: >>11879862

>>11877466
You can’t put any old inductor in it could fry your electronics. It’s part of a buck or maybe a boost converter for your little micro (that are sadly in Tokyo flash watches that’s why you have to charge the damn thing so often at-least the one I had). The micro can take a wide range of voltages so it might be fine if you throw anything in there. But let’s say some how the rates voltage of the micro is 2 volts and you drive it at 5 it might not be fine. Putting in a wrong inductor might give you too much ripple making the microcontroller unstable. Buck and boost converters are like a huge ratios of shit so messing with one thing can have many consequences. If you look up the boost/buck chip they use and check their data sheet usually they recommend a certain inductor. Try their recommended inductor value. 9/10 chance they didn’t change it

Anonymous

Anonymous Wed 08 Jul 2020 05:00:40 No.11879862 Report

Quoted By: >>11879918

>>11878510
Thanks. This watch is from 2008. Not rechargeable. It just takes a normal CR2032 3v watch battery so I'm assuming it's 3v throughout. The inductor is right before the piezo and the watch seems to work fine without the inductor at all, just no sound. From my own experience using "chokes" in car stereos and from what I've read inductors are primarily for filtering certain frequencies (electrical "noise"). From its position on the pcb, it really seems like that's what this one was doing. I'm dimly hopeful that it isn't even entirely necessary but I'm cautiously optimistic that if I bridge it, the worst that might happen is the piezo whines or something (and it drains the battery). I can't imagine any of the ICs being burned out by funky frequencies if it's all 3v right? The LEDs flicker around when you're screwing the battery in but once everything's secure it comes right to life.

Anonymous

Anonymous Wed 08 Jul 2020 05:32:27 No.11879918 Report

Quoted By:

>>11879862
id be really doubtful they'd use an inductor as part of a filter. they are big bulky and expensive the EXACT opposite of what you want in a watch unless you need if for a boost/buck converter or part of something else for whatever reason needs an inductor. you can just use caps and resistors to filter out the noise you dont need an inductor. inductors as filters are usually used in big power supplies where you dont really care about weight and its worth the cost to be more efficient. you need some sort of power supply because your battery will start at 3v and move down a lot as it drains. so you either need to boost it or regulate it down. unless the micro is magical and can just handle a wide voltage range which it might. although this might be completely wrong and tokyo flash engineers were drunk and decided on an inductor as a filter in a watch? either way could be true.

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