Can a choke help filtering out noise in car electrical system?

This is just a hypothetical question but I may build something arduino-based for my motorcycle (yeah I intentionally wrote car and not motorcycle in the subject) and since I have a few, quite large chokes from a scrapped 250A welding unit I was wondering if these can be used together with a cap to help filtering out noise before the 5V voltage regulator? The chokes are "iron core" since this was a 50/60Hz welder but I suspect the chokes may still work well for lower currents even if the noise is high frequency. Probably some kind of powder core would be better but I have these laying around. Might as well put them to use.

I was wondering if these can be used together with a cap to help filtering out noise before the 5V voltage regulator?

Yes but if the choke has such a large current rating it is unlikely it will have a high inductance. The higher the inductance the better it is at suppressing noise.

You want to use two caps and one inductor like the last diagram in this page.

So much depends on what you are calling noise. The inductance of the choke will cause back emf to fill in the spaces between noise pulses if they are low enough in frequency. Higher frequencies will be capacitavely coupled to the output of the choke.


Sounds like using Mjölnir to hammer a row of nails. They have to be a long way apart because the hammer is so big.

Chokes from a 250A welder will be far too high an inductance value, and mayb not designed for high frequencies.
A high value choke is perhaps more likely to cause damage to surrounding circuitry through inductive kick-back
than filter out spikes and high-frequency noise. You'd certainly need to measure the inductance and
size the capacitors to match (as they serve to limit back EMF voltages).

A small ferrite-based RFC is more likely to be suitable. Or a good ferrite toroid.

I measured one of the inductors the other day and @ 1kHz my LCR meter read 370uH so inductance is fairly low. I haven't looked at the DC on my motorcycle with an oscilloscope yet so I don't know what kind of noise and frequency I may or may not have to deal with.

@MorganS: I'm afraid I don't understand what you mean.

I mean "How freaking big are these welding chokes?" You have to protect every wire that enters or leaves your box so a bunch of these chokes is going to make your bike lean over a bit.