Filter an AC circuit

[Cliffh]

My workshop has one AC circuit.  One 110v breaker, and everything runs off of it.  I know it's not proper and will be corrected in the future.  

I just purchased a new battery charger/maintainer, to keep the lawn mower battery up over the winter.  Problem is, when the charger is plugged in and charging/maintaining there's a "buzz" coming through the radio.  I'd appreciate some ideas on how to stop the "buzz".  

I have an old UPS that I could plug the radio into.  Or maybe a surge protector? Or ?

ETA:  The workshop is a steel building.  The charger is in a steel shed, with an extension cord between the two buildings/sheds.  So it's not a proximity thing.

[zahc]

Try one of these on both the charger and radio units

http://www.amazon.com/gp/aw/d/B007Q94CZM/ref=mp_s_a_1_3?qid=1385001864&sr=8-3&pi=AC_SX110_SY165_QL70

But if the charger is sufficiently noisy there is not much you can do. The noise could be being fed into the radio through the cord or the antenna could just be picking it up, or both.

[never_retreat]

The ups won't do anything, most are passive when there is no power problem
Does the charger have a ground prong? If so try using one of those 3 to 2 prong adapters.
I had some audio equipment I used to do that to.

[Phantom Warrior]

But if the charger is sufficiently noisy there is not much you can do. The noise could be being fed into the radio through the cord or the antenna could just be picking it up, or both.

I'm shooting blind but I suspect this is what's happening.  I've observed this with my cheap computer speakers and the cheap PA speakers at school.  Both of which I suspect is due to cell phone usage.

You _might_ be able to rig up some kind of shielding hack.  Put a piece of sheet metal or tin foil over the charger.  But I agree with zahc that it's probably not the current that is the problem.

[230RN]

.01 to .001 200 V or more cap across the charger 110V input line, close to or within the charger case.

Might need similar across the  output line to the battery.

Don't bother trying to filter it with electrolytics, they don't filter higher frequencies too well, and you will frequently find power filter circuits with a small cap as described across the big electrolytics to capture high frequency switching noise.

[Cliffh]

The radio's in one metal shed, the charger's in another metal shed.  There's about 5' distance between the two sheds, about 18' total distance between the radio and charger.  Figure the two metal walls would be enough shielding?

The charger does have a ground prong.  And I've got quite a few of the 3 to 2 adapters.  I can give that a try tomorrow evening.

230RN  I recognize every word you used and have used every one of them in a sentence (except for "electrolytics"), but I'll be damned if I can make heads or tails of what you meant.      I think you're saying to solder a .01 to .001 200 volt capacitor across the positive and negative power leads to the charger.  I'm not familiar with caps and how they work - it wouldn't cause a short if attached to both the + & - leads?

ETA:  If the 3 to 2 adapter doesn't do the trick, I'll try to find some of the ferrite clips locally.  I'd rather not wait for the slow boat from Hong Kong.  

[280plus]

Install a 16 x 25 x 1 PLEATED filter. It's the only answer.

[CNYCacher]

I'm not familiar with caps and how they work - it wouldn't cause a short if attached to both the + & - leads?

Capacitors work by holding two metal plates very close to each other without touching. The proximity of the plates allows for an electrical charge (like static) to build up on the plates. Capacitors act kind of like a tiny battery that can be charged and discharged insanely fast. Used in this context, the capacitor will suck or provide voltage on the incoming line in order to fill in the tiny voltage fluctuations on the line which are the noise.

As long as you are using a cap rated for the voltage it's taking, there is no actual connection inside a capacitor to make the short that you are worried about making.


Normal capacitor:
~ ----| |---- ~

Capacitor given too much voltage:
~ ----|*|---- ~

Install a 16 x 25 x 1 PLEATED filter. It's the only answer.

I see what you did there.

[280plus]

I see what you did there.

It's all in the interpretation.

[Cliffh]

It'd be better if I could get by with a 16 x 20 x 1 filter, then I'd only have to stock one size.

Thanks for the explanation on how a cap works.  To install, I could remove a small portion of the insulation, solder the cap legs to the wires, then re-insulate, right?  Doesn't seem as if there would be a concern with the cap polarity.

I've got a weird work schedule for the foreseeable future, so it'll take a while to test the various methods and complete this project.  Thanks for all the input, I'm sure at least one of the solutions will fix the problem.