Coil winding direction (clockwise/anticlockwise) test?

[peskywinnets]

Just wondering if theere's a prescribed method of establishing whether the wire has been wound clockwise/anticlockwise around a given unknown 'on guitar' pickup bobbin? (to save removing a pickup from the guitar & physically eyeballing it)

I'm thinking that a low voltage - say 9V into the coil (via the guitar's jack socket), ought to reveal something! (ie take a test coil with known 'direction of wind' & known magnet polarity, put a compass up to it, place 9V across it the coil in parallel...observe the result, reverse the winding polarity, carry out the same test - observe the results etc, once you've the data, it should then be possible to apply it to a pickup of unknown winding direction? (ie two bits of info would be to hand....the magnet polarity & DC voltage polarity...just need the third bit of info which I reckon could be extrapolated from that?)

[David Schwab]

That should work, but I would use a lot less than 9V. That will heat up the coil wire!

You also have to watch out for magnets in coils, since you will be producing an electromagnet.

[peskywinnets]

Hmm....back of a ciggie packet calculations - 9V divided by 7,000 Ohms = 1.3mA through the pickup (or just half that for a humbucker) or 12milliWatts (cack all I reckon...even for hairlike 0.05mm wire!)

[Joe Gwinn]

I've run pickups with 70 volts rms across the coil, generally above 5 KHz, when I was testing for harmonic distortion in the magnetic materials. Not forever, but for maybe 5 minutes.

[David Schwab]

OK, so maybe it's not too bad. I just remember making electromagnets as a kid and using one of those lantern batteries the coil would get quite hot.

[Bill M]

I'm thinking that a low voltage - say 9V into the coil (via the guitar's jack socket), ought to reveal something! (ie take a test coil with known 'direction of wind' & known magnet polarity, put a compass up to it, place 9V across it the coil in parallel...observe the result, reverse the winding polarity, carry out the same test - observe the results etc, once you've the data, it should then be possible to apply it to a pickup of unknown winding direction? (ie two bits of info would be to hand....the magnet polarity & DC voltage polarity...just need the third bit of info which I reckon could be extrapolated from that?)

Are you thinking that the 9vdc will change the magnet polarity and you will see this result on the compass? I don't think thats gonna happen with a 9vdc battery. Actually be very careful as DC voltage can be destructive. If the coil has any shorts or any insulation break down you will more than likely damage the pickup. You need to use AC voltage with very low current for testing for insulation break down to be nondestructive.

[peskywinnets]

Are you thinking that the 9vdc will change the magnet polarity and you will see this result on the compass? I don't think thats gonna happen with a 9vdc battery.

It does happen, because even though the coil through the pickup is only 1.5mA (with a 9V battery), the ampere turns is rather high )...eg 8,000 turns x 1.5mA = 12 ampere turns. That a significant amount of Magneto Motive force coming out of the pickup pole pieces. After posting I did a quick check on a sustainer coil (which only has a couple of hundred turns) & the compass needle magnet deflected significantly when the 9V was applied) ...I need to do further tests to bed this one away, but it should be possible to glean the wind direction from such a test.

If the coil has any shorts or any insulation break down you will more than likely damage the pickup. You need to use AC voltage with very low current for testing for insulation break down to be nondestructive.

A simple DC resistance check should reveal any oddities prior to applying a DC voltage ...remember we're talking 9V - so it's hardly worth getting a 'mega' insulation tester out the cupboard to test for potential insulation breakdown! (in fact if my memory serves me right, a DC multimeter has a 9V battery in it anyway, which means every time you do a DC resistance check on your pickup coil, you're applying 9V across it!)

[Bill M]

It does happen, because even though the coil through the pickup is only 1.5mA (with a 9V battery), the ampere turns is rather high )...eg 8,000 turns x 1.5mA = 12 ampere turns. That a significant amount of Magneto Motive force coming out of the pickup pole pieces. After posting I did a quick check on a sustainer coil (which only has a couple of hundred turns) & the compass needle magnet deflected significantly when the 9V was applied) ...I need to do further tests to bed this one away, but it should be possible to glean the wind direction from such a test.

A simple DC resistance check should reveal any oddities prior to applying a DC voltage ...remember we're talking 9V - so it's hardly worth getting a 'mega' insulation tester out the cupboard to test for potential insulation breakdown! (in fact if my memory serves me right, a DC multimeter has a 9V battery in it anyway, which means every time you do a DC resistance check on your pickup coil, you're applying 9V across it!)

Ok I did the the test myself as to not bark up the wrong tree. I took an AL 5 strat pickup and set a compass far enough away as to not have a strong pull on it. I then took a fresh 9v battery and hooked it up to the pickup leads with no deflection of the compass at all. I then reversed the leads on the battery and again the same result, no compass deflection. Go ahead and try it yourself on a regular pickup with about 8k of turns. You didn't take the wire gauge into account when making calculations.

A simple dc resistance check will not show insulation breakdown or shorted winds. An AC resistance check will.

My tektronics meter runs on 120vac and does not put 120vac on my resistance tests.
I do have a Greenley meter that uses a 9v battery and it does not put out 9vdc on my resistance tests. The voltage being put out on a multimeter for resistance testing depends on the amount of resistance being tested( lower ohms = more voltage output of the meter). My Greenly meter w/9v battery put out .5vdc on its lowest ohm setting. Not saying that all meters do, just mine.

[peskywinnets]

When I did the quick test on my sustainer coil, I actually put the compass right up to the pole piece - what I saw was the compass deflect when the battery was connected. (and this was just with a couple of hundred turns)

Wire gauge should have no bearing on the end result for this test.....why do you think it would?

[Bill M]

I have no experience with sustainer coils. Do they use magnetic pole pieces? What gauge is the wire? You did say it only uses a couple hundred turns of wire.

With regard to the wire gauge, A 10awg wire has less resistance per foot, or turn versus42 awg and would have a huge bearing on your test calculations and end result.

Back to your OP. Even if the battery made the compass deflect how would that determine which way the coil was wound? I'm just trying to understand this.

[peskywinnets]

I have no experience with sustainer coils. Do they use magnetic pole pieces? What gauge is the wire? You did say it only uses a couple hundred turns of wire.

They have the same form as a pickup - pole pieces and a coil around them - magnet on the bottom. Just less turns and thicker wire - for the purposes of this theorizing, they are - to all intents & purposes - the same as a pickup.

With regard to the wire gauge, A 10awg wire has less resistance per foot, or turn versus42 awg and would have a huge bearing on your test calculations and end result (amount of deflection)

But I came into this post/thread knowing that? When I said wire gauge will have no bearing on the end result - if the theory is right (& I'll test it more soon) then it'll be binary outcome (ie the needle will deflect one way or the other)....the DC resistance affects is the amount of deflection.

Back to your OP. Even if the battery made the compass deflect how would that determine which way the coil was wound? I'm just trying to understand this.

If the coil is wound one way, the deflection will be a certain way, if it's wound the other way, the needle deflection will be the opposite. (this is why I'd need to get all the permutations squared away, magnet polarity, vs deflection vs known coil wind direction etc)