A question or two...or three...about winding a coil

I figured I'd just reply to this post instead of making clutter with a new one. When I am building

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does it matter specifically whether I use 1/2 or 1/4 watt resistors?

The reason I ask is I have a lot of 1/2 watt lying around.

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Haha, I seem to have messed myself up nicely.

I bought a 3 pack of wire from Radio Shack when I was out of town.

It had 30AWG, 26AWG, and 22AWG.

I found this chart which says 30SWG's closest match is 28AWG.


I must be cursed I tell ya. I can't even find all of the parts on one website...well I take that back, one website had them all (

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), but it costs 26$ shipping because apparently the potentiometers aren't too common in the USA. I even checked ebay, not too many 470k linear pots. Darn UK, hogging all the potentiometers!!! 

Guess I'm off to find some 28 AWG if that'll work.



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		Quote:			Posted by trickyspark
	Haha, I seem to have messed myself up nicely. I bought a 3 pack of wire from Radio Shack when I was out of town. It had 30AWG, 26AWG, and 22AWG. I found this chart which says 30SWG's closest match is 28AWG. I must be cursed I tell ya. I can't even find all of the parts on one website...well I take that back, one website had them all ( You are not allowed to view links. Please Register or Login www.newark.com ), but it costs 26$ shipping because apparently the potentiometers aren't too common in the USA. I even checked ebay, not too many 470k linear pots. Darn UK, hogging all the potentiometers!!!  Guess I'm off to find some 28 AWG if that'll work.

470k linear?? try 500k it is close enough.

Size of wire is not as critical as some believe, on ly if you want MORE dc resistance which actual degrades Q.

If you have access to an LC bridge, try a larger gauge (I have not looked at the link and pdf,) after all, it is NOT the dc resistance that creates any magnetic field, whether PI or even a BFO, it is the amount of current through the wire which is controlled by the impedance/inductance of the coil much more than the dc resistance..... forget dc resistance, forget distributed capacitance (it is too small to be bothered with): get the inductance right. The tiny dc resistance is ADDED to the (ac) impedance, for all practical purposes.

If you can NOT get exact parts, it is not always critical, the difference between 1/4 watt and 1/2 watt resistors is physical size.... the 1/2 watt are bigger, physically, so they have more surface to radiate heat. simple formulae: SAFE power rating = 2(Voltage squared / R) and 2(current squared X R)

For instance, if you are working with standard, 10% accuracy, parts, the difference between 470k and 500k is 6%, or well within range! If you need .0047 uf, .005 or (2 x .0022) .0044uf is acceptable at 6%. BUT, if the circuit calls for 1%, that is a hoss of a different shade.

If you know the circuit volts, across a particular resistor, the safe power rating is straight forward. Note that the two resistance values have to be the same: resistance and power rating has no bearing on resistance value.....

I guess by now I have you thoroughly confused. 

Everybody keeps saying *enamelled wire is best,* well, no, what happened to Litz wire? Enamelled means the wire is closer with each winding, therefore there is greater proximity loss. Go back to Litz and heavier insulation. 

I guess the discussion on Litz wire never happened.

I am not about to let ANYONE forget Litz wire!! 

goldigger


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		Quote:			Posted by trickyspark
	You are not allowed to view links. Please Register or Login http://www.allspectrum.com/store/product_info.php?products_id=2714&osCsid=a55a283b596875d11465978769fd86c4&sdesc=Bare+Copper+Bus+Bar+Wire%2C+1%2F4%22+lb+spool%2C+28+AWG+Model+%23+CONWIRE-28BC Yay I FINALLY found some for sale in the USA. I hated the thought of that international freight on top of shipping costs. I found the pot too, although it was a 500k 20% instead of a 470k 10% tolerance one and a 20k 10% tolerance one instead of a 22k. I figured that would be good enough. Some of you UK people outta open a store in the USA and sell is some of your stockpile  I got the capacitor too. I had to get it as 1000pf  1% instead of 0.001mf. I hadn't thought of converting and looking. Now all I gotta do is sit back and wait for the parts to come, and find some suitable single conductor shielded (audio?) wire. I wonder if cat5 network cable would work.

Stop it, I am laughing too hard, choke! 22k in parallel with 220k = 20k exactly! And .001 mfd = 1000of = .001ufd , no difference there!           

I am sorry, it was just too much! 

I can understand you wanting to build as closely to the original, as you can, but push it too far and you are being... ummmm..... eccentric?

I certainly agree about shipping costs, I bet you have not encountered the ones that charge a huge shipping cost and tell you they have to make money, somehow! I really hate them and will not buy there.

My last big order (Texas) was about 20 pounds of stuff, and it cost about $20US... about $1/pound, which is good, and that was postal service and never spent ANY time in customs. Some companies would want $50 or $60, for the same shipment.

Actually, if you measure and select, you can get 1 or 2 percent, without paying the 1% price.

I hope you did not buy the bare copper bus bar wire, to wind your coils..... it will not work, it is not insulated. Just one big shorted lump...... maybe I am just fearing the worst, here.

goldigger

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		Quote:			Posted by trickyspark
	Guess I should have just kept my mouth shut. I've forgotten most of this stuff as I've had no use for it in the last 8 years. I also posted the wrong link. You are not allowed to view links. Please Register or Login http://www.allspectrum.com/store/product_info.php?products_id=2674&osCsid=a55a283b596875d11465978769fd86c4&sdesc=Magnet+Wire%2C+Plain+Enamel+%28PE%29%2C+Solderable%2C+Class+155%2C+1%2F4+lb+spool%2C+28+AWG+Model+%23+CONWIRE-28MAG That is what I bought. I'll go keep my ignorance to myself.

OK, that is passed, we can ALL stop being embarassed! 

You DID get the magnet wire, that is good.

Well, now you can get on with it, right?

goldigger


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