Formula for coil resistance

[granolaboy]

Okay...I'm a nerd.

Just for fun, the resistance of a coil is:

R = G x (D x pi x W + L)

Where:

R - Total coil resistance
G - Wire resistance for the gauge of kanthal you're using (Ω/mm)
D - Coil diameter
W - Number of wraps
L - Lead length (mm)

So, Say yer doing 6 wraps of 32g kanthal on a 1/16" drill bit for a protank head. That gives us:

G = 0.0436 Ω/mm (see chart below)
D = 1.5875 mm
W = 6 wraps
L = 16 mm (about 8mm of wire each side of the coil to reach the contacts in the bottom)

Then:

R = G x (D x pi x W + L)
R = 0.0436 x (1.5875 x pi x 6 + 16)
R = 0.0436 x (29.9237 + 16)
R = 0.0436 x 45.9237
R = 2.00Ω

In real life, mileage may vary...

 

[PolarGoat]

i use this site for all my calcs Coil wrapping | Steam Engine | free vaping calculators

 

[granolaboy]

Oh! That's much easier!

 

[epicdoom]

i use this site for all my calcs Coil wrapping | Steam Engine | free vaping calculators

+1 ^^ there is another I use also its a spreadsheet and takes into account everything under the sun If I find the link to it I'll post it here it's on this forum someplace though so searching coil calculator will find it

 

[Bunnykiller]

I threw this together on an excel page...
you insert wire dia, ohms per inch, shaft dia of winding jig, # of wraps...

it tells you the ohms for single, dual, triple, and quad coils. also gives you the watts used at voltages from 4.2 - 3.2. and finally, it tells you what amps are being pulled by the 4 coils combinations too...

 

[dirty_luck]

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