Steam engine and Clapton coils/Mixing Wires

[alee132]

I am trying to create a TCR for the dna200 correctly for clapton coils.  I am trying to use 26g Ti grade 1 wire as the core and ni200 30g as the outside wrap.  I have heard that the coil in the center is what the resistance goes by. Does this mean that I don't need to worry about the wire on the outside for the TCR and just whatever I have as the core?  If not, do I just measure the length of wire, figure out the resistance with coil calc and then input both coils into the TCR calc and then use that curve or just use the curve for TI grade 1?  Also what about if I want to twist ni200 and ti or any 2 different kinds of wires?  Do I need to input both into the calculator or just whatever one is going to be the lower of the 2 resistance wise?

[Dampmaskin]

For the best accuracy, you should enter all wires used. For claptons you can approximate the length of the outer wire by doing the following:

(radius of center wire + diameter of outer wire) * pi * 2 * length of inner wire / diameter of outer wire. (I haven't tested this formula, so double check it before you trust it 100%)

But it if it correct, you can then use the coil calculator to jog the resistance around until you hit the length of each wire. Enter these resistances in the TCR calculator for both coil materials, and you should get a pretty decent temp curve.

Twisted is simpler: Just find the resistance of both wires (again you can use the coil calculator for this, as long as you know the lengths), and enter both resistances in the TCR calc.

[alee132]

Dampmaskin said:

For the best accuracy, you should enter all wires used. For claptons you can approximate the length of the outer wire by doing the following:

(radius of center wire + diameter of outer wire) * pi * 2 * length of inner wire / diameter of outer wire. (I haven't tested this formula, so double check it before you trust it 100%)

But it if it correct, you can then use the coil calculator to jog the resistance around until you hit the length of each wire. Enter these resistances in the TCR calculator for both coil materials, and you should get a pretty decent temp curve.

Twisted is simpler: Just find the resistance of both wires (again you can use the coil calculator for this, as long as you know the lengths), and enter both resistances in the TCR calc.

OK so if I got 26g ti wire center and 30g ni200 outer.  I would do:

diameter of center wire 26g ti = .4mm which /2 = radius of .2mm

Radius of center wire .2mm
Diameter of outer wire 30g ni200 .25mm 
Lets say for example a length of inner wire is 100mm

So given these numbers the formula would go:

(.2+.25)*pi*100/.25
(.45)*pi*100/.25
1.413716694115407*100/.25
141.3716694115407/.25

565.4866776461627mm length for outer wire
Length for inner wire 100mm

Now my problem is how do I get the resistances to input from the length?

Also did I even do it the above math right?  If so I just need to figure out how to turn it into resistance to input into the TCR calc

I tried to use the following I found from the calc for formula

Ohms/mm

26g ti grade 1 = 0.00365/mm

100 *  0.00365 = 0.365 ohms

30g ni200 = 0.00189/mm

565.4866776461627 30g ni200 * 0.00189 = 1.068769820751248 ohms

100mm of 26g ti grade 1 wire = 0.365 ohms

565.4866776461627mm of 30g ni200 wire is 1.068769820751248 ohms

I think this is correct.

[Dampmaskin]

For now you will have to go to the coil calculator, select the material and gauge, guess a resistance, and look at the resulting resistance wire length. If too high/low, adjust the resistance accordingly, and check again. Repeat until you're "close enough". 

I'm planning a brand new calculator that will make all this a whole lot easier, but it's an ambitious project that will take some time.

[alee132]

Dampmaskin said:

For now you will have to go to the coil calculator, select the material and gauge, guess a resistance, and look at the resulting resistance wire length. If too high/low, adjust the resistance accordingly, and check again. Repeat until you're "close enough". 

I'm planning a brand new calculator that will make all this a whole lot easier, but it's an ambitious project that will take some time.

Well I noticed that you can pick your wire and you gauge and it gives you a ohm/mm calculation. I used that to figure out the ohms above.  So its not automatic but its not too hard either if you do it. I think I got it now I just need to actually try this out on a coil and see if its working like it should. Because I have heard that the wire with the lower resistance is the only one its going to use. If that's true then using both in the tcr calc is going to be off.

[Dampmaskin]

If the resistances differ by a lot, you can get away with using only the lower resistance. Using both will always be more accurate.

You can find a tutorial about it here if you're interested in learning more.

[alee132]

Dampmaskin said:

If the resistances differ by a lot, you can get away with using only the lower resistance. Using both will always be more accurate.

You can find a tutorial about it here if you're interested in learning more.

Ok good to know. I will do whats going to be more accurate. I will report my results back here. I am still waiting on my wire to get here for the TI grade 1.

[alee132]

I have already used ni200 claptoned with ni200 and it works just fine on the default curve.

[Dampmaskin]

Yes, as long as you use no more than one single coil material, the TCR curve for that material will always be the same, regardless of how you clapton, twist or wrap it, and regardless of the resistance of the coil.