Electronic – required power supply for nichrome heating element

heatpower supply

I am very new to electrical power math. So please be friendly. 🙂

I am getting 28 gauge nichrome wire to make my own heating element. Here are the specs and numbers of what I am attempting to do and what I know. I would appreciate a second pair of eyes confirming my numbers and also help recommending the correct power supply.

A. 10ft of 28 gauge wire, straight = Ohms Resistance 42.52. I plan to coil the wire myself and then loop the coil through ceramic insulators
B. I need to reach temperatures of 450 F (I don't need over, but I def need to consistently hit this temperature.

Using the above info, an online calculator has provided me the following:

Volts = 55.276

Required Amps.  1.3
Required Watts: 71.85
Resistance per foot: 4.252  
Total Resistance: 42.52.

Questions:

  1. Is 55.276 volts the amount of volts needed going into my power supply, or the amount of volts coming out of my power supply?

  2. I have a spare (universal) HP laptop power supply with the following specs, is this power supply sufficient for my needs? :
    Input: 100-240v, 50-60Hz, 2.0A
    Output: 18.5v — 6.5A, 120W

  3. When I cut the laptop connector off I assume I am going to see at least 2, probably three wires. black, white and green (maybe red). Do I connection both black/white to one end of the nichrome wire or do I connect black to one end and white to the other end?

A quick diagram:

110      Power Supply (PS)          PS split      Nichrome Wire
     _________________________    
3]---|>>100/240v | 18v/120W>>|____/---black---o---{Wire EndA}--\
     -------------------------    \---white---o---{Wire EndB}--/
  1. I may have to get 26 or 30 gauge wire…knowing the above, will my power supply still be sufficient with those gauge wires for what I am looking to do?
  2. Lastly, what, if anything am I missing or possibly not understanding?

Thank you in advance. This is all to make my own homemade plastic vacuum molding device.

Best Answer

Is 55.276 volts the amount of volts needed going into my power supply, or the amount of volts coming out of my power supply?

That is the voltage you need to put across the nichrome wire, so it will be the output. You're not going to find a 55.276V power supply on the shelf, you're going to have to make your own.

I have a spare (universal) HP laptop power supply with the following specs, is this power supply sufficient for my needs? : Input: 100-240v, 50-60Hz, 2.0A Output: 18.5v --- 6.5A, 120W

18.5V < 55.276V, so no.

When I cut the laptop connector off I assume I am going to see at least 2, probably three wires. black, white and green (maybe red). Do I connection both black/white to one end of the nichrome wire or do I connect black to one end and white to the other end?

It won't work like you want, so don't bother, but even if it would work, there is no standard for the color or number of wires in laptop power supplies.

I may have to get 26 or 30 gauge wire...knowing the above, will my power supply still be sufficient with those gauge wires for what I am looking to do?

Your power supply isn't sufficicent, but 26 or 30 gauge nichrome wire will have slightly different resistivity than 28 gauge. You'll need to redo your calculations for the gauge you're actually going to use.

It seems like you're pulling a lot of numbers out of thin air. Further, I would be very cautious trusting an online calculator's calculation. The 450F is probably the wire temperature itself. Is that what you really want?

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