Need help calculating heater coil power requirement please.

[Swampy]

Hey there lovely people.

My skill is in my hands so nuts and bolts seem natural because I can see it. But electrickery is invisible and therefore puzzles me, sooo...

What power supply do I need to heat 700mm of 18awg (1mm dia) nichrome wire formed into a 20mm i.d. coil to 192degC?

I have a variety of transformers available also a computer power supply to scavenge from, even mains supply is an option... just that it gets to 900degC in three seconds lol

I can't post a picture for some bizarre reason but maybe I could try upload somewhere and post the link so's you can see it but here it is on ig...https://www.instagram.com/p/BSuBxwxBFzL/

The plan is to slide a 20mm boro tube through it vertically, thermocouple touching the tube through a gap between two windings of the nichrome coil.

Thanks in advance for sharing your knowledge and vape on!

 

[Hippie Dickie]

okay, so that is 28" of wire, around 1 ohm, since 24" of nichrome80 16awg is 0.5 ohm. the thing about nichrome wire is that amps determine temperature ... so you need a power supply that can deliver about 3 amps into what may appear to be a near dead short. that's why i use batteries, good chemistry (LiFePO4, for example) don't care - or say a motorcycle battery or car battery.

there are charts on-line that give amps required for a few temperatures for different awg values - do a google ... i found one that showed for 400F, about 3 amps. but they are theoretical, for a straight wire in a vacuum or some such. adjust after testing.

i hope you are going to add a computer connected to your thermocouple, otherwise you have an Ohm's Law vape, and been there done that - which is why i went to computer control for the Bud Toaster. i got tired of losing 50F when i took a toke and waiting for the heater to recover.

 

[Swampy]

Excellent, thanks mate I'm glad it was you who replied because it was the story of your amazing Bud Toaster that I spent all day yesterday reading. Fascinating, much respect

Yes I scored a controller off Amazon;
https://www.amazon.com/Inkbird-100-...rd_wg=hySkl&psc=1&refRID=2PSPXJFKA8K1EFVV9J3N

This particular build is No.2 Mk.1, utilising the same inverted bell-jar as the heating chamber as build No.1.

Just that instead of a soldering iron with a copper bud-cup in place of the soldering tip, the heater will be similar to yours with the heater coil wrapped around the boro tube and like I say, the bell-jar covering the whole shebang.

The purpose of the large heating chamber is to compensate for the temporary cooling effect you mentioned after oral evacuation of said chamber.

Thanks for the battery tip, I'll give that a try. Also for sharing your knowledge, I appreciate that as it fits in with my lifetime philosophy because how else will our civilisation be enlightened.