/diy/ - Do It Yourself

>>570543
bump

The wire is the resistance.

Look up a nichrome wire resistance calculator and see what the resistance of the wire you have is. Then find out how much wattage you want the wire to have and calculate your voltage from the resistance of the circuit.

The simple answer is to get a variac, plug it in and turn it on slowly until the wire is as hot as you need it to be.

>>570544
But I'm poor to have a variac.
Thank you, I think I found something, my country's internet is sub-african tier, so it will take some time before I can make a decent investigation.

Can't you just use a light dimmer? I think those can be good for more than 100 watts, so put that before the transformer and you should be good, no? I got a dimmer for about $10 (on sale).

>>570559
But I need something stable.

>>570560
It'll work well enough. A piece of wire changes temperature MUCH slower than an electrical circuit can switch at. You could use a variable duty cycle square wave with anything above 60 hz and not notice any difference between that and a variable DC source.

in my experience, a 12V battery will heat up a 60 cm section of nichrome just fine for cutting foam. i measured current at around 2A. if you want hotter, use shorter wire. colder, longer wire.

>>570575
Ok, then I'll use a 12v 2a transformer, i guess, the problem is if I lack amperage, because i'll risk on burning the transformer.

Google Garage of Evil Hot Foam cutter - I've seen a better table but the electronics side is easy to follow.

Look guys, I calculated it online, but i don't know if it's correct, it says I need 1.8a to feed it, so I will get a 2a transformer.

>>570583
Look, I'm not into this stuff, could you please verify this ? Much apreciation.

bump

>>570584
having a 2A transformer just means that it's rated to pass 2A of current. You need to look at the winding ratio to figure out what voltage it will give you when hooked up to 220V mains, and have that match the voltage you need to pull 2A through your wire.

>>570614
Well, a "12v" transformer is presumably called that because it has the right winding ratio to transform 220vac to 12vac.

It seems like a 2A 12V transformer should do the job. Put a fuse in there somewhere though. (slow-blow might be needed to avoid blowing due to inrush current though.)

> It seems like a 2A 12V transformer should do the job.

except you never wanna use a 2A transformer when you want 2A of current. coz it means you're at the limit of what it can deliver, and you always wanna be 25% below the limit, if, for no other reason, than to keep it from getting too hot and giving you the "burnt insulation" smell.

>>570585
What do you need to verify?

Mine is 2 240 to 12v halogen transformers in parallel controlled by a light dimmer. This is linked to a table with a 12 inch nichrome wire.

I'm changing the table soon as the wire slackens when it gets hot and I've seen a better tensioning system using a spring tensioned pivoting top arm.

Thank you everyone for the help, I will use a 2a transformer and I will put a fuse in there.

Just use a 12v dimmable downlight transformer and a dimmer switch. Shouldn't cost much. You need barely any power, mines 25cm long and it would glow red hot on full power.

>>570782
And how much amps does that output?

I made one and used the actual wire as a thermostat.

>Wire stretches with heat
>Contacts open
>Wire cools and shortens
>Contacts close

Just don't push too hard on it wile cutting.

>>570847
4.9

>>571164
And what's the diametter of the wire?

bump

dudes, whats with the variacs and dimmers?
ive seen foamcutter run of 9v batteries.

nab any old walwart and try it out with some wires.
put a bublb in searies if you feel like limiting the current.

primitive as hell but easy and accesible to a layperson

>>573410
It's dangerous to do it without a current limiter.
The wire could overheat and melt, hurting someone.