how to control nichrome wire with arduino?

Hi,

i know that most of the people is against to use nichrome wire directly as is not easy to use and must be isolated too, as is also easy to use a ceramic heaters too, but i have 4 rolls of nichrome wire that are perfectly to experiment in a few project i have, so i need a way i could control the current passed to the nichrome so it doesn't melt and i can also control it's temperature.

i know the properties of the wire, and the calculations that needs to be made to know it's resistance depending the gague and the length, but i'm clueless how i can limit the current.

i have 12v/20A and 5V/5A power supply to use and i could also hook it up directly to 220V (i would like to do this if is possible, so i can power up arduino from a simple 5V / 2A power source and save some resources)

any idea? tutorial? tip? how i should wire it and how i could control it via sofware with arduino?

thanks in advance !

Your description gives me no idea what you want to use the wire for. Can you post a diagram of the sort of circuit you have in mind? A photo of a pencil drawing will be fine.

...R

Hi,

my objective is to heat things :stuck_out_tongue:

actually, i haven’t built anything as my tries always end up melting the wire why i can’t control the current.

anyway, i attached what is my plan.

is something like this: - YouTube but with a lot less nichrome and using arduino to regulate the current.

i want to know how i can regulate the current in the nichrome to have more or less temperature, simple as that :smiley:

mockup-nichrome.jpg

You should be able to use a logic level MOSFET to control power to the wire.

zoomkat: You should be able to use a logic level MOSFET to control power to the wire.

........Using PWM.

As nichrome has a known resistance per meter, you can work out how many watts your piece of wire will dissipate. If the wire is burning out you are dissipating too much. You can use PWM to reduce the average current flow. At 50% duty cycle, you dissipate half the power.

Do you know how much power you need?

You can also use twice the length of wire but have two windings. This way the same heat is dissipated over a greater area of wire so less likely to burn out.

Weedpharma

Nichrome wire does not have a linear temperature coefficient, but it is positive above 20C. So you could do some experiments and figure out a resistance vs temperature curve.

Then you can use PWM to control power to the wire, and then shut it off for a fraction of a second to measure resistance and therefore temperature. And in that way, have the Arduino adjust the PWM to keep the nichrome wire at a selected temperature.

How much nichrome wire? What resistance? Gauge? What wattage is the wire rated at per unit length? Website link to where you bought it?

You are melting nichrome wire? Yikes.

http://www.heatersplus.com/nichrome.html

Note that nichrome has much less variation of resistance with temperature than most
metals and alloys (that’s one of its two key properties, the other being that it doesn’t
oxidize to dust at orange heat in air). So measuring temperature using its resistance
isn’t particularly sensitive. You’re probably better off measuring the power by monitoring
the average current x supply-voltage x pwm ratio. The power dissipation will control the
temperature of the wire quite well its its a heating element in air - it should be pretty
repeatable if the setup has fixed geometry, so once you’ve determined the safe upper
power limit you just keep below it.

Hi,

awesome ! thanks for all the answer, with thiis i have been able to find this tutorial: http://bildr.org/2012/03/rfp30n06le-arduino/ that explain everything thing i need, so as soon i start wiring it, i'll update this thread with my progress :D

The solution above just delivers a solution for power control via PWM. I use a similar setup which forks fine. But I still seek a solution on how to measure the resistance of the nice coil. Currently I heat it up and I want to check the resistance to avoid burning the coil away.

Any ideas on this, I tried to use an opamp as an differential amplifier in the PWM pause but up to now I didn't succeed in getting somehow useful Output for the Arduino ADC.

An issue is the voltage on the nichrome wire when the heater is off. What does your setup look like? A differential amp will still have a maximum common mode voltage.

I would strongly suggest starting your own thread. This thread is 4 years old and it won't be clear that now =you= are the one asking for help.