Variable Resistance control by Arduino

Good day,

Any body can help me in how to build temperature controller with variable resistance in order to develop PID controller? What i need is how to build variable resistance with Arduino to control 500W on 220V AC? Any body can help in building the circuit?

Best regards, Sayed

check out ben heck's solder reflow oven youtube

You're not going to use variable resistance - what you will do is use PWM to control the on/off cycling of power. Warmer needed, leave power on more. Cooler needed, leave power on less, or off even. With 500 W, probably best to use a relay, click it on/off as needed. Not going to be 500 Hz PWM - listen to your toaster oven, can probably hear clicking as bimetallic switch opens & closes as oven heats & cools. Very slow - fastest will be on a few seconds, off a few seconds, as elements heat up, sensor measures it, turns off again.

Thanks tuskiomi,

tuskiomi:
check out ben heck’s solder reflow oven
youtube

CrossRoads thank you for your advise, but the result will kept sinusoidal wave in temperature,
the idea from variable resistance is to eliminate this problem by tuning the PID controller,
what do you think? is there any way to develop PID controller based on on off controller?

CrossRoads:
You’re not going to use variable resistance - what you will do is use PWM to control the on/off cycling of power.
Warmer needed, leave power on more. Cooler needed, leave power on less, or off even.
With 500 W, probably best to use a relay, click it on/off as needed. Not going to be 500 Hz PWM - listen to your toaster oven, can probably hear clicking as bimetallic switch opens & closes as oven heats & cools. Very slow - fastest will be on a few seconds, off a few seconds, as elements heat up, sensor measures it, turns off again.

Sinusoidal at what frequency, and with what temperature swing? Physical stuff has thermal mass to it, it takes time to warm up & cool down. My toaster oven is 1500W - and it takes many seconds to ramp up to a temperature, and then seconds to cool down. You can build a PID controller to react to that kind of stuff. https://www.sparkfun.com/products/retired/81 for an example

thanks very much, the controller need to control incubator temperature and humidity as well, and can you also advise me with free software if available that allow me to design and program arduino if am weak in programming language?

I suggest you learn how to program the Arduino, then.

I have not heard mention of any software on these forums that allows you to program an Arduino without programming an Arduino, which implies that if any exist, they probably aren't useful (IIRC there have been attempts to let you program it blockly style, but I don't think any of them made it to usefulness. It's quite hard to make something that lets you program without programming, apparently; all the attempts I've seen have been terrible, and there's huge interest)

If you prefer to write javascript instead of c, you could go with an Espruino (I also use Espruinos for projects that are complex enough that the thought of writing them in C makes my head hurt. ) - though it's a younger platform, so there aren't as many libraries for it (though I don't suspect you'd need any for this project?). Espruino also has a blockly thing for writing code without writing code, but like every other attempt I've seen, it's useless for anything complicated.