I am trying to control a cooking plate with the arduino. A PT100 should provide the logic with the temperature signal and the arduino should switch a relay on/off to maintain the temperature.
As the cooking plate can consume up to 3500 W, the relay is going to be a fat one. Being an inductive load, I have read from several sources that I need to be extra careful with the load when switching the relay off, as it may deep-fry the logic components.
The basic schematics would be that illustrated in the picture
In this image (on the right), a MOSFET is switched by the Digital Out to close the relay.
The IRFZ34NPbF I chose has 29A drain current (cont.), a Gate Voltage of 2-4V and 16A avalanche current.
The diode MBR745PBF has a forward current of 7.5A and a surge current of 690A.
What do I have to do more in order to protect the logic circuits from the inductive loads? Which kind of array should I take?
Why use a relay.
Your arduino forms the basis of a PID type controller so you'd get better temperature control using an SSR (solid state relay) powered direct from the arduino. You get no arcing and you can pulse power the hot plate. I've done similar on my conventional fan oven and the internal temperature is controlled within 1 degree centigrade. Mind you I didn't use an arduino - rather a complete mains powered 3 term PID controller bought for around £36 from our eastern cousins.
It's not a hot plate, it's an induction cooker. That's why I'm worried about the induced current when the coil turns itself off.
Basically the cooker has the power selector (1200, 2500 and 3500 W) and you just plug it in and it gets to work.
Other users have used a commercial brewing controller(that's what it's gonna be used for) which cost some good money and it didn't work because of solid state relays, that's why it threw me off this idea.
But mind me, the judgement that it didn't work because of the SSRs came from a home brewer and not an electronics experts. And myself being a starter as well, maybe I'm completely off the track...
The above is more of what I had in mind. Plenty of metal within its own structure so bolting to a reasonable piece of sheet metal should give you all the heat-sink you need
This can take the arduino output directly and there's no problems regarding arcing. The triac is either ON or OFF so it acts just like a relay. I therefore see no reason why it shouldn't work with your induction heater.
