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Controlling heating element

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Max Jahnke

Max Jahnke

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Hello.

I'm new to power electronics, so I would like to ask for some suggestions on how to control a heating element (to be applied on a water bath).
I was considering using a thermistor or another temperature sensor to, based on the value read, drive a PWM that would go on the base of a transistor. The transistor would then be used to switch a device (I wouldn't like it to be a relay) so that the current from a 230VAC source to a 3000W heating element could be controlled.
I've read about diacs and triacs, but I was wondering if there wouldn't be any transistor that could switch 230vac "directly", as is the case when switching low DC voltage.
Thanks in advance.
 

Actually I wouldn't like to use electromechanical relays as the one you suggested, since they are noisy and have limited switching capabilities (considering I'll be using a PWM). The approach I forgot to consider, and which might be the simplest of all, is to use a 250VAC/16A SSR controlled by a 3~32VDC/100mA.
 

You can use the Full bridge circuit to control the current , Ofcourse you'll be needing a closed feedback loop ,
Sensor will sense the data and will transfer the data to Microcontroller , after processing the data a PWM signal of desired duty cycle will be generated by microcontroller, which will be used to trigger the Mosfets or IGBT used in H-BRIDGE,
For a better control you can consider a PID controller in software.
 

Max Jahnke said:
Actually I wouldn't like to use electromechanical relays as the one you suggested, since they are noisy and have limited switching capabilities (considering I'll be using a PWM). The approach I forgot to consider, and which might be the simplest of all, is to use a 250VAC/16A SSR controlled by a 3~32VDC/100mA.
Click to expand...


Omron Relays are pretty quiet and they are best choice for regulating ceramic stove tops ON/OFF every few seconds. How often do you expect power to be cycled on/off for a bath over the hysteresis range of a few degrees?

If you want silent control, PWM is overkill and go for the Triac with opto-triac driver if you need isolation. You can get proportional control by adding noise to the error signal, then use zero crossing triac control with what we call hysteretic proportional control by dither method of on/off control.
 
Thanks for the answers. I'll study both approaches and see which one would fit better as soon as I get the time to do so. I'm looking forward to implementing this and sharing the results here. :)
 

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