mk42 heated bed PID project


i have a spare mk42 heater bed and I would like to use it has a plant heated bed for sprouting.

I only have to reach a maximum of 35 °C.

I was thinking of using a MOSFET and the Arduino PID library, but I don't know if this would work with a small 12v power supply, like 2a or 5a ?

The mk42 is used on 3d printers (similar to MK2 heated bed) and is powered by 300w+ PS.

What if the PID library set the PWM output to 1024 (basically all open) ? would a 20 to 50w power supply fail since the resistance of the mk42 is about 0.9 ohm ? Or it would just work more slowly ?

Thank you,

If your power supply can not deliver the current, the voltage will start to droop. At 12V and 1 ohm, you need a 12A power supply. Even if you use PWM, you are essentially drawing 12A every time you turn on your MOSFET, even for a brief period. If you go with a very small PWM value, the PS may be able to handle it, but I wouldn't recommend it.

You will need a driver to handle the heater current in all cases. A logic level MOSFET and two gate resistors (180 Ohms to Arduino output, 10K to ground) are all you need.

I suggest to use a relatively low voltage heater power supply (5V, 5A) until you have a better understanding of the power requirements.

You may also find the resistance in the heater is a ptc ( ntc?) type and will control its own temperature naturally ( resistance increases as it warms up , lowering its power dissipation) .
You need to check that .