Project by Steve - Medical Heat Pad

Hi I’m interested in using the Electric Heating Pad - 10cm x 5cm SKU: ADA1481 and adding a N-channel power MOSFET - 30V / 60A
SKU: ADA355 transistor and a dial and make it 240 volt compatible. This is for a medical application I am developing that needs a small heat pad that can accurately sustain between 36 and 42 degrees celsius for 30 minutes - preferably with a timer and auto switchoff function. I’m not a technician or a person with electrical knowledge, however if this could be assembled into an item that is ready to use I’d like some advice on what components I would need.
Any and all assistance greatly appreciated :slight_smile:

Hi Steven,

First up, the disclaimers: The products we sell are not intended for use in medical applications. They are generally intended for maker and educational use. Medical products require extreme levels of reliability and need to comply with a whole stack of regulations and standards.

It is illegal in Australia for an unlicensed person to perform work on mains (or higher) voltage electrical equipment. 240V is lethal, for you, someone using what you’ve worked on, or for someone working on something you’ve worked on. I’d suggest using a pre-designed and certified 240V AC to DC supply to power your project - that way you’re only working with safe voltages.

Now with all that out of the way, if you still want to make something to explore the theory of operation, let’s get started!

For power, I’d suggest something like this:

And use one of these and one of these to connect things up.

For the brains of the operation, I’d suggest an Arduino Uno:

Use the Mosfets you’ve identified to PWM the power to the heater pad. You’re also going to need some kind of temperature sensor. A thermocouple would do the trick, or one of these:

And finally, to join it all together, I’d suggest implementing a PID controller. There’s a PID library for Arduino:

ElectrNoobs has a really good tutorial on exactly this setup:

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Wow Oliver,
Thanks so much for the info you provided. I’ve ordered everything you’ve suggested and can’t wait to “connect the dots” and create this thing. Great work, rapid intelligent response - Thanks again and a Big Thumbs UP,