Looking for an efficient and safe way of heating a rigid pad

I’m looking for a safe way to heat and maintain a pad (probably aluminium covered in some sort of skin plastic or wood), at 110-120F/ 43C-49C about. I know I can use resistors, Diodes (Specifically LEDs in a grid generate enough heat for what I need), peltier plates, PTCs, resistance wire, fire, etc. But what is the most efficient and safe way to maintain a constant temperature across a plate. Like a heating pad but rigid and can maintain a temperature for hours without burning out or over heating.

Essentially my cat keeps sleeping on my laptop and phone and causing them to overheat. I can keep her off of them with better storage, but I’m a softy and want to give her a nice warm place to cuddle up.

I’ve got a bunch of micro-controllers in the Arduino family that I’m comfortable with and I will use a relay to control whatever the heating element ends up being, so I’m just looking for help on the heating side of it (I don’t mean to be rude, but I’ve seen discussions on other more specific forums get really side tracked about controlling “x physical thing”).

I want to use a few heating elements (so resistors would be fine if they’re an efficient way of delivering the heat, but I’m guessing there’s better), across the pad to maintain even heat. If it comes to safety vs efficiency (or long term cost in this scenario), lean towards safety. And if it’s choice between longterm cost and a significant (3x-4x times cost) initial cost, please just say it’s a crap shoot.

Thanks in advance for helping my very very tired self.

You could use heatbeds for 3d printers or silicone heating mats. Both use heating wire (which is a very efficient way of producing heat). They can be controlled via MOSFET or solid state relay,

Another option would be to use infrared heating lamps (hanging over the sleeping place). Power regulation would be possible with ligth dimmer, but not so easy for an exact temp.

A 3d printer heated bed seems to be like a good and inexpensive idea; consider adding a thermal cutoff so that if a thermistor fails it doesn’t overheat. They are cheap insurance. For a cat heater, a very low value TCO would make sense… Something like this inline, and physically connected to the heat bed. You’ll need to provide electrical insulation because the body is electrically connected to one of the leads; kapton tape is commonly used,

You could also use two temperature sensors so that if one fails, you can recognize the failure.

You could even use Marlin 3D printer firmware to control the temperature. See whether you know anyone who has upgraded to more advanced 3d printer controller board and has an old one sitting around? :slight_smile:

I would try this: https://www.adafruit.com/product/1481
with PWM control from an Arduino or the many controllers you can find on Amazon.

I know it’s not a hack, but why not a nice soft electric blanket? They also make small warmers for reptiles too.