I was looking for a solution for keeping tea and coffee warm while working at my desk.
I bought one online, but after using it I was really dissappointed in how it worked. It would heat up to a maximum of around 40 degrees on the plate and wouldn't pass much of this onto the mug - making it pretty much useless.
I decided instead to design one myself using solidworks and then put the 3D printer to work creating the parts I needed to make a better one myself.
Since I coule make most of the parts with the printer all I really needed extra was a heat source and a USB power supply.
To provide the heat I decided to use a Peltier Unit that cost £2.27($3.56) on Amazon
To power it from my computer all I needed was an old USB cable, these are cheap but I had plenty lying around for things that I didn't use anymore.
Cutting the end off a USB cable leaves you with four wires; green, white, red and black. The red and black wires were what I needed as these are the wires for power inside the cable - so after cutting off the green and white cables I had PC power supply I needed for the peltier heater.
Connecting the positive wires (red) and ground wires (black) on the Peltier and USB cable was all that was necessary to have it heat up when I plugged it into the USB port at the pront of my computer.
The result was far more successful, measuring the temperature of my drinks warmer it was able to get to 66 degrees and was much better for keeping drinks warm on my desk!
I decided to take it a little further after that by adding a switch, so that I could turn it on and off on my desk without unplugging it. I also added some LED's to shine through the sides of the case to give it a nicer effect - and to remind me when I'd left it on!