I always like when I come home and have packages on my doorstep. Now that my other project for making the tank tracks is starting to grow I can use some of the funds from that to pay for parts for other related projects. The main reason that I need these hot plates is to heat the molds up and cure the resin faster. A decent digital controlled hotplate runs about $200 and I am planning on building three of them.

The first parts that arrived today were the heater elements, the LCD screens and the USB power converters.

I am planning on using an Arduino Uno to control the hot plates so I will need to power them. I will have AC power coming in and powering the heaters through a solid state relay. So I needed a way to convert this to 5 vdc. The cheapest and easiest solution was some phone chargers. I got a pack of three for $8.95 just a tad under $3 each. I can't cant think of a cheaper solution than that. I decided to open up the chargers and get access to the circuit board directly. This will make it easier to mount and connect wires to. Here is the tear down photos.

It would be easy to use use a usb cable to connect the arduino to this. However, I would like to leave the usb open for programming the hotplate after it is built. So I will need to connect directly to the 5 vdc and ground pins instead. I plan to check these on the oscilloscope at work first to make sure the power coming out is not too noisy for that. But i think it will be okay. To make it easier to work with I removed the two short blue wires and replaced it with longer black and white wires of the same gauge. I also removed the usb socket and added a black and red wire to the power and ground pins directly. The last step was to use a little super glue to glue the two halves of the board together.

For less than $3 I have a nice little AC to 5 VDC power converter which should power the arduino nicely.