I did some testing of a large amperage relay using parts from SparkFun and ESawdust this weekend. SparkFun has a project called Controllable Power Outlet that allows a microcontroller to switch a household receptacle, the obvious use for which is a Blender Defender. I ordered a couple of their PCBs and necessary parts. They did not have any 1N4148 small signal diodes in stock, but fortunately my local RadioShack did.

I picked up a bundle deal on a Arduino and Chameleon 1 Enclosure. You should hurry and buy yours now; they only have two left. The enclosure is a fine piece of engineering.

The ultimate goal is to finish the mobile cooler battery boxes I started like two years ago. The purpose of the test circuit today is to try out a relay that will cut out the power to the coolers if the battery voltage drops below a specific level. Technically, the controller will only turn on the relay when the voltage is within range -- it is normally off. I wrote a tiny Arduino sketch that turns the relay on for five seconds, then off. That is what you see in the video. I apologize for the terrible production quality of the video and my extraordinarily messy workbench. Also, the circuit diagram is meant to communicate the conceptual design, not be an accurate schematic. With those disclaimers in place, enjoy: