Very simple to DIY the controller. Using 555 timer IC, some resistors, capacitors etc. Simpler than DIY the box itself. In fact I get dama to do for me the box at $25.
I'v forgot how to do the controller, need to open up the controlller again, or just look in the net.
I used these below are my references to build my controller and the box.
DIY controller
Another DIY controller