V1.0 used hand built versions of the schematics below; v2.0 introduces its own custom board that simplifies the building of these circuits. A dozen boards were made using DirtyPCBs for less than $40 shipped (not including components). SainSmart premade boards from a source like Amazon can also be used.
The circuits below use a 0-5vdc control signal and a common 24vdc supply. The control signal can be digital or analog (PWM).