got me to design and build the UBW (USB Bit Whacker) project
to solve his problem of disappearing parallel ports on computers. The UBW design has exceeded all of my expectations
. As well as meeting the original design objectives, it has proven itself a great platform for many forms of firmware. But there was still a problem! Bruce traditionally used the UCN5804B stepper motor driver chip for his EggBot
classes because it is easily breadboardable and very simple to use. Unfortunately, they are now $17 each and very difficult to find. Bruce wondered if I could design and build a replacement driver that would still be mountable on a breadboard, would still just need two input lines (step and direction) and would drive bi-polar stepper motors. And so now we have the EasyDriver design.
Each EasyDriver can drive up to about 750mA per phase of a bi-polar stepper motor. It is permanently
set to use 8 step microstepping mode. (So if your motor is 200 full steps per revolution, you would get 1600 steps/rev using EasyDriver.) It is a chopper microstepping driver based on the Allegro A3967
driver chip. For the complete specs of the design, read the A3967 datasheet. It has a variable max current from about 150mA/phase to 750mA/phase. It can take a maximum motor drive voltage of around 30V, and includes on-board 5V regulation, so only one supply is necessary. The best part - low cost. The parts cost is maybe $10, less if you make the board yourself.
-- above text and all designs are from Brian Schmalz's Project page