I have designed a circuit board for the SLA7062M Unipolar 3-Amp microstepping driver IC from Allegro/Sanken.
With CNC applications in mind, it features optically isolated inputs and an idle current reduction circuit.
As long as the board is receiving STEP pulses, it delivers full current to the motor. (The full current value is set with a potentiometer)
When the STEP pulses cease, the board will drop the motor current to 50% after a 2-second delay.
It also has a jumper to invert the DIRECTION signal if your motor is turning in the wrong direction. (No more need to swap the motor wires)
The boards are currently being fabricated & will be available for sale on November 1, 2005.
The PC board is $10, the SLA7062M is $12 and a modest $3 shipping charge.
www.techkits.com