I am wondering how to add direction reversing to a 90 VDC motor that is around 1/10 horsepower. The motor is connected to a variable speed controller/ 115 VAC input power supply by a 3 foot long cable. The power supply case is about 4” wide x 4” high x 8” long, with a little bit of space underneath the cover near the DC output connector where there is clear access to the output wires.