RC Wheelchair 2

After my attempts to modify the settings of the existing wheelchair controller I accidentally erases all the board settings and was left with an inoperable board. Since it is almost impossible to locate the correct file for my particular controller, I decided to construct a new motor controller. This would give me the added advantage of full control over each wheel motor, and I could write all my own control algorithms (though these do not necessarily come easily).

1 - DC motor controller (H-bridge)

Like the original wheelchair, I needed to operate two 24V DC motors. I was not sure of the amperage, but I know that the batteries have an inline fuse for 12A, and that the original controller operates with just 4 single TO-220 mosfets on each motor (part numbers indicated rated for 30A). I couldn't test the motors under load very easily without a controller, so I estimated that a motor controller of 20-30A would do the job.

I bought a cheap Chinese h-bridge board but it failed almost instantly, so for my next attempt I decided to roll my own. I based my design on the open source Robot Power OSMC, with some changes. Firstly, I reduced the number of power mosfets by 1/4, since the original OSMC is rated for 160A, and I didn't need anywhere near that much power. So, instead of 4 mosfets on each branch, there is just one. The rest of the controller remains the same, which mostly consists of the HIP4081A mosfet controller. Next, I doubled up the controller, adding a second channel so I could drive a second motor.

File:Wchmotor2-board.png

Board layout for the dual H-bridge controller

Eagle files for this board can be found here: File:Wchmotor2-eagle.zip