The Drive System Pt 2

Control Box Containing the drive board and future control boards. 

Simple hand held control box with two pots (forward/reverse, left/right)

The very first thing I wanted to do was to get the drive system working.  The electric motors on this wheelchair seems to suffer from proprietary syndrome paralysis.  I was able to obtain the motor's part number quite easily off its nomenclature but failed to find its data sheets on the Internet nor was I able to convince the people at the company that manufactured the motor to provide me with anything.  The wheelchair manufacturer was of little help as well.  If you're going to hack an electric wheelchair, expect limited help from the manufacturer or distributor on data.

0.100 Shunt Resistor

What I did do was use a motor shunt resistor (0.100 ohm) in series with the motor and 12 VDC battery to document its locked rotor and running currents ratings.  With this information, I was able to select a motor drive.  In this case I selected  a model Sabertooth 2X12 manufactured by Dimension Engineering.  I also decided at this point to use analog input signals to control myRobot.  You have a number of options here from pots to computer interface.  I selected two pots simply because I wanted to complete the drive portion. 

Main Control Box

A look inside the control box presently containing the drive board, and battery hookup and distribution.  The motor leads can be seen at the top left and right corners.  The control lead to the hand held control box can be seen leading from the drive board an threading out at the bottom left corner. 

The plan is to eventual put into the left side an embedded controller.  Preferable a SPLat MMi202.  This controller would provide wireless control via a hand held joystick wired to a transmitter.  It would also provide I/O abilities interfaced with the laptop via RS232.  At the moment, I'm also considering an Arduino UNO as a possible choice.  More on that later.

Drive System Field Test

This is the field test of the drive system.  Actually, this the second test.  The first test was conducted in the car port next to my car.  I didn't programme the dip switches properly and as a result the controls didn't behave as expected.  I now have a new dent on the side of my car.  Need I say more about where to test your machine?  By the way, turn down the volume.  You're listening to everything from the jet overhead to the lawnman next door.