BS2 & a powerhair controller??

MINI-IZED

I am trying to interface a Basic Stamp 2 to a powerchair controller. I would like to replace the joystick controller and just use the stamp. I have done some testing on the joystick controller and just confused myself even more. It’s a Dynamic DL5.2i controller. There are six wires that go to the controller from the joystick, power and ground 5 volt, and a pair each for the X and Y axis. For example there is a white and blue wire when the stick is moved full left the white voltage goes up and the blue voltage goes down. Now if the stick is moved full right the opposite happens. I have done lots of probing and testing and have lots of numbers but didn’t want to post them all. If anyone would like some specific info let me know. Any help would be greatly appreciated.

W9GFO

I have used a digital pot to replace the joystick on an Invacare electric wheel chair. The joystick that I replaced had four wires and was of the type that uses potentiometers.

On another wheelchair, a Jazzy, the joystick does not use pots but instead uses hall effect sensors. This one had six wires.

The BS2 would work well sending commands to a digital pot but I don't think that it would work well directly replacing the joystick.

Rich H

MINI-IZED

This joystick uses a set of five coils, one is attached to the end of the joystick rod and passes over the other four, which are at each end of the X and Y axis. I know that the voltage changes, and I am pretty sure that it isn't a digital signal, but I am not sure how to emulate that with a basic stamp. What kind of hardware would I need?

Spiral_72

You could replace each axis of the joystick with a digital pot like W9GFO mentioned. The would incorporate the existing controller and be the simplest solution.

Another idea is to use two standard RC servos and push/pull the joystick mechanically. It's kind of Rube Goldberg, but it'd work and could look neat.

MINI-IZED

W9GFO wrote: »

I have used a digital pot to replace the joystick on an Invacare electric wheel chair. The joystick that I replaced had four wires and was of the type that uses potentiometers.

Hey W9GFO, did you end up making those control boards? If not, would you care to share the schematic?

Next question, how do I determine which digital pot to use to get the correct voltage range?

MINI-IZED

Ok, I have done some testing and here is what I came up with. The joystick has six wires going to the wheelchair controller, RED, BLACK, YELLOW, BROWN, BLUE, and WHITE. The RED and BLACK are power and ground, about 5v. When the joystick is centered YELLOW, BROWN, BLUE, and WHITE are all at about 2.5v in reference to both power and ground. Now when the joystick is full left the BLUE wire is at about 1.1v and the WHITE is at 3.9v. When the joystick goes full right the BLUE wire is 3.9 and the WHITE is 1.1. My test points where between the BLACK the BLUE and WHITE. If I move the test from the BLACK to the RED the voltages are reversed. Forward and reverse on the joystick have a similar voltage swing on the YELLOW and BROWN wires. I got a hold of a mechanical potentiometer 1M Ohm, at 1M Ohm I had 2.4v and at 44K Ohm I had 1.6v. Even maxed out I couldn’t get the pot to give me the 3.9v that I need to get in to the high end of the joystick movement. What kind of circuit or IC chip do I need to have a Basic Stamp emulate these voltage swings?

W9GFO

MINI-IZED wrote: »

Hey W9GFO, did you end up making those control boards? If not, would you care to share the schematic?

Next question, how do I determine which digital pot to use to get the correct voltage range?

Looks like I missed your post, sorry.

I did make a few prototypes. the schematic is here.

I used the MCP42010. The voltage is determined by the command you send to the digital pot. If you send a command of "127" then the voltage coming out of the wiper will be half of the input voltage. The digital pot does have a max voltage that it can accept into it, something just barely over 5 volts I think. That max voltage limitation prevented me from using it in my Jazzy controller but it was not a problem for the Invacare.

It sounds like you will have to hook yours up differently than mine. For mine the voltage was read off the wiper, A goes to power and B to ground. For yours it seems that the voltage will be read off the A and B terminals and the wiper goes to either power or ground.

Rich H