Introduction: IR Proximity Wheelchair Controller
A 4-directional controller for motorized wheelchairs.
Step 1: Construction Overview
- 2"x4" plank (at least 8" long)
- 3 conductor cable
- 8x 3-pin molex connectors
- 3x 2-pin molex connectors (or 6-pin)
- Molex pins
- 1/8" female audio mount
- 4-channel IR obstacle avoidance sensor module
- Digital I/O box for wheelchair
- 9-pin D-sub. connector (Connector for I/O box)
- Project box
- 16x machine screws (#10 x 1")
- 16x internal threads (#10-32)
- Velcro tape
- Double sided tape
- Heat shrink tubing (1/2")
- Table saw
- Band Saw
- Drill press
- 3D Printer
- Heat gun
- Wire stripper
- Molex crimper
- Phillips screwdriver
To avoid eye damage, wear safety glasses while cutting wood with the table/band saw. Practice caution and precision while using the heat gun and drill press.
Step 2: Prepare Connectors
Cut the 3-conductor cable to a length that will fit the wheelchair, allowing the cable to wrap from the back housing to where the controllers will be. Using the wire stripper and molex crimper, expose the internal conductors and crimp the molex pins on them. Insert the crimped pins to their corresponding molex connectors (male/female). After testing the connections, use the heat gun and shrink tubing to protect any exposed wiring.
9-pin D. Sub:
This project was based off an Invacare Mk5 wheelchair. The digital I/O box for this chair uses a 9-pin d.sub. connector to interact with the wheelchair. Use the connector specified by the wheelchair manufacturer. Using the wire stripper and molex crimper, add female molex connectors to the connector not used by the I/O box. Using the soldering iron, connect the emergency stop wire to the 1/8" audio mount. This will allow the use of a button to reset the controller if something goes wrong.
Pin out for the Mk5:
- Attendant Overide (Not used)
- Emergency Stop
- Common (-)
- +15v (Not used)
Step 3: Prepare IR Mount
Using a 3D printer, print out a node for each IR sensor. Files have been provided in .SLDPRT, .STL, and .IGS format.
Using the table saw, cut the 2"x4" planks to 4" segments. You will need one square per IR sensor. Drill a 1.5" hole in the center of each square. Center the sensor puck on the square and mark where the screws will be. Use a bit that is at least .200" to bore out holes to mount the IR puck. A hammer can be used to insert the internal threads from the bottom of the wooden puck.
Adjust the table saw and cut a 1/2" channel for the IR sensor wire on the bottom of the wooden mount. Use a belt sander or band saw to round the edges of the wooden puck, then sand the whole mount smooth.
Place the IR sensor into the 3D printed mount and secure with clay. Lower the mount and sensor into the center hole of the wooden puck and secure with screws. Doubled sided tape was used to cover the bottom, but velcro works as a less permanent alternative.
Step 4: Prepare Project Box
Mill out a window for the IR control board so that the LED indicators are visible and the IR adjustment pots are accessible. Drill a hole for the 3.55 mm jack, as well as holes on the end that are slightly smaller than the connector wires. The box will act as a clamp when tightened. Add velcro or double sided tape to the bottom of the box for mounting to the wheelchair.
Insert the 3.55 mm jack and secure with its corresponding nut. The jack will be wired to the emergency stop and ground pins as indicated by the wheelchair I/O interface. This will allow an operator to reset the controller should a signal malfunction.
Connect the d-sub wires to the I/O terminals and the IR wires the their respective channels. Close and tighten the project box.
Step 5: Connections and Testing
Connect the IR sensor cables to the sensor with the molex connectors and the the d. sub to the I/O interface. Connect the I/O to the wheelchair controller accessory port or as indicated by the chair manufacturer for external controllers.
Turn the wheel chair on, but keep the driver profile on joystick control, power should still be supplied to the IR sensors for fine tuning. Alternatively, use a DC power supply to provide 5v to the sensor box. The LEDs will turn on when the sensors are detecting an object, in this case a hand. Using a screwdriver and keeping the area above the sensor clear, adjust the power output using the potentiometers on the sensor board until the LED for the channel being adjusted is on the boundary of turning on. Wave your hand over the sensor, this is the maximum range that the sensor can detect without a false signal. Adjust further as needed.
Connect the emergency stop button through the 3.5 mm jack, and set the wheelchair to accept alternative control. See the manual or contact the manufacturer to determine how this process works.
Mount the sensor to a lap tray or other configuration and test for correct movement. Continued adjustments may be made to the sensor range using a screwdriver. Congratulations, the chair should now have proximity control.
5 years ago
Do you currently have any already made for purchase?
Reply 5 years ago
This was an orphan project that took place over a school semester led by an undergraduate at Georgia Tech. Unfortunately there was only one copy made for a specific elementary student.
6 years ago
Is this meant to prevent accidents? Like proximity brakes on a car? Keep someone from driving wheelchair into a wall, pedestrian, etc?
I apologize if I haven't read thoroughly.
Reply 5 years ago
No problems, apologies for the late reply. This project was for a student who needed a new way to operate their wheelchair. Alternative efforts, including eye tracking, sip and puff, and joysticks, had not worked out for them. The goal was for the student to begin by being able to turn and face who they were talking to, and if that worked well graduate to full directional control.
6 years ago
Very interesting Instructable. Thanks for sharing.
I have two questions regarding this Instructable:
Are the IR sensors going to be used to control movement of the chair by the person in the wheelchair?
Sorry for asking, but is this to allow for better control of the chair due to disability of the hand/arm?
I have recently completed two electric wheelchair projects:
1 - Dual PWM motor speed controller for a wheelchair
2 - Electric Wheelchair Controller
The projects were to replace a faulty Shark controller after the chair was damaged by lightning while on charge.
Reply 6 years ago
Apologies for the late reply, we just finished relocating to a new space.
The IR sensors were designed with the intent to be used by the person in the chair, however an assistant has the opportunity to kill the sensors should something go wrong and stop all movement. This particular chair has 4 driver modes, and we set one of them to accept this form of control. The pucks allow for multiple configurations and easy storage. The entire unit is basically held in place by velcro.
The student this was designed for lacks fine motor control and had attempted joystick, capacitive, and eye tracking forms of control without much success. We are currently awaiting more feedback as the new semester begins on the success of this attempt, but the goal was to facilitate left/right turning so the student could face different people in class without need of an assistant. Pending that outcome, eventually transition to full directional control.
We began this project with much the same intent as your own (they look great), to give functionality to someone on a reasonable budget. I will attempt to monitor this feed more closely if you have any more questions.
Reply 6 years ago
Thanks for your feedback. I hope your design will assist the student.