Experimental Joystick and Motor Controller Board
Figure 1. Joystick Motor Controller
WARNINGS and ADVISORIES
This is an experimental prototype electronics board, which has not been
fully tested or evaluated for safety. The design is maintained as a
collaborative effort by volunteers, and is constantly evolving.
It may have software or hardware bugs. Use at your own risk.
If you plan to use this device to control the motors, make sure that the wheel chair is operated away
from dangerous locations such as stairs, water, roadways,sidewalks, or other un-level locations where the
wheelchair could fall, in the event that the controller board loses control. An adult should always be
present when the wheelchair is used with this controller board.
Please note that we are a small group of volunteers, and can not provide much
technical support. If you are not technically savvy you may need
to find someone who is who can help you.
Figure 2. JOY-MOTOR-CTRL-KIT: Includes Joystick Motor Control board, Joystick with Joystick PCB
Board, 3D Joystick enclosure, Power Switch, Ethernet cable, Battery and Motor Wires.
||Joystick Motor Controller board Kit. See figure above to see what is included.
We are using the Joystick and Motor Controller Board as the brains of
the wheelchair that members of our foundation have collaboratively
designed. It is under continual development, and we hope to
further refine it over time.
All documentation for the board including
assembly drawings and software is provided here so that you can build
your own from
scratch and make modifications, or you can purchase a unit form our
website. Purchases of
this experimental motor controller board help fund The Wheelchair
It is comprised of an H-Bridge PWM motor driver and microcontroller
with software. It will read a 2 axis Joystick and convert
those readings into appropriate motor movements. It has a USB port
which can be used to update board settings such as the maximum speed,
and to upgrade the firmware. It has 5 diagnostic LEDs, 4 of
which indicate motor activity, and 1 which indicates a heart beat for
indicating that the board is powered and operational.
The kit also includes a joystick board, which is soldered on to the
joystick terminals. This board has an Ethernet plug, so you
merely need to plug in the included Ethernet cable, and then wire the
other end of the cable to the terminal blocks of the controller board.
The power switch is also plugged into the joystick board.
You will need to solder this board to the joystick.
We now include a black joystick enclosure in this kit. The joystick enclosure
is a 3D printed part. You can use the supplied part, or print your own if
you want it in a different color or finish. You can download the 3D STL file
if you want to print it yourself: JoystickEnclosure.STL
The controller board has 3 terminal blocks that are used to connect wires
to the other electrical components:
- TB1: Battery Inputs
- TB2: Motor Outputs
- TB3: Joystick inputs and outputs.
You can open the and close the terminal block terminals with a small
flat head screw driver. Turning the screw clockwise will open
the terminal, and counter clockwise will close the terminal.
If you are in doubt as to the position of pin 1 on a
terminal block look at the back of the board, and you will see that pin
1 has a square ring around the hole. The board has text next
to each of the terminals indicating the wire color and function of the
Left and right motors are referenced to
the child's left and right if he/she where sitting in the chair.
Connect all of the terminal blocks using the following tables:
|TB1: Battery Inputs
||+12V, Battery Positive Terminal
||GND, Battery Negative Terminal
|TB2: Motor Outputs
||Motor1 A-LEAD, Right Motor.
||Motor1 B-LEAD, Right Motor.
||Motor2 A-LEAD, Left Motor.
||Motor2 B-LEAD, Left Motor.
|TB3: Joystick Inputs/Led Output
||3.3V Output. Connects to both joysticks, and LED.
Power On Input. Tie this to the power on switch. Tie to ground to turn on power
to the board. If left untied to anything (floating) the board
will be un-powered.
||LED Output. This can be
connected to an optional LED to indicate that the board is functional.
||Joystick Y input. Tie this to
the middle pin of the joystick Y.
||Joystick X input. Tie this to
the middle pin of the joystick X.
||Ground. Tie this to
GND. This connects to the GND pin of each joystick and to one
side of the power switch.
Figure 3. Joystick PCB Board
Follow these steps to wire up and verify the joystick and motor controller board:
- Plug in the power switch connector to the joystick board.
- Plug in the Ethernet cable into the corresponding socket on the joystick board.
- Wire up joystick controller according to the wiring diagram for TB3.
- Make sure the power switch on the Joystick enclosure is off.
- Wire up the battery according to the wiring diagram for TB1.
- Turn on the power switch.
- Verify that the heart beat LED is blinking.
Turn off the power switch, and verify that the heart beat LED stops blinking.
Wire up the motorsaccording to the wiring diagram for TB2.
For steps 9 through 13, tilt the wheelchair, or prop it up such that the
wheels do not touch anything and can freely rotate.
Turn on the power switch and verify that the motors are off. When the joystick is not pressed, the motors should be off.
- If it isn't blinking make sure that the polarity of the battery is correct.
- Make sure that the power on input (pin 2 on TB3) is tied to ground through the switch.
- If the heart beat LED is blinking rapidly, rather than once per second, recheck the wiring.
Press the joystick forward, and verify that both motors rotate in the forward direction.
- If the motors are on, verify that joystick is wired correctly.
Press the joystick backward, and verify that both
motors rotate in the backward direction.
Press the joystick to the left, and verify that the
left motor reverses, and that the right motor rotates forward.
Press the joystick to the right, and verify that the
left motor rotates forward, and that the right motor rotates backward.
You are now ready to test the movement of the wheelchair, by setting it on
the ground so that all 4 wheels touch. Run the wheelchair
without anyone in it to verify that it is responding well to joystick commands.
Calibrate the joystick via the USB port by running
the 'c" command. See the following section for details on
configuring the controller board via the USB port.
The maximum speeds for forward, reverse, and rotate can be adjusted through
the USB port. See the following section for details on
configuring the controller board via the USB port. You reduce
the maximum speeds if you are worried that it will go too fast.
- If they rotate in the wrong direction, reverse the polarity on their
respective A/B leads. Note that changing the leads on the
motor changes the direction of rotation.
Configuration Via USB Port
The controller board has a USB2.0 port which can be used to update motor
settings, and firmware. When using the USB port remove all power and
wires to it. Connect it through a USB hub to your computer.
A serialcommunications program must be used to access the board.
While theboard will work with most any serial communications
program, we recommend Termite for
Windows. If you are having difficulties, get it working with termite first, then switch to your desired program.
When you plug a USB Comm device into your computer it will randomly assign a
comm port number. To determine which comm port the device has been assigned to do the following:
Now that you have the correct comm port number for the device, you can
- Open Windows device manager. This can be access through the control panel.
- Plug in the USB device. You should see the device under the tree node labeled: "Ports (COM & LPT)"
- When you un-plug the USB device, that device should disappear. You now know the correct comm number.
- Open the Termite Program.
- Push the "Setting" button on the too bar.
- Select the comm port that you determined from the steps above.
- Set the Baud Rate to 9600.
- Data bits should be 8.
- Stop bits should be 1.
- Parity should be none.
- Flow Control should be none.
- Under the "Transmitted Text" group box, select "Append CR".
- Select Okay to close the Settings box.
- Put the cursor on transmit text line, at the very bottom, and type random
text, and hit the enter key. The logger should respond with an
error message. At this point you know that the settings are
correct, and you can start sending correctly formatted commands.
- If you ever disconnect the USB port from the board, you will need
to restart the USB connection in Termite, by twice pressing the large COMX button at the
top of the terminal window.
||Displays the help menu.
||Calibrate resting state of the joystick. Make
sure the joystick is not pressed and is at rest before you run this
||Get the joystick resting state calibrated offsets.
||Displays the current software version.
||Toggle enable or disable of the LEDs.
||Get the current maximum speeds. Saved speeds may be slightly different than what was entered, due to how the numbers are represented internally.
Set the maximum speeds. The square brackets denote fields, and are not used as part
of the command. Example:
speeds 50,50,50; Sets all of the maximum speeds to 50%.
Diagnostic (Heart Beat ) LED
The controller board has several LEDs: four of which indicate the directions of the motor, and 1 which
is a diagnostic LED. When the board is correctly powered, the diagnostic LED should blink at a rate of about once per second.
When there is an error condition, it will blink about 5 times per second.
The diagnostic LED will blink rapidly at 5 times per second under the
The USB cable is plugged in. When the USB cable is plugged in, the motors
are turned off. To fix this condition, unplug the USB.
The joystick is pressed away from the origin upon power up. To fix
this condition, make sure that the joystick is free floating, and power
cycle the power switch.
One of the joystick wires has become loose or has broken. To fix this condition, do a visual
inspection, or use an ohm meter or continuity tester to verify that the
point to point connections are correct.
To trouble shoot you will need a low cost multimeter, which you can get
from a hardware store, or www.amazon.com.
The diagnostic LED keeps blinking rapidly indicating an error state.
The Fuse keeps blowing.
- Make sure you have removed the USB cable from the board.
- Read the voltage on the X and Y joystick inputs as follows:
Connect the black lead of the probe to Terminal Block TB3-Pin 6 (GND) and the
red lead to TB3-pin 5 (Joystick input X). The multimeter
should read about 1.65V. If not then there is a problem with the cable.
Connect the black lead of the probe to Terminal
Block TB3-Pin 6 (GND)
and the red lead to TB3-pin 4 (Joystick input X). The
multimeter should read about 1.65V.
If not then there is a problem with the cable.
Try calibrating the joystick rest state via the USB. Use the
calibrate command. See the "Configuration Via USB Port"
section. After you are done calibrating it, make sure you
remove the USB cable, and power cycle the power switch.
If the fuse is blowing, it could be the result of a mechanical problem such as the wheels being
too stiff to turn. The controller is meant to be used with small
children, and not for heavier loads. If there is too much weight
on the wheelchair it could also blow the fuse. We are using a
15A automotive fuse, but you could also try a 20A fuse. Never
short out the fuse as this could cause irreversible damage to the
Firmware Upgrades Via USB Port
The controller can be updated with the latest firmware via the USB port, by
downloading a executable file, using our update console program
utility. This will be posted later when we have a firmware upgrade that
we want to distribute.
If you want to develop your own custom code for the board see the
software section below.
Detailed Design Documentation
Since our design is completely open, if you are curious and have good engineering skills you are
welcome to look at our detailed design documentation. This will be beyond the skill level of the
average wheel chair user.
[Terms and Policies]
© Copyright 2015 Open Wheelchair Foundation. All rights Reserved.
The Open Wheelchair hardware design is licensed under CERN Open Hardware Licence v1.2 and the Software is licensed under
the GNU General Public License Version 3. By viewing or using the design posted on this website you are agreeing to these
licenses. To view the license see our license page.