This was our final lab project for Vanderbilt's biomedical instrumentation class. The idea is that a simple sensor could be implemented to control a quadriplegic vehicle.
Our approach to this problem was by utilizing an accelerometer that could be easily attached to a hat. The vehicle would then be controlled by the degree of tilt on the accelerometer as the user tilted their head in the desired direction of travel. In the case of our project, we used an RC car as our proxy in place of an electric powered wheel chair.
Step 1: Materials and Tools Necessary
All Materials Needed:
- Arduino Uno
- 22 Gauge Hookup Wire
- ADXL 335 (We used Sparkfun's version)
- RC car (goo.gl/XBqhS5)
- Four 150kOhm and four 100kOhm Resistors
- Zip ties
- Soldering Kit
- Small Philips Screwdriver
- Wire Cutters
- Wire Strippers
Step 2: Attach Accelerometer to Hat
First, use a marker to mark the locations of where to punch the holes.
Using a small philips head screwdriver, two holes are punched on the bill of the hat.
The accelerometer is then secured into place by using a small zip tie.
Step 3: Connecting the Accelerometer to the Ardiuno Controller Unit
We wanted the controller unit to be potentially located on the vehicle and not directly attached to the head.
4 wires that are roughly 1 meter in length were cut and the ends were stripped. These wires will be used to connect the outputs of the accelerometer to the analog inputs of the arduino.
X connected to Analog A0
Y connected to Analog A1
Z connected to Analog A2
GND is connected to GND
VCC is connected to 3.3V - This is especially important, since 5V will fry the accelerometer
Step 4: Voltage Divider Circuit
It was found that a 3V source was necessary to operate the RC transmitter, through trial and error with a multi-meter and power source.
When an output of 3V was present on the controller's inputs, the vehicle was "OFF." When the inputs were shorted, the controller was then "ON." It was found that voltages above 4V would cause the controller to behave erratically. Therefore, between the RC transmitter and the arduino controller, several voltage dividers were necessary.
In the picture, the white wires were the outputs into the RC control and the green wires were our inputs from the arduino controller.
Step 5: Connecting the RC Controller to the Arduino
The Arduino digital outputs were connected to the voltage divider which was then connected to the specific terminals on the RC transmitter.
From Arduino to RC controller:
Arduino GND is connected to controller GND
Arduino Digitial 7 is connected to Forward terminal
Arduino Digital 8 is connected to Reverse terminal
Arduino Digital 9 is connected to Right terminal
Arduino Digital 10 is connected to Left terminal
Step 6: Solder the Voltage Divider Outputs to Their Respective Controller Terminals
In the image, the original buttons were removed and in their place the wires were soldered into the terminal.
The voltage divider was then secured to the controller with zip ties.
Note: the outer rim from the terminals are connected to ground. The transmitter is activated by essentially shorting the terminal to ground through the Arduino.
Step 7: Code for the Arduino
Attached is the code we used for our vehicle.
Step 8: Power Everything on and Wirelessly Control Your Vehicle!
Now power everything on and upload the Arduino code, and everything should work!
Hope you enjoyed our tutorial! If you have any questions, please leave your comments down below!