Cell Phone Controlled Linear Actuators

This project was created by Professors Saleh Kalantari and Ebrahim Poustinchi of the School of Design and Construction at Washington State University. They are responsible for the idea, and physical construction. I am responsible for the electronics and programming.

The purpose of this project was to create an interactive art sculpture. The creators wanted a piece that would change shape based on the desire of the operator. It had to be remotely controlled.

This uses linear actuators controlled by an Arduino microcontroller and an Android cell phone through bluetooth.

Hardware:

19, linear actuators, these have an 18" draw and 12V motors

Arduino Mega 2560

Bluetooth transceiver, HC-05

10, L298N Dual H-Bridge Motor Controllers

25' 16 gage stranded wire, red

25' 16 gage stranded wire, black

3, 8 position terminal blocks

12V power supply capable of at least 30A

12V to 9V power converter or separate 9V power supply for the Arduino

male to female jumper wires

This project required the actuators to be arranged in a spherical shape so triangular pieces of wood were cut and the actuators were mounted in the center and then connected to each other at angles to form the sphere as seen in the photos.

Foam triangles were attached to the ends of the actuators to provide large surface area for stretching the spandex material that would cover the entire project.

Once mounted on its base, the wires of each actuator were left hanging down the opening in the bottom.

An additional 18"-24" of wire was added to the provided cables of each actuator to provide enough length to reach the Arduino where it was to be installed in the base.

For wiring, the line out from the power supply was connected to one end of each terminal block.

Jumpers were added to each position of the terminal block to make every other position positive and every other position negative.

The positive and negative leads were connected to each motor controller.

Each motor controller can control two motors, connect two motors to each controller, one to the header on the left side, one to the header on the right side, the outputs to control each motor are right next to each other.

The digital outputs from the Arduino connect to the header pins on the motor controller. Two digital outputs are required per motor, this project required 38 digital I/O pins to fully control.

Make careful note of which Arduino digital output goes to which controller and which controller position. Positions 1 & 2 on the controller will control the motor connected to the left, positions 3 & 4 control the motor to the right.

Wire the voltage converter per the appropriate data sheet. Connect the 9V power to the Arduino Mega power in. An adapter will be useful or you can solder the wires directly.

Connect the bluetooth transceiver to the Arduino.

Connect Vcc to +5V out on the Arduino

Connect Gnd to Gnd on the Arduino

Connect Txd to pin 0, RX0 of the Arduino

Connect Rxd to pin 1, TX0 of the Arduino

Arduino code

The motor controllers will turn the motor output on and off in one direction or another based on the Arduino digital outputs. If pins 1 & 2 are both low, no current will flow through the associated motor.

If controller pin 1 is low and controller pin 2 is high, current will flow through the motor controller output on the left of the controller in one direction. If this is reversed and controller pin 1 is high and controller pin 2 is low, current will flow in the opposite direction. The same goes for pins 3 & 4 and the motor connected to the right side of the controller.

I don't know how to write a cell phone app so I used MIT App Inventor 2 to create an app using their very simple drag and drop interface for Android. When you create the app, it provides an easy to use QR code to scan and install on your phone. I found it very easy to use.

MIT App Inventor 2 aia file

MIT App Inventor 2 screenshots

Enable the bluetooth on your phone, select the correct module from the app and you can now control each linear actuator from your cell phone!