Code and Wiring

We made this setup for simple variable speed of a 12V DC motor using a potentiometer. The accompanying code is below. Now we have to figure out how to configure this type of setup to work with four motors hooked up to a motor shield in such a way that the motors on same sides run together and have each side run independently ( two joysticks).

int potPin = A0;

int motorPin = 9;

int potValue = 0;

int motorValue = 0;

void setup() {

 Serial.begin(9600);

}

void loop() {

 potValue = analogRead(potPin);  

 motorValue = map(potValue, 0, 1023, 0, 255);

 analogWrite(motorPin, motorValue);  

 Serial.print("potentiometer = " );     

 Serial.print(potValue);

 Serial.print("\t motor = ");

 Serial.println(motorValue);

 delay(2);    

}

Progress

The top half of a lightweight tubular aluminum chair has been fastened the the rear section of the chassis using several pieces of aluminum C-channel and secured tightly so it doesn't snap off and send someone flying. The chair is mounted very close to the chassis so that it keeps the center of gravity as low as possible for tipping reasons.

The dual battery setup was placed in the very center of the chassis, held in place by three L-brackets, one on each side and one behind the batteries that holds it tight against the chassis' crossbar. A cover was mounted over the battery with foam insulation to help protect the leads from getting damaged or somehow connected if something fell on them.

The positive lead of the batteries were connected to the 120A circuit breaker via a short piece of 6 gauge wire with the appropriate connectors crimped to each end.

We decided to create a small display panel that mounts to the front end of the chassis. It will contain an on/off toggle switch connected to the 9V battery running to the Arduino barrel connector so we don't have to remember to unplug it. We also utilized the small LCD screen that came in the Arduino starter kit; this will be used to display the instantaneous voltage of the 12V batteries. Along with the LCD screen we have 9 small LED's mounted across the top of the panel which will all be on at full battery life and at 10% increments shut off as the battery loses voltage.

Progress

The chassis has been TIG welded and is one solid piece.

The chassis is surprisingly light for its size.

Both the left and right side drivetrains have been assembled and the chains/sprockets are set up to reduce the rpm values coming directly out of the 12V DC motors into a more practical and easier to control speed.

This is the basic set-up of the robot (just the drivetrain mounted to the chassis). Although the chassis was

very lightweight, the addition of the drivetrain makes the robot much heavier, almost too heavy to lift.

To power the robot we have taken two large 12V batteries and connected them via 6" bolts from lead to lead in parallel, then duct taped so they stay together indefinitely. This gives us twice the available amperage thus doubling our battery life. 

(Running these in parallel is important because if we ran them in series we would have doubled the 

voltage to 24V, which could result in the failure and destruction of several components of the robot.)

For safety and piece of mind we are going to run the power from the batteries to this 120A circuit breaker before it goes to the motor controller. This will allow us to simply push a button to kill the power to the system so we don't have to scramble to disconnect the battery leads if something bad starts happening.

We decided to power the Arduino board itself separately from the rest of the robot as a secondary security measure to make sure the robot doesn't start moving if the main 120A breaker is left on. We will have a 9V battery attached to the drum plug input connector on the Arduino with a simple toggle switch spliced into the positive wire.

SolidWorks 3D Parts and Assemblies

Four of these CIM motors (12V DC)

will be used on our drivetrain.

Six of these 8x1.5 high 

friction wheels will be used.

Our chassis will be one solid piece of welded aluminum mainly consisting of 3/4" box aluminum extrusion and 2" angle aluminum, as well as an assortment of other aluminum pieces.

These four parts along with two motors will be used to construct a left and a right side drivetrain.

This is a rough estimate of what one side of the drivetrain will look like.

(not including driveshafts, sprockets and chains)

And finally here's a look at what the completed chassis/drivetrain will be.

Design

          Our team has decided to create a somewhat large robot that will be able to have one adult sized passenger ride on top of it. This robot will be controlled using a game console controller that will distribute power to four large 12V DC motors. The drive train of this robot will be the four 12V DC motors powering six high friction wheels by a means of chains and sprockets for improving the ratio. The resulting driving style will be that of a tank, minus the tank treads. The center wheel on each side of the robot will have a slight vertical drop compared to the four corner wheels, this drastically improves the turning ability of the robot because at any given time only four of the six wheels will have contact with the ground. Our drive train will be contained by an all aluminum welded chassis that will provide us with an excellent strength to weight ratio.

Team Members

From left to right: Colin Joyal, Vladimir Albin, Dylan Faherty

Cool/Useful YouTube Videos

Possible ways to control DC motors

Cool use of an Arduino Uno