Two Wheel Drive Robot

In this lesson we will learn how to use the knowledge we have from analog write lesson to actually build a robot that moves around, It will b driven by two motors , that`s why we call it Two Wheel Drive or 2WD. For Steering we will use Differential Steering.

Components Needed

Main Board	USB Cable
Arduino	Body
2 pieces Motors	2 pieces Wheels
Hood	2 pieces Spacers
17 pieces/ M3 Flat Washer	4 pieces M3 nylon washers
10 pieces M3 x 8 Screws	2 pieces M4 x 45 screws
8 pieces M4 hex nuts	4 pieces M4 nylon Washers
2 pieces M4 Lock Washers	4 pieces M4 Flat Washers
Caster Whel	Screw Driver
Pliers	6 pieces/ M3 x 30 Screws
10 pieces/ M3 Hex Nut	12 pieces/ M3 Lock Washer

Step 1:

Install Mainboard on the body [|] For that, you need to use M3 x 10 screws in the installation holes with Nylon washers touching the Mainboard, [|]To protect the mainboard against scratches and possible short circuits]] , then using flat washers touching body and nylon washers and lock washers after that and then hex nut.] using screw driver and pliers.

Step 2:

Install the Caster Wheel on the Main Board using M4 Screws Like here.

Step 3:

Install the motors on the both sides of the body [|] We use the in body configuration for motors][|]as described here]] , Where the Wires of the motors come out of them should face the walls.] using 6 M3 x 30 screws, 12 flat washers , 6 lock washers and 6 hex nuts.

Step 4:

Connect [|] For that, you need to place the Arduino on top of the Arduino pin headers [|]the two big 30 holes pin headers]] , the USB port of it facing the edge of the board, and while you can see the access pins of the pinheader at both sides of the Arduino board, then push it in place to ensure the board is in place.] the Arduino to the Main board.

Step 5:

Plug in the USB cable[|] the USB type B to Micro USB, which you can get from a cellphone charger also] to the Micro USB port of Arduino and then plug it to the USB port of the computer.

Step 6:

Upload [|] Follow this] the following code to the Arduino.

int M1A=3;
int M1B=4;
int M2A=2;
int M2B=5;


void setup() {
 
pinMode(M1A, OUTPUT);
pinMode(M1B, OUTPUT);
pinMode(M2A, OUTPUT);
pinMode(M2B, OUTPUT);
}
  
void loop() {
 
// Forward
  //M1 Forward
digitalWrite(M1B,LOW);
digitalWrite(M1A,HIGH);
  //M2 Forward
digitalWrite(M2B,LOW);
digitalWrite(M2A,HIGH);

delay(2000);
 
// Backward
  //M1 Backward
digitalWrite(M1B,HIGH);
digitalWrite(M1A,LOW);
  //M2 Backward
digitalWrite(M2B,HIGH);
digitalWrite(M2A,LOW);

delay(2000);

//Right
  //M1 Backward
digitalWrite(M1B,HIGH);
digitalWrite(M1A,LOW);
//M2 Forward
digitalWrite(M2B,LOW);
digitalWrite(M2A,HIGH);

 delay(2000);

//Left
  //M1 Forward
digitalWrite(M1B,LOW);
digitalWrite(M1A,HIGH);
//M2 Backward
digitalWrite(M2B,HIGH);
digitalWrite(M2A,LOW);

 delay(2000);

//Stop
  //M1 Stop
digitalWrite(M1B,LOW);
digitalWrite(M1A,LOW);
//M2 stop
digitalWrite(M2B,LOW);
digitalWrite(M2A,LOW);

 delay(2000);
 
}

Step 7:

Remove the USB cable from the USB port of Arduino.

Step 8:

Connect the motor wires to M1 and M2 Screw terminal using the screw driver. The red wire goes to The Terminals closer to Cellpack, the black wires goes to the terminals away from Cellpack.

Step 9:

Install the spacers by removing the two screws at the hood part of the robot and placing the spacers on top and fastening the screws from beneath having the Nylon washers touching the Mainboard and flat washer and spring washers under it .

Step 10:

Install the Hood on the body with M3 x 10 screws.

Step 11:

Install the Cellpack in its place [|] [using M3 x 8 screws and Lock washers] and connect the DC power jack Connector to female DC connector on the Mainboard.

Step 12:

Put the 2C , 3C , 4C and 5C Jumper Caps [|] [The blue tiny plastic parts in the Main Board that act as a switch and allow the pins to connect to the motor drivers , they are not connecting if you can see one of the pins, to connect them you need to remove them and place it on top of the two pins and push it down.] in the connecting state so the two corresponding pins connect to each other.

Step 13:

Turn the Cellpack on [|] [Rocker switch turned towards the ON side and then pressing the Start switch at the top] and check the movement of the robot, we have four movements, robot forward, robot backwards,robot turning right, robot turning left.

Congratulations! You have your own Robot now.

Code Explanation

• In lines 1 ,2 ,3 and 4 [|] [We define four integer values that represent the four pins who control our motor driver [|] [A motor driver is an electronic device that controls the speed and direction of an electric motor. It receives signal from Arduino and controls the voltage level and polarity every motor receives .] two for every motor , which we refer to as M1A and M1B, for motor M1` and M2A and M2B for motor M2. They are pins 2 , 3 , 4 and 5 of the Arduino]
• In lines 7 to 13 ,[|] we have the void setup part of the code.] .
• In lines 9 to 12,[|] we define our motor driver pins as outputs.] .
• In lines 17 to 23,[|] we make the robot go forward by creating a potential difference across each motor and they will run full speed.] .
• In lines 19 and 20,[|] we digital write pin B of motor 1 LOW, giving it zero volts and digital write pin A of motor 1 HIGH, giving it maximum voltage available.] .
• In lines 22 and 23,[|] we digital write B pin of motor 2 LOW and digital Write A pin of motor 1 HIGH, making the motor rotate in a direction that makes our robot go forward.] .
• In line 25,[|] we delay 2000 milliseconds or 2 seconds for robot to go forward.] .
• In lines 29 to 33,[|] we digital write our pins the opposite way of the previous time which will make our robot go backwards .] .
• In line 35,[|] we wait 2 seconds again for the robot to have the chance to go backwards.] .
• In lines 37,to 43, [|] [we perform our going right maneuver , for that we move our M1 motor which is our right motor going backwards and our M1 motor which is our left motor go forward to make differential steering [|] [ Differential steering is the means of steering a robot by applying more drive force to one side of the vehicle than the other. That can be positive driver in one side and negative drive on the other side too] in order for robot to turn right. Note that this way the robot will rotate almost in it`s place with a shorter radius of rotation. We could just stop the right motor and move the left motor forward or stop the left motor and move the right motor backward, those would yield different tracks but the same result]
• In lines 47 to 53,[|] we perform our going left maneuver , for that we move our M1 motor which is our right motor going forward and our M2 motor which is our left motor go backwards to make the robot go left. Again there are more strategies for going left that we used one here] .
• In lines 57 to 63,[|] We make the robot stop by digital writing all the control pins going to both motor drivers LOW. That will feed the motors with 0 volts.] .

Further Experimentation

• Try using analog write instead of digital write for 3 and 5 pins and try giving the robot different speeds.
• Try using other turning strategies like one motor pause, the other one going forward or other one going backwards.
• Try increasing the delay times and see for the going forward part the robot exactly goes on a straight line, if not , try calibrating the motors by giving different speeds to motors.

Practical Usage For our Projects

• We will use these codes for all kinds of robots on wheels and will combine that with other configurations to build remote controlled robots and transformer robots.