In this instructable, lets make a simple low cost wheeled robot toy that you can make for yourself or your kids. I can guarantee you, your kids will remember it for life that you made a toy for them. Toy will look something like attached image and you will drive it through a controller with two switches.

Let's get started.

Supplies

To make a wheeled robot, you are going to need following parts.

A chassis or body to hold everything together.
- We will use cardboard for this purpose, this will also help us in keeping the cost low.
Wheels and motor to drive them, this includes balance or castor wheels(it is third wheel that provide balance to the robot).
- We will use 2 plastic wheels with rubber tyres and 2 plastic gear DC motors will actuate them.
A motor driver to interface motors with rest of the electronics safely.
- We will use L293D motor driver module with few resistors and wires.
Batteries and power regulators.
- We will use 6 AA battery cells to power this toy and we will need a cell holder.

Step 1: Video

Take a look at quick fun video for the view of complete process.

Step 2: First Create the Body

The body holds the robot together, it is fundamental to the decision of how robot is made. We will be using cardboard as the body/chassis of toy as it is cheap and easily available.

Here are little steps to create body for the toy-

Cut a cardboard to the dimension of 11 cm by 13 cm, you can use simple paper cutter or a scissor.
If not already done purchase 2 plastic gear DC motor using link in the supplies.
Use any adhesive like hot glue or Fevicol to adhere plastic gear motors to the cardboard, paste them towards the edges of one side with motor axis pointing outside as shown in attached image or video in previous step.
Use adhesive to paste castor wheel at the center of tow motors at the opposite end, as shown in the attached image.
Attach wheels to the shaft of motors, shafts are tapered on side for wheels to fit properly.

That's it, this should make one strong cheap body for the toy.

Step 3: Power for the Toy

Robot needs power for the motors to function. DC motor i.e. Direct Current motor gets actuated once a constant voltage is applied between its terminals. If the terminals are reversed, motor reverses its direction.

We will use 6 AA battery cells to power up this toy, get yourself a 6 AA battery cell holder with a DC jack and place 6 AA cells in it. You should get a voltage of around 9 volt across this battery holder.

Step 4: Power on the Body

Follow below mentioned steps to attach battery pack to the body of the toy.

Paste double sided tape on the back of battery pack.
Peal off the cover on double sided tape and paste the battery pack towards the motor end of the toy.
Cut a small cardboard of the size of battery pack.
Paste double sided tape on one side of the small cardboard.
Peal off the cover on double sided tape and paste the cardboard on top of the battery pack.

Step 5: Motor Controller

Motor controller allows us to control the motor i.e. it helps us stop and move the motor. There are many DC motor control modules available in market. They tend to have two channels to control 2 motors. Cheap ones tend to be based on L293D chips. We will be using an L293D based break out module for this purpose and attach a female barrel jack. Attached images contain the schematic and implementation of the same using a breadboard and the driver module. You will need few male to female jumper wires to implement the circuitry.

Once the circuit is implemented, Use a double sided tape to adhere driver module on top of the battery pack. Put a double sided tape under small bread board too.

Schematic_cheap wheeled robot_Sheet_1_20190927074741.pdf
Download

Step 6: Connect Motors to the Driver

Motor driver will have contact points for connecting to motors, normally they are in the form of screw terminal. Connect motor to the driver module and secure them using a screw driver.

Step 7: Remote for the Toy (part 1/2)

To drive around the toy car we need a remote. For this toy car we will design a wired remote. Follow below mentioned steps to create parts of the remote.

Get 4 wires of at-least 1 meter in length.
Peal off their ends using a wire stripper.
Attach them to a Single Pole Single Throw switch.
Use solder to secure the connections.

Step 8: Remote for the Toy (part 2/2)

Once the switch is connected to long wires.

Cut out a piece of cardboard to look like a house with 2 windows of the size of switch.:)
Pass switch wires through these holes.
Fix switches in the holes.

Once done connect switch to the bread board according to the attached schematic and power up the toy by connecting battery pack to the motor driver.