I am very found of making robots and wanted to gift one to my cousin who is just 7 years old. There are many robots on the Internet, I wanted to make a robot which would easily fit in my hand, and the design should be appealing to the child.

I wanted to keep everything simple, so I went with a circular shape design like to 3PI Robot. I really liked to 3PI Bot design and wanted to make something similar. So, without further adieu let's get started.

Supplies

The Main Items necessary for the BOT are:

3D Printer (optional)

9V/1 Adapter x1 for charging the robot

18650 Batteries x2

18650 for 2 Battery Holder x1

N20 Gear Motor with Bracket Holders x2

N20 Gear Motor Wheels x2

Arduino Pro Mini x1

FTDI Module (This is for Programming the Arduino Pro Mini)

DRV8833 Adafruit Module x1

5V Buzzer x1

RN42 Bluetooth Module (you can also use HC05/HC06)

BQ24005 IC x1

Multi-color Flashing LEDs x6

etc.

Rest of the Active and Passive Components are mentioned in the Step 2 (Assembly Drawing and BOM pdf). Please go through it

Step 1: CAD Design

For CAD designing I generally use Fusion 360. I tried my best to design, in a modular way and 3D Printed with ABS Material. I also added a 12mm Circular Rocker Switch which is tiny enough and suits with the body. I couldn't find 12mm Circular Rocker Switch CAD file that's why I didn't included in my CAD Design. You can make a hole as per your convenience wherever you want, but at the back it suits perfectly.

NOTE: Make sure you cut the leads of the rocker switch short enough otherwise it would touch the Battery internally and the Top lid won't properly fit.

I have attached all the Design Files below. And tried my best to document each and everything. If facing any issue do comment below.

Please go through the Top Assembly_1/2 files I have mentioned all the Components.

Step 2: PCB Design and Assembly

I usually design all my PCB's in Altium Designer. I tried to keep the Schematic as simple as possible and tried to use minimum no of Components. The Robot also has a charging facility, behind the robot there is a power jack, where you can plug the 9V/1A adapter to charge the robot.

Make sure you grease the Motor for the long run, otherwise it would make a weird sound. Also note the motor connections are soldered to a 4PIN Header, center 2pins are left empty.

At the Bottom Solder 6 Multi-Color Flashing LEDs. I sanded the LEDs with 150 grit sandpaper to diffuse the light.

The Battery Connector is near to the Power switch header. The Battery Voltage also needs to be supplied to the Motor Driver Board. So, I crimped two pair of wires one for the battery and other for the motor driver (check Image for reference).

Link for Gerber Files:

https://drive.google.com/file/d/1X-OPMQDLneXktcYUKUpfdLzcFuVqgWt3/view?usp=share_link

Step 3: Casing and PCB Assembly

I assembled all the Parts the Casing, PCB, the LEDs as a front and rear headlight. The BOT is now ready for Programming.

Step 4: Programming

I Programmed the Arduino Pro Mini with my Sparkfun FT232RL Module, but you can use any of the FTDI Module which ever is available at your place.

Connection are as follows:

Arduino Pro Mini -> Sparkfun FT232RL

TX -> RX

RX -> TX

VCC -> VCC

GND -> GND

GRN -> DTR

Note: While Uploading the code make sure you remove the RN42 Bluetooth Module, else it would show uploading and you would try scratching your head why the code is not getting uploaded.

Check below for the Code. For the Bluetooth part I am using "Bluetooth RC Controller" app because of it's simplicity.

Link: https://play.google.com/store/apps/details?id=braulio.calle.bluetoothRCcontroller&hl=en_IN&gl=US