Video lesson

Build & Test Your PICO BOT

Welcome to the complete PICO BOT Assembly & Hardware Testing Guide.

In this tutorial, you will assemble your robot, connect the motors, motor driver, servo motor and ultrasonic sensor, and finally use the Thinking Robot PICO Tester to check everything before moving to programming lessons.

Follow the video and this guide together. Do not rush the wiring section.

What You Will Do

By the end of this guide, you will:

Assemble the PICO BOT chassis
Mount all 4 BO motors
Install the wheels and battery holder
Mount the L298N motor driver
Mount the ESP32 and breadboard
Install the servo motor and ultrasonic sensor
Complete all ESP32 connections
Flash the Hardware Tester
Test the servo
Test both motor sides
Check motor speed and direction
Read live ultrasonic distance

1. Assemble the Robot Chassis

Start with the main PICO BOT chassis plates supplied inside your kit.

Mount the four BO motors in their respective positions using the supplied clamps, screws and nuts.

Make sure all motors are tightly mounted, but do not overtighten the screws.

Both motors on one side of the robot will work together.

After mounting the motors, install the battery holder and remaining chassis hardware as demonstrated in the video.

BO Motor Mounting

2. Install the L298N Motor Driver

Mount the L298N Dual H-Bridge Motor Driver on the robot.

The L298N allows the ESP32 to control:

Motor direction
Forward movement
Reverse movement
Left and right turning
Motor speed using PWM

Motor Output Connections

L298N Output	Connect To
OUT1 + OUT2	Right-side BO motors
OUT3 + OUT4	Left-side BO motors

The two motors on each side are connected together so that they operate as one side.

If one side rotates in the wrong direction during testing, reverse the two motor wires for that side.

3. Connect L298N to ESP32

For the PICO BOT Hardware Tester, use the following pin connections.

L298N Label	ESP32 Pin	Function
PWMA / ENA	GPIO 2	Right motor speed
DIRA1 / IN1	GPIO 4	Right motor direction
DIRA2 / IN2	GPIO 15	Right motor direction
DIRB2 / IN3	GPIO 25	Left motor direction
DIRB1 / IN4	GPIO 26	Left motor direction
PWMB / ENB	GPIO 27	Left motor speed
GND	GND	Common ground

Important

If your L298N has jumper caps fitted on ENA / PWMA and ENB / PWMB, remove them.

GPIO 2 and GPIO 27 are used by the tester to control motor speed using PWM.

Never power the BO motors directly from the ESP32.

The motors are powered through the L298N motor driver.

4. Install the Wheels

Push the supplied wheels firmly onto the BO motor shafts.

Make sure:

All four wheels are properly seated
Wheels can rotate freely
No wheel touches the chassis
Motor wires are not touching the wheels

5. Install the Servo & Ultrasonic Sensor

Mount the servo motor at the front of the PICO BOT.

Attach the ultrasonic sensor to the servo mounting arrangement as demonstrated in the video.

The servo allows the ultrasonic sensor to rotate and look in different directions.

Servo and Ultrasonic Mount

6. Servo Motor Connections

The Hardware Tester uses:

Servo Signal → GPIO 18

Servo Wire	Connection
Signal	GPIO 18
VCC / Red	Regulated 5V
GND / Brown or Black	GND

Important

Do not connect the servo VCC to the ESP32 3.3V pin.

Use a proper 5V supply.

The ESP32 and servo power supply must share a common GND.

The Hardware Tester limits servo movement to a safer working range instead of repeatedly forcing it against its mechanical end stops.

7. Ultrasonic Sensor Connections

The PICO BOT uses an HC-SR04-type ultrasonic distance sensor.

Ultrasonic Pin	ESP32 Connection
VCC	5V
TRIG	GPIO 5
ECHO	GPIO 34
GND	GND

Important — ECHO Voltage

A standard HC-SR04 can output approximately 5V from its ECHO pin, while the ESP32 uses 3.3V GPIO logic.

For safe operation, reduce the ECHO voltage before connecting it to GPIO 34.

Example voltage divider:

HC-SR04 ECHO
     |
    1kΩ
     |
     +-------- GPIO 34
     |
    2kΩ
     |
    GND

This reduces the ECHO signal to approximately 3.3V.

8. Mount ESP32 on the Breadboard

Place the ESP32 on the supplied mini breadboard as demonstrated in the video.

Complete the jumper-wire connections carefully.

Before powering anything, check:

Motor driver connections
ESP32 GPIO numbers
Servo signal wire
Servo polarity
Ultrasonic TRIG and ECHO
Battery polarity
Common GND

ESP32 Wiring

9. Open the PICO Hardware Tester

Once your robot is assembled and wired, connect the ESP32 to your laptop using a USB data cable.

Open:

Open PICO Tester

For the best experience, use the latest Google Chrome or Microsoft Edge on a laptop or desktop computer.

PICO Tester Website

10. Flash the Hardware Tester

On the PICO Tester page:

Connect the ESP32 to your computer.
Click FLASH HARDWARE TESTER.
Select the ESP32 / USB serial port.
Start the installation.
Wait until flashing reaches 100%.
Close the flashing window after installation.
Click CONNECT TO TESTER.
Select the ESP32 serial port again if requested.

Once connected, the page will show:

Thinking Robot Hardware Tester Connected ✓

Do not disconnect the ESP32 while firmware is being installed.

11. Test the Servo

Open the Servo Test section.

Start with:

90° — Centre Position

Then try:

60°
90°
120°

You can also use the slider or click Run Servo Test.

The servo should move smoothly and finally return to the centre position.

If the servo vibrates continuously, immediately check:

Power supply
Ground connection
Signal connection
Mechanical obstruction

12. Test the Motors

Open the Motor Test section.

Start with a low motor speed.

Use:

Forward
Backward
Left
Right
Stop

You can also test the left motor side and right motor side individually.

The motor controls are designed as press-and-hold controls.

When you release the direction control, the motors stop.

The tester also contains a safety timeout that stops the motors if communication with the browser is lost.

13. Check Motor Direction

Press Forward.

Both sides of the robot should drive the robot forward.

If one side rotates backward:

Power the robot OFF.
Reverse the two motor output wires for that side.
Power the robot again.
Test Forward again.

Do not change multiple connections at the same time.

14. Test the Ultrasonic Sensor

Open the Ultrasonic Test section.

Click:

START LIVE DISTANCE

Place your hand in front of the sensor.

You should see a live value such as:

32.4 cm
21.7 cm
10.5 cm

Move your hand closer and farther away.

The displayed distance should change accordingly.

Hardware Tester

15. Hardware Test Complete 🎉

Before moving to the programming lessons, confirm:

Left Motors      ✓
Right Motors     ✓
Motor Direction  ✓
Motor Speed      ✓
Servo Motor      ✓
Ultrasonic       ✓

If all tests are working, your PICO BOT hardware is ready.

You can now continue to the next lesson and start learning how each part of the robot works through code.

Download the Tester Code

Want to explore the code or manually work with the tester firmware?

Download PICO BOT Hardware Tester Code

For the normal Hardware Testing process, you do not need to install Arduino IDE or manually upload this code.

Simply use:

thinkingrobot.in/pico-tester

The downloadable code is provided for students who want to explore the firmware and learn how the robot works internally.

Quick Pin Reference

L298N Motor Driver

PWMA / ENA  → GPIO 2
DIRA1 / IN1 → GPIO 4
DIRA2 / IN2 → GPIO 15

DIRB2 / IN3 → GPIO 25
DIRB1 / IN4 → GPIO 26
PWMB / ENB  → GPIO 27

GND → ESP32 GND

Servo

Signal → GPIO 18
VCC    → 5V
GND    → GND

Ultrasonic Sensor

VCC  → 5V
TRIG → GPIO 5
ECHO → GPIO 34 through 5V → 3.3V divider
GND  → GND

Safety Notes

Check battery polarity before connecting power.
Never short the battery terminals.
Never connect BO motors directly to ESP32 GPIO pins.
Do not connect 5V directly to an ESP32 GPIO input.
Disconnect power before changing motor wiring.
Keep loose wires away from the wheels.
Do not force the servo beyond its mechanical range.
Use a USB data cable, not a charge-only cable.
Ask an adult for help if you are unsure about any connection.

Build it. Test it. Understand it.

Thinking Robot — Learn Robotics by Building.

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