Build a mini robotBeginnerLesson 2687 min read

Choosing parts on a budget

A simple two-wheel robot needs a small board, a motor driver, two geared motors, sensors and batteries. Learn what each part does and how to choose without overspending.

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Choosing parts on a budget

A simple two-wheel robot needs a small board, a motor driver, two geared motors, sensors and batteries. Learn what each part does and how to choose without overspending.

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In simple words

Building a robot is like cooking a simple dal. You need a few basic things: dal, water, salt, a pot and a stove. You do not need the most expensive pot. A robot also needs a few basic parts: a brain, muscles, senses, a body and energy. Start simple, make it work, then improve it.

A small two-wheel robot is made of a few parts that each do one job. You can buy them separately or as a kit. Prices change and differ by place, so compare a few sellers and check the current price yourself. This lesson helps you know what to buy and why.

The parts of a mini robot

Job	Common generic part	Notes
Brain	Arduino Uno or Nano, ESP32, or Raspberry Pi Pico	Runs your code and reads the sensors
Muscles	Two geared DC "TT" motors with wheels	Yellow plastic gearbox motors, common in robot kits
Motor driver	A dual motor driver board, such as L298N or TB6612FNG	The board cannot power motors directly; the driver does
Senses	HC-SR04 ultrasonic sensor, two IR line sensor modules	The same sensors as in the virtual labs
Body	A two-wheel chassis with a caster wheel, or stiff cardboard	A kit chassis is easy; cardboard works for a first try
Energy	An AA battery holder (for example 4 × AA) with a switch	Rechargeable AA cells save money over time
Wiring	Jumper wires, a small breadboard, screwdriver	A multimeter is very useful for checking voltages

Choosing the brain

Board	Good for	Keep in mind
Arduino Uno or Nano	First projects; lots of beginner examples	Works with 5 V signals; no Wi-Fi on the classic boards
ESP32	Robots you control over Wi-Fi or Bluetooth	Uses 3.3 V signals; some 5 V sensors need care
Raspberry Pi Pico	Python on a microcontroller (MicroPython)	Uses 3.3 V signals; the Pico W version adds Wi-Fi

Watch out

Voltage matters. Boards that work at 3.3 V (ESP32, Pico) can be damaged by 5 V signals on their pins. The HC-SR04 usually runs on 5 V, and its echo pin then gives a 5 V signal. With a 3.3 V board, use a simple voltage divider (two resistors) on the echo pin or a sensor version made for 3.3 V. Check your board's pin labels and datasheet.

Choosing the motor driver

L298N-type boards

Very common and easy to find
Big heatsink, bulky
Loses a noticeable part of the battery voltage as heat, so motors get less

TB6612FNG-type boards

Small and more efficient
Lower maximum current, fine for small TT motors
Has a standby (STBY) pin that must be set HIGH to run

Both work for a first robot. Whatever you choose, read its datasheet: the maximum voltage and current, and which pins do what.

Batteries

TT motors are usually made for low voltages, often around 3 to 6 volts. Check the label or seller's details. Four AA alkaline cells give about 6 V when fresh; four rechargeable NiMH AA cells give a bit less. Motors draw more current than the board, especially when starting or stalled, so a weak battery makes the board reset when the motors start. That is a very common beginner problem.

Danger

Battery safety. Batteries store a lot of energy. Never connect the two ends of a battery with a wire, a coin or a tool (a short circuit): wires can get very hot and cells can leak or catch fire. Lithium cells (for example 18650 cells and flat LiPo packs) need extra care: use only a proper holder and the right charger, never charge them unattended, and never use a cell that is swollen, dented or hot. Beginners should start with ordinary AA cells. Younger learners should work with an adult.

Saving money sensibly

Build the virtual robot first, so you know which sensors you actually need.
Start with a basic kit or the parts above. Upgrade one thing at a time.
Share tools like a soldering iron and multimeter within a school or club.
Reuse: cardboard, old toy wheels and bottle caps can work for a first chassis.
Do not save money on safety: a proper battery holder with a switch, and a correct charger.

Try this. Write a parts list for your robot with one line per part: what it is, its job, and one question you must check before buying (for example: "Does this sensor work at 3.3 V?").

Watch and read more

Arduino documentationArduino · reading Raspberry Pi Pico documentationRaspberry Pi · reading

Lab

A checked parts list and a simple power plan for your own two-wheel robot.

~30 min

The problem

This is a paper (or spreadsheet) lab. No coding needed.

Make a table with columns: part, job, quantity, voltage it needs, what I must check.
Fill it for: one board, one motor driver, two TT motors with wheels, a chassis, an ultrasonic sensor, two IR line sensors, a battery holder, wires.
Draw a simple power plan: which battery powers the motors, what powers the board, and where all the grounds (GND) connect.
Write three safety rules you will follow when building, including one about batteries.
Do not write prices from memory; if you add a price column, fill it from current listings and date it.

You are done when

Every part has a clear job and a voltage noted from its label or datasheet
The power plan shows the motors powered through the driver, not from the board pins
All grounds are connected together in the plan
The safety rules include battery care and testing with the wheels off the ground

Hard questions

Try to answer before you reveal. If you can answer these, you understood the lesson.

Q1Your friend wants to power two TT motors from the Arduino's 5 V pin "to save a battery". What do you tell them?Reveal

That pin is meant for small loads like sensors. Motors can draw much more current, especially when starting or stuck, which can make the board reset or damage its regulator or the USB port powering it. Power the motors from a battery through the motor driver, and connect the grounds together.

Q2Why might a robot on 4 × AA cells feel slower with an L298N-type driver than with a TB6612FNG-type driver?Reveal

L298N-type drivers lose a noticeable part of the voltage inside the driver, turned into heat. With only about 6 V from the battery, the motors then get noticeably less voltage and turn slower. The TB6612FNG-type driver loses less, so more of the battery voltage reaches the motors. Check both datasheets for the exact figures.

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Questions people ask

Should I buy a full kit or separate parts?

A kit is easier: the parts usually fit together and come with instructions. Separate parts let you choose and learn more, but you must check that everything works together. Both are fine for a first robot. Read reviews and the included parts list carefully.

Can I connect a motor straight to the Arduino pin?

No. A board pin can supply only a very small current, far less than a motor needs. Connecting a motor directly can damage the board. The motor driver takes a small signal from the board and switches the bigger battery current to the motor.

Do I need to solder?

Not always. Many modules come with pins, and you can use jumper wires and a breadboard. Some TT motors come without wires attached, and then soldering is the reliable way. If you solder, learn with an adult first; see the next lesson for safety.

Why does my Arduino reset when the motors start?

Usually the battery voltage drops for a moment when the motors start, and the board resets. Use fresh or charged batteries, make sure all grounds are connected, and consider powering the board and the motors from separate supplies with a shared ground.

Lesson test

5 questions. Get 3 right (60%) to pass and complete this lesson.