Build your first robot around one observable behavior: press a button, drive briefly, and stop when a bumper is pressed or the timer expires. That small project teaches the essential loop of robotics—sense, decide, act—and gives you a result you can test.
This project uses a Pololu 3pi+ 32U4 Turtle Edition, either assembled or built from its matching kit. It is a specific learning platform for the worked example. Other chassis need their own wiring, power checks and software. Allow time to learn uploading and basic C++ editing; a mentor should handle unfamiliar soldering work.
Define success before buying parts
Write the requirement in your notebook: “After a deliberate button press, the robot moves forward for at most three seconds. A front bumper press or another button press ends the run. It stays stopped until restarted.” Start on a clear floor area with a person supervising. The program has no stair detection, remote stop or obstacle avoidance.
The manufacturer’s 3pi+ 32U4 guide documents the integrated controller, motor drivers and bump sensors. Turtle is the slower variant. You need four AAA alkaline or NiMH cells, a data-capable USB Micro-B cable and a computer. A kit also needs the tools and soldering described in its assembly instructions; an assembled version skips that work.
A matched kit removes several compatibility decisions from the first project. When you later build a custom chassis, specify motor voltage and current, driver limits, controller logic levels, battery requirements, mechanical mounting and connectors as one system. A component list becomes useful when each connection has a documented destination and rating.
Prepare and inspect the hardware
Build the kit using the illustrated official assembly sequence, including its board test and orientation checks. Disconnect power before correcting assembly. Use the manual’s diagrams for exact placement.
Make your own acceptance record as you work. Photograph the completed chassis, note the edition and display type, and inspect for loose parts or rubbing wheels. With power off, check that each front bumper flap moves and returns freely. Then use the supplied demonstration to check the individual subsystems before replacing it with your sketch. Investigate a failed subsystem now, while the cause is easier to isolate.
USB supports programming, while the motors require the battery supply. Follow the battery maker’s charging instructions; rechargeable cells use a suitable external charger.
Upload a short, supervised behavior
Install the Arduino IDE and Arduino AVR Boards through Boards Manager. Add https://files.pololu.com/arduino/package_pololu_index.json to Additional Boards Manager URLs, install Pololu A-Star Boards, and select Pololu A-Star 32U4 and its port. Upload Blink with changed timing. See the official programming instructions for recovery steps.
In Library Manager install Pololu3piPlus32U4 and its dependencies. Its source and examples document the motor and bumper interfaces used below. Download FirstRobot.ino, save it in a folder named FirstRobot, and open it in the IDE.
Our sketch starts stopped. Keep the bumper released during its startup calibration. A press-and-release of button A requests a run; another press-and-release stops it. Either bumper and the three-second limit also stop it. The power switch remains the direct way to remove motor power. These are educational software behaviors, not protective safety functions.
bumps.read();
if (button.getSingleDebouncedRelease()) {
running = !running;
started = millis();
}
if (bumps.leftIsPressed() || bumps.rightIsPressed() ||
(running && (uint32_t)(millis() - started) >= 3000)) {
running = false;
}
motors.setSpeeds(running ? 60 : 0, running ? 60 : 0);The complete download includes declarations and startup calibration. A command of 60 is a motor-control value, not 60 millimeters per second. It deliberately uses a modest command on the specified Turtle platform. The code was compile-checked; physical operation needs the checks below because no robot hardware was available for this article.
Test each claim separately
- Check the stopped state. Support the chassis securely with the wheels clear, then switch it on without pressing A. Keep hands, hair and loose items clear of the wheels. It should remain still.
- Check direction and timeout. Press and release A once. Both wheels should turn in the direction that propels the robot forward, then stop after three seconds. A second press-and-release should stop a run early.
- Check each bumper. Start another supported run and gently actuate one front flap from clear of the wheels. Repeat for the other flap. Each should end the run; releasing the flap should leave the robot stopped.
- Try a clear floor. Disconnect the USB cable, place the robot on a clear level floor away from edges, and repeat the bounded run. Use a light, stable cardboard obstacle for a supervised contact test after the stationary bumper checks pass.
- Record five runs. Note start position, approximate travel, surface and stop reason. Change only one factor before repeating.
| Observation | Check next | Evidence of recovery |
|---|---|---|
| Upload fails | Confirm a data-capable cable, selected board and device port; close another program using the port. | A changed Blink timing appears after upload. |
| LED works; wheels stay still | Check the battery supply and power switch; USB programming power alone does not run the motors. | Both wheels move during the short test. |
| Robot rotates instead of advancing | Check left/right motor direction against the kit wiring orientation. | Both wheels propel the chassis forward. |
| Bump is always reported | Release both bumper flaps, restart calibration, and check mechanical binding. | Idle reading is zero; each flap gives a response. |
| Bump is never reported | Inspect flap movement and sensor example readings before another floor run. | A stationary bumper test reliably changes the reading. |
| Distance varies | Record surface, battery condition, speed command and wheel slip. | Repeated runs provide a range, not one claimed distance. |
If a motor direction is reversed, compare the wiring with the assembly guide. The library also provides flipLeftMotor(true) and flipRightMotor(true) for correcting direction in software. Change only the affected motor, record the change, and repeat the supported test.
Use the build and test log to preserve your configuration and observations. A good entry records a failed test as carefully as a successful one.
Add one new capability
After the bounded drive is reliable, try a turn with unequal wheel commands, keeping the same timeout. Predict the direction, observe the result, and explain any discrepancy. Next, investigate the manufacturer’s encoder example to measure wheel movement, or its reflectance-sensor example to distinguish a line from the surrounding surface. Check sensor readings while stationary before making them control motion.
Separate commanded motion, measured wheel motion and movement across the floor. Wheel slip explains why these can disagree. For a very different kind of motion problem, the guide to six-axis robot geometry shows how industrial robots position and orient tools.