23 August 2026 · Bharat Raj · originally published on Compoden
The Bluetooth RC Car Kit: PWM Is the Whole Point
Plenty of kits let you build a car that starts and stops from your phone. The Bluetooth RC Car Kit with Arduino Uno & HC-05 (₹1,390) is about the part in between: an HC-05 module streams continuous joystick coordinates from an Android app, and your Arduino code converts them into graded PWM signals — so the car accelerates gently, corners in smooth curves, and stops without overshooting. This is an Intermediate kit, a 4–5 hour build with zero soldering, and its real subject is proportional control: the difference between a toy that lurches and a vehicle that drives. If "jerky on-off robot" describes your last project, this kit is specifically the cure. Everything needed is in the box, including the 18650 cells that give it 30+ minutes of driving per charge.
What's in the box
Arduino Uno R3, HC-05 Bluetooth module, L298N motor driver, two TT gear motors, 2WD chassis with castor wheel, two 18650 cells with holder, a support-parts set (100Ω and 10kΩ resistors, 100nF capacitors, 1N4007 flyback diodes) and 50 jumper wires. All connections use jumper wires, pin headers and screw terminals — no soldering anywhere in the build. You supply an Android phone; free apps that transmit joystick values over Bluetooth serial (the sample code is written for "Arduino Bluetooth RC Car"-style apps) act as the controller.
What you'll learn
- Serial parsing in real time — reading a continuous Bluetooth stream and extracting delimited X-Y values inside the Arduino loop without blocking.
- PWM motor control — generating variable-duty signals and using the L298N's enable pins for forward and reverse at any speed.
- Differential steering math — mapping a joystick's 0–255 range into independent left and right motor values, which is what turns "left button" into a smooth arc.
- Failing gracefully — filtering Bluetooth dropouts so a lost packet means the car coasts predictably instead of running away.
The build, honestly
The mechanical assembly is quick; the interesting hours are in wiring and code. Two places reliably trip builders. First, the HC-05 shares the Uno's serial pins, and having it wired during a sketch upload blocks the upload — disconnect, flash, reconnect becomes muscle memory. Second, power: the product page is blunt that a 9V battery cannot run TT motors for more than seconds, which is exactly why the 18650 pair is in the box — resist the urge to "just test quickly" on a 9V. The joystick-to-motor mapping is where the learning concentrates: your first version will steer too sharply, and tuning the mapping curve until turns feel natural is genuinely satisfying engineering rather than a defect in the kit.
Who it's for — and who should skip it
A strong second project. CBSE Class 11–12 students who have done blink-and-button practicals get a substantial step up; first-year ECE/EEE students get serial communication and PWM made physical before semester projects demand both. Because the result is fun to drive, it is also the kit most likely to get non-engineer siblings interested.
Skip it if you want autonomy rather than control — this car does exactly what your thumb says and nothing on its own. For self-driving behaviour at a similar level, look at our Obstacle Avoiding Robot Kit or the Maze Solving Robot Kit. If you specifically want gesture control instead of a touchscreen, the Gesture Controlled Robot Kit is the sibling project built on the same drive base with a wearable transmitter.
FAQ
Which phone app do I need?
Any Android app that sends analog joystick values over Bluetooth serial. The kit's sample code is written for the clean X-Y coordinate streams of apps like "Arduino Bluetooth RC Car" or "Bluetooth RC Controller" on the Play Store.
Can I run it on a 9V battery?
No — TT gear motors draw more current than a 9V battery can sustain; it would run for seconds. The included 18650 cells and holder deliver proper voltage and current for 30+ minutes of driving.
Is any soldering required?
None. Every connection uses the included jumper wires, pin headers and screw terminals.
The kit arrives pre-loaded in Soldr, our AI build assistant, which generates the wiring, the joystick-parsing firmware and troubleshooting for this exact car.