How to Make an RC Helicopter Circuit Board: What It Does and How to Build One
The circuit board in a small RC helicopter combines a radio receiver, a gyro (IMU), a microcontroller that runs the stabilisation loop, and motor drivers (MOSFETs) for the main and tail motors, all on one tiny board. You can make your own with a small microcontroller, an IMU sensor, a 2.4 GHz radio module and logic-level MOSFETs, designed as a custom PCB. It’s an advanced electronics project; for most people, replacing a broken board with a spare or using a hobby receiver and flight controller is easier.
By Kyle HilsonUpdated: October 20263 min read
What the board does
| Block | Job |
|---|---|
| Radio receiver | Receives stick commands from the remote |
| IMU (gyro + accelerometer) | Measures rotation and tilt |
| Microcontroller | Runs the control loop, mixes commands with gyro data |
| Motor drivers (MOSFETs) | Switch battery power to the motors with PWM |
| Servo outputs (CP helis) | Drive swashplate servos |
| Power regulation | 3.3 V for logic, battery for motors; low-voltage detection |
Parts for a DIY board
- Microcontroller: a small ARM board (e.g. STM32-based) or an ESP32 for prototypes.
- IMU: a 6-axis gyro/accelerometer such as the MPU-6050 or similar.
- Radio: an nRF24L01 or a hobby receiver with serial output (SBUS, CRSF).
- MOSFETs: logic-level N-channel with low on-resistance for brushed motors, or small ESCs for brushless.
- Flyback diodes, capacitors, a 3.3 V regulator, connectors.
- PCB design software and a PCB service, or perfboard for a first prototype.
Steps
- Prototype on a breadboard: microcontroller, IMU and one motor with MOSFET.
- Read the IMU and print gyro values to make sure axes and signs are correct.
- Add the radio and read stick values.
- Write a simple PID loop for the tail (yaw) first: gyro rate vs stick command.
- For coaxial helis, control the speed difference between the two rotors for yaw.
- Design the PCB small and light; keep motor current paths short and away from the IMU.
- Test on a tethered helicopter before free flight.
The control loop
The microcontroller runs a fast loop (hundreds to thousands of times per second): read the gyro, read the sticks, compute the error between desired and actual rotation, and adjust motor or servo outputs with a PID controller. Tuning the gains is most of the work: too low and the heli drifts, too high and it oscillates. Open-source flight control firmware for multirotors shows the principles well.
Safety
Test with the blades removed, then with the heli tied down. Add a throttle-hold switch and a failsafe that stops the motors when the signal is lost. LiPo batteries can deliver high currents; fuse the supply during development and never leave a charging pack unattended.
Easier alternatives
- Buy a replacement board for your model if one is sold.
- Convert to a hobby receiver plus a flybarless unit on larger helis.
- Start with a simpler RC car board project; see how to make an RC car circuit board.
- Build the whole helicopter step by step; see how to make an RC helicopter.
What you’ll learn
Even if the first board never flies well, you learn sensors, motor control, radio links and control loops: the same building blocks as drones, robots and self-balancing machines. Documenting each step and keeping the design simple helps when debugging.
FAQ
What is on an RC helicopter circuit board?
Receiver, gyro, microcontroller, motor drivers and power regulation.
Can I replace a broken board?
Yes, if spare boards are sold for your model.
Can I use an Arduino?
For learning and testing; small ARM boards suit flight better.
Why does my helicopter spin without a gyro?
Without gyro correction the tail can’t hold heading.
More on this topic: the complete RC Helicopters guide covers the basics behind this article.
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
