Power and Grounding
Voltage levels, power distribution, ground loops, signal integrity, and noise avoidance on drones.
What is Power Distribution?
Every component on a drone — flight controller, sensors, GPS, companion computer, radio — needs clean, stable power at the correct voltage. Power distribution is how you get the right voltage to the right place while keeping electrical noise from corrupting sensor readings and communication buses.
Getting this right is the difference between a drone that flies reliably and one that suffers mysterious glitches.
How It Works
Voltage Levels
Drones deal with multiple voltage levels simultaneously:
Battery voltage (3S–6S, 11.1–25.2V)
LiPo battery
ESCs, motors
5V
BEC or power module
Flight controller, CAN peripherals, GPS, radios
3.3V
On-board regulator (from 5V)
MCU logic, sensors, communication interfaces
The flight controller and all Pixhawk standard peripherals run on 5V supplied through their connectors. The 5V rail is typically provided by a power module or a BEC (Battery Eliminator Circuit) that steps down the battery voltage.
The 3.3V level is internal to each board — the MCU and sensors operate at 3.3V, but this is regulated on-board from the 5V input. You generally don't need to supply 3.3V externally.
Power Module Role
ARK power modules (ARK PAB Power Module, ARK 12S PAB Power Module) do two things:
Regulate battery voltage down to clean 5V for the flight controller and peripherals
Measure battery voltage and current, reporting it to the flight controller over I2C.
5V Power Through CAN
On ARK systems, the CAN bus carries both data and power on the same cable. Pin 1 of every 4-pin JST-GH CAN connector is 5V. This means DroneCAN peripherals are powered through their CAN cable — no separate power wiring needed.
Power budget matters. Every device in the CAN daisy chain draws current through the same cables and connectors. If the total current draw exceeds what the source can provide, voltage will drop and devices will behave erratically. Check the current draw of each peripheral and ensure the power module or BEC can handle the total.
Ground Loops
Ground is not an ideal zero-ohm conductor. Every wire and trace has finite resistance and inductance, so when current flows through a ground path it creates a small voltage drop. If two circuits share a ground path, the return current from one circuit creates noise that the other circuit sees. When multiple ground paths between devices form a closed loop, that loop also acts as an antenna — picking up and radiating electromagnetic interference proportional to the loop area.
On a drone, where ESCs are switching tens of amps at high frequency just centimeters from a GPS receiver trying to hear signals at -130 dBm, even microvolts of ground noise are enough to corrupt sensitive measurements.
Use a star grounding topology. In a star ground, every subsystem's ground return connects back to a single common point — typically at or near the battery/power supply return. This means:
No shared impedance — each subsystem has its own dedicated ground return, so motor drive currents never flow through the IMU's ground path.
No loops between subsystems — with only one path from each device to the common point, there is no closed loop to act as an antenna.
One unambiguous ground reference — all voltages are measured with respect to the same point, eliminating ground potential differences between boards.
Keep every current return path short. Every current that flows out on a signal or power trace must return to its source, and that outgoing path plus return path form a loop. The radiated EMI and noise susceptibility of that loop is directly proportional to the enclosed area. Keeping return paths short and close to their signal paths minimizes this area. In practice: route ground returns parallel and adjacent to their signal or power traces, don't break ground planes under signal traces, and place decoupling capacitors as close to IC power pins as possible.
Additional tips:
Avoid mounting electronics directly to a conductive (carbon fiber) frame without insulation — this creates unintended ground paths that form loops.
Keep signal wires away from high-current motor wires to reduce inductive coupling.
For a deeper dive on grounding, see Analog Devices' Staying Well Grounded and TI's PCB Design Guidelines for Reduced EMI.
Signal Integrity and Noise
Digital communication buses (CAN, UART, I2C, SPI) all depend on clean signal transitions. Electrical noise can corrupt these signals, causing:
Intermittent sensor dropouts
CAN bus errors or node disconnects
Garbled serial console output
I2C bus lockups
Major noise sources on a drone:
Motor commutation
kHz–MHz
All buses, especially I2C and analog
ESC switching
10–100 kHz
Power rail ripple, sensor noise
USB
480 MHz (harmonics into GHz)
GPS reception — USB is a major source of RF interference in the L-band
Radio transmitter
GHz
Possible digital bus upset at close range
High-current wires
DC–kHz
Magnetometer — motor wires and battery leads create strong magnetic fields
PWM servo signals
50–400 Hz
Ground bounce on shared connectors
Noise reduction strategies:
Keep sensor cables short and routed away from motor/ESC/power wires
Use shielded cables for long runs (>15 cm) on sensitive interfaces
Ensure all connectors are fully seated — intermittent contacts cause noise
Twist signal pairs to reduce pickup
GPS Placement
GPS modules are particularly sensitive to both RF interference (which degrades satellite reception) and magnetic interference (which corrupts the built-in compass). Proper placement is critical for reliable position and heading data.
For detailed guidance on interference sources, mounting best practices, and common mistakes, see the dedicated GPS Placement page.
Servo and Actuator Power Isolation
Servos and other actuators with motors are among the worst power consumers on a drone. A stalled servo can draw several amps, and even normal operation causes large current spikes that collapse the voltage rail it shares with other devices.
Never power servos from the same regulator as the flight controller. A servo stall or jam can brown out the entire 5V rail, causing the flight controller and all CAN peripherals to reboot mid-flight. Always use a dedicated BEC for servos and actuators.
This applies to any high-current load: gimbal motors, LED arrays, radio amplifiers, or payload actuators. If it can draw more than a few hundred milliamps, give it its own power supply with only a shared ground to the flight controller.
Common Pitfalls
Under-rated power supply — a BEC that can handle bench testing may brown out under load when motors spin up. Size your power supply for worst-case current draw plus margin.
Ground loops through the frame — carbon fiber frames are conductive. If two boards are bolted to the frame and also connected by a cable, you have a ground loop. Use nylon standoffs or insulating tape.
Long I2C runs — I2C/Serial is highly susceptible to noise and capacitance. Runs longer than 10–15 cm are unreliable on a drone. Use CAN bus for any peripheral that isn't directly next to the flight controller.
Servos on the flight controller BEC — see Servo and Actuator Power Isolation above. A stalled servo will take down your entire avionics power rail.
GPS mounted near USB or motor wires — see GPS Placement. USB interference and magnetic fields from high-current wires are the two most common causes of poor GPS and compass performance.
Ignoring decoupling — if you're building custom hardware, every IC needs 100 nF decoupling capacitors on its power pins. ARK products include these, but custom carrier boards sometimes omit them.
Assuming USB power is sufficient — USB provides 5V but limited current (500 mA from USB 2.0). A flight controller may boot on USB power but behave erratically because peripherals are under-powered.
Further Reading
CAN Bus — CAN wiring and 5V power delivery
Connectors and Wiring — connector types and pinouts
Communication Buses (I2C, SPI) — bus noise susceptibility comparison
Last updated