TECHNICAL SUPPORT
Published 2026-04-20
When you connect two or moreservomotors to a single power source, the most common problem is unexpected resetting, erratic movement, or complete loss of control. This happens becauseservos draw high peak currents, and a shared supply cannot handle the combined demand. The definitive solution is simple:never rely on the receiver’s or controller’s built-in 5V output for more than one standardservo. Instead, use a dedicated external power supply that matches the total current draw of all servos combined, and always connect the ground (negative) lines together with the controller.
This guide provides the exact, step-by-step method to power multiple servos reliably, based on real-world testing with common hobbyist setups.
Every servo motor has two current ratings:stall current(when the motor is locked or under maximum load) andidle current(when not moving). The stall current is the value that matters for power supply sizing.
Micro servos (e.g., 9g size):Stall current ~0.8–1.2A per servo. Idle ~0.1A.
Standard servos (e.g., 20–30g size):Stall current ~1.5–2.5A per servo. Idle ~0.2A.
High-torque or large servos:Stall current can reach 3–6A or more per servo.
Example – A 6-DOF robot arm using 6 standard servos:
Total worst-case stall current = 6 × 2.5A = 15A.
Your power supply must deliver15A continuouslyat the operating voltage (typically 5V or 6V). Using a 5V/5A supply will cause voltage drops, servo jitter, and controller resets.
Action rule:Calculate total stall current forallservos that could move simultaneously, then add 20% safety margin.
Donotuse USB ports, phone chargers, or computer power supplies unless they are specifically rated for the required current and voltage.
| Power Source | Suitable For | Key Requirement |
|--------------|--------------|------------------|
| NiMH battery pack | Mobile robots, arms (4–6 servos) | Capacity (mAh) must support peak current. Example: 6V,3000mAh pack with 15A discharge rate. |
| LiPo battery (2S or 3S) | High-torque, many servos | Use a 5V/6V UBEC (Universal Battery Elimination Circuit) to regulate voltage. Never connect LiPo directly to servos (voltage too high). |
| AC-DC switching power supply | Benchtop testing, stationary projects | Metal-case type (e.g., 5V/20A). Must have short-circuit and overload protection. |
| Multiple separate wall adapters |Not recommended– different ground potentials cause erratic behavior. If unavoidable, tie all grounds together. |
Real-world case:A common six-legged walking robot with 12 standard servos used a 6V/20A AC-DC supply. Initially, the builder tried two 6V/5A adapters, one for each side. The robot walked unevenly and often reset. After switching to a single 20A supply with all grounds shared, the robot operated smoothly.
Star connection(all servos get power from the same point) is mandatory for stable operation. Donotdaisy-chain power from one servo to the next.
Step-by-step wiring (for any controller like Arduino, Raspberry Pi, or PCA9685):
1. Connect thepositive (+)wire of the external power supply to apower distribution boardor aterminal block.
2. Connect thenegative (-)wire of the same power supply to theGND terminalof your controller/receiver.
3. Connect thenegative (-)wire of the power supply to theGND pin of every servo (using the distribution board).
4. Connect the positive (+)wire of the power supply to theV+ pin of every servo (via distribution board).
5. Connect each servo’s signal wire directly to the controller’s PWM pin.
Critical rule: The ground (GND) of the power supply, the controller, and every servo must be common. If grounds are separate, the signal reference voltage floats, causing random movements.
If your controller board has its own power input (e.g., USB or barrel jack), you can keep it separate from the servo power supply as long as the grounds are still connected.
Correct method:
Controller powered via USB (5V) or a dedicated 9–12V adapter.
Servos powered by a high-current 5V/6V supply.
One and only one wire connects the GND of the controller to the GND of the servo supply.
Incorrect method: Powering servos from the controller’s 5V pin. Most controller onboard regulators provide only 0.5–1A, sufficient for one micro servo at most.
Servo motors act as inductive loads. When they start or stop, they generate voltage spikes and sags. Adding capacitors stabilizes the power rail.
Place a large electrolytic capacitor (1000–2200µF, 10V or higher) across the + and – terminals of the power distribution board.
Place a smaller ceramic capacitor (100nF) as close as possible to each servo’s power pins.
This is especially important when using battery packs, which have higher internal resistance than AC-DC supplies.
After wiring, perform these three tests without loading the servos (e.g., disconnect mechanical linkages):
1. Voltage check: Measure the voltage at the furthest servo’s power pins while all servos are idle. Should be within 0.2V of the power supply’s output.
2. Load test: Command all servos to move to their stall position (e.g., against a hard stop) simultaneously while monitoring voltage. If voltage drops below 4.5V (for 5V servos), your supply is undersized or wiring resistance is too high.
3. Temperature check: After 1 minute of continuous movement, the power supply case should be warm but not hot. The wires should not feel warm. Warm wires indicate insufficient gauge (use thicker wire, 18AWG or lower for >10A).
Do not power more than one standard servo from your controller’s 5V pin. This is the single most common cause of malfunctions.
Calculate total stall current, then add 20%. A 5A supply cannot run four 1.5A stall current servos – you need at least 7.2A.
Use a single, high-current power supply (AC-DC or battery + UBEC) rather than multiple smaller supplies.
Connect all grounds together – controller ground and servo power supply ground must be tied.
Add a 1000–2200µF capacitor at the power distribution point to absorb spikes.
Test with a multimeter while stalling all servos to confirm voltage stability.
Following this method, a common 6-servo robotic arm or a 12-servo hexapod will operate without resets, jitter, or erratic behavior. For larger systems (20+ servos), apply the same principles but use multiple isolated power zones, each with its own supply and common ground reference.
Update Time：2026-04-20
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