TECHNICAL SUPPORT
Published 2026-04-09
The short answer:You can typically run only 2 to 3 standard smallservos directly from a Micro board’s built-in 5V regulator.Trying to run more without external power will cause the board to reset, glitch, or permanently damage the voltage regulator. The limiting factor is almost never the number of signal pins—it’s the electrical current draw of theservos.
A typical hobbyist connects four 9g microservos to a Micro board, powers the board via USB from a laptop, and writes code to move all servos at once. When the servos start moving, the laptop immediately disconnects the USB port (overcurrent protection) or the board resets. This happens because each 9g servo can draw 200–300 mA when moving, and up to 800 mA at stall. Four servos can easily demand 1.2–2.4 A, while the Micro’s on-board 5V regulator (through USB or the Vin pin) can safely provide only500 mA(when powered by USB) or1 A(when powered by 7–12 V DC via Vin, with good heat sinking).
Signal pins: The Micro board has 20 digital I/O pins. Any digital pin can generate servo control pulses using libraries likeServo.h. With external power, you can technically run up to 20 servos (one per pin).
PWM pins: The Micro has 7 hardware PWM pins (3,5, 6, 9, 10, 11, 12). However, theServolibrary does not require hardware PWM on AVR-based boards; it uses timers to generate signals on any pin. So the PWM count is irrelevant for servo control.
Thus, the only real constraint ispower delivery.
Powered via USB (default, most common): The USB port usually provides 5 V, but the host (computer, hub) limits current to 500 mA (USB 2.0) or 900 mA (USB 3.0). The Micro’s onboard polyfuse is rated for 500 mA. Safe continuous load: ≤400 mA.
→ Result: Only 1–2 micro servos if moving gently; 1 servo if you want reliability.
Powered via Vin (7–12 V DC input): The onboard 5 V regulator (MIC5219 or similar) can deliver up to 500 mA continuously without heat sink, or up to 1 A with good airflow and short bursts. However, thermal shutdown occurs quickly above 800 mA. Practical safe limit: 500 mA continuous.
→ Result: 2 micro servos (each 250 mA avg) or 1 standard servo.
Direct 5 V supply to 5V pin (bypassing regulator): You can feed regulated 5 V directly to the 5V pin. The board’s logic and servos share this rail. The 5V pin has no overcurrent protection except your external supply. In this case, the limit is your external power supply’s rating.
→ Result: As many servos as your external 5 V supply can handle, up to 20 (signal pins).
To run 4, 6, or more servos from a Micro board, follow this exact method:
1. Use an external 5 V power supply rated for the total servo current + 20% margin.
Example: 6 micro servos (6 × 300 mA = 1.8 A) → use a 5 V, 3 A supply (or a 5 V UBEC from RC hobby).
2. Connect all servo power wires (red) to the external 5 V supply’s positive terminal.
3. Connect all servo ground wires (black/brown) to the external supply’s negative terminal AND also to the Micro’s GND pin (this creates a common ground reference).
4. Connect each servo signal wire to a separate digital pin on the Micro.
5. Power the Micro board separately – either via USB (for programming) or via its own Vin/5V pin. Do not power the servos through the Micro board.
Why this works: The signal pins draw less than 5 mA each. The heavy current flows through the external supply, not the Micro’s regulator.
Up to 20 servos – one per digital I/O pin (pins 0 and 1 are RX/TX, avoid them if using serial; pins 2–19 are usable).
Real-world limitation: Servo control timing. The Servo.h library uses timers. On the Micro (ATmega32U4), you can control up to 12 servos smoothly without jitter if you use Servo objects correctly. For 13–20 servos, you may need to use a different library (e.g., PWMServo) or external PWM driver board (e.g., PCA9685). But strictly electrically, 20 servos is possible.
The Micro board’s built-in 5V regulator cannot safely power more than 2–3 small servos. To run 4 or more servos, you must use an external 5V power supply that directly feeds the servos, while keeping signal and ground connections shared with the Micro.
Never power high-current servos through the Micro’s 5V pin or Vin regulator – that is the single most common cause of board failure in servo projects.
[ ] Total servo stall current
[ ] Common ground: external supply’s GND connected to Micro’s GND
[ ] No red (5V) wire from servo connected to Micro’s 5V pin
[ ] Micro powered separately (USB or Vin)
[ ] For 4+ servos, add a 470–1000 µF low-ESR capacitor across the external supply’s +5V and GND (prevents voltage dips)
By following this guide, you will never reset or damage your Micro board due to servo current draw. Remember: Power externally, signal from the board, ground together – and you can run up to 20 servos.
Update Time：2026-04-09
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