TECHNICAL SUPPORT
Published 2026-04-29
If you find that the servo is vibrating irregularly when using a Raspberry Pi to control the servo, and is unable to stay at the specified angle position stably, this situation is generally not caused by damage to the servo itself, but is caused by problems with the control signal or power supply. This article gives a complete set of troubleshooting solutions from software to hardware. If you operate in sequence, more than 90% of jitter problems can be solved within 15 minutes.
1. Check the power supply capability. If the servo vibrates, the most common reason is a momentary insufficient current. When a standard servo is started, the current can reach 1 to 2A, and the maximum output of the Raspberry Pi's 5V pin is only about 500mA. An independent 5V power supply, that is, a power supply of more than 2A, must be used to power the servo, and the Raspberry Pi GND and the servo power supply GND must be grounded together.
2. Confirm the stability of the PWM signal: the waveform accuracy generated by the Raspberry Pi hardware PWM pins (i.e. GPIO12, GPIO13, GPIO18, GPIO19) is far more accurate than the software simulated PWM. If you use software PWM of RPi.GPIO, interference will cause jitter. Priority should be given to migrating to hardware PWM, or using the pigpio library (which provides microsecond-accurate pulses).
3. Reduce the control frequency and load. For the steering gear, the typical PWM period is 20ms, which is 50Hz. When the pulse width is in the range of 500-2500μs, it corresponds to 0-180 degrees. If the duty cycle is updated frequently in the code, such as once every 1ms, this will cause overload and jitter in the internal circuit of the servo. The update interval should be controlled to more than 20ms, and the same angle should be prevented from being written continuously in the loop.
Case 1: The user uses Raspberry Pi 3B+ and connects the MG996R servo. The servo keeps shaking when the code is running.
After checking, the servo is powered by the Raspberry Pi 5V pin. After changing to an external 5V/3A power supply, the jitter phenomenon disappeared. The conclusion is: Raspberry Pi cannot directly drive high-power servos.
Case 2: Between different angle commands, the servo made a "sizzling" sound and trembled.
It was detected by the logic analyzer that the period of the PWM waveform drifted in the range of 18 to 22 milliseconds. Then I switched to the hardware PWM of the pigpio library, and then the waveform became stable and the problem was solved. The conclusion drawn is that the software PWM lacks accuracy and causes jitter.
The necessary related items are as follows: Raspberry Pi, a servo responsible for specific functions, a 5V/2A DC power supply that provides a certain electrical potential energy, and a breadboard or connecting cable for connecting various electronic components.
Wiring steps：
1. Servo red wire (positive pole) → external power supply positive pole
2. The brown or black wire of the servo, which is the negative pole, should be connected to the negative pole of the external power supply. At the same time, it should also be connected to any GND pin of the Raspberry Pi.
3. The yellow-orange wire of the servo, which is the signal wire, should be connected to the PWM GPIO of the Raspberry Pi hardware, such as GPIO18。
4. It is necessary to connect the negative pole of the external power supply to the Raspberry Pi GND. Otherwise, if the signal lacks a reference level, it will inevitably produce jitter, which will cause the signal to jitter.。
# Installation: sudo apt install pigpio and sudo systemctl enable pigpiod import pigpio pi = pigpio.pi() pi.set_mode(18, pigpio.OUTPUT) # Set 50Hz PWM, pulse width range 500-2500μs pi.set_servo_pulsewidth(18, 1500) # Medium 90 degrees time.sleep(0.5) pi.set_servo_pulsewidth(18, 1000) # 0 degrees # Stop signal: pi.set_servo_pulsewidth(18, 0)The key parameter is that after each angle command, you need to wait at least 20 milliseconds before sending the next command to avoid signal conflicts.
Q1: What should I do if the servo still vibrates after being powered alone?
A: Check the common ground connection. When the negative end of the external power supply is not connected to the GND of the Raspberry Pi, the signal is left floating, causing jitter.
Q2: The servo still shakes slightly after using hardware PWM?
Reduce the PWM frequency to the middle of the range of 40 to 60Hz. At the same time, make sure that there are no other GPIOs in the code that operate frequently and cause interference.
Q3: Jitter only occurs in a specific angle range?
If the situation mentioned in A is, it is possible that the servo potentiometer is worn, then the servo needs to be replaced and tested. If it is ruled out through testing, then it is necessary to check whether there is an overflow in the pulse width calculation.
Q4: How to solve the problem of simultaneous vibration of multiple servos?
For A, to calculate the total current requirement, each servo needs a range of 1 to 2 amps. It is necessary to use a power supply of 5 volts and a current greater than or equal to IO amps. An additional electrolytic capacitor with a capacitance of 1000 microfarads must be installed for filtering.
Q5: Why is it easy to shake when using software PWM?
A: Raspberry Pi Linux is a non-real-time system. Software PWM will be affected by system scheduling. Its pulse width error reaches ±200μs. There are errors in hardware PWM.。
[ ] The servo power supply is independent of the Raspberry Pi, and the current is ≥ 2A?
[ ] Are the negative pole of the external power supply and the Raspberry Pi GND connected?
[ ] The signal line is connected to one of GPIO12/13/18/19?
[ ] Does the code use pigpio, or does it use wiringPi hardware PWM?
[ ] Angle update interval ≥ 20ms?
[ ] Not driving more than 2 medium-sized servos at the same time?
The essence of the jitter phenomenon in the Raspberry Pi control servo is: insufficient power supply, lack of PWM accuracy, or missing common ground link. Independent power supply, hardware PWM method, and common ground connection are the three ironclad principles to solve this problem. It is recommended that the following measures be implemented immediately:
1. Remove the servo and use an external 5V/2A power supply for separate power supply.
2. Migrate the code topigpioLibrary's hardware PWM output.
3. Use a multimeter to measure the resistance between the servo power supply and the Raspberry Pi GND. It should be 0Ω.
After implementing these three steps, 90% of jitter problems will disappear within ten minutes. If it still exists, then check the special circumstances in the above questions and answers one by one. Remember: Never try to use software to simulate pulse width modulation to drive the servo - this is the lowest reliability solution.
Update Time：2026-04-29
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