TECHNICAL SUPPORT
Published 2026-03-07
The problem of theservovoltage being too high will most likely be encountered by friends who play with robots or make automated products. I myself have been troubled by this problem many times during the debugging process. Today I will talk to you about the secrets here, hoping to help you avoid detours.
The most direct cause of increasedservovoltage is usually a problem with the power supply. For example, if the output voltage of the power adapter you use is unstable, or the nominal 12V measurement results in no-load measurement, it reaches 14V. In this case, the servo will definitely not be able to handle it.
Another common situation is that other high-power devices, such as motor drive boards or lighting systems, are running simultaneously in the circuit. When these devices suddenly stop operating or perform energy feedback operations, a reverse electromotive force will be generated, which will instantly increase the voltage. As a result, the steering gear will encounter adverse conditions. I have personally seen a friend’s servo burn out during a drone project when the electronic brake was applied.
The issue of power supply parameter matching is easily overlooked by many people. When we choose a power supply, we can't just look at the voltage, the current output capability is equally important. If the output current of your power supply is too small, the servo will pull down the voltage when working with high torque, and when the servo is suddenly unloaded, the power supply voltage will rebound and increase instantly.
This kind of voltage fluctuation is particularly harmful to the control board inside the servo. The capacitors and driver chips on the control board have a withstand voltage value and often withstand this kind of impact. Over time, parameter drift will occur, and even direct breakdown damage will occur. Therefore, it is best to leave more than 30% margin when matching the power supply.
If the motor winding inside the steering gear fails or there is a problem with the drive circuit, it will indeed cause an abnormality in the voltage of the entire system. For example, when a local short circuit occurs in the motor winding, it is like adding a large additional load to the power supply. In this case, the current will increase sharply. At the same time, the voltage drop on the power supply line will also change accordingly, causing the actual voltage obtained by the servo to fluctuate.
There is also the filter capacitor inside the servo. Once it ages or is broken down, it will no longer be able to stabilize the voltage. At this time, the power ripple will be superimposed directly on the operating voltage of the servo. If observed with an oscilloscope, the waveform will look like a sawtooth. If the system operates in such an environment for a long time, the control accuracy of the servo will be significantly reduced, and in serious cases it may even crash.
If the servo is in a state where the filter capacitor is aged or broken down for a long time and the voltage cannot be stabilized, the power supply ripple will be directly superimposed on the operating voltage, and a sawtooth-like waveform will appear on the oscilloscope. If you continue to work in such an environment, the steering gear control accuracy will be significantly reduced, and in severe cases, it will directly crash.
The factor of line connection is easily overlooked. If the power cord is too thin or the connector has poor contact, contact resistance will occur. When the steering gear operates with a large current, a voltage drop will occur on the contact resistor, resulting in a low voltage at the steering gear end. And when you measure the power supply terminal voltage, it may be normal.
Interestingly, when the servo is not working, the current is very small and the voltage drop on the contact resistor is almost zero. At this time, the voltage at the servo terminal will suddenly increase to close to the power supply voltage. This sudden high and low change is more dangerous than continuous high voltage. The chip inside the steering gear is easily damaged by this voltage shock.
If the PWM signal given by the control system is in an unstable state, it will indeed cause problems with the steering gear voltage. For example, at the moment when the microcontroller is reset, the IO port may output a high level, causing the servo to suddenly rotate to the extreme position. In this case, the steering gear motor will become blocked, the current will increase sharply, and the power supply voltage will be instantly pulled down, and then rebound and increase again.
This series of changes clearly shows the impact of unstable PWM signals on the steering gear voltage. When the steering gear motor is blocked and the current increases sharply, the power supply voltage is pulled down, which will interfere with the stable operation of the entire system. The subsequent rebound of the increased voltage may also cause other potential problems, such as impact on other electronic components. Therefore, it is crucial to ensure that the PWM signal given by the control system is stable, which is related to whether the steering gear and the entire related system can work normally and stably.
In addition, if there is interference on the signal line, the servo control board will mistakenly think that frequent reversal is needed. When the motor switches between forward and reverse rotation, it will generate back electromotive force, and this energy will be superimposed on the power line if it has nowhere to be released. Therefore, it is best to separate the power lines for the servo from the power lines. It is safer to use twisted-pair shielded wires for the signal lines.
The influence of ambient temperature on the operating voltage of the steering gear is also worthy of attention. Most of the servos we use are PWM controlled and have an internal voltage stabilizing circuit to supply power to the control chip. When the ambient temperature increases, the voltage stabilization accuracy of the voltage stabilizing chip will decrease, and the output voltage may deviate from the design value.
In addition, the heat dissipation conditions are not good, and the internal heating of the steering gear is quite serious. The resistance of the motor winding will increase with the increase of temperature. When it is in this situation, the back electromotive force characteristics of the motor will change, which will cause the actual voltage obtained by the steering gear to be different from the no-load measurement value when it is working. Therefore, when designing the installation location, be sure to leave sufficient space for heat dissipation for the servo.
What weird voltage problems have you encountered during the debugging of the servo? Welcome to share it in the comment area. Let's analyze it together. If you find the content useful, don't forget to give it a like and share it with more friends.
Update Time：2026-03-07
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