Does The Servo Keep Turning When Powered On? Don't Panic! Three Steps To Solve This Annoying Problem

I believe that many friends who play with robots and model airplanes have encountered this annoying problem: as soon as theservois powered on, it starts spinning wildly and completely loses control. Don't worry, this is actually a very common "minor problem". In most cases, it is not theservothat is broken. Today we will talk about how to fix it when yourservostarts to "dance solo".

Is the signal cable connected wrongly?

Is your steering gear like this too? It just keeps spinning when plugged in, completely ignoring your control instructions. This is actually probably because you confused the signal cable and the power cable. The servo generally has three wires: positive power wire (red), negative wire (black or brown) and signal wire (yellow or white). If the signal line is not connected correctly, or not connected at all, the servo is like a soldier who cannot hear commands and can only perform the "default action" - crazy rotation.

Check your wiring to make sure the signal wire is correctly connected to the PWM output pin of the control board. Many times, this is just a simple physical connection problem that can be solved by re-plugging and unplugging to confirm. You can use a multimeter to test it, or check the servo manual carefully. Don't let this small detail delay your big project.

Is the PWM signal normal?

After connecting the wires correctly, the servo still rotates? Then we have to see if there is any problem with the commands issued by the brain. The "command" mentioned here is the PWM signal, which is the pulse width modulation signal. Simply put, the control panel uses this signal to tell the steering gear which angle to turn. If the parameters of this signal are wrong, for example, the pulse period is out of order, the servo will not understand the instructions and will turn randomly.

You can use an oscilloscope or logic analyzer to look at the PWM signal from the control board. The period of a standard servo signal is usually about 20 milliseconds, and the high level time is between 0.5 milliseconds and 2.5 milliseconds, corresponding to 0 degrees and 180 degrees respectively. If your signal exceeds this range, the servo may interpret it as a "keep turning" command. Check the parameters in the code to confirm whether the pulse width range you set is correct.

The power supply is stable and unstable

Another very critical point is whether the steering gear is full. When the steering gear is started and running, it requires a very large current. If the power supply is insufficient, the voltage will drop instantly, causing the circuit inside the servo to "crash" or reset, resulting in uncontrolled and crazy rotation. This is like working on an empty stomach, it is easy to make mistakes.

You need to confirm whether the voltage and current of the power supply are sufficient. For example, for an ordinary 9-gram servo, the instantaneous current may reach more than 1 amp. If your power supply is a small battery box or USB power supply, it may not be able to carry it.It is recommendedto use a regulated power supply or a large-capacity lithium battery, and connect a large-capacity electrolytic capacitor (such as 470uF) in parallel to both ends of the servo power supply, which can effectively stabilize the voltage and prevent this "hungry faint" situation from happening.

Is the servo itself damaged?

If you have tried all the previous methods and it still doesn't work, then you have to wonder if there is something wrong with the "body" of the servo itself. The most typical ones are that the potentiometer is worn or the gear is stuck. The potentiometer is the "eye" used by the servo to detect the angle. If it is broken, the servo will not know where it is turning and can only keep turning to find the position that it can never find.

You can try to gently turn the output shaft of the servo with your hands to feel if there is any obvious stuck or unsmoothness. If so, the gear may be broken. If it rotates smoothly but still rotates randomly after power is turned on, then the potentiometer or the internal circuit board is most likely broken.Don't bother yourself at this time. Replacing a new servo may be the most efficient option.

How to avoid happening again

After solving the current problem, we have to think about how to solve it once and for all to avoid encountering this kind of trouble in the future. The most important thing is to develop good wiring habits.It is recommended thatbefore powering on the servo, use a multimeter to test your wiring to make sure there are no short circuits or wrong connections. At the same time, develop a good habit of adding capacitors to the power line. This is like buying a "voltage insurance" for the steering gear, which can effectively absorb spikes and stabilize voltage.

In addition, the initialization of the code is also important. At the beginning of the program, clearly set the control pin of the servo to output mode and output a PWM signal in a neutral position (such as a high level of 1.5 milliseconds), and then energize the servo. This ensures that the servo knows to stop in the middle position as soon as it is powered on, instead of turning aimlessly.

What other hidden traps are there?

For some problems with "the steering gear keeps turning", the cause may be hidden deeper. For example, if you are using multiple servos, they may interfere due to common ground issues. Imagine if all the servo currents flowed back through a thin ground wire, voltage drops and interference would occur, leading to signal disorder.It is recommendedto separate the power supplies of the servo and control board, or use a "star grounding" method to keep the return path of each device the shortest.

Another point that is easily overlooked is that if you are using a digital servo, its frequency requirements for the PWM signal may be different from those of the analog servo. Digital servos can usually accept higher frequencies. If your control program drives the digital servo at the 300Hz frequency of the analog servo, it may also cause abnormal operation. Therefore, when selecting and using it, clearly seeing whether the servo is analog or digital, and then matching the corresponding program can help you avoid many pitfalls.

Seeing this, have you found a way to solve the problem? If you encounter any "weird" problems during the debugging of the servo, please share them in the comment area so that more friends can help you come up with ideas!