TECHNICAL SUPPORT
Published 2026-02-24
When playing with theservo, if it keeps shaking and cannot turn in place, it is probably because the "median value" is not set correctly. To put it bluntly, this thing is the "middle point" where theservoshould stay when it does not receive a signal. Not sure, your robot will either have a crooked neck or have Parkinson's disease. Don't worry, it's easy to find out the way to this thing. Let's explain it clearly today.
If you want to find the median value, the most simple way is to "try". First connect the servo to your control board (for example), write the simplest program, and let it continuously output a 90-degree signal (generally the servo pulse width is 1.5ms). Then, gently twist the servo rocker arm with your hand to feel its "strength". The ideal midpoint is the point where you feel the most balanced resistance on both sides when you twist it with your hands. Of course, this is only an approximation.
A more precise approach is to fine-tune the pulse width value bit by bit in the program. For example, start from 1.5ms, increase or decrease by 0.01ms each time, and observe whether the servo is still "buzzing". Until you find that at a certain value, the servo becomes completely quiet, and if you gently turn it, it will rebound smoothly to the middle position. Congratulations, this value is the middle value you want. Record it and use it during program initialization later.
If the median value is not found correctly, the first trouble will be "unsteady standing". You clearly gave it a command to stop in the neutral position, but it deviated a little, causing your robotic arm or car to deviate. If you use it on a photography gimbal, the picture will always be crooked, and post-production editing can drive you crazy.
The more serious ones are "heating" and "shaking". Because the median value is wrong, the position fed back by the potentiometer inside the servo is always inconsistent with the position desired by the chip, and it keeps "battling" there, trying to correct it. This continuous tiny jitter and current consumption not only consumes power, but also burns out the driver chip inside the servo over time, causing your servo to be scrapped early, and the gain outweighs the loss.
Don’t worry, correct adjustment of the median value will not affect the service life, but is a good habit to protect the steering gear. Just like a person's muscles will get tired if they are stretched all the time, if the steering gear works in an inaccurate state for a long time, the internal motor and gear set will always be under stress, and the wear will increase.
Of course, the premise is that you have to adjust it "gently". Don't try to break the working servo with your hands, and don't use the violent method of writing extreme values directly into the register. The median value we found through trial and error through the program is to allow the servo to work at its most natural mechanical zero position, with all forces being most balanced. This is precisely the best way to extend its life.
Let’s use the most common example as an example. The operation is very simple.
️Step one: Wiring. Connect the SD5 signal wire (usually the yellow wire or white wire) to pin 9 (PWM pin), and the red wire and brown wire to 5V and GND respectively. Be careful not to connect it wrong, otherwise it will burn immediately.
️Step 2: Write code. UseServolibrary. Insetup()function, use.(9)to connect. Then write a loop and use.(1500)to turn the servo to the theoretical median value. Then you can modify the number 1500, such as 1480 or 1520, until you find the perfect midpoint. After finding it, solidify the final value into the program.
This is actually a hardware difference issue. The potentiometer, gear set, and even the main control chip in each servo have slight tolerances. Even for SD5s shipped from the same batch, the median value may differ by one to twenty microseconds between individuals. Just like there are no two identical leaves in the world, there are no two servos with exactly the same median value.
So don’t be lazy, don’t expect to download someone’s parameters from the Internet and use them directly. Especially if you are making a multi-axis robotic arm, the servos of each joint must be calibrated individually. If you use someone else's median value, the movement may go out of shape, or the servos may act "differently" to each other, causing the current to surge instantly, and your control board may start to smoke.
Many times after you finish the robot, you find that the median value is deviated. You can't carry a desktop computer to the site. At this time, you have to rely on "physical buttons + program logic".
You can reserve two "fine-tuning modes" in your code. For example, when it detects that a button is pressed when powering on, it enters calibration mode. Then press two more keys, one to increase the median value and one to decrease the median value. Each time you press it, the program writes the new value and saves it. In this way, you can hold a small screwdriver and observe the posture of the robot while making fine adjustments on the spot until it stands perfectly straight. This is real practical skills.
After talking so much, I wonder if the most troublesome problem you encounter when adjusting the steering gear is that it keeps shaking, or that you can't find the median point at all? Come to the comment area to chat, like and share, so that more friends who play servos can avoid detours.
Update Time：2026-02-24
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