TECHNICAL SUPPORT
Published 2026-03-04
Have you also encountered these problems when playing with the SG90servo? ——You obviously bought a standard model, but after installing it, you find that it cannot rotate; or when you rotate it, it shakes like a sieve, making it completely useless. Don't worry, this is actually because you don't understand its temper yet. As an entry-level microservomotor, the parameters of SG90 directly determine what it can and cannot do. Today we will break it down and explain it clearly so that you can avoid detours.
When you get aservo, the first thing you often see are the numbers of torque, speed and angle. The torque of SG90 is usually between 1.2kg·cm and 1.8kg·cm, which refers to how many objects can be pulled at a distance of 1 cm. For example, a torque of 1.5kg·cm can probably drive a small and lightweight mechanical claw, but it would be difficult to lift a glass of water. The speed parameter is generally marked as 0.12 seconds/60 degrees, which means that it takes 0.12 seconds to turn 60 degrees. This speed is just right for the small robot's leg and foot movements. If it is too fast, it will easily lose control, and if it is too slow, it will look clumsy.
In terms of angle, the standard SG90 is a 180-degree version, which means it can only turn half a circle. If you need continuous rotation, you have to choose the 360-degree version. Many novices find that they cannot transfer to the position they want after buying it, often because they do not distinguish between the two. Another parameter that is easily overlooked is the working voltage. SG90 usually supports 4.8V to 6V. The higher the voltage, the greater the torque, but never exceed 6V, otherwise it will easily burn out the internal circuit.
Almost every friend who does small projects will struggle with this problem. Whether the torque is sufficient depends on what you use it to drive. For example, to make a simple camera gimbal, the torque of the SG90 is completely sufficient because the camera itself is very light. But if you want to use it as the shoulder joint of a robotic arm, even the smallest joint, you will find that it cannot be lifted - this is a typical manifestation of insufficient torque.
A practical way to tell is to multiply the weight of the object you want to drive by the length of the moment arm. Assuming that the object weighs 50 grams and is fixed at a position 3 centimeters away from the steering wheel axis, the required torque is 50 grams × 3 centimeters = 150 grams·cm, which is 0.15kg·cm. The SG90’s 1.5kg·cm seems more than enough, right? But don’t forget that the friction of the structure itself and the inertia during movement will consume additional torque, so it is best to leave more than 50% margin. Calculated in this way, the SG90 is most suitable for driving light connecting rods and small wheel steering in scenarios where the load is not large.
Jitter is the most troublesome problem of SG90, especially when you install it on a project for debugging, it becomes unusable when it shakes. The most common reason behind this is insufficient power supply. The current when the SG90 is started can reach several hundred milliamps. If you use an ordinary onboard 5V power supply, the servo will start to twitch as soon as the voltage drops. The solution is to use an external power supply to power the servo separately, such as a 4.8V battery pack or a voltage stabilizing module that can output more than 1A current.
Another easily overlooked reason is signal interference. The control signal of the servo is a PWM wave. If the line is too long or there are high current lines nearby, the signal will be deformed. Try shortening the signal wire or using shielded wire. If it still shakes, check if there is anything stuck on the servo arm. Sometimes small mechanical resistance will cause the servo to repeatedly adjust its position, making it look like it is shaking. Finally, don’t forget to add a dead zone setting in the code so that the servo will not move within a small range of error, which can effectively reduce micro-shake.
There are a variety of SG90s on the market, some are labeled "metal teeth" and some are labeled "waterproof". How should you choose? Let’s look at the gear material first. The standard version has plastic teeth, which are cheap but easy to clean, and are suitable for static displays or projects that occasionally move. If your servo needs to move frequently, such as when a robot walks, it is best to choose a metal gear version, which is much more wear-resistant and only a few dollars more expensive. Secondly, there are the bearings. The single-bearing SG90 will shake slightly when turning, but the double-bearing one is more stable and suitable for gimbals that require precision.
Look at the line sequence again. The common ones are brown, red and orange, with brown negative pole, red positive pole and orange signal. However, there are also some merchants who have reversed the order of the wires, causing them to smoke as soon as they are connected after buying them. It is recommended to use a multimeter to measure it after you get it. The resistance between the positive and negative electrodes should normally be above tens of kiloohms. Finally, if you need to be waterproof and dustproof, you can choose a version with a sealed shell, but you must pay attention to heat dissipation, as it can easily overheat after working continuously for too long. In short, don’t just look at the appearance, the motor and circuit board inside are the key.
When installing the SG90, do not tighten the screws too much, especially the screws that fix the servo ears. Over-tightening will crush the internal structure. Standard M2 or M2.3 screws are just fine, and it is best to add spacers. When connecting the servo arm and the connecting rod, make sure it rotates smoothly and don't hold back, otherwise the servo will always be in an overloaded state, causing serious heating and greatly reducing its service life. If you find that it cannot be turned manually after installation, it is due to mechanical interference and the position must be readjusted.
In terms of wiring, in addition to the separate power supply mentioned earlier, attention should also be paid to the common ground. That is, the negative electrode of the servo must be connected to the GND of the main control board, otherwise the signal cannot form a loop. The signal line is best connected to the PWM pin of the main control board, such as ports 9 and 10. Some novices plug it directly into ordinary digital ports and find that the servo does not respond because those ports do not support PWM output. Another point is that when wiring, connect the negative pole first, then the positive pole, and finally the signal. This can avoid current shock during hot plugging.
I just soldered the circuit and tried powering it on, but the servo didn't move at all. Everyone would be anxious at this moment. Don't panic yet, check it out step by step. The first step is to touch the servo shell. If it is cold, it means that it is not powered on at all; if it is slightly hot, it means that it is powered on but is stuck. The second step is to listen to the sound. If there is a buzzing sound after power is turned on, it means that the motor is trying hard to rotate but cannot. It is usually due to mechanical jamming or insufficient torque. At this time, disconnect the power supply and manually turn the servo arm to feel where the resistance is.
If it's an electrical problem, the most common one is insufficient voltage. Use a multimeter to measure the voltage at the power supply terminal of the servo. If there is 5V when there is no load, but it drops below 4V when it is started, it means the power supply is insufficient. Try changing to a higher current power supply. If the voltage is normal, then check the PWM signal and use an oscilloscope or logic analyzer to see if the waveform is correct. The pulse width should be between 0.5ms and 2.4ms, corresponding to 0 to 180 degrees. There is another remedy: take apart the servo and see if there are any foreign objects in the gears inside, or if the motor solder joints are loose. However, disassembly is risky, so novices should be cautious.
After reading this, are you sure about SG90? Have you ever been tricked by a servo when working on a project? Or do you have any unique debugging skills? Welcome to share it in the comment area so that everyone can communicate and learn together. If you think this article is useful to you, don’t forget to like it and forward it to more friends who play servos, so that everyone can avoid detours.
Update Time：2026-03-04
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