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Published 2026-03-11
The most troublesome thing when playing withservos is looking at the SG90 in your hand and the rows of pins, but not knowing where to insert the three red, black and yellow wires. Once the wiring is wrong, theservowill not turn at least, or it will burn out directly, which is really a bit crazy.
The three most common wires of SG90 are brown, red and yellow. This color scheme is generally within the industry standard. Among them, the brown wire serves as the negative pole and should be connected to the GND pin of the development board; the red wire serves as the positive pole and needs to be connected to the 5V power supply; and the yellow wire serves as the signal wire, whose responsibility is to transmit the PWM waveform to achieve precise control of the steering angle.
Some merchants may use black, red and white or orange instead. Black corresponds to the negative electrode, and orange or white is the signal line. No matter how the color changes, remember one rule: the middle wire is always the positive pole of the power supply, and the two sides are ground and signal respectively.
You can connect directly, but you have to be careful during the process. In the no-load state, the operating current of the SG90servois approximately in the range of 100 to 200 mA. When a stall occurs, the current may soar to more than 500 mA. The maximum current that the 5V output pin can provide is about 500 mA. If only one servo is connected, it can barely be used normally.
If you want to control multiple servos, or need to run them for a long time, it is recommended to equip the servos with a separate external 5V power supply. The positive electrode of the power supply is connected to the red wire of the servo, and the negative electrode is connected to the GND. This can not only ensure stable power supply, but also avoid burning out the development board.
The consequences of incorrect wiring are no joke. The most common thing is to reverse the positive and negative poles. Although the SG90 has a protection circuit inside, it will still get hot if it is reversed for a long time. In serious cases, it will smoke and be scrapped.
Another situation is that the signal cable is not connected correctly, and the servo will vibrate, not turn, or bump around when it reaches the extreme position. A more hidden error is insufficient power supply, the steering gear has no power to rotate, or the movement is stuck. You think there is a problem with the program, but after checking for a long time, you find that the power supply is not enough.
Come, let's walk through this wiring process step by step. First, carefully check the three wires on the servo side. The brown wire should be connected to GND, the red wire should be connected to the 5V positive pole, and the yellow wire should be connected to the digital pin of the development board, such as pin 9. In addition, don’t forget to connect an electrolytic capacitor of about 100 microfarads in parallel between the power supply and ground. This electrolytic capacitor can effectively filter out the spike interference caused by the rotation of the steering gear.
Next, after completing the servo wiring, we need to check the entire wiring situation again to ensure that each wire is connected firmly and accurately. Then, turn on the power of the development board, observe whether the servo can respond normally, and start to rotate according to the predetermined program. If it is discovered that the servo is abnormal during this process, such as not rotating smoothly or making abnormal noises, then you need to carefully check the wiring again to see if there is any looseness or wrong connection, and make timely adjustments to ensure that the servo can work stably and normally, and successfully complete various subsequent tasks and functions based on the servo.
If you are using an external power supply, you need to connect the red wire of the servo to the positive terminal of the power supply, and connect the black wire to the GND of the development board. The signal lines are still connected to the digital pins in the original way. In this way, the development board and the servo have independent power supply channels, but they share a ground plane. Only in this way can the signal transmission remain stable.
️ The servo only beeps but does not sound: It is usually a sign of insufficient power supply. Check whether the output current of the power supply reaches the standard.
️ Inaccurate rotation angle: Check whether the signal line is in good contact and whether the PWM frequency is 50Hz.
️ The servo is seriously hot: Touch the motor and driver chip first. The heat is normal, but if it is so hot that you dare not touch it, it is probably because the rotor is blocked or there is a problem with the wiring.
️ Multiple servos interfere with each other: It is best to run the power line of each servo separately, the common ground must be reliable, and the signal line should avoid high current lines as much as possible.
Don’t rush to write complicated programs after connecting the wires. First upload a simple servo test code to make the servo swing back and forth between 0 degrees and 180 degrees. Watching it rotate smoothly indicates that the wiring and basic functions are normal.
Then you can use the serial port monitor to send instructions to control the angle manually, and then check the linearity and centering accuracy. If jitter or uneven steps are found, it is most likely that the pulse width calculation in the code is inaccurate. The standard range of SG90 is usually 0.5ms to 2.4ms corresponding to 0 to 180 degrees.
Generally speaking, when performing relevant operations, you can follow the above steps. First, use the serial port monitor to issue instructions to manually control the angle to check the linearity and centering accuracy. If you notice jitter or uneven steps, there is a high probability that the pulse width calculation in the code is incorrect. The standard range of SG90 is generally 0.5ms to 2.4ms, which corresponds to 0 to 180 degrees.
When playing with the servo, wiring is the first and most important step. What is the strangest servo failure you have ever encountered when working on projects? Let’s chat in the comment area, and give a like so that more friends who play servos can see this article~
Update Time：2026-03-11
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