TECHNICAL SUPPORT
Published 2026-03-03
I think many friends will worry about those three colorful wires when they first come into contact withservos, or when they are working on robot or smart car projects: How to connect them? Will it burn if connected incorrectly? Don’t worry, today we will thoroughly understandthe three lines of the steering gear, so that you will no longer be confused.
The most commonservos, such as the SG90 or servos we use in daily play, generally have fixed color markings on these three lines. Generally speaking, the brown or black wire is the negative pole (GND), which is the ground wire of the power supply and is often connected to the GND terminal of the control board. The red wire is the positive pole (VCC), which supplies energy to the motor and control circuit inside the steering gear. As for the orange, yellow or white wire, it is the signal wire, which is responsible for receiving the PWM signal from the main control board (for example) to tell the servo to which angle to rotate. Keeping this color pattern in mind, you can identify 90% of servos at a glance.
Among many servos, SG90 or similar ones are very common. Each of these three lines has a specific color code. Generally, the brown or black wire serves as the negative pole (GND), which is the ground wire of the power supply, and is usually connected to the GND terminal of the control board. The red wire serves as the positive pole (VCC), which provides energy support for the motor and control circuit inside the servo. The orange, yellow or white wire is the signal wire, which is responsible for receiving the PWM signal from the main control board (such as the main control board), thereby telling the steering wheel the angle to turn. Remember this color pattern, and you can quickly identify most servos.
This is the biggest concern for many newbies. I can tell you with certainty thatif you accidentally connect the positive and negative poles of the power supply reversely, the servo will most likely "strike" on the spot or even burn down. Because the motor and control chip inside the servo have clear polarity requirements, reverse connection will cause the current to reverse and breakdown the components on the circuit board. At worst, the servo will have no response and just get hot, or at worst, a puff of green smoke will appear and it will be scrapped directly. Therefore, be sure to double-check before wiring. Red is connected to positive, and brown/black is connected to negative. This is like using chopsticks when eating. It is a hard rule.
The signal line is the brain of the servo. This wire needs to be connected tothe pin on the main control board that can output a PWM (Pulse Width Modulation) signal. For example, on UNO, the pin marked with the "~" symbol is the PWM pin. Its working principle is like sending a series of pulses of different widths to the servo. The pulse width is 1ms corresponding to 0 degrees, 1.5ms corresponding to 90 degrees, and 2.5ms corresponding to 180 degrees. You only need to write the corresponding angle in the program, and the main control board will automatically tell the servo where to turn through this line, which is very precise.
You may ask, can't the motor rotate with just two wires? Why do we need three servos? This is actuallythe reason why the steering gear is called a "servo motor". Two wires can indeed make the motor rotate, but there is no way to precisely control where it stops. The extra signal line is for closed-loop control. The steering gear integrates a motor, reduction gear and a position detection potentiometer. The signal line is responsible for receiving the target position command, and the red and black power lines are responsible for power supply. The internal circuit board will continuously compare the current position and the target position, and then drive the motor to correct it until it is accurate.
What should I do if the servo I buy has no information or the color is not standard? At this time,the multimeter is our best helper. Set the multimeter to the buzzer or resistance setting, and use the red and black test leads to test the three wires and plugs of the servo. Usually, the widest copper piece or the one connected to the casing is most likely the negative pole. You can also judge by measuring the resistance: after connecting the power supply, use the voltage level to measure. If it is about 5V, that wire is the positive terminal, and the remaining wire is the signal wire. This method is stable and reliable, and is especially suitable for verifying your judgment.
When you connect the wires with confidence, you are surprised to find that the servo is motionless. Is that momentary feeling of collapse coming over you? Don't panic, let's check it step by step.️First focus on the power supply: When the servo rotates, the demand for current is considerable. Especially for metal servos with high torque, the 5V output is very likely to be unable to drive, so an external power supply is required to supply power. ️Thencheck the wiring: carefully check whether the three wires are plugged incorrectly and whether their contacts are in good condition. ️Finalverification procedure: Be sure to confirm whether the PWM pin number plugged into the signal line is consistent with what is written in the program, and whether the PWM frequency setting is accurate. In fact, in many cases it is not the hardware that fails, but these small details that are easily overlooked that cause problems.
Many times, it's not that the hardware is broken, but that these small details are not noticed. Just like when troubleshooting steering gear problems, be thorough and meticulous. ️Lookat the power supply first: the servo has a large current demand during operation, especially for high-torque metal servos. The 5V output may not be able to meet its needs, so an external power supply is required. ️Lookat the wiring again: Carefully check whether the three wires are plugged incorrectly and whether the contact between them is good. ️Finally, look at the program: Make sure the PWM pin number inserted into the signal line matches the one set in the program, and whether the PWM frequency is set correctly. Many times, the fault does not lie with the hardware itself, but with our neglect of these key details.
After talking so much, I wonder if you ever made any jokes or burned out a few servos due to wiring problems when you were working on the project? Welcome to share your "rollover" experience in the comment area, let's all have fun together, and by the way, give the newbies a warning! If you find the article useful, don't forget to like and share it so that more people can see it.
Update Time：2026-03-03
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