TECHNICAL SUPPORT
Published 2026-03-21
Friends who are engaged in product innovation and making smart devices, I believe that many of them stumbled over the wiring aspect when they first came into contact with serial portservos. I obviously bought a good thing, but when I plug it in, it either doesn't respond or smokes and burns, which makes me feel depressed. Today I’m going to talk to you about serial portservowiring, and I’ll explain all the problems that are troubling you at once.
Try connecting the power cord backwards. I have seen many friends who connected 5V directly to GND without distinguishing the red and black wires. As a result, the driver chip inside the servo instantly broke down, a smell of paste wafted out, and something worth hundreds of dollars was scrapped. Some people have wrongly connected the signal lines, confusing TX and RX, and the servo cannot receive instructions. You say "turn 90 degrees" and it doesn't move at all. You thought the program was wrongly written, but it took a long time to find out that it was a wiring problem.
What's more troublesome is that if you control multiple servos at the same time and one of them is connected incorrectly, the entire system may be brought down through the shared power line. This is the case for a customer of mine who makes a robotic arm. Six servos were connected in parallel, and one of the signal lines was short-circuited, causing the serial port chip on the control board to burn out. The entire board was returned to the factory for repairs, which delayed the construction period for a whole week.
Serial servo generally has three wires, red, black, yellow or brown, red and orange are the most common color combinations. Red or brown is the positive terminal of the power supply, black or brown is the ground wire, and yellow or orange is the signal wire. But don’t memorize the colors by rote, as different manufacturers may have different line sequences. The most reliable way is to look at the label or manual on the servo. It will be marked VCC, GND, TX or RX.
You can think of the power cord as a blood vessel, responsible for delivering energy to the steering gear; the signal wire is a nerve, responsible for transmitting the instructions you give. If the power cord is connected incorrectly, "internal bleeding" will occur, and if the signal cable is connected incorrectly, it will cause "mental disorder". The safe way is to use a multimeter to test it first, confirm which wire is the positive wire and which wire is the ground wire, and then connect it up. Spend a minute testing it, which can save a lot of trouble.
Many novices ask "Can the serial port servo be connected to 5V" when they first start. This question depends on the specific model. Small serial servos usually support 4.8V to 6V, and large ones can support 7.2V or even higher. If the voltage is low, the servo will have no power to rotate and will easily vibrate; if the voltage is high, the internal circuit will be burned directly. I suggest you look through the parameter list of the servo, find the "Operating Voltage" column, and follow the recommendations.
If you are using lithium batteries, be aware of voltage fluctuations. For example, the 2S lithium battery has a nominal rating of 7.4V and can be fully charged to 8.4V, which is beyond the endurance range of many servos. At this time, a voltage stabilizing module must be added to stabilize the voltage within a safe range. Don't try to save trouble, just plug it in and try it. If you are lucky, it will last for a few days, but if you are not lucky, it will smoke as soon as you turn it on.
When you need to control several serial servos at the same time, the wiring becomes a bus structure. The power and ground wires of all servos should be connected in parallel, that is, twist all the red wires together to connect to VCC, and twist all the black wires together to connect to GND. The signal lines are also connected in parallel, but please note that the serial port communication is one-to-many. You have to ensure that the serial port of the control board can drive so many servos.
There is another issue that is easily overlooked: power capacity. When one servo is working normally, the current may be less than 1A, but if multiple servos are started at the same time, the instantaneous current may reach several amps. If your power supply is not powerful enough, the voltage will drop instantly, causing the servo to restart or the control board to freeze. So remember to leave enough margin for the power supply, at least 30% to 50% larger than the total current.
Don't immediately suspect that the servo is broken. Eighty percent of the time it's because you connected it incorrectly. The first step is to use a multimeter to measure the power supply voltage to see if there is power at the servo. The second step is to check whether the wiring terminals are firm. Especially when using DuPont wire, poor contact often occurs. The third step is to confirm whether the signal lines are connected reversely. The TX of the serial servo must be connected to the RX of the control board, and the RX must be connected to the TX of the control board. This is the easiest to get confused.
If these are OK, take another look at your program and baud rate settings. The serial servo has a default baud rate, usually 9600 or so. You have to set it to the same baud rate in the code. If that doesn't work, use an oscilloscope or logic analyzer to capture the signal waveform to see if the control board sends out data. I had a project before that was stuck at this step. In the end, I found that the baud rate was missing a 0. After changing it, it became normal immediately.
Searching for "serial servo wiring diagram" online will bring up a variety of pictures, some of which don't match your model at all. The most reliable thing is to download the technical manual from the official website of the steering gear brand, which will have detailed pin definitions and wiring examples. For example, if you buy a serial port servo of a certain brand, go to its official website and look for the "Product Center" or "Technical Support" section. There is usually a PDF document you can download.
If you cannot find the information, please contact the manufacturer's customer service or technical support directly. Regular manufacturers will provide wiring diagrams and FAQs. After getting the official information, check the wires one by one against the real thing. Don't pick it up based on memory. Many manufacturers now also provide wiring video tutorials, which are more intuitive than looking at pictures. Remember, using information from official channels can save you 90% of detours.
When you first connected a serial port servo, what problems did you encounter that drove you crazy? Welcome to share it in the comment area so that other friends can avoid the pitfalls.
Update Time：2026-03-21
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