TECHNICAL SUPPORT
Published 2026-03-28
When engaging in secondary development ofservos, the biggest headache is wiring. If you accidentally connect the wrong wires, theservos may not respond, or the control board may be burned directly. Many people get the control board and look at the dense solder joints and pin headers. They don't know where to start. The wiring diagrams found on the Internet are all kinds of and they don't match up. Don't worry, today we will break it down and thoroughly talk about the secondary development and wiring.
Many novices fail to distinguish the line at the first step. There are usually three types of interfaces on the control board: VCC is the positive pole, GND is the ground wire, and the rest is the PWM signal line. If you look carefully at the board, there will usually be small white characters printed on it. If you can't see clearly, use a multimeter to test it. 5V or 7.4V is the power supply. Remember an iron rule: if the power supply is connected reversely, the board will be burned, so be sure to use a magnifying glass to confirm the positive and negative poles before powering on. The same goes for theservoend. Brown or black is the ground wire, red is the positive wire, and yellow or white is the signal wire. If the color is correct, it will basically be correct.
When actually wiring, you need to connect the VCC on the control board to the red wire of the servo, connect the GND to the brown wire of the servo, and connect the signal wire to the corresponding PWM output port. If you want to control multiple servos at the same time, be sure not to connect the power supplies of all servos in parallel to the 5V output of the control board. If the current is too large, the board will burn. The correct way is to connect an external stabilized power supply, connect the red wires of all the servos together to the external power supply, connect the black wires together and share the ground with the GND of the control board, and connect the signal wires to each port respectively. This is both stable and safe.
Many people have encountered a strange thing: when testing the servo alone, it works very well, but as soon as three or four are connected, the servo starts to shake or simply stops moving. This is not because the wiring is wrong, but because the power supply is not keeping up. The instantaneous current of a standard servo can reach 1-2 A. If you use USB to power the control board, the maximum is only 500 mA, which cannot be driven at all. Therefore, during secondary development, the first priority is to solve the power supply problem. Don’t try to save trouble.
How to pick it up specifically? You need an independent regulated power supply module, connect its output to the servo power bus, and then connect the control board and the ground wire of this power module together. Remember, it must be "common ground" and not "common voltage", which means that the power module only supplies power to the servo and not to the control board. The control board still uses USB or its own power port. After doing this, you will find that the servo moves crisply and neatly, and there will no longer be any draft due to insufficient current.
Wiring is not just as simple as connecting a few wires, but you also have to figure out what "language" is used to communicate between the control board and the servo. There are two mainstream servos on the market: PWM servos and bus servos. The PWM servo has three wires, and the signal wire controls the angle by pulse width, so the connection method is the simplest; the bus servo generally has four wires, and with additional data transceiver lines, these servos can be strung together to save IO ports, but when wiring, pay attention to distinguish between TTL and RS485 protocols.
If you are using a bus servo, be sure to read the instructions before wiring. For TTL protocol servos, the signal lines are directly connected to the TX and RX of the control board. Note that it is a cross connection. The TX of the control board is connected to the RX of the servo, and the RX of the control board is connected to the TX of the servo. If it is RS485 protocol, a conversion module is also needed. I recommend that novices play with PWM servos first. The wiring is simple and it is quick to get started. Once they understand the basic principles, it is not too late to start playing with bus servos.
Many people think that secondary development means writing code, and then just transfer it to the board after writing. But in fact, the wiring method when burning firmware is sometimes different from the wiring method for normal operation. For example, for secondary development, when burning the program, you need to connect the TX, RX, and GND of the USB to TTL module to the corresponding ports on the control board, and some boards need to hold down the reset button before burning in.
More importantly, during the burning process, it is best to disconnect all external devices from the control board first, especially the servos. Because the IO port status is unstable during programming, it may output abnormal signals, causing the servo to rotate randomly, or even burning the computer USB port due to a large instantaneous current. The correct sequence is: first disconnect the servo, finish burning the program, unplug the burner, then connect the servo and power supply, and power on for testing. Developing this habit can help you save a lot of maintenance costs.
We have talked so much about basic wiring, but in fact the ultimate goal of secondary development is often to build a multi-degree-of-freedom system, such as a six-axis robotic arm. At this time, the wiring is no longer simple point-to-point. You have to consider the arrangement of the cables, the shielding of interference, and the position feedback of each joint servo. Six-axis means six-channel servos. You need a control board that supports at least 6 channels of PWM output, and each channel must be powered independently, and the current calculation must be accurate.
When connecting such a complex system, my experience is layered wiring: first combine the power lines and ground wires of all servos together to form a power backbone network, and then draw branch lines from the backbone network to supply power to each servo. The signal lines are grouped according to the layout and tied with cable ties to avoid crossing. The most important thing is to test each circuit every time you connect it. Don’t connect all of them before turning on the power. Otherwise, if you connect something wrong, you will crash when troubleshooting.
The last step in wiring, and the most overlooked, is the safety check. Many people turn on the power directly after connecting the wires, only to regret it when they smell a mushy smell. Before powering on, you should use a multimeter to test whether there is a short circuit between the positive and negative poles of each servo power supply, and whether there is a short circuit between the signal line and the power line. If you use battery power, it is best to connect a multimeter to measure the total current to see if it is within the tolerance range of the servo and control board.
In addition, it is best to wrap the terminal blocks with heat shrink tubing. Exposed copper wires can easily cause accidental short circuits. If you are using a servo with a DuPont cable, make sure it is inserted all the way in. Poor contact will cause the servo to vibrate. Develop this habit of "checking after wiring" and your development efficiency will double. You will no longer have to delay several days due to a small mistake.
When you were developing wiring for the second time in the past, the most troublesome problem you encountered was that the power supply connected to the board burned back, or that the power supply for multiple servos could not be driven? Welcome to share your pitfall experience in the comment area, and let’s discuss solutions together. If you think today's content is helpful to you, remember to give it a like and forward it to your friends who are also struggling with steering gears, so that more people can avoid detours.
Update Time：2026-03-28
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