What Is The Signal Control Of The Servo? It Is Easy To Understand The PWM Square Wave

Have you ever encountered this situation: You want to make a small robot or aircraft model project, and you buy aservo, but you are confused when you look at the three wires - what kind of signal does this thing need to move? Don't worry, today we will break down the steering gear signal and explain it clearly.

What does theservosignal look like?

To put it simply, what theservoneeds is a square wave signal called PWM. You can think of it as a heartbeat signal, beating regularly with highs and lows. This signal is sent to the servo through the yellow signal wire, telling it "Hey, which position to turn to."

This PWM signal has several key parameters, namely period, frequency and pulse width. The cycle represents the time it takes for a complete heartbeat, the frequency reflects the number of heartbeats per second, and the pulse width refers to the duration of the high level during each heartbeat. This is the real core of the command. Once the pulse width is different, the angle of rotation of the servo will change accordingly.

Why can PWM signal control the servo?

There is a little secret in the steering gear: there is a circuit board inside it, which is responsible for interpreting this PWM signal. There is a reference circuit in this circuit board that continuously generates a fixed pulse signal. When an outside PWM signal comes in, the circuit board compares the two signals.

If the incoming signal pulse width is longer than the reference signal, the servo will rotate in a specific direction; if the incoming signal pulse width is shorter than the reference signal, the servo will rotate in the opposite direction; and when the incoming signal pulse width is the same as the reference signal, the servo will remain stationary. This process is very similar to when we use the remote control to adjust the temperature of the air conditioner. When the set temperature is higher than the actual temperature, the air conditioner will start the cooling function. If the set temperature is lower than the actual temperature, the air conditioner will turn on the heating function. Once the set temperature is consistent with the actual temperature, the air conditioner will stop running.

How to choose the steering gear signal frequency

Standard servos generally work at a frequency of 50Hz, which is a cycle of 20 milliseconds. This frequency is like the "language rhythm" of the servo. If it is too fast, it cannot understand; if it is too slow, it will not respond. It's like when you're talking to someone, you speak too fast and the other person can't keep up, or too slow and anxious.

But some of the current digital servos can support higher frequencies, such as 200Hz or even higher. When the frequency is increased, the response of the servo will become faster and the operation will be smoother, but this also depends on whether your controller supports it. ️It is recommended that if you are just starting to play, use the standard 50Hz frequency first, and then try to adjust the frequency after you are familiar with its characteristics.

What is the difference between digital servo and analog servo signals?

The analog servo is like an honest person. It reacts when you give a signal. When the signal is gone, it stops moving. It has an internal 50Hz reference signal that refreshes the position 50 times per second. The digital servo is different. It can run to hundreds of Hz internally, just like an athlete on a high.

Specific to the signal level, both can receive standard PWM signals, but the microprocessor inside the digital servo will "translate" this signal into a higher frequency drive signal to the motor. The result is that the digital servo responds faster, has more accurate positioning, and has stronger holding power. Of course, it is also more expensive.

What will happen if the servo signal voltage is incorrect?

This problem is extremely common in actual operations, especially for novices who are new to related fields, and it is easy to get into trouble here. The steering gear is generally equipped with three wires, namely the positive power supply wire, the ground wire and the signal wire. Among them, the voltage of the signal line usually has specific requirements, usually 3.3V or 5V. The specific value needs to be determined according to the specifications of the servo. If your controller outputs a 5V voltage, but the servo only supports 3.3V signals, then a level conversion device must be added.

Adding a level shifter is critical to ensure that the servo receives the appropriate signal voltage to operate properly. Servos of different specifications have different voltage requirements for signal lines, so when connecting devices, be sure to carefully check the specifications of the servo to determine the accurate voltage requirements. Only in this way can the stability and normal operation of the entire system be ensured and problems such as steering gear failure caused by voltage mismatch be avoided.

The situation caused by voltage mismatch is the same as plugging a 110V electrical appliance plug into a 220V socket. In this case, the mild manifestation is that the appliance is unresponsive, while in severe cases, it may smoke or even be scrapped. There is also a more hidden problem, that is, insufficient power supply. When the servo rotates, the voltage will be quickly pulled down, causing signal recognition to fall into chaos, and the servo will continue to vibrate as a result. ️Remember one thing: check the specifications first, then connect the wires to ensure safety.

How to distinguish the colors of steering gear signal lines

This is a practical tip. Although the standards are not completely unified, most servos follow this rule: brown or black is the ground wire, red is the positive terminal of the power supply, and orange, yellow or white is the signal wire. This is just like the fire ground of our household sockets, there are rules to follow.

However, do not rely entirely on the color to judge the status of the servo. The safest way is to consult the manual or official website information that comes with the servo. Because some counterfeit servos may have confusing colors, in this case, use a multimeter to measure the voltage between the signal line and the ground wire to confirm the actual condition of the servos. ️Develop a good habit. After getting the servo, check the specifications first and take a minute to understand it. This can avoid a lot of trouble.

Having said so much about steering gear signals, you should have a clearer understanding of it now, right? I would like to ask you, during actual project operations, have you ever encountered a strange situation where the steering gear fails to operate? You are welcome to share your relevant experiences in the comment area. If you find these contents useful, don’t forget to like them so that more people can see them. You can also search the official website of the steering gear manufacturer to see the latest technical information!