Don’t Worry About Reversing The Servo. Wiring And Programming Are The Two Most Common Steps.

Friends who play withservos must have encountered this situation: the program is written correctly and the wiring has been checked several times, but theservostarts to "ventilate" as soon as the power is turned on - either turning sharply in the opposite direction, or not listening to the instructions at all. Don't worry, this is not because you are unlucky or the steering gear is broken. It is most likely caused by several common reasons. Today we will talk about how to reverse the steering gear. From software to hardware, from principle to practical operation, we will thoroughly clarify this matter.

Is the most common reason for reverse rotation of theservodue to incorrect connection of the signal wire?

The first reaction of many friends who are new to steering gear is "the signal wire is connected backwards". In fact, the colors of the three wires of the servo are generally quite regular: brown or black is the ground wire, red is the power supply, and yellow or orange is the signal wire. But if you are using a non-standard servo, or the wire has been cut and reconnected, it is indeed easy to get confused.

There is a simple solution: the servo will not move if the signal line is connected to the ground wire, but it may rotate randomly or even burn out if it is connected to the power line. You can first use a multimeter to test the voltage of the servo plug to confirm which one is the power supply and which one is the ground. If you are really unsure, find a breadboard to power the test separately, don't try it directly on the project board. I suffered this loss once, when a micro servo was connected to the signal wire backwards and smoked directly.

How to quickly correct servo rotation through programming

If you confirm that there is no problem with the wiring, but the servo still rotates in the reverse direction, it is probably because the pulse width range does not match. Standard servos generally range from 0.5ms to 2.5ms corresponding to 0 to 180 degrees, but the pulse width ranges of different brands of servos actually vary. Some domestic servos may be 0 degrees in 1ms and 180 degrees in 2ms. Of course, if you use the standard library, it will go wrong.

The solution is also simple: adjust the pulse width range in the code. Take the Servo library as an example.(9, 500, 2500)Just change 500 and 2500 to the values actually supported by the servo. If you cannot find the parameters, you can first set the range wider, such as 400 to 2600, observe the extreme position of the servo and then slowly narrow it.

Will the servo drive board rotate randomly if the power supply is insufficient?

This issue is particularly easy to overlook. The current when the servo is started is very large. A standard 9g servo can reach more than 500mA when it is blocked. If you use the 5V pin of the development board to directly connect multiple servos, once the voltage drops, the control signals will be messed up, and the servos will rotate randomly.

I have seen a friend who makes a robotic arm. When the four servos are moved together, they all vibrate and occasionally reverse. Later, an external voltage stabilizing module was added, and the 12V battery was used to reduce the voltage to 5V to power the servo alone. The problem was immediately solved. You should remember one principle: the servo power supply and the main control power supply should be separated, sharing the ground but not the common power. Especially when doing high-torque projects, power supply cannot be overemphasized.

What will happen if the steering gear potentiometer is damaged?

There is a small potentiometer inside the steering gear, which is used to tell the control board "which position I am turning to now." If this potentiometer is worn or has poor contact, the feedback signal will be intermittent. If the control board cannot receive accurate position information, it will mistakenly think that the servo is not in place yet, so it will continue to drive the motor - the result is that the servo keeps turning in one direction, or shakes wildly.

This situation is more common on servos that are used frequently. You can gently turn the servo output shaft to feel if there is any jamming or free travel. If it is determined that the potentiometer is the problem, either disassemble the servo and replace the potentiometer, or directly replace the servo with a new one. It doesn’t have to be painful to repair something that costs dozens of dollars.

How to judge whether the servo itself is broken or there is a setting problem

There is a very practical troubleshooting method: first write your program simply, just one line.write.write(90), and let the servo turn to the neutral position. If it still reverses, change the servo you have determined and test it. If it works normally after replacing it, then the original servo is broken; if it still runs reversely after replacing it, then there is a problem with your program or wiring.

Don't take it too much trouble. The most fearful thing about hardware development is "it feels like there should be no problem." I'm used to keeping a test servo on hand specifically to troubleshoot this kind of failure. Sometimes after struggling for a long time, I finally find that the signal cable is just a little loose. So you should rule out the software and wiring first, and then doubt the servo itself. Don’t reverse the order.

Which steering gear brands are prone to problems with factory settings?

To be honest, not all brands are adjusted accurately from the factory. For the purpose of cost control, some cost-effective servos have a relatively arbitrary pulse width range. Even within the same batch of products, there are differences between individuals. If you use multiple servos of the same type in your project, some turn 90 degrees and some turn 100 degrees. This is normal.

In this case, either you calibrate the pulse width range of each servo and write it in the code, or choose a more stable brand. The official website of the more formal steering gear manufacturer will provide detailed technical manuals to tell you the precise pulse width correspondence. It’s not shameful to go to the official website to look up information. It’s much more efficient than guessing on your own for half a day.

To put it bluntly, although the reverse rotation of the servo is annoying, as long as you check it in order - first look at the wiring, then the program, then check the power supply, and finally suspect the servo itself - you can basically find the cause. Have you ever encountered a servo disobedient when working on a project recently? How was it solved? Welcome to chat in the comment area, and don’t forget to like it and forward it to your friends who also play servos. Maybe the pit you have encountered is the pit they are jumping into.