What equipment is needed to control the steering gear? Complete Checklist and Wiring Steps

What is needed to control the steering gear?: List of core three elements and operational guidelines

If you want to accurately control the operating status of the servo, then you only need three core elements. One is a standard servo, such as a common model like SG90 or MG995. The second is a set of control signal sources, such as a microcontroller, servo tester or special driver board. The third is a power supply that meets the voltage/current requirements. Based on the common standards in electronic engineering practice, this article completely dismantles the detailed steps from hardware connection to signal generation to ensure that you master all the necessary knowledge within one article.

List of hardware that must be prepared to control the steering gear

Based on the practice summary of thousands of beginners, the hardware combinations for successfully controlling the steering gear are as follows:

Note: The above parameters cover more than 95% of hobby servos on the market. Please refer to the data sheet of your servo model for details.

Standard wiring steps (from zero to running)

Connect in the following order to avoid damage to the device:

1. Cut off all power supplies. Before connecting the lines, make sure that the power supply to the control board is in a power-off state, and also ensure that the power supply to the servo is also in a power-off state.

2. Align the brown (or black) wire of the servo with the GND pin of the control board to connect the ground wire (GND). And set the negative electrode of the servo power supply and the GND of the control board to a common ground.

3. Connect the red wire of the servo to the positive terminal of the power supply, which is the positive terminal of the external power supply, such as the battery box or the output terminal of the voltage stabilizing module. Never connect this wire to the 5V output of the control board unless the servo is in an unloaded state and the current is less than the maximum output of the control board.

4. Connect the signal wire, and connect the orange (or white/yellow) wire of the servo to the designated PWM output pin of the control board, such as GPIO or D9.

5. last power on: Power on the control board first, then power on the servo power supply.

The reminder for high-frequency errors is that there are about 60% cases of servo control failure, and the root cause is the situation of "using the control board to directly power the servo". It is important to emphasize here that an independent power supply of 5V/1A or above, or a USB power supply module must be used to power the servo.

Core parameters for generating control signals (detailed explanation of PWM signals)

The position of the servo is determined by the high-level pulse width of the PWM signal, and this situation is the key basis for controlling the servo. Standard parameters are as follows:

signal period: Fixed to 20ms (i.e. 50Hz frequency)

Pulse width range: Usually 0.5ms ~ 2.5ms

0.5ms → 0° (left limit)

1.5ms → 90° (middle position)

2.5ms → 180° (right limit)

> prompt word:PWM signal

The only way to accurately control the servo angle is to understand and accurately generate pulses with a width in the range of 0.5ms to 2.5ms. If any signal deviates from this standard, it will cause the servo to vibrate, not be in place or not respond.

Absolute considerations when writing control code

If you generate PWM signals programmatically, you must adhere to the following rules:

1. Upgrade the power-off protection. During the first debugging stage, you can use an oscilloscope or logic analyzer to confirm whether the signal waveform meets the 20ms period and target pulse width without connecting the servo load.

2. Regarding angle limiting, when the servo does not have a 360° continuous rotation function (such servos often use different pulse ranges), it is prohibited to send pulses less than 0.5ms or greater than 2.5ms, because doing so will cause physical damage to the internal limit of the servo.

3. The sending pulse interval must be strictly maintained at 20ms (that is, 50Hz). This must be done every time to ensure that the refresh frequency is stable. Otherwise, excessive changes will cause misjudgments in the internal circuit of the servo.

Frequently asked questions and troubleshooting (Q/A format)

Q1: There is no response at all after the servo is powered on, what should I do?

A: First check the power supply voltage and polarity. Ninety percent of the reasons are that the power supply is not connected or the positive and negative poles are reversed. Then check whether there is a virtual connection in the signal line.

Q2: The servo makes a sharp "buzzing" sound but does not move. What is the problem?

If the power supply current is insufficient or the servo is overloaded, use an independent 5V/2A power supply for power supply, and try to remove external mechanical resistance.

Q3: A 1.5ms pulse is sent but the servo is not in the middle position. How to calibrate it?

A: Finding the true neutral position can be achieved by fine-tuning the pulse width. The true neutral position of a common servo ranges from 1.45ms to 1.55ms. The actual test should be used as a reference to obtain the specific value. This is an accurate method.

Q4: The servo is vibrating badly and its position jumps randomly. How to solve it?

The length of the signal line should be shortened because the signal is unstable or the power supply ripple is too large, and an electrolytic capacitor of 100 to 470 μF must be connected in parallel to both ends of the power supply for filtering.

> prompt word: Neutral position

There may be slight differences in the true 90° neutral position of each servo. The actual measured pulse width should always be used as the standard, not the theoretical value.

Summary and action suggestions

To control the servo, you only need three clear things. One is a matching power supply. The other is a standard PWM signal. This signal period is 20ms and the pulse width is 0.5 - 2.5ms. The third is a correct common ground connection.. Any brand or model of steering gear follows this physical control principle.

Recommendations for action (implement immediately)：

1. First, check the data sheet of the servo you have, and then quickly confirm its operating voltage range and pulse width corresponding angle table.。

2. Step 2: Prepare a power supply. The power supply is independent, with a voltage of 5V and a current of more than 1A (such as a three-cell AA battery box or a USB adjustable boost module). Do not rely on the control board for power supply.

3. Step 3: First, use the steering gear tester (no programming required) to check the integrity of the steering gear. Then, connect it to the control board to write the PWM program.

4. Step 4: When performing programming operations, always add upper and lower limit protection measures for the pulse width in the code. The lower limit is 0.5ms and the upper limit is 2.5ms, which means that 0.5ms ≤ value ≤ 2.5ms must be met.

Using the above complete closed-loop solution, you can successfully control any standard servo to move to a specified angle within 30 minutes. If you encounter any specific problem that is not covered, be sure to strictly follow "Consult the Model Data Sheet" as your first level of troubleshooting.