An article analyzing 51 microcontroller PWM dual servo control

　　Introduction to PWM

　　Pulse width modulation is a very effective technology that uses the digital output of a microprocessor to control analog circuits. It is widely used in many fields from measurement and communication to power control and conversion.

　　Pulse width modulation is an analog control method that modulates the bias of the transistor base or MOS tube gate according to changes in the corresponding load to change the conduction time of the transistor or MOS tube, thereby achieving the output of the switching regulated power supply. Change. This method can keep the output voltage of the power supply constant when the working conditions change. It is a very effective technology for using the digital signal of the microprocessor to control the analog circuit.

　　What is a steering gear

　　The steering gear is a position (angle) servo driver, suitable for control systems that require the angle to continuously change and be maintained. The steering gear is a large deck machinery on the ship.

　　This article mainly introduces the 51 microcontroller PWM dual servo control. Follow the editor to learn more about it.

　　Detailed explanation of 51 microcontroller PWM dual servo control

　　The steering gear used - Shenghui SG90 steering gear (standard version)

　　The working principle of Shenghui SG90 steering gear

　　First, there is a reference voltage inside the steering gear. If we want to control the rotation of this servo. Then we have to give it a certain period of DC bias voltage through a certain signal line.

　　Finally, the servo will internally compare the DC bias voltage with the internal reference voltage to obtain a voltage difference output. Finally, the positive and negative voltage difference is output to the motor driver chip to determine the forward and reverse rotation of the motor.

　　After such a simple description, we roughly know how to control the forward and reverse rotation of the steering gear.

　　Let's find out what kind of periodic DC bias voltage should be given to it?

　　Let’s take a look at the concept of duty cycle (picture):

　　As shown above: duty cycle = t/T;

　　To control the servo, we need a period T = 20ms. The high level small t is equal to such a square wave between 0.5ms-2.5ms.

　　Why is this parameter?

　　Through the above basic conceptual knowledge, we have roughly understood the working principle of the steering gear. Next, let's take a look at how to use C51 microcontroller PWM to adjust and control it.

　　for T = 20ms. We can count with timer 0 (mode 1). 0.1ms each time. If the count reaches 200, it means that a cycle has arrived and the count is cleared to 0.

　　Replenish:

　　For t = 0.5ms—–2.5ms we can use global variables. Let the global variable be equal to 5-25, because a counting period of my servo is 0.1ms, so the 5-25 of the global variable is exactly 0.5ms-2.5ms

　　With this correspondence, the program becomes simple: