51 MCU peripherals: Motor

Motors are usually mechanical devices that convert electrical energy into kinetic energy . Generally, it can be divided into ： alternating current dynamo 、 DC motor 、 Stepper motor 、 Servo motor, etc . 

DC motor

AC motor and DC motor usually have two pins , The positive and negative poles of the AC or DC power supply can rotate , Power off and stop . Cannot be precisely controlled .

When using , Pass it through the current amplification chip , Connected to the two pins of the MCU , Then set these two pins separately 0 Harmony 1 that will do .

Be careful ： DC motor is not divided into positive and negative , Positive and negative connections correspond to positive and negative .

DC motor experiment
The DC motor is directly connected to the main board of the development board VCC and GND Check whether the motor rotates on the outlet interface , It can also be exchanged VCC and GND Check whether the motor reverses .
Single chip microcomputer IO Mouth is a digital mouth , Its driving ability is very small （ most 20mA Level ）, This driving capacity is with immovable motor . Therefore, the general single-chip microcomputer needs to use a special drive chip to drive the motor . The function of the drive chip is to convert the small current control signal of the single chip microcomputer into a logically identical drive source of large current . This is the so-called weak current control strong current . Use motor driver chip to drive DC motor , The specific circuit analysis will be detailed later when we talk about stepping motor . Let's skip here for a moment .

The code is as follows ：

/************************************************************

 date ：2022 year 7 month 23 Japan 

 author ： Stars 

 The contents of the document ： Motor demonstration 

**************************************************************/

#include<reg51.h>

sbit P30 = P3^0;
sbit P31 = P3^1;

/*************************************************************

 Function entrance 

**************************************************************/
void main(void)
{
    P30 = 1;
    P31 = 0;  
}

Stepper motor

Stepper motor is more complex than DC motor .

Stepping motor is a kind of motor which converts electric pulse signal into corresponding angular displacement or linear displacement . Each input pulse signal , The rotor turns an angle or moves forward , The output angular displacement or linear displacement is proportional to the number of input pulses , The speed is proportional to the pulse frequency . therefore , Stepping motor is also called pulse motor .

Most of the stepping motors used now use permanent magnet rotors . The reason why permanent magnets are widely used is high efficiency , Advantages of high resolution .

Step angle ： step
The stepper motor has an inherent step angle , This parameter is related to the stepping motor itself .

Generally, stepper motors can only move with integral multiples of the inherent step angle , The movement of this inherent step angle is called a beat .

The motor also has a motion method that can be smaller than the inherent step angle , This method is called subdivision , Supported by motor driver .

Phase number ： It refers to how many winding groups the motor has . Commonly used two-phase 、 three-phase 、 Four phases 、 Five phase stepping motor .

This article takes 2 Take phase stepping motor as an example .

Polarity ： Unipolar 、 Bipolar .

Number of beats （ a key ）： One way four beat 、 Biphasic four beat 、 Half step and eight beats .

Single phase four beat         A/ B A B/         Positive rotation （ Just reverse the order ）
Biphasic four beat         A/B  AB  AB/ A/B/         Positive rotation （ Just reverse the order ）
Half step and eight beats         A/  A/B  B  AB  A  AB/  B/  A/B/         Positive rotation （ Just reverse the order ）

Single phase four beat , Energize one winding , The other winding is not energized ,A and A/ Just reverse the level , But usually, who does the current timing belong to , Who is the high level . The level sequence of the four lines is as follows ：
A   A/   B   B/
0    1     0     0         The first 1 pat
0    0     1     0        The first 2 pat
1    0     0     0         The first 3 pat
0    0     0     1         The first 4 pat
4 The beats add up to a complete cycle , Power the stepping motor according to this cycle , Then the stepping motor will rotate 1 A step angle .

Biphasic four beat , The levels of the four wires are as follows ：
A   A/   B   B/
0    1     1     0          The first 1 pat
1    0     1     0          The first 2 pat
1    0     0     1          The first 3 pat
0    1     0     1          The first 4 pat

4 The beats add up to a complete cycle , Power the stepping motor according to this cycle , Then the stepping motor will rotate 1 A step angle .

Two phase four beat has higher load than single-phase four beat , But it consumes more electricity , Choose according to the actual situation .

Half step eight beat is a compromise between the above two . Temporal logic is the same .

Controllers and drives
A stepping motor system needs three parts ： controller + Driver + Stepper motor
In general ： The controller is a single chip computer , The driver is usually connected to the MCU IO Special motor drive chip on the port （ For example, on our development board TC1117）
The controller is responsible for generating timing signals , The driver is responsible for converting the timing signal to the success rate driving signal for the stepping motor .

Look at the schematic

The driver chip can be regarded as a current amplifier , Only connect the signal input end to the pin of the MCU , Connect the signal output to the stepping motor , Then the stepping motor can be driven to rotate by providing the stepping signal according to the time sequence .

Code implementation

I connect the input terminal to the chip P3.0、P3.1、P3.2、P3.3 Four pins , Then the output of the amplifier chip is used to control the A/ A B/ B.

Use single-phase four beat （A/ B A B/） To drive , Then the beat of these pins in a cycle is ：

1000

0001

0100

0010

The code is as follows ：

/************************************************************

 date ：2022 year 7 month 23 Japan 

 author ： Stars 

 The contents of the document ： Motor demonstration 

**************************************************************/

#include<reg51.h>


/*************************************************************

 Function entrance 

**************************************************************/
void main(void)
{
    while(1)
    {
        P3 = 0x1;
        P3 = 0x8;
        P3 = 0x2;
        P3 = 0x4;
    }
}

It's no problem to write the sequence like this , But download it to the development board , No response , Instead, there is a strange noise inside , And the fever is more serious . Editor's Note it ？ The wire is connected incorrectly ？ Check it out. No problem .

Access to information online , See the following statement ：

Exclude the first and second , That's what happens when the frequency is too fast .

So I added a delay before each cycle , as follows ：

while(1)
    {
        Delay();
        P3 = 0x1;
        P3 = 0x8;
        P3 = 0x2;
        P3 = 0x4;
    }

But it doesn't work . Confirm that it is not after the inter cycle delay , I added a delay between each beat , as follows ：

/************************************************************

 date ：2022 year 7 month 23 Japan 

 author ： Stars 

 The contents of the document ： Motor demonstration 

**************************************************************/

#include<reg51.h>

void Delay(int count);

/*************************************************************

 Function entrance 

**************************************************************/
void main(void)
{
    while(1)
    {
        P3 = 0x1;
        Delay(5);
        P3 = 0x8;
        Delay(5);
        P3 = 0x2;
        Delay(5);
        P3 = 0x4;
        Delay(5);
    }
}

void Delay(int count)
{
    int i = 0, j = 0;
    
    for(i; i < count; i++)
    {
        for(j; j < 100; j++);
    }
}

The motor finally turned ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I think , Is the delay added to give the motor response time , Or the previous beat hasn't had time to produce the corresponding effect , The next beat is coming , Too fast won't work ？？？？？？？？？？？？？？？？？？

I won't go into details , Remember first .

More start beats , And reverse rotation , Because it's easy , I won't go into that .

The rate is controlled by the delay between beats ; Turn it in the opposite direction and turn it upside down ; The same is true for other beats .