Project 5: Automatic Doors and Windows

Description

Automatic doors and windows need power device, which will become more automatic with a 180 degree servo and some sensors. Adding a raindrop sensor, you can achieve the effect of closing windows automatically when raining. If adding a RFID, we can realize the effect of swiping to open the door and so on.

Component Knowledge

Servo:

Servo is a position servo driver device consists of a housing, a circuit board, a coreless motor, a gear and a position detector.

Its working principle is that the servo receives the signal sent by MCU or receiver and produces a reference signal with a period of 20ms and width of 1.5ms, then compares the acquired DC bias voltage to the voltage of the potentiometer and obtain the voltage difference output.

The IC on the circuit board judges the direction of rotation, and then drives the coreless motor to start rotation. The power is transmitted to the swing arm through the reduction gear, and the signal is sent back by the position detector to judge whether the positioning has been reached, which is suitable for those control systems that require constant angle change and can be maintained.

When the motor speed is constant, the potentiometer is driven to rotate through the cascade reduction gear, which leads that the voltage difference is 0, and the motor stops rotating. Generally, the angle range of servo rotation is 0° –180 °.

The pulse period of the control servo is 20ms, the pulse width is 0.5ms

2.5ms, and the corresponding position is -90°~ +90°. Here is an example of a 180° servo:

In general, servo has three lines in brown, red and orange. The brown wire is grounded, the red one is a positive pole line and the orange one is a signal line.

Pin

The servo of the window	5
The servo of the door	13

Project 5.1 Control the Door

Test Code

from machine import Pin, PWM
import time
pwm = PWM(Pin(13))
pwm.freq(50)

'''
Duty cycle corresponding to the Angle
0°----2.5%----25
45°----5%----51.2
90°----7.5%----77
135°----10%----102.4
180°----12.5%----128
'''
angle_0 = 25
angle_90 = 77
angle_180 = 128

while True:
    pwm.duty(angle_0)
    time.sleep(1)
    pwm.duty(angle_90)
    time.sleep(1)
    pwm.duty(angle_180)
    time.sleep(1)

Test Result

The servo of the door turns with the door, back and forth

Project 5.2 Close the Window

Description

We will work to use a servo and a raindrop sensor to make an device closing windows automatically when raining.

Component Knowledge

Raindrop Sensor: This is an analog input module, the greater the area covered by water on the detection surface, the greater the value returned (range 0~4096).

Test Code

# Import Pin, ADC and DAC modules.
from machine import ADC,Pin,DAC,PWM
import time
pwm = PWM(Pin(5))
pwm.freq(50)

# Turn on and configure the ADC with the range of 0-3.3V
adc=ADC(Pin(34))
adc.atten(ADC.ATTN_11DB)
adc.width(ADC.WIDTH_12BIT)

# Read ADC value once every 0.1seconds, convert ADC value to DAC value and output it, and print these data to “Shell”.
try:
    while True:
        adcVal=adc.read()
        dacVal=adcVal//16
        voltage = adcVal / 4095.0 * 3.3
        print("ADC Val:",adcVal,"DACVal:",dacVal,"Voltage:",voltage,"V")
        if(voltage > 0.6):
            pwm.duty(46)
        else:
            pwm.duty(100)
        time.sleep(0.1)
except:
    pass

Test Result

At first, the window opens automatically, and when you touch the raindrop sensor with your hand (which has water on the skin), the window will close.