Welcome to Pico Robot Car repository
5.8 Light follow
5.8 Light Follow
In Section 4.1, we use the photosensitive sensor to detect the light intensity and display the result on the OLED. In this section, we use this light intensity result to achieve light tracking.
Note that the search light is affected by the ambient light, please use it in a place where the indoor light does not change much or is dark.
The motor speed is affected by the battery power. The routine is when the battery power is high (the power value is above 26000), if the battery power is low, it needs to be charged in time or the motor speed should be modified.
1. Learning Objectives
1. Learn the motor, OLED, photosensitive sensor, and programmable RGB lights of the Raspberry Pi Pico 2/Pico board and the car expansion board to realize the car light search.
2. Understand the realization of the car's light seeking.
2. the use of hardware
This course uses the motor, OLED, photosensitive sensor, and programmable RGB lights of the Pico 2/Pico board and the car expansion board. The car is placed in an open space without obstacles in front of it. Please connect the jumper cap to the Light pin header before running, have a light source ready (flashlight or your phone's camera light).
In the program, we read the values of the two photosensitive sensors, compare the two values, and judge the position of the light source, thereby controlling the car to search for light.
3. program analysis
Complete program location: Pico Robot Supporting Materials -> Appendix -> Course code -> 3.Robot course -> 8. Lighting follow.py
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import timefrom machine import Pin, I2C, PWM, ADCfrom _car import SSD1306_I2C, _car, ws2812bMotor = _car()Motor.Car_Stop()num_leds = 8 # Number of NeoPixels# Pin where NeoPixels are connectedpixels = ws2812b(num_leds, 0)pixels.fill(0,0,0) pixels.show()#Light1 -> GP27#Light2 -> GP26light1 = machine.ADC(27)light2 = machine.ADC(26)#initialization oledi2c=I2C(1, scl=Pin(15),sda=Pin(14), freq=100000)oled = SSD1306_I2C(128, 32, i2c)light_down = 0.9light_up = 1.1while True: #get value LightS1 = light1.read_u16() LightS2 = light2.read_u16() print("light1 is %d"%(LightS1) ) print("light2 is %d"%(LightS2) ) #Display sound on OLED oled.text('Light1:', 0, 0) oled.text(str(LightS1), 60, 0) oled.text('Light2:', 0, 10) oled.text(str(LightS2), 60, 10) #Control action if LightS1 > (LightS2*light_down) and LightS1 < (LightS2*light_up): Motor.Car_Run(120,120) for i in range(num_leds): pixels.set_pixel(i,150,150,150) pixels.show() elif LightS2 > (LightS1*light_down) and LightS2 < (LightS1*light_up): Motor.Car_Run(120,120) for i in range(num_leds): pixels.set_pixel(i,150,150,150) pixels.show() elif LightS1 > (LightS2*light_up) or LightS2 < (LightS1*light_down): Motor.Car_Run(120,0) pixels.fill(0,0,0) pixels.set_pixel(0,150,0,150) pixels.set_pixel(1,150,0,150) pixels.set_pixel(2,150,0,150) pixels.set_pixel(7,150,0,150) pixels.show() elif LightS2 > (LightS1*light_up) or LightS1 < (LightS2*light_down): Motor.Car_Run(0,120) pixels.fill(0,0,0) pixels.set_pixel(3,150,0,150) pixels.set_pixel(4,150,0,150) pixels.set_pixel(5,150,0,150) pixels.set_pixel(6,150,0,150) pixels.show() else: Motor.Car_Stop() oled.show() oled.fill(0) time.sleep(0.01)from pico_car import SSD1306_I2C, pico_car, ws2812b
Using pico_car's SSD1306_I2C, pico_car, ws2812b, encapsulates the motor driver, RGB lights, and OLED libraries.
import time
The "time" library. This library handles everything time related, from measuring it to inserting delays into programs. The unit is seconds.
from machine import Pin, I2C, ADC, PWM
The machine library contains all the instructions that MicroPython needs to communicate with Pico and other MicroPython-compatible devices, extending the language of physical computing, using the Pin, PWM, ADC and I2C libraries here.
Motor= pico_car()
Initialize the motor drive.
pixels = ws2812b(num_leds, 0)
Initialize RGB lights, we have 8 RGB lights, here num_leds is set to 8.
pixels.fill(0,0,0)
Set all lights to 0,0,0, that is, turn off all lights, the parameters are (red, green, blue), and the color brightness is 0-255.
pixels.show()
Display the set lights.
pixels.set_pixel(0,150,0,150)
Set the first headlight to purple.
i2c=I2C(1, scl=Pin(15),sda=Pin(14), freq=100000)
Set the IIC 1 pin to SCL 15, SDA 14, and the frequency to 100000.
oled = SSD1306_I2C (128, 32, i2c)
Initialize the size of the OLED to 128*32, and pass in the IIC parameters set earlier.
Motor.Car_Run(120,120)
To control the car to move forward, the speed is set to 120, the parameters are (left motor speed, right motor speed), and the speed range is 0-255.
Motor.Car_Stop()
Control the car to stop.
light1 = machine.ADC(27)
Initialize ADC port 27, a total of two photosensitive sensors, and set pins 27 and 26 respectively.
oled.text (str (LightS1), 60, 0)
Convert the photosensitive value into a string and display it at the 60,0 position of the OLED.
oled.show ()
Display the set OLED content.
oled.fill (0)
Clear the settings and prepare for the next display.
LightS1 = light1.read_u16()
The light1.read_u16() function is used to detect the value of the sound sensor and assign it to the variable LightS1.
4. Experimental phenomenon
After the program is downloaded, we can see that the first line of the OLED displays the value of photosensitive sensor 1, and the second line displays the value of photosensitive sensor 2. At the same time, the Shell will also print the value of the photosensitive sensor. Use the flashlight to move left and right in front of the car, you can Control the left and right movement of the car.
Because the photosensitive sensor is easily affected by ambient light, please use it in a place where the indoor light does not change much or is dark. If the light-seeking effect is not good, you can adjust the detection range appropriately, that is, the variables light_down and light_up.