This article is for anyone who wants to work with ev3 in Python. This time, I would like to perform various operations using the color sensor.
◯ ev3 (tank), color sensor, touch sensor ◯ Personal computer (VS Code) ◯ bluetooth ◯ microSD ◯ Material (It is recommended to proceed while watching this.)
colorsensor00.py
#!/usr/bin/env python3
from ev3dev2.sensor.lego import ColorSensor
from ev3dev2.sound import Sound
cs = ColorSensor()
spkr = Sound()
while True:
if cs.color == 5:
spkr.speak('Red is detected')
** Point **: A program that says "Red has been detected" when the color sensor responds to red.
** Point **: Colors are defined in advance corresponding to numbers, and colors are treated as numbers in the program.
color Color detected by the sensor, categorized by overall value. • 0: No color • 1: Black • 2: Blue • 3: Green • 4: Yellow • 5: Red • 6: White • 7: Brown
colorsensor01.py
#!/usr/bin/env python3
from ev3dev2.motor import MoveTank,OUTPUT_A,OUTPUT_B
from ev3dev2.sensor.lego import ColorSensor
tank_drive = MoveTank(OUTPUT_A,OUTPUT_B)
cs = ColorSensor()
while True:
if cs.reflected_light_intensity < 15:
tank_drive.on(10,0)
else:
tank_drive.on(0,10)
** Point **: A program that runs along the line, depending on the reflectance of the light detected by the color sensor.
** Point **: Line trace Light reflectance is different between black and white. White reflects light well, and black reflects less light. It is a common line trace to run while detecting a black line on a white field by taking advantage of the different reflectance.
colorsensor02.py
#!/usr/bin/env python3
from ev3dev2.motor import MoveTank,OUTPUT_A,OUTPUT_B
from ev3dev2.sensor.lego import ColorSensor
from ev3dev2.sensor import INPUT_1,INPUT_2
tank_drive = MoveTank(OUTPUT_A,OUTPUT_B)
cs_1 = ColorSensor(INPUT_1)
cs_2 = ColorSensor(INPUT_2)
while True:
if cs_1.reflected_light_intensity > 15:
if cs_2.reflected_light_intensity > 15:
tank_drive.on(10,10)
else:
tank_drive.on(10,0)
else:
if cs_2.reflected_light_intensity > 15:
tank_drive.on(0,10)
else:
tank_drive.on(-10,10)
** Point **: Line trace program using two color sensors
** Point **: Program image
cs_1 detects white and cs_2 detects white: go straight cs_1 detects white and cs_2 detects black: go to the right cs_1 detects black and cs_2 detects white: go left cs_1 detects black and cs_2 detects black: rotate on the fly (search for lines)
colorsensor03.py
#!/usr/bin/env python3
from ev3dev2.motor import OUTPUT_A, OUTPUT_B, MoveTank, SpeedPercent, follow_for_ms
from ev3dev2.sensor.lego import ColorSensor
tank = MoveTank(OUTPUT_A, OUTPUT_B)
tank.cs = ColorSensor()
try:
tank.follow_line(
kp=11.3, ki=0.05, kd=3.2,
speed=SpeedPercent(30),
follow_for=follow_for_ms,
ms=4500
)
except LineFollowErrorTooFast:
tank.stop()
raise
** Point **: Line trace program using PID control
** Point **: PID control PID control is a type of feedback control that controls the input value so that the output value approaches the target value.
Output value: Light reflectance Target value: Light reflectance near the line Input value: Motor rotation speed (When line tracing with one color sensor)
Point : follow_line(kp, ki, kd, speed, target_light_intensity=None, follow_left_edge=True, white=60,off_line_count_max=20, sleep_time=0.01, follow_for=
PID line follower kp, ki, and kd are the PID constants.
** Point **: Reference article about PID control
** Point **: Reference article about python exception handling
Python exception handling (try, except, else, finally)
colorsensor04.py
#!/usr/bin/env python3
from ev3dev2.sensor.lego import ColorSensor,TouchSensor
from ev3dev2.display import Display
cs = ColorSensor()
ts = TouchSensor()
dsp = Display()
color_list = [1,2,4,5]
while True:
dsp.update()
if ts.is_pressed:
if cs.color in color_list:
dsp.text_pixels(cs.color_name + ' is detected',True,0,52,font = 'helvB' + '12')
else:
dsp.text_pixels('No such color in the color_list',True,0,52,font = 'helvB' + '10')
else:
dsp.text_pixels('please set the color !!!!',True,0,52,font = 'helvB' + '12')
** Point **: Hold down the touch sensor and hold the color. If the color you hold at that time is a color that exists in color_list
Point :
python
Processing `` `
** A program called ** that executes processing if element a is included in b (list in this case)
Reference article
[Determine whether a list etc. contains a specific element with the Python in operator]
(https://note.nkmk.me/python-in-basic/)
### 1-5. A program that saves colors in a list
#### **`colorsensor05.py`**
```py
#!/usr/bin/env python3
from ev3dev2.motor import OUTPUT_A,OUTPUT_B,MoveTank
from ev3dev2.sensor.lego import ColorSensor,TouchSensor
from ev3dev2.sound import Sound
from time import sleep
cs = ColorSensor()
ts = TouchSensor()
spkr = Sound()
tank_drive = MoveTank(OUTPUT_A,OUTPUT_B)
color_list = []
for i in range(4):
ts.wait_for_bump()
sleep(0.1)
color_list.append(cs.color)
spkr.speak(cs.color_name)
for c in color_list:
sleep(1)
if c == 1:
spkr.speak('turn left')
tank_drive.on_for_rotations(0,50,2)
if c == 2:
spkr.speak('go forward')
tank_drive.on_for_rotations(50,50,2)
if c == 4:
spkr.speak('turn right')
tank_drive.on_for_rotations(50,0,2)
if c == 5:
spkr.speak('go back')
tank_drive.on_for_rotations(-10,-10,2)
** Point **: Add the color that was held up when the touch sensor was pressed to the empty color_list.
After adding, the process associated with the color is executed in order from the top of the list.
Point : append() You can add elements to the end of the list
Reference article Append, extend, insert to add an element to a list (array) in Python
Thank you for reading! !! Next time, I would like to write about ultrasonic sensors!
I want to make a better article ◯ This is easier to understand ◯ This is difficult to understand ◯ This is wrong ◯ I want you to explain more here We appreciate your opinions and suggestions.
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