Chapter 11 Potentiometer & LED

We have learned how to use ADC and DAC before. When using DAC output analog to drive LED, we found that, when the output voltage is less than led turn-on voltage, the LED does not light; when the output analog voltage is greater than the LED voltage, the LED lights. This leads to a certain degree of waste of resources. Therefore, in the control of LED brightness, we should choose a more reasonable way of PWM control. In this chapter, we learn to control the brightness of LED through a potentiometer.

Project 11.1 Soft Light

In this project, we will make a soft light. We will use an ADC Module to read ADC values of a potentiometer and map it to duty cycle of the PWM used to control the brightness of a LED. Then you can change the brightness of a LED by adjusting the potentiometer.

Component List

ESP32-WROVER x1		GPIO Extension Board x1
Breadboard x1
LED x1	Resistor 220Ω x1	Jumper M/M x5	Rotary potentiometer x1

Circuit

Schematic diagram
Hardware connection
If you need any support, please contact us via: support@freenove.com

Code

Move the program folder “Freenove_Ultimate_Starter_Kit_for_ESP32/Python/Python_Codes” to disk(D) in advance with the path of “D:/Micropython_Codes”.

Open “Thonny”, click “This computer” -> “D:” -> “Micropython_Codes” -> “11.1_Soft_LED” and double click “Soft_LED.py”.

11.1_Soft_LED

Click “Run current script”. Rotate the handle of potentiometer and the brightness of LED will change correspondingly.

The following is the code:

from machine import Pin,PWM,ADC
import time

pwm =PWM(Pin(25,Pin.OUT),1000)
adc=ADC(Pin(36))
adc.atten(ADC.ATTN_11DB)
adc.width(ADC.WIDTH_10BIT)

try:
    while True:
        adcValue=adc.read()
        pwm.duty(adcValue)
        print(adc.read())
        time.sleep_ms(100)
except:
    pwm.deinit()

In the code, read the ADC value of potentiometer and map it to the duty cycle of PWM to control LED brightness.

Project 11.2 Soft Colorful Light

In this project, 3 potentiometers are used to control the RGB LED and in principle it is the same as the Soft Light project. Namely, read the voltage value of the potentiometer and then convert it to PWM used to control LED brightness. Difference is that the original project only controlled one LED, but this project required (3) RGB LEDs.

ESP32-WROVER x1		GPIO Extension Board x1
Breadboard x1
RGBLED x1	Resistor 220Ω x3	Jumper M/M x13	Rotary potentiometer x3

Circuit

Schematic diagram

Hardware connection

If you need any support, please contact us via: support@freenove.com

Code

Open “Thonny”, click “This computer” -> “D:” -> “Micropython_Codes” -> “11.2_Soft_Colorful_Light” and double click “Soft_Colorful_Light.py”.

11.2_Soft_Colorful_Light

Click “Run current script” and control the change of RGBLED color by rotating the handles of three rotary potentiometers.

The following is the program code:

from machine import Pin,PWM,ADC
import time

pwm0=PWM(Pin(15,Pin.OUT),10000)
pwm1=PWM(Pin(2,Pin.OUT),10000)
pwm2=PWM(Pin(5,Pin.OUT),10000)
adc0=ADC(Pin(36))
adc1=ADC(Pin(39))
adc2=ADC(Pin(34))
adc0.atten(ADC.ATTN_11DB)
adc1.atten(ADC.ATTN_11DB)
adc2.atten(ADC.ATTN_11DB)
adc0.width(ADC.WIDTH_10BIT)
adc1.width(ADC.WIDTH_10BIT)
adc2.width(ADC.WIDTH_10BIT)

try:
    while True:
        pwm0.duty(1023-adc0.read())
        pwm1.duty(1023-adc1.read())
        pwm2.duty(1023-adc2.read())
        time.sleep_ms(100)
except:
    pwm0.deinit()
    pwm1.deinit()
    pwm2.deinit()

In the code, read the ADC value of 3 potentiometers and map it into PWM duty cycle to control the control 3 LEDs with different color of RGBLED, respectively.

Project 11.3 Soft Rainbow Light

In this project, we use potentiometer to control Freenove 8 RGB LED Module.

Component List

ESP32-WROVER x1	GPIO Extension Board x1
Breadboard x1
Freenove 8 RGB LED Module x1	Jumper F/M x3 Jumper M/M x3

Code

Open “Thonny”, click “This computer” -> “D:” -> “Micropython_Codes” -> “11.3_Soft_Rainbow_Light” and double click “Soft_Rainbow_Light.py”.

11.3_Soft_Rainbow_Light

Click “Run current script”. Rotate the handle of potentiometer and the color of the lights will change.

If you have any concerns, please contact us via: support@freenove.com

The following is the program code:

from machine import Pin,ADC
import neopixel
import time

np = neopixel.NeoPixel(Pin(2, Pin.OUT), 8)

brightness=0.1         #brightbess
red=0                  #red
green=0                #green
blue=0                 #blue

adc0=ADC(Pin(36))
adc0.atten(ADC.ATTN_11DB)
adc0.width(ADC.WIDTH_10BIT)

def wheel(pos):
    global red,green,blue
    WheelPos=pos%255
    if WheelPos<85:
        red=(255-WheelPos*3)
        green=(WheelPos*3)
        blue=0
    elif WheelPos>=85 and WheelPos<170:
        WheelPos -= 85;
        red=0
        green=(255-WheelPos*3)
        blue=(WheelPos*3)
    else :
        WheelPos -= 170;
        red=(WheelPos*3)
        green=0
        blue=(255-WheelPos*3)

while True:
        adcValue=adc0.read()//4
        for j in range(0,8):
            wheel(adcValue+j*255//8)
            np[j]=(int(red*brightness),int(green*brightness),int(blue*brightness))
        np.write()
        time.sleep_ms(100)

The logic of the code is basically the same as the previous project Rainbow Light. The difference is that in this code, the starting point of the color is controlled by the potentiometer.