Chapter 10 Potentiometer & LED

In the previous section, we have finished reading ADC value and converting it into voltage. Now, we will try

to use potentiometer to control the brightness of LED.

Project 10.1 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

ESP8266 x1	USB cable
Breadboard x1
Rotary potentiometer x1	Jumper wire M/M x8
LED x1	Resistor 220Ω x1

Circuit

Use pin A0 on control board to detect the voltage of rotary potentiometer, and use pin 4 to control one LED.

Schematic diagram

Hardware connection. If you need any support, please feel free to contact us via: support@freenove.com

Code

Move the program folder “Freenove_Ultimate_Starter_Kit_for_ESP8266/Python/Python_Codes” to disk(D) in advance with the path of “D:/Micropython_Codes”.

Open “Thonny”, click “This computer” -> “D:” -> “Micropython_Codes” -> “10.1_Soft_LED” and double click “Soft_LED.py”.

10.1_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 ADC, Pin, PWM
import time
adc = ADC(0)
pwm = PWM(Pin(4))
pwm.freq(1000)
try:
    while True:
        adcValue = adc.read()
        pwm.duty(adcValue)
        time.sleep(0.1)
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 10.2 Color Light

In this project, a potentiometer is used to control the RGB LED. The RGB LED is bright red when the potentiometer is near the midpoint, green when the potentiometer rotates to the “left” and blue when the potentiometer rotates to the “right”.

Component List

ESP8266 x1	USB cable
Breadboard x1
Rotary potentiometer x1	Jumper wire M/M x9
RGBLED x1	Resistor 220Ω x3

Circuit

Schematic diagram

Hardware connection. If you need any support, please feel free to contact us via: support@freenove.com

Code

Open “Thonny”, click “This computer” -> “D:” -> “Micropython_Codes” -> “10.2_Color_Light” and double click “Color_Light.py”.

10.2_Color_Light

Download the code to ESP8266, rotate the potentiometers, then the color of RGB LED will change.

The following is the program code:

from machine import Pin,PWM,ADC
import time

pwm0=PWM(Pin(13,Pin.OUT),1000)
pwm1=PWM(Pin(14,Pin.OUT),1000)
pwm2=PWM(Pin(12,Pin.OUT),1000)
adc0=ADC(0)
def setColor(r, g, b):
    pwm0.duty(r)
    pwm1.duty(g)
    pwm2.duty(b)
    time.sleep_ms(100)
try:
    while True:
        adcValue=adc0.read()

        if(adcValue>=0) and (adcValue<=345):
            setColor(1023, 0, 1023)
        elif (adcValue>345) and (adcValue<680):    
            setColor(0, 1023, 1023)
        elif(adcValue>=680) and (adcValue<=1024):    
            setColor(1023, 1023, 0)        
except:
    pwm0.deinit()
    pwm1.deinit()
    pwm2.deinit()

In the code, you can read the potentiometer ADC value, judge the range of ADC value, to control the RGB LED color.

Project 10.3 Soft Rainbow Light

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

Component List

ESP8266 x1	USB cable
Breadboard x1
Freenove 8 RGB LED Module x1	Rotary potentiometer x1	Jumper wire F/M x3 Jumper wire M/M x7

Circuit

Use pin A0 on the control board to detect the voltage of rotary potentiometer.

Schematic diagram

Hardware connection. If you need any support, please feel free to contact us via: support@freenove.com

Code

Open “Thonny”, click “This computer” -> “D:” -> “Micropython_Codes” -> “10.3_Soft_Rainbow_Light” and double click “Soft_Rainbow_Light.py”.

10.3_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

adc = ADC(0)

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 = adc.read()
        for j in range(0,8):
            wheel(adcValue/4+j*255//8)
            np[j]=(int(red*brightness),int(green*brightness),int(blue*brightness))
        np.write()
        time.sleep_ms(10)

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.