024 - MicroPython TechNotes: Slider Switch

Mar 30, 2021 · 4 min read · MicroPython tutorials ·

Introduction

In this article, we will learn how to use Slider Switch with ESP32 using MicroPython programming language. A slider switch is basically a variable resistor that changes resistance according to slider wiper position. With that knowledge, we can used MicroPython’s ADC function to interpret slider switch position.

Pinout

G – for the ground pin.
V – for the supply voltage.
S – for the signal pin.

Bill Of Materials

ESP32 development board to serve as the brain for the experiment.
ESP32 shield from Gorillacell ESP32 development kit to extend ESP32 pin to pin headers for easy circuit connection.
3-pin female-female dupont wires to connect slider switch to ESP32 shield pin headers.
Slider Switch module from Gorillacell ESP32 development kit.

Hardware Instruction

First, attach the ESP32 on top of the ESP32 shield by making sure that the pins are properly aligned and both USB ports are on the same side.
Next, attach the dupont wires to the Slider module by following the color coding which is black for the ground, red for the VCC, and yellow for the signal pin.
Next, attach the other end of the dupont wires to the ESP32 shield by matching the colors of the wires to the colors of the pin headers such as black to black, red to red, and yellow to yellow. For this experiment, I choose GPIO 32 to serve as the input signal pin from the Slider module.
Next, power the ESP32 shield with external power supply with a type-C USB connector and make sure that the power switch is set to ON state.
Lastly, connect the ESP32 to the computer through the USB cable with micro-USB type cable. Demo circuit is now ready.

Software Instruction

For this experiment, I prepared to example source code for you to try.

Copy and paste it to Thonny IDE.

Please feel free to modify it and adapt according to your needs.

Happy tinkering.

Video Demonstration

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Source Code

1. Example # 1, basics of reading an analog input such as the slider switch:

 1# More details can be found in TechToTinker.blogspot.com 
 2# George Bantique | tech.to.tinker@gmail.com
 3
 4from machine import Pin, ADC
 5from time import sleep_ms
 6
 7p32 = Pin(32, Pin.IN)
 8slider = ADC(p32)
 9slider.atten(ADC.ATTN_11DB)
10
11while True:
12    print(slider.read())
13    sleep_ms(300)

...

2. Example # 2, simple application in using a slider switch:

 1# More details can be found in TechToTinker.blogspot.com 
 2# George Bantique | tech.to.tinker@gmail.com
 3
 4from machine import Pin, ADC, PWM
 5from time import sleep_ms
 6
 7p32 = Pin(32, Pin.IN)
 8slider = ADC(p32)
 9slider.atten(ADC.ATTN_11DB)
10
11boot = Pin(0, Pin.IN)
12led = Pin(2, Pin.OUT)
13
14red = PWM(Pin(25, Pin.OUT))
15grn = PWM(Pin(26, Pin.OUT))
16blu = PWM(Pin(27, Pin.OUT))
17red.freq(60)
18grn.freq(60)
19blu.freq(60)
20
21r = 0
22g = 0
23b = 0
24steps = 0
25
26def map(x, in_min, in_max, out_min, out_max): 
27    # This will not handle x value greater than in_max or 
28    #                      x value less than in_min 
29    return int((x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min) 
30
31while True:      
32    if steps==0:
33        # Set the RGB from r, g, b values
34        red.duty(r)
35        grn.duty(g)
36        blu.duty(b)
37        if boot.value()==0:
38            steps = 1 # go to setting red
39            print('RGB are {} {} {}'.format(r, g, b))
40            
41    elif steps==1:
42        # Set the red color
43        r = map(slider.read(), 0, 4095, 0, 255)
44        red.duty(r)
45        grn.duty(0)
46        blu.duty(0)
47        if boot.value()==0:
48            steps = 2 # go to setting green
49            print('R is set to {}'.format(r))
50            
51    elif steps==2:
52        # Set the green color
53        g = map(slider.read(), 0, 4095, 0, 255)
54        red.duty(0)
55        grn.duty(g)
56        blu.duty(0)
57        if boot.value()==0:
58            steps = 3 # go to setting blue
59            print('G is set to {}'.format(g))
60            
61    elif steps==3:
62        # Set the blue color
63        b = map(slider.read(), 0, 4095, 0, 255)
64        red.duty(0)
65        grn.duty(0)
66        blu.duty(b)
67        if boot.value()==0:
68            steps = 0 # write the r,g,b to RGB LED
69            print('B is set to {}'.format(b))
70    
71    sleep_ms(300)
72    if steps==1 or steps==2 or steps==3:
73        led.value(not led.value())
74    else:
75        led.value(0)