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Built-in project · Raspberry Pi 5

Potentiometer through an MCP3008 on a Pi, on a Raspberry Pi 5

gpiozero MCP3008 on a Raspberry Pi 5: a knob read through the ADC on SPI0 sets the brightness of an LED on GPIO18, and the reading is printed twice a second. The whole build, a Raspberry Pi 5 and 4 more parts, runs here in your browser on the Python below; open it in the editor to change the wiring or the code and run it again.

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The parts retail for about $66. On Mokxi they're free.

Potentiometer through an MCP3008 on a Pi · Raspberry Pi 5live0.000 s 0.00x
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The circuit itself, running here on the simulator. Press what can be pressed; click anything else to open it in the editor.

The code

The Python exactly as the editor opens it. Change a line there and press Run: the board runs main.py in a Python engine in the page, with gpiozero and RPi.GPIO, and nothing to compile.

main.py · Raspberry Pi 5
# A potentiometer through an MCP3008 on a Raspberry Pi 5, with gpiozero.
# The Pi has no analog inputs, so the MCP3008 converts: CLK to GPIO11 (pin 23),
# DOUT to GPIO9 (pin 21), DIN to GPIO10 (pin 19), CS to GPIO8 (pin 24, CE0).
from gpiozero import MCP3008, PWMLED
from time import sleep

pot = MCP3008(channel=0)    # spidev0.0: SPI0 with chip select CE0
led = PWMLED(18)

led.source = pot            # the knob sets the LED's brightness

while True:
    print("value %.3f  raw %4d  %.2f V" % (pot.value, pot.raw_value, pot.voltage))
    sleep(0.5)

Parts list

6 parts, plus the jumper wires. They retail for about $66; on Mokxi they're free.

How it is wired

11 connections, pin by pin, read from the circuit itself. Each line is one set of pins joined together, by a jumper wire or a breadboard strip.

  • Raspberry Pi 5 pin 3V3; Eight-channel ADC, MCP3008 pin VREF; Eight-channel ADC, MCP3008 pin VDD
  • Ground: Raspberry Pi 5 pin GND; Eight-channel ADC, MCP3008 pin DGND; Eight-channel ADC, MCP3008 pin AGND; LED, green pin C
  • Ground: Raspberry Pi 5 pin GND; Potentiometer pin 1
  • Raspberry Pi 5 pin GPIO18; Resistor, 330 Ω pin 1
  • Raspberry Pi 5 pin 3V3; Potentiometer pin 3
  • Raspberry Pi 5 pin GPIO10; Eight-channel ADC, MCP3008 pin DIN
  • Raspberry Pi 5 pin GPIO9; Eight-channel ADC, MCP3008 pin DOUT
  • Raspberry Pi 5 pin GPIO11; Eight-channel ADC, MCP3008 pin CLK
  • Raspberry Pi 5 pin GPIO8; Eight-channel ADC, MCP3008 pin CS
  • Eight-channel ADC, MCP3008 pin CH0; Potentiometer pin 2
  • Resistor, 330 Ω pin 2; LED, green pin A

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