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JEJunior Engineer LabPico W + micro:bit course
07 30 minutes

Brightness knob

An analog input turns a physical twist into a number

Brightness knob project
Illustration of the finished idea. Build from the diagram and connection table, not the photo.

Mission goal: Wire a 10 kΩ potentiometer into ADC0 on GP26 and use its reading to set the LED's PWM brightness in real time.

Section 1

Understand

New ideas

  • Analog versus digital inputs
  • A potentiometer as an adjustable voltage divider
  • read_u16 and its reported 0 to 65535 range
  • The difference between reported range and real precision
  • 1A knob (potentiometer) turns a twist into a voltage.
  • 2The ADC reads that voltage as a number from 0 to 65535.
  • 3That number sets the LED brightness directly.

Safety first

  • Unplug before wiring the potentiometer.
  • Take 3.3 V from 3V3 OUT at physical pin 36. Never use VBUS or VSYS, which carry 5 V.
  • Make sure the two outer pot legs are not both in the same breadboard row, which would short 3.3 V straight to ground.