• Use a MAX44009 to measure environment light
  • Use an Arduino Pro Mini 3V3 modified to be battery supplied
  • The Arduino 3.3V 8mhz can handle down to roughly 2.8V and the Nrf24l01+ down to 1.9V. Hence the batteries can not be NiMH rechargeables - Alkaline or Lithium required. We use a CR2032 coin cell which gives 3.3V.
  • Possible later improvement: Program the BOD to 0xFE = 1.8V.
  • Prepare the Arduino Pro Mini for use with a battery supply: remove the power LED, remove the voltage regulator.
  • Prepare the MAX44009 module to be supplied by 3V.

The result


e box

Used Components


Component Pin Wire/Component Pin Component
ArduinoProMini3V VCC red plus Battery CR2032
ArduinoProMini3V GND black min Battery CR2032
AdapterProMiniForNrfSmd IRQ green D2 ArduinoProMini3V
MAX44009-Light-Sensor VCC red VCC ArduinoProMini3V
MAX44009-Light-Sensor GND black GND ArduinoProMini3V
MAX44009-Light-Sensor SCL A5 Purple ArduinoProMini3V
MAX44009-Light-Sensor SDA A4 Green ArduinoProMini3V
NRF24L01+SMD IRQ Blue D2 ArduinoProMini3V


  • Select as board: Arduino Pro or Pro Mini
  • Processor: ATmega328P (3.3V, 8MHz)
  • Serial monitor: 19200 Baud
  • Use platformio

Code at: LightSensor.ino

I2C scanner

The I2C scanner software gives:

I2C device found at address 0x4A  !

First sign of life

System Message: WARNING/2 (<string>, line 142)

Literal block expected; none found.
Tags: domotica nodes