Rain Sensor

A rain sensor will detect droplets of water when they fall on the sensor board.


Rain Sensor Module

The sensor board has two traces on it and the microbit can measure the resistance between the two. In this example, it connects to a module which converts the analog signal from the rain sensor to a digital output.

Which Sensor?

A search for ‘FC-37’ or ‘YL-83’ or ‘Arduino Raindrop Sensor’ will yield the sensor that’s required.

The sensor usually comes with two modules. One part detects the raindrops, the other takes a signal from the sensor and outputs it as an analog or digital signal. It’s possible to use the big raindrop detector module on its own; see the Soil Moisutre Sensor entry on how to do it.

Setting Sensitivity

First we need to provide power to the sensor to set its sensitivity:

An LED will light on the module.

There is a small potentiometer on the module. This sets the level of sensitivity required for the sensor to output a digital signal to say it has detected water.

Add a few ‘rain drops’ to the sensor. Rotate the potentiometer until the second the LED lights. At this level, the sensor will return a 1 digital signal.


Warning Notes

Providing constant power to the rain sensor degrades the board. Electrolysis occurs when it’s wet.

Power to the board can be controlled if it’s connected to one of the microbit’s 0, 1 or 2 pins. Turn on the sensor only when a reading is being taken.

Analog or Digital?

In this example we will use a digital output: the sensor will return HIGH or 1 if there is rain present. There are four pins on the module; one of them is marked A and the other is marked D.

We will take the digital signal so we connect to the ‘D’ pin.

Circuit & Hookup

Rain Sensor PinMicrobit Pin
D or DigitalPIN1


from microbit import *

while True:

    pin0.write_digital(1)  # Turn on the sensor
    sleep(500)  # Wait for the sensor to settle

    if pin1.read_digital():
       display.show(Image.SAD) # it's raining
      display.show(Image.HAPPY) # not raining

    pin0.write_digital(0)      # turn off sensor
    sleep(600000)  # Sleep for 10 minutes
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Published: December 23, 2016 Updated: December 23, 2016

Rain Sensor

A simple way of detecting rain droplets with a FC-37 or YL-83 Rain Sensor.

Jez Dean