rain-sensor.md

title	How to use a rain sensor with the microbit.
layout	text-width-sidebar
meta-description	Rain detector on the microbit with FC-37 or YL-83 Rain Sensors.
share	true
author	jez
about	A simple way of detecting rain droplets with a FC-37 or YL-83 Rain Sensor.
cats	external
simple-description	Rain Sensor
date	2016-12-23 10:20:00 UTC
date-updated	2016-12-23 10:20:00 UTC

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

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Component

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:

• Connect the two modules together
• Connect the GND pin on the small module to the microbit's GND pin.
• Connect the module's VCC or + pin to the microbit's 3v pin.

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.

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Electronics

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

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Rain Sensor Pin	Microbit Pin
VCC	PIN0
GND	GND
D or Digital	PIN1

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Code

Python MS Blocks

{% highlight python %} 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
else:
  display.show(Image.HAPPY) # not raining

pin0.write_digital(0)      # turn off sensor
sleep(600000)  # Sleep for 10 minutes

{% endhighlight %}