Optical Rain Sensor

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Introduction: Optical Rain Sensor

Measuring rain with a laser? It is possible. Follow this Instructable to make your very own Opical Rain Sensor.

Step 1: Material List

Particle Photon

  • Breadboard
  • Wires
  • Resistor
  • Light sensor
  • Laser diode
  • 1 Large piece of wood
  • 2 Small pieces of wood
  • Large Perspex block with corners cut off 45°
  • Double-sided tape

Step 2: Particle Photon

Our first step is to connect the breadboard to the Particle Photon. The Particle Photon should be positioned in the middle row of the breadboard towards the end of the breadboard. Make sure the micro USB-port is positioned away from the breadboard.

Step 3: Wiring

  • Connect the GND to the - side on the right
  • Connect the 3v3 to the + side on the right
  • Connect the laser diode to the point left of where the 3v3 is connected and on the - side on the right
  • Place a resistor on the - side on the right and the other end somewhere in the middle
  • Connect the resistor to A4 with a wire
  • Also on A4 connect one side of the light sensor and the other side of the sensor put in the same row on the + side on the right

Step 4: Building Setup

Building the setup is an important step. The first thing you need is a block of perspex. The corners need to be cut off at an angle of 45°, so the laser is able to reflect within the block. Instead of perspex also glass or another transparent material can be used. To keep the perspex under an angle without falling over, a large wooden block is used. We made a angle in the wooden block and with double-sided tape attached it to the perspex. On both of the cut off sides of the perspex block there needs to be attached a small block of wood. One for the laser and one for the light sensor. We put the light sensor inside a piece of black plastic so it is less affected by the surrounding light. Both of the wooden blocks were attached with double-sided tape. Make sure the wooden block are correctly calibrated before attaching them so the laser beam goes precisely into the light sensor. Finally we put some plastic over the top and backside so our breadboard doesn’t get wet.

Step 5: Programming

Step 6: Finished

Now you have a working Optical Rain Sensor. All is left is calibrating the values in the code, so it corresponds with the right rainfall.

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    2 Comments

    Nice design !

    Just to make sure I properly understand
    : the laser beam goes through the Perspex with an angle of 45° and makes
    multiple reflections inside the plastic and finally goes onto the sensor. When
    a rain drop goes onto the surface, the reflection is disturbed and the optical
    signal rapidly changes. You measure the stability of the signal and when the sigma
    is high, you conclude that it rains. Is it the way it works ?

    Do you know
    what happens when the Perspex surface is full of drops, or even is getting
    dirty over the time ?

    That would be interesting to use when I lived in Okinawa, we don't get much rain where I live now. Neat idea :)