Visual Rain Sensor

An other rain sensor, it consists of the typical rain sensor with the line shaped PCB where the rain falls, a microphone per-amplifier, an amplifier, a VU meter and a power supply to drive all the above.

The idea is simple, lets say you have no access to weather conditions but you want to know if it is raining. Not only that, but you would like to be aware on how strong the rain is

You can watch a video here:
.http://youtu.be/moz-xQcK9iA

Step 1: OPERATION

General idea

The rain sensor will become active at the presence of water drops. with the use of a relay then all other circuits will be powered.

Following, a microphone per-amplifier located under a reversed stainless steel bowl (acts like a bell), collects the sound of the rain drops. The amplifier multiply the signal from the per-amplifier and drive the VU meter where must be visible and most likely indoors, near you.

If it drizzle, some leds will light up but not all. If the rain is strong enough then all the leds will light up and with greater frequency. So, using this method one can have an idea on rain conditions.

This instructable is for one (1) set of pre-amp + amplifier + VU meter.

Step 2: GATHERING THE MATERIALS

Two (2) set of the above can be used.

A 3 wire cable plus ground = 4 wires, Length = from the VU meter to Project placement + 1meter.

A 2 wire cable for powering the circuits. Length = from the 12VDC power supply to Project placement.

A Rain Sensor like the one I used. SMART KIT 1080
http://www.quasarelectronics.com/smart-kit/1080-liquid-level-sensor-or-rain-alarm.htm
http://www.smartkit.gr/electronic-kit/automation/liquid-level-sensor-rain-alarm-m.html

A plastic waterproof box for the above.

A 8 wire electric screw connector. A plastic waterproof box for the connections.

A microphone Pre – Amplifier capable to drive an electret microphone. SMART KIT 1193
http://www.quasarelectronics.com/smart-kit/1193-super-microphone-preamplifier.htm
http://www.smartkit.gr/electronic-kit/preamps-mixers/microphone-pre-amplifier.html

The tiny LM386 amplifier (see my instructable) or any low power less than 1watt.

LM3915 VU meter.

A box for the above

Stabilized power supply, 12VDC / 500mA. Purchase one or build the circuit from this instructable.

Thin stainless steel bowl with diameter of 16cm – 20cm.

Piece of wood, thickness about 1 cm x bowl diameter.

Some water proof wood protective varnish for the above.

TESA moll - self adhesive rubber for windows, not more than 50cm.

Instant glue,use it to glue the sensor PCB at the top of the rain sensor’s box.

About 15 stainless screws of 4mm in diameter x 20mm long , nuts and washers.

Aluminum, stainless or wooden rod about 50cm long. A bracket base to hold the rod depending on where you are going to place it.

Step 3: CONSTRUCTION

I have included step by step pictures for the construction to make it easy for everyone to follow.

This instructable is for one (1) set of pre-amp + amplifier + VU meter.

Two sets can be built to do the following

For the first set, MIC pre-amp can be adjusted at the maximum sensitivity. That way the MIC can pick up the raindrops even when drizzle. For the second set, mic pre-amp can be adjusted to be a bit "deaf", that way it will respond only to heavy rain drops. Using this trick we can have better results.

The key to better adjustment is the multi-turn trimmer (POT) on both the LM386 amp and the LM3915 VU meter.

Step 4: LM3915 VU Meter

PARTS LIST

R1 = 1 KOhm

R2 = 680 Ohm

P1 = 10 K vertical multi-turn trimmer (POT)

C1 = 10uF / 25V electrolytic capacitor

U1 = LM3915 + 18 pin case

D1-11 = 3mm Led any color

Connectors = 2 pin screw PCB connector (x2)

JP1 = 2 pin PCB jumper (male,female) pitch: 2.54mm (= 0.1”)

Spare wire from used resistors

A plastic box to place everything inside

Step 5: 12VDC STABILIZED POWER SUPPLY

PARTS LIST
R1 = 680 Ohm
C1 = 1000uF / 25V polarized electrolytic capacitor
C2,3 = 100nF / 50V ceramic capacitor
C4 = 10uF / 25V polarized electrolytic capacitor
BR1 = 1A / 250V bridge
U1 = LM7812 & heat sing
One screw about 4mm in diameter x 10mm long,nut and washer
D1 = Led 5mm red
Connectors = 2 pin screw PCB connector (x2)
TR1 = transformer 15VAC / 500mA
SW1 = ON / OFF 1A, switch
FUSE case & fuse 1A
220VAC MAINS wire with plug
A plastic box to place everything inside

Step 6: FINAL ASSEMBLY AND CONNECTIONS

The rain sensor PCB and the rain sensor circuit goes to one waterproof plastic box.
Collect all cables to one waterproof box and make the appropriate connections using the 8 wire electric screw connector following the connections diagram.
Using small metal corners, screw to the rod the rain sensor box, the connections box and the bowl construction.  
Now you will always knew when, and how much it rains...
Have fun!