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Topic: Capacitive Rain Sensor (Read 6355 times) previous topic - next topic

dasc93

Hello together!

I want to built a capacitive rain sensor for Arduino which can tell me when it rains and how much about (drizzle, normal, heavy rain), maybe 4-5 possible states, depending on the heaviness of the rain.

I currently using a normal eBay rain sensor from China, which is based on resistance but its not very "precise" and does not work with drizzle and oxidizes after one week.

I have found the Arduino "CapacitiveSensor" library and tried to used the shield from the actual rain sensor with a plastic tape on it. I basically works, but the values fluctuate heavily. I used a 1M, 2M and 4.7M resistor between the two pins and a 100pF, 1000pF and 100nF capacitance to Ground.

Maybe you have a better idea to solve this problem, with other components or values or also a complete new circuit.


Thank you in advance for your suggestions!

jremington

Before attempting to design and build a capacitive rain sensor, I suggest to investigate how commercial capacitive rain sensors work and how many categories of precipitation are reported.

Here is one example: http://www.telecontrolli.com/it/downloads-2/category/21-sensor.html?download=84:rain_sensor_applic_note

dasc93

jremington, thank you for your reply!

I have already seen this document and I know how this sensor works. I don't want such a complex sensor with heater and temperature sensor. I need support with designing or creating a simple sensor.

jremington

#3
May 04, 2015, 10:40 pm Last Edit: May 04, 2015, 10:42 pm by jremington
Quote
I need support with designing or creating a simple sensor.
What reason do you have to believe that a "simple" sensor can be made to do what you want? The lack of such commercial options suggests that this is not an easy task.

pantonvich

you could try something like this to see it works
http://www.techlib.com/electronics/raindetectors.htm

modified to just the penny-insulator-nickel with 100k ohm and read with the analog:

//   rain_detector
//          +-----------A
//          |
//  ||----+----100K---5+
//  +-----------------gnd

penny to gnd
insulator
nickel - analog - resistor - 5v+

see attached to compare rain bucket vs the 6cent sensor


dasc93

you could try something like this to see it works
http://www.techlib.com/electronics/raindetectors.htm

modified to just the penny-insulator-nickel with 100k ohm and read with the analog:

//   rain_detector
//          +-----------A
//          |
//  ||----+----100K---5+
//  +-----------------gnd

penny to gnd
insulator
nickel - analog - resistor - 5v+

see attached to compare rain bucket vs the 6cent sensor


Thanks for this idea!

I will try this, as I have a bit more time! Maybe you can share your code or the formula for this sensor?

pantonvich

sure

#define rain_detector_apin 4
analogRead(rain_detector_apin)

I take a reading every 5 mins and save it to a flat file




pantonvich

#7
May 06, 2015, 01:20 am Last Edit: May 06, 2015, 01:21 am by pantonvich
also you could put some type of heat on it when it gets wet to make it dry quicker - I've not done that

dasc93

sure

#define rain_detector_apin 4
analogRead(rain_detector_apin)

I take a reading every 5 mins and save it to a flat file




Thank you! I thought that you have used the analog value to calculate the "heaviness" of the rain. Maybe I will try to interpret the analog value to get a more descriptive result!

pantonvich

if you look at the plots - it looks like harder rains give lower values - if you experiment with the resistor value you likely can get more range - sticking the 6cents in water gives lower values than what I get from rain events

frak68

#10
Aug 14, 2015, 10:59 am Last Edit: Aug 27, 2015, 03:14 am by frak68

Boardburner2

#11
Aug 27, 2015, 04:43 pm Last Edit: Aug 27, 2015, 07:09 pm by Boardburner2
This explains the theory.


http://www.ti.com/lit/an/snoa927/snoa927.pdf

It is relativley easy to make your own sensor by etching a thin ds pcb.
A simple resistive sensor has the wrong footprint for a reliable capacitive sensor


This may fit the bill, i think all the car ones are optical.

rain sensor

karch

Interesting RAIN SENSOR thread!

Boardburner2

My car has a rain sensor for the wipers.
It is optical.

This can be had but is a bit pricey.
http://shop.weatherstations.co.uk/hydreon-rg-11-optical-rain-sensor-800-p.asp

hammy

Used optical car rain sensors are on eBay , and are cheap
- need a hack to use ?

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