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Rain sensor

rain sensor

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#1 Giuliano

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Posted 04 February 2013 - 07:25 PM

Good day everyone,

 

Does anybody know where I can get a rain sensor I can use in my project? My car has a rain sensor that activates the windshield wipers automatically even with a sprinkle, the problems I can't find where is located to see how it look.

 

Please advise.

 

 



#2 CW2

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Posted 04 February 2013 - 07:43 PM

Most likely it is on the windshield - if you don't see it, it is probably behind the rear-view mirror. Usually, it looks like small box attached to the windscreen (from inside), it can be integrated into the rear-view mirror holder. From outside it should look like some kind of lens surrounded by black area.
 
The wikipedia article provides description of how it works...
 
But for simple rain detector, a PCB with a few separate traces should be enough - you measure the resistance or capacitance, which changes after raindrop shorts adjacent traces, something like this.

#3 emg

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Posted 04 February 2013 - 07:50 PM

look up around the rear view mirror. The ones I've seen are optical and use an IR led and sensor. They work by sensing a change in the amount of light reflected from the windshield, which changes when there are water droplets on the glass over the sensor.



#4 JerseyTechGuy

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Posted 04 February 2013 - 08:24 PM

The rain sensor in a vehicle is a non conductive rain sensor.  Boats, weather stations and basement water detectors work on a conductive (resistive) method knowing that water conducts some amount of electricity between the contacts... but back to the automotive non conductive version...

 

The sensor in your car is nothing more than a IR emitter and detector pair that monitors for changing environmental conditions.  In order to detect those conditions the windshield is needed as it reflects back some amount of the IR thus the mounting position on the dashboard or Rear View mirror.  As rain lands on the windshield the reflectivity changes causing more of the IR to be reflected back due to the obstruction.

 

So you should easily be able to build one using a standard IR xmit/recv sensor, but you'll need something to act as the windshield like a plastic dome of some type.

 

Here is a commercial one:

Hydreon Optical Rain Sensor

 

The other option is go to your local Mercedes or BMW dealer and try to buy the replacement sensor which you can likely connect to an analog input.  You'll just need the plastic dome to make it work.



#5 Verdris

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Posted 04 February 2013 - 11:42 PM

Another way to make a rain sensor is to combine a disdrometer and a humidity sensor. You can hack together a disdrometer with a simple piezo disk wired to an ADC. The humidity sensor is to verify that the readings coming from the piezo are indeed correlating with rain.

 

As rain hits the piezo, the force will cause a small voltage change which the Netduino's ADC can measure. You can even science out drop size and velocity (my research group builds these all the time) and then track changes in humidity.



#6 Giuliano

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Posted 05 February 2013 - 06:01 PM

Really interesting. Thanks everyone for the input.



#7 Giuliano

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Posted 05 February 2013 - 08:50 PM

 

The rain sensor in a vehicle is a non conductive rain sensor.  Boats, weather stations and basement water detectors work on a conductive (resistive) method knowing that water conducts some amount of electricity between the contacts... but back to the automotive non conductive version...

 

The sensor in your car is nothing more than a IR emitter and detector pair that monitors for changing environmental conditions.  In order to detect those conditions the windshield is needed as it reflects back some amount of the IR thus the mounting position on the dashboard or Rear View mirror.  As rain lands on the windshield the reflectivity changes causing more of the IR to be reflected back due to the obstruction.

 

So you should easily be able to build one using a standard IR xmit/recv sensor, but you'll need something to act as the windshield like a plastic dome of some type.

 

Here is a commercial one:

Hydreon Optical Rain Sensor

 

The other option is go to your local Mercedes or BMW dealer and try to buy the replacement sensor which you can likely connect to an analog input.  You'll just need the plastic dome to make it work.

 

Hi Dave, have you used the Hydreon sensor with the Netduino?



#8 JerseyTechGuy

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Posted 05 February 2013 - 08:59 PM

I have not however someone I know used it with a Sparkfun weather shield to capture various weather conditions.  They however were using an Arduino not a Netduino.



#9 Giuliano

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Posted 05 February 2013 - 09:44 PM

Thanks for the input Dave. So on theory it can be done using its serial output, right?

#10 JerseyTechGuy

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Posted 05 February 2013 - 10:09 PM

Thanks for the input Dave. So on theory it can be done using its serial output, right?

 

That is correct. It should connect however is is RS232 (like) connection 1200baud according to the doc so you'll likely need something like an RS232 shield as the Netduino doesn't support RS232 levels directly.



#11 Giuliano

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Posted 06 February 2013 - 12:50 AM

That is correct. It should connect however is is RS232 (like) connection 1200baud according to the doc so you'll likely need something like an RS232 shield as the Netduino doesn't support RS232 levels directly.

 

Oh I see, can you recommend a RS232 shield?



#12 JerseyTechGuy

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Posted 06 February 2013 - 01:13 AM

check this thread. Chris Walker recommended one in post #5.  http://forums.netdui...o-rs232/?p=4986



#13 Giuliano

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Posted 06 February 2013 - 10:49 PM

Hi Dave,Is this the weather station your friend is using?https://www.sparkfun.com/products/8942

#14 JerseyTechGuy

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Posted 06 February 2013 - 11:04 PM

I think he pieced it together himself.  That one from sparkfun looks pretty nice.  Didn't even know they had it.  Might need to get one for myself. :D



#15 Giuliano

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Posted 08 February 2013 - 06:51 AM

I think he pieced it together himself.  That one from sparkfun looks pretty nice.  Didn't even know they had it.  Might need to get one for myself. :D

 

Right, it looks pretty cool, I need to get my hands on it but I already ordered the Hydreon RG-11 but I am still need to get a RS232 shield for it.



#16 Giuliano

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Posted 23 February 2013 - 06:34 PM

I ordered the RS232 shield below:

 

http://www.cutedigi....or-arduino.html

 

I'll le you know how it works once it arrives.



#17 Giuliano

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Posted 05 March 2013 - 11:16 PM

I got the RS232 Shield and found out that it will work just fine with the Netduino Plus and Arduino but not with the Netduino Plus 2 since the pins on it are not designed to work with the Netduino Plus 2 unless I am wrong and there is way to get it to work, of course it would be nice to mount it on top of the N+2.http://www.cutedigi....or-arduino.htmlAny ideas? Is there a RS232 shield built for the N+2?

#18 Giuliano

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Posted 07 March 2013 - 10:09 PM

Moving my last question to the N+2 forum.

#19 Fahdil

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Posted 28 January 2014 - 07:36 AM

If I were u... maybe I will try to using... resistant wire.... (cheap solution)

 

if any water falls on the cable... it will change it's resistance and you can trigger any digital I/O. I was use it as water level recorder.

 

and I found this solution on my bike fuel tank also.

 

wire the cable like this (it's 1 cable), once any water drop in the middle of string it will changes its resistance. 

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#20 Giuliano

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Posted 28 January 2014 - 11:52 PM

Good suggestion, I'll give it a try, thanks Fahdil.






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