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Need ideas for rain sensor

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#1 kathyastro

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Posted 25 September 2020 - 08:12 AM

I have a rain sensor on my observatory that uses a commercial water leak detector.  Two wet-leaf sensors on the roof cause the detector module to send a signal to the dome controller to close up.  It works well.

 

Too well, in fact.  The wet-leaf sensors do not distinguish between rain and dew.  So even though I use a solid-tube Newtonian in a dome, about the most dew-proof configuration possible, my sessions get cut short by a little bit of dew.  (The good news is that I know I am well-protected against rain, but it is annoying.)

 

So, I am looking for ideas for a sensor that would detect rain but not dew.  Anyone have a creative solution?



#2 SarverSkyGuy

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Posted 25 September 2020 - 08:16 AM

What about using a dew heater to negate the dew hits?


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#3 sickfish

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Posted 25 September 2020 - 08:27 AM

A lot of sprinkler systems have rain detectors of different sensitivities.


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#4 xthestreams

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Posted 25 September 2020 - 08:46 AM

Buy an RG11, built in heater and droplet sensitivity - only downside is that it requires 12-13.8v  https://rainsensors.com/ 

I love mine, saved my bacon 5 times this year. 


Edited by xthestreams, 25 September 2020 - 08:47 AM.

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#5 ssagerian

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Posted 25 September 2020 - 08:57 AM

Buy an RG11, built in heater and droplet sensitivity - only downside is that it requires 12-13.8v  https://rainsensors.com/ 

I love mine, saved my bacon 5 times this year. 

Funny... their website... RG11.."Sophisticated, but inexpensive to produce." $59 each



#6 TOMDEY

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Posted 25 September 2020 - 09:43 AM

I have a rain sensor on my observatory that uses a commercial water leak detector.  Two wet-leaf sensors on the roof cause the detector module to send a signal to the dome controller to close up.  It works well.

 

Too well, in fact.  The wet-leaf sensors do not distinguish between rain and dew.  So even though I use a solid-tube Newtonian in a dome, about the most dew-proof configuration possible, my sessions get cut short by a little bit of dew.  (The good news is that I know I am well-protected against rain, but it is annoying.)

 

So, I am looking for ideas for a sensor that would detect rain but not dew.  Anyone have a creative solution?

Hi, Kathy... this one is sure creative! >>>

 

There was an old episode of "Watch Mister Wizard" from the 1950's. He was always making nifty gizmos from things around the house that demonstrated the principles of physics, chemistry, astronomy, electronics, physiology, psychology, engineering, etc. His rain detector was a clothespin with an aspirin tablet in the jaws, and an upward-pointing funnel above the tablet. Two wires in an alarm circuit contacted when the jaws closed. You would, of course, have to re-set the thing after each trpping!    Tom


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#7 xthestreams

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Posted 25 September 2020 - 07:31 PM

For what it does it’s reasonably priced IMHO

 

Functionality wise, its about the size of a tennis ball and contains a series of optical sensors, a relay, a heater (to dry itself to ensure readings are accurate) and a microprocessor to that enables everything drop simple rain drop detector (No/NC switch) to a droplet counter with a variable sensitivity for detection events and a user selectable guard timer to reduce hysteresis (don’t reopen relay until 0-15m after last rain drop just in case another drop is on its way).
 

If I was to try and build that myself with something like an Arduino that’s still rugged (like Kathy I looked at a lot of options) $60 went pretty quickly and I could be sure it would be reliable. “off the shelf” the only thing that came close was at the AAG/Boltwood level of pricing, so $60 seemed like a fair trade of time, money and sophistication. But $60 is also $60 to your point.

 

Funny... their website... RG11.."Sophisticated, but inexpensive to produce." $59 each


Edited by xthestreams, 25 September 2020 - 07:33 PM.

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#8 DavidTrap

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Posted 25 September 2020 - 08:13 PM

If you just want to detect rain, get the Hydreon optical sensor.   

 

I use one as a last line of defence in a remote autonomous observatory.

 

The roof motor controller has a staircase timer - if it's not prodded with an open command every 90 seconds from the software, it automatically closes the roof (assuming the PC has failed) after the staircase timer has expired.

 

If for some reason, the AAG weather sensor was providing bad data to the roof control software, it could continue to send that open command every 90 seconds and the roof would stay open in spite of rain.

 

The Hydreon optical sensor is wired, via it's normally closed relay, in the cable that runs from from the software controlled relay box to the motor controller.   If the optical rain sensor is triggered, the normally controlled relay is opened and the regular open signal to the roof controller won't get through - the staircase timer will then close the roof.

 

I've located the optical rain sensor inside the observatory - ideally, it should never see any rain, because the roof would have been closed.

 

It's never false triggered from the dew as it has an inbuilt dew heater.

 

I've tested it with a few drops of water and it does what I want it to do.    Cheap insurance IMHO.


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#9 my-spot

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Posted 25 September 2020 - 09:40 PM

Hi Kathy,

 

I currently use a Hydreon RG-11 in tipping bucket mode along with my DIY WX station/software. One minor issue is that I sometimes get a false positive and it can be slow to detect rain. However, I cannot be sure that it is the RG-11 or my DIY WX station. For my next station, I intend to use a Kemo M152K capacitive rain sensor. It doesn't measure rain like the RG-11 but a single drop triggers it. Also, the pad is heated so it should control dew, melt and detect snowfall, and it dry the drops off after the rain stops. The biggest problem, like so many things lately, is finding one of these in North America.

Attached Thumbnails

  • Kemo_Rain_Detector_800.jpg

Edited by my-spot, 25 September 2020 - 09:43 PM.

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#10 kathyastro

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Posted 26 September 2020 - 08:28 AM

Summarizing the options:

 

- RG11: (+) Simple installation; (-) cost, sensitivity(?).

- Kemo M152K: (+) simple, sensitive; (-) cost.

- dew heater under existing sensor: (+) simple, sensitive; (-) cost.

- DIY heater under existing sensor: (+) cost; (-) some assembly required.

 

I have seen comments about the sensitivity of the RG11, that it may take a few minutes of rain for it to respond.  One of the things I like about my existing wet-leaf sensor is how it responds instantly.

 

The Kemo unit uses the same principle as my existing sensor, but with a heater built-in.  However the price is in the same ballpark as the RG11.

 

The dew heater option looks appealing, but the cost of a heater strap and controller total more than the RG-11.

 

The DIY heater cuts a few buck off the cost of a dew heater, but still requires the PWM controller.  Probably not worth the hassle of building it.

 

It looks like I have to decide between the RG11, with many recommendations, or the Kemo, with good response time and sensitivity.  I appreciate all the comments.  Please keep them coming.


Edited by kathyastro, 26 September 2020 - 08:31 AM.


#11 dghent

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Posted 27 September 2020 - 12:40 AM

Hmm, I came across this thread randomly and this RG-11 has piqued my interest from a small electronics project point of view. It seems like something that would be pretty handy to have wired into an arduino or RPi and an ASCOM Safety Monitor driver created for it.



#12 dghent

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Posted 27 September 2020 - 12:42 AM

Hi Kathy,

 

I currently use a Hydreon RG-11 in tipping bucket mode along with my DIY WX station/software. One minor issue is that I sometimes get a false positive and it can be slow to detect rain. However, I cannot be sure that it is the RG-11 or my DIY WX station. 

Could you use two (or even more) RG-11s and trigger if they all agree that it's raining? Kinda provide some checks on a false-positive (or even false-negative!) and perhaps even some redundancy.


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#13 OhmEye

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Posted 27 September 2020 - 09:34 AM

I got one of RG-11 also https://rainsensors....products/rg-11/

I haven't wired it up yet, it has several modes. I plan to start with just the "It's raining mode" and only add a second one if I get false positives.


Edited by OhmEye, 27 September 2020 - 09:38 AM.


#14 xthestreams

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Posted 27 September 2020 - 10:01 AM

The only false positives I’ve had is when I suddenly move my hand onto the dome/sensor area, I guess it rapidly changes the total internal reflection profile and hence “it’s raining”. 
 

as for missing a droplet, not once, and I do mean even a single raindrop. 
 

having said that, I’ll look into the Kemo, looks elegant.

 

final point, there’s a great open source weather station that is INDI compatible that I suspect could be made ASCOM ready (Windows... shivver.... ;-) that I’ve hacked the RG11 code into. 
 

Could you use two (or even more) RG-11s and trigger if they all agree that it's raining? Kinda provide some checks on a false-positive (or even false-negative!) and perhaps even some redundancy.



#15 rpineau

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Posted 27 September 2020 - 01:29 PM

The RG-11 can be very sensitive.. if you set it to the proper mode using the dip switches inside.

I have it configured for  Mode 1 , "it's raining"  using the dip switches inside (detailed in the doc too) :

1 - off
2 - off
3 - on
4 - off
5 - on
6 - off
7 - off
8 - off

1,2 off = Very sensitive-- first detected raindrop
3 on = Output Monostable Extended by 15 minutes so that it doesn’t do a close, open, close, open, .. dance and wait 15 minutes (aka stays closed for 15 minutes).
4 off = no dark detect .. we’re trying to detect rain … not when it’s dark.
5,6,7 = mode select = mode 1, it’s raining.
8 off = Disable Micro-power Sleep Mode, leave internal heater on -> prevents dew.


So this is not the default configuration and that might be why people are seeing a lag in rain detection with the RG-11.


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#16 my-spot

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Posted 27 September 2020 - 09:08 PM

Another sensor I was looking into was this one...

 

https://www.radiocon...ain-sensor.html

 

The only problem I had was I was looking into these during the covid lookdowns and shipping from Italy at that time was not a sure bet.


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#17 xthestreams

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Posted 19 October 2020 - 02:56 AM

The Kemo looks like my new Cloudwatcher, not a fan of the rain sensor compared to the RG11. One drop triggered the RG11 last night, it took a much larger amount of water to get the Cloudwatcher to pick it up and there’s the annoying problem of calibration.

 

im loving my RG11 more every day 



#18 deonb

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Posted 19 October 2020 - 08:49 PM

Is the RG15 a better RG11 or a different thing altogether?

How do either of these fair with very very fine light rain? Something like a mist-rain (Seattle).

 

I have a Tempest WX and it only detects our rain about 25% of the time.


Edited by deonb, 19 October 2020 - 08:52 PM.


#19 rpineau

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Posted 19 October 2020 - 08:55 PM

The RG15 is missing the “It’s Raining” mode so i's really meant to be used as a digital tipping bucket.

The new RG9 has the “It’s Raining Mode” and is $10 cheaper than the RG11 and can be sued in the same way as thr RG11 if you want to close on first drop.

https://rainsensors....del-comparison/

 


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#20 Raginar

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Posted 20 October 2020 - 01:26 PM

https://rainsensors.com/

 

Works really well and has a heater/can determine between dew and rain.  



#21 xthestreams

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Posted 23 October 2020 - 05:07 PM

I’ve not had experience with mist rain, but I assume a spray bottle mister could simulate it? happy to try 




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