Real Time Rain sensor


Active Member
Do you know of any rain sensor that would trigger a signal just as the first few drops of rain are starting to fall? I think that some cars have this sensor for turning on the wipers, but for HA all what I have seen are irrigation sensors. They will trigger the signal after being saturated, and will drop the signal after the sensors have dried off (at the same rate that soil uses to dry). This is good for irrigation control, but does not tell me when it is raining at home.

The rain gauge is another option, but it also takes long to react.

I want to know when it starts/stops raining at home. I found something here:
but I dont know if this is real time and second, but not less important, it is waaayyyy out of budget.
Actually you can make one yourself. Check THIS out. This home made sensor triggered just after a few drops of water hit the coils.

I did this just for the proof of concept one day.
Cool, I would spend the four bucks and get Eric's sensor. You have an Elk correct? You could hook it up as an analog zone and use a rule to trigger a warning when it detects rain. I'm going to order a couple and will report back

Sorry for the slight Hijack of this thread, but here goes. Hey Eric. Since I'm ordering stuff on your site... I'm in a "spending" mood (which is rare for me) but unfortunately a lazy one also (it's 11:30 PM now). Can you kindly list everything I would need to incorporate two or three of your Temperature Sensors and one Wind Instrument with a one wire solution that I can run around my home and read these numbers as HomeSeer (ver 1.7.43) devices? What software is available to plot/store the results? I've read about some weather station type software. What is a reasonable solution.

I'm looking for everything I would need including adapters, power supplies, etc... ;) I will probably go with the serial interface and use my Edgeport 8 (any problems using those with your serial interface? Any advantages if I were to go USB instead?)

How accurate are the temp sensors (resolution in degrees F)? I would like to get this up quickly (will get pre-made cables/adapters if necessary as I'm not interested in creating a science project) so I appreciate the effort. Do you provide schematics of how this all fits together? Also, I would like everything pre-assembled (not looking for DIY kits, especially with surface mount components). Also, I may want to use the temp sensors outdoors (do you offer a weatherproof design)?

All of my wiring (cat 5e or RG-59 coax) lands inside my wiring closet, so I would probably use a "star" type topology (if that's the best solution, looking for advice here).



I don't mind helping you figure out what you would need but to get a bit more info on 1-Wire you may want to take a look at our How-To's.

This reply may come out in a random order since it is getting a bit late here but hopefully I will answer all your questions.

Using an Edgeport will work fine. I have one on my test machine (a laptop with no serial ports).

If you want to go with a star topology then it would be best to go with a Hub. Since you want to go serial and don't have an existing setup I would recommend the 6 Channel Master Hub since it is cheaper than the Serial Adaptor and the 6 Channel Hub which it replaces.

For cabling you can use standard network cables. Currently we don't offer any cables except for an Adaptor cable to connect the Wind Instrument's RJ-12 to our standard RJ-45.

The resolution of the temp sensors is something like 0.01C but the accuracy is 0.05C.

It is really easy to hook everything up because almost all of our devices have dual RJ-45 jacks on them so you can just wire them up in a daisy-chain fashion, or with a hub you can use a star topology.

We don't have a "weatherproof" enclosure but if you get the Moisture Resistant Coating and use one of our cases (or shield the device from most of the elements) the device should work for a long time outdoors. We have many customers that have our devices mounted outdoors that have been working for years. An additional step you can take to enhance the weather resistance would be to put a spare RJ-45 connector in any unused jack on devices used outdoors.

Here is a suggested list that will get you up and running and have the ability for future expandability.

- 6 Channel Master Hub
- AC Adaptor (You can use an adaptor that can provide 9-24v DC with a 2.1mm venter positive connector)
- Wind Instrument
- Adaptor Cable for the Wind Instrument
- Temperature Device (How ever many you want to add)
- Temperature Case (You don't have to have these, except I would definitely use them on any devices to be used outside)

I don't use HomeSeer anymore but one of the MCS1Wire plug-in supports almost all of our devices and I think it has the plot/store you are looking for.

Also since this is getting way off topic we may want to continue this thread in the Hobby Boards support forum.

Let me know if you have any other questions.


Thanks for the reply. I will start a new thread over at the Hobby Boards forum.


The five dollar sensor from Eric still seems to be the best value. I'm going to order a couple and play around with biasing it (or maybe no bias is even necessary) and connecting it up to the Elk M1 Gold.
That's probably true that these sensors are cheaper but for us users that don't even know what "biasing" is and considering contact closure is about the limit of my understanding, I would have to go with the simple stuff. I'm so electronically challenged that it's scary.
Rupp said:
That's probably true that these sensors are cheaper but for us users that don't even know what "biasing" is and considering contact closure is about the limit of my understanding, I would have to go with the simple stuff. I'm so electronically challenged that it's scary.

I quickly glanced at that product and didn't see that it provided contact closure. I'm thinking it works the same way Eric's sensor works in that it changes resistance when water is in contact with it.

The Elk M1 Gold has a lot of input options, so a user may only have to connect these type of sensors to a zone (I just don't know the proper configuration option at this point till I get one in and play around with it). Once I know the resistance change I can post how to make these work with items such as a power flash, Elk M1 Gold, Analog to Digital boards, etc...
For those of you following the "Hobby Boards" portion of this thread, I started a new thread HERE in order to keep this one on track. (PS I could really use some HomeSeer advice in that new thread).

We now continue with the original thread topic...
Rupp, "biasing" simply means adding a fixed offset voltage or current in order to get a device's response in the range or sensitivity that you need. This is used a lot in electronics. A mechanical analogy would be a situation where you designed a fancy new mousetrap mechanism that works great, but needs 50 grams in order to trip it, but a mouse weighs only about 20 you add a 45 gram weight to the trip mechanism to "bias" is so that only 5 more grams is enough to trip it. :)

BSR, the thing about Elk analog inputs is that there is no easy way to remove the internal 2200 ohm pullup, which might make certain devices hard to interface. It would be nice if Elk offered a input board version with jumpers for this.
Exactly what I was thinking Guy. I'll get this in and play around with it and see what it does in terms of water/no water resistance (value) changes.

BTW: I think Spanky (David) said the surface mount resistor could be easily bypassed/shorted!?!