How to connect wired rain sensor to 2 gen2 controllers?

How do I connect a single wired rain sensor (Rain Bird CPRSDBEX) to 2 independent gen2 sprinkler controllers? Do I just splice in additional wires to the rain sensor and connect them with same connections as shown for single controller?

Are your controllers outdoors or indoors? If outdoors do you have a rachio outdoor housing? How comfortable are you with DIY projects (do you prefer easier but more expensive solution or cheaper solution which can involve some soldering)?

Hi Gene,

One unit is indoors and the other unit is outdoors with the rachio housing. I’m very comfortable with DIY projects and use my soldering iron often. I’m an elect. eng. My concern is with splicing is that the unit must be driving a voltage to the rain controller. Having two units driving a voltage on the same wire, probably not a good thing. I imagine the easy solution you may be thinking of is using two different rain sensors. I thought of that but would prefer not to go that route if possible.

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Great, me too.

Actually I was going to suggest a simple relay

DPDT like this (Amazon)

Here is the user manual

I’ve added a schematic in the later post (here)
Total cost less than $10 if you don’t need a water proof housing.

Let me know if it works for you.

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How far apart are the controllers?

Pending the distance between controllers, it may be easier to install a second rain sensor. There’s a wired sensor available for $15 on Amazon or a wireless sensor available for $35 on Amazon.

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Hi Gene,

I would like to thank you for your help. I do want to implement your relay recommendation. However, I’m not an expert on relays and can’t equate how to connect the relay as you outlined using the schematic you provided. Could you tell me the connections to the relay via the terminal posts numbers 1 through 8 shown in the schematic? Thanks again.

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Let me know if this makes it any clearer. Don’t hesitate to ask questions :slight_smile:

Rain sensor polarity does not matter, relay will be CLOSED when Rain Sensor is CLOSED and visa versa. Setup your rachios as needed to use Normally Closed rain sensor on S1.

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thanks Gene! Exactly what I was looking for.

I’ve thought about this rain sensor. It only has two wires going to it. I’m thinking it is a simple mechanical on/off (SPST) switch. When the water reaches a certain level the circuit is either open or closed. Let’s assume S1 is sourcing the voltage. Then couldn’t we just use one of the controllers S1 connection to the rain sensor (red) and then run both SC connections to the remaining connection (black) on the rain sensor? This of course assumes one S1 connection can drive two controllers. This would eliminate the need for relay. I should probably dig out my multimeter to see if this is the case.

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How are your controllers wired now? Are valve commons (C terminals) connected together?

S1 terminals are inputs, SC is actually the terminal sourcing AC voltage.

If your commons are tied together (there is no meaningful AC voltage between the C terminals of the two rachios). Than you can try running a wire from S1 terminal of one rachio to S1 terminal of another. Set them up as Rain sensor and make sure that neither rachio shows that rain sensor is activated. If everything looks to be working so far, than you can connect that wire via the rain sensor to SC terminal of one of the rachios.

Warning! Only attempt this if your Rachio units share a common wire to your valves. The wire between SP terminals is optional. I’m not sure if you will end up needing it.

Note: This setup is prone to noise on the wire. When it rains Rain sensor will disconnect and leave the two inputs floating. Flawless operation is not guaranteed.

Perhaps @emil may provide better details on how the rain sensor data is interpreted. From what I understand, as soon as rain sensor dries out rachio will resume business as usual.

Having never used a rain sensor I do not know if, for example, automatic schedule will be skipped in the evening if rain sensor got wet during the day (but has since dried out).

Because of this I’ve never connected my old rain sensor to my rachio (even though I had one available). In reality you are much better off using an actual rain measurement from one of your local weather stations. If you don’t have a good one available, you can try searching Weather Underground and porting the data via API.

Hi Gene,

Again, thanks for the input. I think at this point I’m going to have one unit enabled with the rain sensor (it’s already connected).and the other without the rain sensor. I can always disconnect the rain sensor if I’m not happy with the performance.


Hey @rysktkr-

You may be able to set up an applet with IFTTT to rain delay your other controller without the sensor a certain number of days when your rain sensor triggers- would you be interested in trying that? Sounds like it may be easier than the dual installation…

McKynzee :rachio:

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Sounds like a plan :slight_smile: Make sure that rain sensor is worth the trouble.

By the way, another way to use the rain sensor with both rachios is to put it physically inline with your valve common wire. So Rain sensor would connect to where ever your valve commons currently connect and your valve commons would connect to the other rain sensor wire.
This would physically prevent watering during the rain (which is the purpose of the rain sensor), but would not show up as any sort of event in rachios.

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@Gene, correct. The rain sensor acts as a switch that stops all active schedules when it’s enabled.

This feels like a trick question :wink: …at this time, the data from your rain sensor is not used in weather intelligence (i.e. Rain Skip) calculations. However, most of the time we’ll know it rained and skip your schedule.