Rain Bird rain sensor does not work with Mini-8
I have one of these RainBird sensors: https://www.amazon.com/Rain-Bird-CPRSDBEX-Mounting-Bracket/dp/B005MICVDY/
I noticed today that this sensor when connected to my recently installed RainMachine Mini-8 didn't seem to be working.
I verified that the 2-wire connection has continuity (is 'shorted') with a reading of .2 ohms when dry, and infinity (no reading) when wet. This morning I checked and confirmed that the circuit was 'open' when wet.
As soon as I connect the wires to my Mini-8 (per the documentation here: https://support.rainmachine.com/hc/en-us/articles/227832747-Rain-Sensor) the delay LED turns off after a few seconds - which explains why the Mini-8 has not been detecting rain. Apparently the Mini-8's definition of "open circuit" is... um, problematic.
Any advice on this issue?
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Additional information: I inserted a 4.7 megohm resistor in series with the "open" (wet) rain sensor and the delay LED energized. When the sensor is "closed" (dry) the delay LED goes out even though the total circuit resistance is approximately 4.7 megohms! Anyone else would call that an open circuit, especially since the sensor is designed to switch 24VAC at about an amp or so.
It would appear the Mini-8's test for open circuit is problematic, or I've got a defective unit. What are the specs for "open circuit"?
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You may need to go into the RainSensor settings on the RainMachine and switch it from Normally open to Normally closed (The RainBird default) and see if this helps.
We also want to make sure its wired correctly as in the diagram above.
After double checking both, let me know if you still have trouble.
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Hi Brandon - The sensor is wired correctly per the diagram and as noted it is normally closed (closed when dry, open when wet). That is how the RainMachine is set as well.
I found this post while searching so apparently this is a known issue. However, unlike the OP's sensor my RainBird sensor is brand new. I would think that for RainMachine rain sensor purposes any circuit resistance > 1K ohms or so should be "open".
https://support.rainmachine.com/hc/en-us/community/posts/115006894547-Rain-Sensor-Compatibility
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No, your software setting is correct - if I open the circuit by removing one of the wires (or as noted, add a 4 to 5 megohm resistor in series with the wet/open sensor) then the Delay LED is lit. If I short the circuit with a jumper (or when the sensor is dry, and therefore closed) then the Delay LED is not lit. If you like I can put a potentiometer across the Common / Rain Sensor terminal and tell you exactly what the trip point is - but we know empirically it is > 5 megohms. I suspect many rain sensor leads will have megohm resistance when wet/open just due to moisture levels, salt air, or whatever.
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Thanks - that is exactly what I did. Is this fixable in firmware or would it require a hardware change? I'll speculate that the two customers discussing this here https://support.rainmachine.com/hc/en-us/community/posts/115006894547-Rain-Sensor-Compatibility and myself are not the only customers who will be encountering this issue.
I appreciate the great support!
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Ian,
the trip resistance is 5.6Meg. There is a hardware hysteresis that prevents bounce, but other than that, any resistance under ~5.6Meg is detected as "no rain". Having a resistor of 1.5Meg in series with the sensor does one thing: it shifts the range upwards, allowing the usage of sensors which - when disconnected - don't show infinite resistance, but something around a few Megs. So, when the sensor is dry and shorted, the overall resistance of the circuit will be 1.5Meg and the input will read "dry sensor" because it is under the ~5.6Meg threshold. When the sensor is wet, the overall resistance will be 4.7Meg + 1.5Meg > 5.6Meg and the input will see a "wet sensor".
Istvan
RainMachine Support
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