rain sensor status unstable

[ramblinwreck]

Hi Ray, et al,

I’ve got the Arduino based OpenSprinkler v2.1s + Zone Expansion Board v2.0 (my setup shown here: http://rayshobby.net/phpBB3/viewtopic.php?f=10&t=784), and it has been working flawlessly until last night when we got a lot of rain. OpenSprinkler is giving very odd behavior on the rain sensor status.

I’ve got a Hunter rain sensor wired into my OS controller (simple non-powered, non-wireless model), and the sensor is enabled. Up until last night it has correctly indicated “no rain”. Last night, we got about 2.5″ of rain in about 8 hours so I expect the sensor to ‘tripped’ (indicating rain). But what is happening is that the sensor status is toggling every few seconds between “no rain” and “rain detected”. I have determined this by:
(a) Observing the LCD screen — the little rain cloud icon appears, disappears, and then reappears every few seconds
(b) Manually reloading the webpage hosted on the device repeatedly shows the status is not stable (i.e. sometimes “no rain”, sometimes “rain detected”)
(c) When loading Samer’s mobile app, it sometimes does not indicate rain detected (initially thought this was a bug in the app, until I discovered (a) and (b))

Any ideas what’s going on? Does this sound like a bad rain sensor (it’s brand new, hasn’t been physically damaged far as I can tell), or maybe I’ve hooked up something wrong?

Anyhow, my limited understanding of the rain sensors is that it’s either a normally closed (or normally open) switch, and when it gets wet, it opens (or closes) the switch. So can I test the sensor with a simple continuity check using my multimeter?

One more thing — I have the rain sensor ‘normally open’ option *unchecked*, as this seemed to produce a constant “no rain” status when it was dry (and checking the ‘normally open’ option produced a constant “rain detected” status when dry). So I think (normally open == unchecked) setting is correct. But even if I had it wrong, I wouldn’t expect that to cause this unstable behavior (I’d expect it to tell me it’s raining when it’s not, and vice versa). Anyhow, I tried checking “normally open” and I still get the unstable/toggling status behavior.

Let me know if you guys have any ideas what I should check. Even though I can manually disable/enable irrigation from my phone, I do like the idea of an actual sensor disabling the system in case I forget.

Thanks
Chris

[ramblinwreck]

OK, powered off the OpenSprinkler, unplugged the rain sensor wires. Powered unit back on. Observations:

* OS unit indicates a steady/stable “rain indicated” status (I suppose this is expected since OS configured for “normally closed” sensor, and unplugging opens the circuit?)

* DMM indicates steady/stable “open circuit” across the 2 rain sensor wire ends (I suppose this is also expected for a “normally closed” sensor that is currently wet). I checked on continuity setting (reading: no continuity), and on resistance/ohm setting (reading: overloaded).

* Power OS off. Re-attach plug to wires, and reinsert plug to OS. Power ON. Unstable rain sense status again. 🙁

Seems to me like the rain sensor is behaving as expected by providing an continuous/steady open circuit. What should I check next?

[Ray]

Which type of Hunter rain sensor do you have? Can you post the model number? I think it has to do with either the way this particular sensor works, or there may be a loose connection somewhere.

If it’s a simple normally closed sensor, when it detects rain the two wires on the rain sensor should remain open-circuit. You can use a multimeter to verify this. Normally open sensors are the reverse way. If the multimeter shows that it connects and disconnects and repeats like that, then the sensor will not work with OpenSprinkler.

[ramblinwreck]

@ray wrote:

Which type of Hunter rain sensor do you have? Can you post the model number? I think it has to do with either the way this particular sensor works, or there may be a loose connection somewhere..

I am 99% sure it’s the Hutner Mini-Clik, but I will confirm when I get home. Here it is:
(product page) http://www.hunterindustries.com/irrigation-product/sensors/mini-clik
(manual) http://www.hunterindustries.com/sites/default/files/IC_MiniClik_dom.pdf

@ray wrote:

If it’s a simple normally closed sensor, when it detects rain the two wires on the rain sensor should remain open-circuit. You can use a multimeter to verify this. Normally open sensors are the reverse way. If the multimeter shows that it connects and disconnects and repeats like that, then the sensor will not work with OpenSprinkler.

Everything I read suggests that it is a simple normally closed sensor (there is a 3rd wire to provide support for normally open controllers, but this isn’t used in my installation). I confirmed with my multimeter that it showed “open circuit” when the sensor itself was wet. I did not measure the wires while they were attached to the controller, but rather disconnected them and then measured at the tips of the disconnected wires. It was not inconsistent — I had a solid/stable “open circuit” reading. I did not test the sensor with a meter when it was dry, but I will do that this evening (that said: the “no rain” status has been working correctly, the problem occurs only when the sensor gets wet).

[ramblinwreck]

Ray, just confirmed that my rain sensor is in fact the Hunter Mini-Clik (see previous post).

Tonight I re-tested the rain sensor wires (disconnected from OpenSprinkler) with my multimeter. As the external sensor itself was dry, I had to use the little “self test” button on top of the sensor to trigger the rain shut-off function (i.e. open circuit). What I found:

No rain (self-test button not depressed): closed circuit — almost 0Ω reading between the wires
Rain (self-test button depressed): reading between 4 to 5 MΩ between the wires

I re-checked several times, tested by connecting to the screws on the plug, as well as on the raw wires (green plug removed), and I was always getting 4-5MΩ reading.

Do you think this could be the problem? I wonder how I can tell if this is “in spec” for this particular sensor (in which case the sensor is just not compatible with OS), vs the sensor is truly defective. Is this outside what OpenSprinkler expects to see?

[Ray]

just confirmed that my rain sensor is in fact the Hunter Mini-Clik

Just checked the spec of this and it should work with OS. I suppose it’s normally closed.

No rain (self-test button not depressed): closed circuit — almost 0Ω reading between the wires
Rain (self-test button depressed): reading between 4 to 5 MΩ between the wires

This sounds good.

I re-checked several times, tested by connecting to the screws on the plug, as well as on the raw wires (green plug removed), and I was always getting 4-5MΩ reading.

I didn’t quite understand this: do you mean that when it’s connected to OS, it always appears as open circuit (i.e. 4-5Mohm reading), even when you don’t press the self-test button? Because it’s normally closed, it should be almost 0ohm when self-test button is released. I can’t imagine how connecting it to OS would affect this.

[ramblinwreck]

@ray wrote:

I re-checked several times, tested by connecting to the screws on the plug, as well as on the raw wires (green plug removed), and I was always getting 4-5MΩ reading.

I didn’t quite understand this: do you mean that when it’s connected to OS, it always appears as open circuit (i.e. 4-5Mohm reading), even when you don’t press the self-test button? Because it’s normally closed, it should be almost 0ohm when self-test button is released. I can’t imagine how connecting it to OS would affect this.

No, sorry I was not clear. In all cases the rain-sensor was disconnected (i.e. unplugged) from the OpenSprinkler controller itself when I measured with the meter.
What I’m saying is that I checked, when the self-test button was depressed:
(a) by leaving the green plug on the rain sensor wires and touching the meter probes to the two screws on the plug
(b) be removing the green plug from the rain sensor wires and touching the meter probes to the wires directly

I wanted to rule out that the possibility that the plug itself was defective and was somehow shorting the two rain-sensor wires making it appear closed (i.e. no rain) when it should have been open (i.e. rain detected). But that wasn’t the case — I got the 4-5MΩ reading both ways (i.e. using ‘a’ and ‘b’ methods). So I don’t think the plug is defective.

—

So I think we’re in agreement that the rain-sensor is operating correctly and that it should work with OpenSprinkler? In that case, does this suggest I might have a defective unit? Is there anything else I can check here?

[Ray]

Earlier you said

the little rain cloud icon appears, disappears, and then reappears every few seconds

This is quite strange and the only thing I can think of is if there is a loose wire somewhere. In any case, you can send an email to [email protected] to arrange for a replacement.

[ramblinwreck]

Just a final update to say problem solved. There is/was no problem with OpenSprinkler. Problem was in the long run of underground wire that connected my OpenSprinkler (inside garage) to where the rain sensor was mounted externally (sitting on an outside fence post).

I dismounted the rain sensor from fence post and connected it directly to the OpenSprinkler with a short 6″ wire and tested it and it worked perfectly. I also re-connected long underground wire (formerly connected to external rain sensor) to OpenSprinkler without the sensor on the other end so that it should present “open circuit” to OpenSprinkler, and when I did that I got the toggling on/off status problem. So I reckon there must be some kind of short in the underground wire that was root cause of issue.

I ran a new wire to the external sensor and now all seems to be working properly.

I should have thought to do this check earlier, but in any case, thanks for the support.

[Author]

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