water leak sensor confusion

[littlebill]

so im building a water leak alarm

i bought eBay auction: #231594180289 this

the issue i am having is, i apparently have no idea how to read the sensor or its broke. i ordered another one but it will be a couple weeks

i was expecting this to act like a reed switch or VAR,

using my ohm meter, there is no difference with dropping it in water,

using a arduino i did a analog read and it shows continuity regardless of touching it or not,

but tieing it to a digital pull up pin, and tieing the other wire to ground, does not trigger a state change.

i cut it apart and there are smd 10k resistors and a diode on 1 side (well there was)

i had continuity on 1 wire and not on the other to the pins?

does this sound normal? any idea's? they obviously don't show a schematic

[picandmix]

As you have said they and other sellers of that item do not provide any circuit / connection details, and as you have destroyed yours its a bit of a lot cause, unless you want to order some more.

There are masses of water detectors for the Arduino out there, here is just one.
http://forum.arduino.cc/index.php?topic=5961.0

What kind of leak / area are you trying to protect  ?

[Gyro]

Reading the description the function seems pretty clear...

 Switch Type: Water or liquid touches the two copper contacts simultaneously to form loop circuit, and then send out the warning signal

It's simply a couple of copper contacts which press against whatever non-conducting material you fix it to - wooden floor etc, and when it gets wet you'll get a high impedance connection between them (depending on the conductivity of the water. Impedance will probably be in the 10s to 100s of k ohms for tap water.

You would get the same effect if you put a couple of screws in the floor and measured the resistance between them, though this does look a bit neater.

I think you're unlikely to have electrically damaged it. 

[nixxon]

And be very careful with the connections: "Connection mode: the red line contacts "positive pole"; the white line contacts "negative pole"" 

I will soon post a picture of a free and much better way to make a multi sensor solution that includes as many leakage sensor points as you like. It probably has an operating voltage of 0 - 250 Volts AC and DC!

I just need to get home and take a picture of what we have installer under the sink in our kitchen 

Can anyone guess what kino of multi sensor gadget I am refering to?

[littlebill]

well like i said it has diodes and resistors in it, or at least it did. i did order another one, i thought it was going to be simply 2 metal probes directly to the wires. but again not sure

im trying to detect water coming up through the floor in the basement, i want something fool proof, was hoping these would work

i wasn't sure i need resistors or anything, like i said i was expecting a reed like setup.. i know i can do 2 wires, was hoping this was cleaner

[Gyro]

Just thinking on my earlier comment. It sounds from your description that there is a transistor in the package that senses leakage with the contacts across its Collector-Base junction. Hard to think it can be any more complex because there are only two wires, so nothing to power it when triggered.

Hook it up to a PSU or 9V battery, White to ground, Red to Positive via a 1-10k resistor. Monitor the voltage on the Red lead when you dab a couple of wet fingers across the contacts. If the voltage drops to a couple of volts or less then I have done them a disservice.

[littlebill]

its destroyed... everything was potted. i had to cut it apart to find this out. i only had continuity on 1 wire, i thought the other was broke somewhere.

i will try again when the boat gets over here

[picandmix]

Have you got the space for one of the small cheap plastic float switches under the floor boards .

They use an internal  reed switch so interface to the Arduino could not be simpler  - indeed why use an ardunio, just the float switch ,battery and peizo sounder could do.. ?

[littlebill]

floor is concrete, and its being hooked to a air raid siren since my parents can't hear the piezo version which is currently there

[picandmix]

You say there is a peizo unit there already, could it not be hooked up to a relay so you can power a bigger siren.

Also consider this circuit which as well as turning on a  led can also be easily modified to turn on a relay.
http://www.instructables.com/id/Simple-Water-Sensor/

Even if you used such a sensor which would activate as soon as any water came though, such sensors are not the most reliable and I would suggest that you also use a  small float switch as a last line of defense,  so an inch ( or less)  of water would sound the alarm .

[nixxon]

I will soon post a picture of a free and much better way to make a multi sensor solution that includes as many leakage sensor points as you like. It probably has an operating voltage of 0 - 250 Volts AC and DC!

I just need to get home and take a picture of what we have installer under the sink in our kitchen 

Can anyone guess what kino of multi sensor gadget I am refering to?

Enclosed is a photo of the multi sensor. It is simply a flat cable with a pair of 1 mm² solid leads, like the ones you connect to door bells or really old speakers. The guy who installed it simply took his knife and shaved off a bit of the insulation every 10 cm or so to expose the wires next to each other. Then the sensor wire was attached with some hot glue to the bottom of the cabinet and underneath that, on the floor, under the dishwasher as well.

If the resistance gets low enough, the system thinks there is a water leak and a solenoid valve cuts off the main water supply to the house. Shorting the sensor cables does not trip the solenoid valve. I tested with an old resistor, maybe 1k or something, and that made the system shut off the water supply.

[LabSpokane]

If you can wait for a few hours, I will post a liquid detection circuit using an LM10 that will allow pretty much any reasonable electrodes.

[littlebill]

ordered a new sensor and got it working, link below is to the finish product.

http://www.dslreports.com/forum/r30170203-Water-leak-Alarm