Newbie - water detector circuit help please

Initially I was just thinking of just using etched copper board as we used to in school - is there a better/more reliable alternative?

Thanks,

Mal

--
I can help you, but what are you planning on using for moisture
probes?

--- Depends. I you're looking for the difference between wet and dry, that's probably as good a way to do it as any, but if you want to detect 'damp' then something like, say, blotter paper sandwiched between two wire grids would be better.

In either case, though, the circuitry will be the same, so the choice of sensor is largely moot.

-- John Fields Professional Circuit Designer

There are commercial water detection devices available to warn of water in the basement

I don't know the brand but the plumber installed one when I had a back up sump pump installed in the house where I used to live. I made a loud beeping sound when it got wet. It ran off a battery

--

Dan Hollands

1120 S Creek Dr Webster NY 14580 585-872-2606 snipped-for-privacy@USSailing.net

I had a similar problem about 20 years ago. Some time later I wrote an elementary article about the resultant project in an electronics hobbyist magazine, which you might find useful. My output was a miniature loudspeaker, not LEDS, but you may be able to adapt it.

The magazine illustration scan is very poor, but the key schematic is shown separately.

--
Terry Pinnell
Hobbyist, West Sussex, UK

Yeah Just wet vs dry is enough for me - mearly knowing that water has been present since I last checked is enough to tell me there is a problem that I'll need to call the plumber back for.

As water's not pouring out I'm in favor of an LED warninfg rather than buzzer as being woken at 2 in the morning wouldnt be appreciated by the girlfriend ;-)

Having said all that I'm looking at this as a learning excercise as well and like the thought of damp detection with wire grids/blotter paper - would it be a massive undertaking to do an LED scale (say 1-5) measuring how damp it had been? (i.e. if it is just damp 1 LED lights, under water = all 5 light with the display "locking" at the highest level recorded since last reset? - this is beyond what I need to do but if still fairly straightforward would be more fun!)

Thanks again for your help!

Mal

The tank itself is stood in a tray, but it's seems the leak was (is?) from a connecting pipe - the leak would have only be sporadic (pressure too high - cold/warm pipes - something else) and must have run down the pipe beyond the tray...

Thanks anyway!

Mal

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No, but the probe will be tricky.

One day Malcx got dressed and committed to text

Not an electronic solution but in our part of the world concealed storage tanks are usually installed in a 'tray' fitted with a drain to waste which would take care of the floor spoiling effect.

-- Regards ..... Rheilly Phoull

Not a good idea, since the LED will run down the 9v battery very quickly. You probably want an AC powered device, possibly with battery backup.

Some CMOS logic chips or a low power version of the 555 timer chip can be used for the latch circuit that stays on after being tripped.

The most basic wet/dry sensor is a piece of circuit board with the copper foil divided in two parts. Board size is dependent on the expected size of the wet/damp area (or the drip area, as appropriate).

Cable length would need to be varying length depending on where I place the unit - but none would need to be more that 750mm (shortest - probably about 150mm)

I was planning on using a 9v battery, but other posts here suggest that it'd wear down pretty quickly if an led is on permenantly to indicate power.

I dont really have access to a wall socket here so it will need to be battery powered - is there another/better/less energy hungry way of indicating there is still enough juice?

Cheers,

Mal

Have a look at this circuit

It is inexpensive and should work quite well. The piezo sounder output

volume is however a bit low with a 3 volt supply. The circuit will however

accommodate supplies up to 15volt. I would recommend a 6volt or 9volt

supply for better sensor sensitivity and operation (74HC93 or 74HC132

devices are however only spec ed for supply voltages up to 6 volt).

To accurately measure conductivity an AC voltage should be applied to a

sensor probe. In this simple moisture probe the current set-up should suffice.

Advice by other members in the group on how to construct a moisture probe

might result in a good enough sensor for the job.

It would be better to have short leads for the probe and extend the

leads of the piezo sounder to locate it at a convenient site where it

would be noticed.

As a challenge add a latching circuit, with a manual reset, that beeps only

once a minute and a battery low detect :-) Another 4093 and a simple

voltage detect circuit should be able to do it.

As for waking the girlfriend - add a kill switch to the piezo.

She should be pleased that your gadget managed to save the ceiling and carpets :-).

GvdBerg

I don't think he's interested - I suggested that (with full details) up-thread about 5 days ago!

--
Terry Pinnell
Hobbyist, West Sussex, UK

Thanks Terry -- for being diplomatic -- I had your URL -- My horrible post is hopefulle now fixed with the correct URL - maybe it could help someone else :-).

Have a look at this circuit

or the .pdf version es/103102di.pdf Circuit checks "swamp-cooler" water level - form EDN Magazine 2002-10-31

It is an inexpensive circuit and should work quite well. The piezo sounder output volume is however a bit low with the 3 volt supply. The 4093 circuit will however accommodate supplies up to 15volt. I would recommend a 6volt or 9volt supply for better sensor sensitivity and operation (74HC93 or 74HC132 'equivalent' devices are however only speced for supply voltages up to 6 volt).

To accurately measure conductivity, an AC voltage should be applied to a sensor probe using chemically inert electrodes. (By applying a DC voltage, in a damp environment, to probe metals such as copper and tin, can grow all sorts of low impedance current paths). You could try stainless steel as a probe material. Soldering stainless requires special solders, so it might be better to crimp the probe leads to the stainless electrodes. Remember to keep the crimps dry by covering them with a dab of silicon (bath) sealant. (screw terminals for joining wires can be used, if you do not have crimp tools)

Advice by other members in the group on how to construct a moisture probe might result in a good enough sensor for the job.

It would be better to have short leads for the probe and extend the leads of the piezo sounder to locate it at a convenient site where it would be noticed.

As a challenge add a latching circuit, with a manual reset, that beeps only once a minute and a battery low detect :-) Another 4093 and a simple voltage detect circuit should be able to do it, else remember to replace the batteries every year or two.

As for waking the girlfriend - add a kill switch to the piezo. She should be pleased that your gadget managed to save the ceiling and carpets :-).

I hope you don't get to many false alarms. (Watch out for ceiling rats and bats - they can foul moisture probes :-)

Gerhard