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Newbie - water detector circuit help please

M

Malcx

Jan 1, 1970
0
Hi all,


I've not dabled with any electronics since High school (about 10 years)
and have a fairly specific requirement for a detector that I want/need
to put together....

Background:
My storage tank leaked and ruined the flooring - the plumber couldnt
find anything obviously wrong with the tank but replaced the pieces
that showed signs of wear and we've had no obvious leakage since...

Now before the floor is re-laid I want to be doublly sure there no slow
leak going on...

As the storage tank gets warm, any surface (i.e. detectable) water will
evaporate pretty quickly while other moisture will seep out of sight
and do damage...

Specification:
I envisgae all being contained in a small box with probes coming out on
lengthy wires.

The box will have an LED that is permenantly on when the battery has
power (I'd envisage a 9v cell...)

There would need to be 2 or 3 moisture detection probes, when any 1
probe registers moisture another led on the box will be lit. This led
remains lit even after the probe dries. Only 1 led will be needed for
all of the probes - i.e. there does not need to be an led for each
probe.

A reset button will be required to reset the state of the device back
to "power led on only" mode.

(Ideally the sensitivity of the probes would be adjustable)

Can anyone help me with this seemingly simple circuit design? (I can
fit it all together, pcb design etc once I've the circuit diagram)

Thanks for your help in advance!

Mal
 
J

John Fields

Jan 1, 1970
0
Can anyone help me with this seemingly simple circuit design? (I can
fit it all together, pcb design etc once I've the circuit diagram)
 
M

Malcx

Jan 1, 1970
0
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
 
D

Dan Hollands

Jan 1, 1970
0
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
[email protected]
www.QuickScoreRace.com
 
J

John Fields

Jan 1, 1970
0
Initially I was just thinking of just using etched copper board as we
used to in school - is there a better/more reliable alternative?

---
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.
 
T

Terry Pinnell

Jan 1, 1970
0
Malcx said:
Hi all,


I've not dabled with any electronics since High school (about 10 years)
and have a fairly specific requirement for a detector that I want/need
to put together....

Background:
My storage tank leaked and ruined the flooring - the plumber couldnt
find anything obviously wrong with the tank but replaced the pieces
that showed signs of wear and we've had no obvious leakage since...

Now before the floor is re-laid I want to be doublly sure there no slow
leak going on...

As the storage tank gets warm, any surface (i.e. detectable) water will
evaporate pretty quickly while other moisture will seep out of sight
and do damage...

Specification:
I envisgae all being contained in a small box with probes coming out on
lengthy wires.

The box will have an LED that is permenantly on when the battery has
power (I'd envisage a 9v cell...)

There would need to be 2 or 3 moisture detection probes, when any 1
probe registers moisture another led on the box will be lit. This led
remains lit even after the probe dries. Only 1 led will be needed for
all of the probes - i.e. there does not need to be an led for each
probe.

A reset button will be required to reset the state of the device back
to "power led on only" mode.

(Ideally the sensitivity of the probes would be adjustable)

Can anyone help me with this seemingly simple circuit design? (I can
fit it all together, pcb design etc once I've the circuit diagram)

Thanks for your help in advance!

Mal

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.

http://www.terrypin.dial.pipex.com/Images/DampDetect.jpg
http://www.terrypin.dial.pipex.com/Images/DampDetect.txt
http://www.terrypin.dial.pipex.com/Images/DampDetector.gif
http://www.terrypin.dial.pipex.com/Images/DampFigs.gif

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

Malcx

Jan 1, 1970
0
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
 
R

Rheilly Phoull

Jan 1, 1970
0
One day Malcx got dressed and committed to text
Hi all,


I've not dabled with any electronics since High school (about 10
years) and have a fairly specific requirement for a detector that I
want/need to put together....

Background:
My storage tank leaked and ruined the flooring - the plumber couldnt
find anything obviously wrong with the tank but replaced the pieces
that showed signs of wear and we've had no obvious leakage since...

Now before the floor is re-laid I want to be doublly sure there no
slow leak going on...

As the storage tank gets warm, any surface (i.e. detectable) water
will evaporate pretty quickly while other moisture will seep out of
sight and do damage...

Specification:
I envisgae all being contained in a small box with probes coming out
on lengthy wires.

The box will have an LED that is permenantly on when the battery has
power (I'd envisage a 9v cell...)

There would need to be 2 or 3 moisture detection probes, when any 1
probe registers moisture another led on the box will be lit. This led
remains lit even after the probe dries. Only 1 led will be needed for
all of the probes - i.e. there does not need to be an led for each
probe.

A reset button will be required to reset the state of the device back
to "power led on only" mode.

(Ideally the sensitivity of the probes would be adjustable)

Can anyone help me with this seemingly simple circuit design? (I can
fit it all together, pcb design etc once I've the circuit diagram)

Thanks for your help in advance!

Mal

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.
 
M

Malcx

Jan 1, 1970
0
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
 
J

John Fields

Jan 1, 1970
0
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?

---
No, but the probe will be tricky.
---
(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!)

---
The circuitry's pretty straightforward but, again, the probe will be
tricky, so, first things first and I'll generate something for you for
the wet/dry unit.

BTW, how long do the cables have to be and what kind of a power supply
do you want to use to run the thing?
 
J

John

Jan 1, 1970
0
Hi all,


I've not dabled with any electronics since High school (about 10 years)
and have a fairly specific requirement for a detector that I want/need
to put together....

Background:
My storage tank leaked and ruined the flooring - the plumber couldnt
find anything obviously wrong with the tank but replaced the pieces
that showed signs of wear and we've had no obvious leakage since...

Now before the floor is re-laid I want to be doublly sure there no slow
leak going on...

As the storage tank gets warm, any surface (i.e. detectable) water will
evaporate pretty quickly while other moisture will seep out of sight
and do damage...

Specification:
I envisgae all being contained in a small box with probes coming out on
lengthy wires.

The box will have an LED that is permenantly on when the battery has
power (I'd envisage a 9v cell...)

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).
 
M

Malcx

Jan 1, 1970
0
The circuitry's pretty straightforward but, again, the probe will be
tricky, so, first things first and I'll generate something for you for
the wet/dry unit.

BTW, how long do the cables have to be and what kind of a power supply
do you want to use to run the thing?

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
 
G

Gerhard v d Berg

Jan 1, 1970
0
John said:
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).

Have a look at this circuit
http://www.terrypin.dial.pipex.com/Images/DampDetector.gif
<Circuit checks "swamp-cooler" water level>
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
 
G

Gerhard v d Berg

Jan 1, 1970
0
Previous post now fixed -
I don't think he's interested - I suggested that (with full details)
up-thread about 5 days ago!

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
http://www.edn.com/article/CA253786.html?spacedesc=designideas
or the .pdf version
http://a330.g.akamai.net/7/330/2540/20021024153820/www.edn.com/contents/imag
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
 
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