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'[OT] Fountain Project- Help Me Pick A Sensor?'
2006\04\09@052832 by Jinx

face picon face
Bob, three gold-plated wires would do as a simple SPST switch. If
#2 is 1" longer than #1 and #3 is 1" longer than #2 you have a switch
with #2 as the common. The end of #1 is at the high water mark. If
level falls below #2, then #2 and #3 are not shorted and the pump
turns on. When water shorts #1 to #2 it turns off

You could make them very fine, even colour them the same as the
fountain so they'd not be too obvious

2006\04\09@100953 by Bob Axtell

face picon face
Jinx wrote:

>Bob, three gold-plated wires would do as a simple SPST switch. If
>#2 is 1" longer than #1 and #3 is 1" longer than #2 you have a switch
>with #2 as the common. The end of #1 is at the high water mark. If
>level falls below #2, then #2 and #3 are not shorted and the pump
>turns on. When water shorts #1 to #2 it turns off
>
>You could make them very fine, even colour them the same as the
>fountain so they'd not be too obvious
>
>  
>
Jinx, that looks pretty good! Use AC, i.e. 12VAC, so the wires won't be
eaten away?
and the currents would be small...and it just means only 3 wires to bury.

I like it.

--Bob

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2006\04\09@102238 by Jinx

face picon face
> Use AC, i.e. 12VAC, so the wires won't be eaten away ?

Yes, if you can. I made an electric fence to keep snails out of the
veges. It was a border of upright 6" planks with two wires around,
1/2" apart. Originally I had 12V and 0V but the wire, even though
it was galvanised, corroded quite quickly. I replaced it and switched
to AC and had no more problems. A couple of seasons later I had
to do the same to a location not within easy reach of power, so it
had to run off a battery. I made a retriggerable one-shot driving a
trigger transformer. 5ms every 5s as I recall. Worked just as well
and 4 * D batteries lasted a very long time

2006\04\09@184125 by Russell McMahon

face
flavicon
face
> ... I made an electric fence to keep snails out of the
> veges.

You could sell the concept to Gallagher.


       RM

2006\04\09@190349 by Jinx

face picon face

> > ... I made an electric fence to keep snails out of the
> > veges.
>
> You could sell the concept to Gallagher.

I made the first in the mid-80s, long before anything like the
Interweb was around, and don't recall it not being an original
idea. However, it's fairly easy to find similar products these
days, eg

http://www.snailaway.com/press/press_images/snailaway_assembly/index.html

2006\04\09@190724 by Bob Axtell

face picon face
Russell McMahon wrote:

>>... I made an electric fence to keep snails out of the
>>veges.
>>    
>>
>
>You could sell the concept to Gallagher.
>
>
>        RM
>
>  
>
Is Gallagher still around? Hasn't run out of melons yet?

- - -

Actually, Jinx and his gold wires look like a fix. I am driving it with
an "AC driver" through all six sections of a CD40106. A PIC16F676
will sense the inputs, smooth everything, then drive the a solenoid value.
I am also making the PIC time the fountain... I am having it come on
for 14 hrs after detecting daylight, defined as at least two hours without
light, followed by at least 15 minutes  OF light...but when you mash the
red switch you can break the cycle momentarily, making the fountain go
on at will. The "AC" swings from +5V to -5V to prevent etching the gold
wires.

After buying the parts on the web, I discovered that ALL ELECTRONICS
(a surplus house) sells battery-operated water-level detectors.... Oh will,
mine will be more complex and hopefully work better,,,

BTW, you have tossed out some good informative links lately. Do you
EVER sleep?

--Bob

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2006\04\09@193009 by Jinx

face picon face
> After buying the parts on the web, I discovered that ALL
> ELECTRONICS (a surplus house) sells battery-operated
> water-level detectors

Oh, any chump can BUY one ;-)  (not for a minute suggesting
you're a circuit-buying chump you unnerstand)

2006\04\09@212438 by William Chops Westfield

face picon face

On Apr 9, 2006, at 4:30 PM, Jinx wrote:

>> I discovered that ALL ELECTRONICS sells battery-operated
>> water-level detectors
>
> Oh, any chump can BUY one ;-)

I find that it puts a serious crimp in my enthusiasm if there
is a commercial product that comes very close to doing what I
want my project to do :-(

BillW

2006\04\09@230245 by Jinx

face picon face

> > Oh, any chump can BUY one ;-)
>
> I find that it puts a serious crimp in my enthusiasm if there
> is a commercial product that comes very close to doing what I
> want my project to do :-(

I know - it's a terrible decision to make sometimes. "Is 'very
close' close enough to stop me making one right now, or will I
one day get sick of what it can't do and make it then ?"

A couple of times though I've done it anyway and come across
a much better way than the commercial product. And subsequently
made no attempt to commercialise that way ;-(

2006\04\10@154727 by alan smith

picon face
Sprauge used to make a water level detect chip....sensors were ac driven.  Built some to monitor my overflow and washer tanks on my truck

Bob Axtell <engineerspamKILLspamcotse.net> wrote:  Russell McMahon wrote:

{Quote hidden}

Is Gallagher still around? Hasn't run out of melons yet?

- - -

Actually, Jinx and his gold wires look like a fix. I am driving it with
an "AC driver" through all six sections of a CD40106. A PIC16F676
will sense the inputs, smooth everything, then drive the a solenoid value.
I am also making the PIC time the fountain... I am having it come on
for 14 hrs after detecting daylight, defined as at least two hours without
light, followed by at least 15 minutes OF light...but when you mash the
red switch you can break the cycle momentarily, making the fountain go
on at will. The "AC" swings from +5V to -5V to prevent etching the gold
wires.

After buying the parts on the web, I discovered that ALL ELECTRONICS
(a surplus house) sells battery-operated water-level detectors.... Oh will,
mine will be more complex and hopefully work better,,,

BTW, you have tossed out some good informative links lately. Do you
EVER sleep?

--Bob

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2006\04\10@181526 by Bob Axtell

face picon face
Browsing the technical literature I found a GREAT way to measure the
presence of epid water.  It is similar to how liquids are measured
in a flow meter.

You place a resistor and a thermistor in close proximity at the end of an
insulated probe. You shroud it slightly with a plastic shield to trap
the heat
except that water can still flow into the shield easily.

When the water is NOT touching the probe, the resistor heats the
thermistor to a steady-state point, above normal ambient.

When water touches the probe, it removes heat from the probe constantly
and reduces the temperature... reflected by the R-value of the thermistor.

Even better than the gold wires, which depend on the conductivity of the
water itself, which varies according to the chlorine inserted into the
water and the water useage rate....

Comments welcome.

--Bob

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2006\04\10@182506 by David VanHorn

picon face
I suppose a gamma switch is out?

--
Feel the power of the dark side!  Atmel AVR

2006\04\10@182703 by Richard Prosser

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On 11/04/06, Bob Axtell <engineerspamspam_OUTcotse.net> wrote:
{Quote hidden}

Or combine the 2 & use a PTC?
You only need to measure the voltage accross it to figure out if it's
in the water - provided you don't go overboard with the drive current.

RP

2006\04\10@190549 by Jinx

face picon face
> When the water is NOT touching the probe, the resistor heats the
> thermistor to a steady-state point, above normal ambient.

> Comments welcome.

Bob, that method sounds OK, but would definitely need more set-up
time spent on it. Unless you're after developing it for another application
that deserves the complexity, is it worth the time ?

2006\04\10@191916 by Bob Axtell

face picon face
Jinx wrote:

>>When the water is NOT touching the probe, the resistor heats the
>>thermistor to a steady-state point, above normal ambient.
>>    
>>
>
>  
>
>>Comments welcome.
>>    
>>
>
>Bob, that method sounds OK, but would definitely need more set-up
>time spent on it. Unless you're after developing it for another application
>that deserves the complexity, is it worth the time ?
>
>  
>
I am designing it both ways, I think. I am only making 4 PCBs, two
fountains and a spare
PCB for both of 'em (my neighbor wants one too).

--Bob

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2006\04\11@071759 by Russell McMahon

face
flavicon
face
>> You place a resistor and a thermistor in close proximity at the end
>> of an
>> insulated probe. You shroud it slightly with a plastic shield to
>> trap
>> the heat
>> except that water can still flow into the shield easily.
>>
>> When the water is NOT touching the probe, the resistor heats the
>> thermistor to a steady-state point, above normal ambient.

With some thought this could serve to both measure water temperature
AND to detect absence of water.

Heat resistor (or PTC) enough to raise its temperature in air to say
80 C +.

When water is present sensor temperature will drop to a known
temperature above water's temperature. The better the heat transfer
provisions the better they match.

Air cooling rate will also vary as water cooling ability is varied.
Calibration probably required.

A Peltier device may be useful here.

A pulsed sensor where delta temperature rise with time is sensed would
allow liquid temperature measurement AND detection of liquid absence
without having to operate the sensor at a high temperature in air.


       RM

2006\04\11@114129 by Peter

picon face


On Sun, 9 Apr 2006, William Chops Westfield wrote:

> I find that it puts a serious crimp in my enthusiasm if there
> is a commercial product that comes very close to doing what I
> want my project to do :-(

And one of the best known ways to stifle certain developments of the
competition is to pre-announce a device that does just what they are
developing (or counteracts it). Don't fall for it, do your calcs and if
it looks good do it. After all, if they are selling it and di not go
bust, then it means there is a market for it.

Peter

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