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PICList Thread
'[OT]: Fountain Project- Help Me Pick A Sensor?'
2006\04\09@050921 by Bob Axtell

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My wife bought a ceramic fountain. It has a pump that draws water
from the bottom and pumps it to the top, so the birds can bathe in it
and it srips down to the bottom again. Looks neat, works nice, kills
some of the road noise.

The problem is that in So Arizona, the water evaporates so fast, I
can't discipline myself to keep it filled. So... I am gonna design a
slick way to sense when the water level is low so it can kick on a
solenoid and pump some back into it. I don't want to use anything
ugly, or big (like a float valve). I had in mind a  non-contact sensor,
perhaps a capacitor. The whole sensor/solenoid deal could then
be automatic.

What would work reliably? I am leaning toward a probe with two
insulated contacts, that I can make part of a tuned circuit; when
the water is missing between the probes, the frequency is at a
certain range, with the water between the probes, the frequency
is detuned. Another idea was to mount a  tiny magnetic float  in
a plastic tube, and when the  float  is high enough, it triggers a
hall device.

Any other ideas? Lotsa talent here. I have piles of PICs, can always
help control the solenoid that way...

--Bob

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2006\04\09@114923 by Danny Sauer

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Bob wrote regarding '[OT]: Fountain Project- Help Me Pick A Sensor?' on Sun, Apr 09 at 04:12:
> can't discipline myself to keep it filled. So... I am gonna design a
> slick way to sense when the water level is low so it can kick on a
> solenoid and pump some back into it.

The ultrasonic ("cold mist") humidifiers I've had all use a single
piece of wire that senses water.  I think similar things are used for
detecting leaks in places like server rooms and basements.

Kinda like what these people make and sell:
http://www.rletech.com/products/waterdetection.html

That might be something to further research - maybe just how those
things work... :)

--Danny

2006\04\09@120847 by blackcat

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Could be using TDR ( time domain reflectometry )
example:   http://www.tscm.com/tdr.html
water causes short

POD

On 2006-Apr 09, at 9:49 AM, Danny Sauer wrote:

Bob wrote regarding '[OT]: Fountain Project- Help Me Pick A Sensor?'  
on Sun, Apr 09 at 04:12:
> can't discipline myself to keep it filled. So... I am gonna design a
> slick way to sense when the water level is low so it can kick on a
> solenoid and pump some back into it.

The ultrasonic ("cold mist") humidifiers I've had all use a single
piece of wire that senses water.  I think similar things are used for
detecting leaks in places like server rooms and basements.

Kinda like what these people make and sell:
http://www.rletech.com/products/waterdetection.html

That might be something to further research - maybe just how those
things work... :)

--Danny

2006\04\10@165425 by Peter

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Water kettle method. Float with magnet inside, reed outside. Metal strip
runs outside and keeps float from wandering off.

Peter

2006\04\11@055003 by Tony Smith

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> The problem is that in So Arizona, the water evaporates so fast, I
> can't discipline myself to keep it filled. So... I am gonna design a
> slick way to sense when the water level is low so it can kick on a
> solenoid and pump some back into it. I don't want to use anything
> ugly, or big (like a float valve). I had in mind a  non-contact sensor,
> perhaps a capacitor. The whole sensor/solenoid deal could then
> be automatic.


Make a capacitor.  Take a plastic tube, and run 2 strips of adhesive foil
down opposite sides.  You could use that stuff you put on windows for
alarms, or copper foil that stained glass people use.

I used the copper foil (because I had some), added wires to one end, then
water-proofed it by putting some heatshrink over it (but I put some
sealant on the ends first).

The capacitance changes as the water level goes up & down.  Works well.
Won't corrode like bare wires either.  Use clear tubing & heatshrink and
it might not stand out all that much either.

Of course, you'll need a PIC to measure the capacitance... and fire the
solenoid...

I got this from the Parallex website (Basic Stamp), there's an article
about it on there somewhere.

Tony

2006\04\11@091629 by Bob Axtell

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Tony Smith wrote:

{Quote hidden}

would it operate 25' from the fountain? I was trying to avoid having the
electronics close
to the fountain, or splitting it up...my planned electronics box is near
the water spigot &
outside electrical outlet...

I already have copper shielding foil and a support to hold it...Do you
think I could use that
low-loss TV interconnect cable for a 25' run? That could be buried
alongside the power
cable to the pump motor.

Good tip, thanks.

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2006\04\11@092434 by Bob Axtell

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But, ya know, if I mounted a PIC10 right at the top of the probe itself, I
could simply send a 5V "level" signal, can easily go 25', and no cable
capacitance issues.

My wife has some leftover 2-part clear epoxy that seals HARD. No
moisture problems with that.

I'm intrigued. Gonna look at Parallex site.

--Bob

{Quote hidden}

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2006\04\12@054316 by Tony Smith

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I found the article on the Parallex website:
<http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv27.pdf>

I still think it's a neat solution, cheap too.

I did something similar a few years back, measuring the water in a tank.
I connected a tube to where a tap went at the bottom, and joined it the
the 'capacitor guage' stuck on the outside.  A PIC drove a 7 seg led,
showing 0 (empty) to 9 (full).  I can't remember exactly how I measured
the capacitance though... like PC joysticks, I guess.  Charge then bleed
through a resistor, time how long it takes.

It was close to the house so running power to it wasn't a problem.  It
occurs to me now that if I'd used clear tubing, you could see the water
level too.   Drop in a bright red bead to act as a float, like a kettle,
but where's the fun in that.

It also occured to me that it may not work if you stuck it in the middle
of a pond, as opposed to the side of a tank, but I can't see why not.  The
capacitance depends on the amount air between the plates, having water on
both sides won't make a difference.

If you put a PIC on top, you might as well send back the exact water level!

Tony



{Original Message removed}

2006\04\12@070407 by Alan B. Pearce

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>I found the article on the Parallex website:
><http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv27.pdf>
>
>I still think it's a neat solution, cheap too.

I was envisaging a tube that went down into the water. have to think how I
can apply this to a water butt.

>If you put a PIC on top, you might as well send back
>the exact water level!

True, but also measure the temperature and turn on some mild warmth if it
looks like freezing, so the water butt doesn't get damaged, in my case.

2006\04\13@044914 by Tony Smith

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The tube can be open ended, no need to seal it.  I thought it might not
work, but can't think of a reason.  The capacitance would read the same.
For the tank, I put the tube on the outside because it was easier, and
well, it never really occured to me to put it inside.

Hmmm, motorcycle fuel gauge...

I was originally going to put a small magnet on a float inside the tube,
and have a few reed switches outside.  That would work for a pond level
indicator (reed switches are easier to deal with than hall effects), but
you need to figure out how to stop the magnet spinning.

Tony



{Original Message removed}

2006\04\13@090055 by Howard Winter

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Tony,

On Thu, 13 Apr 2006 18:49:06 +1000 (EST), Tony Smith wrote:

>...
> I was originally going to put a small magnet on a float inside the tube,
> and have a few reed switches outside.  That would work for a pond level
> indicator (reed switches are easier to deal with than hall effects), but
> you need to figure out how to stop the magnet spinning.

Mount it vertically, then it won't matter if it spins...

Cheers,


Howard Winter
St.Albans, England


2006\04\13@102833 by Bob Axtell

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Tony Smith wrote:

>The tube can be open ended, no need to seal it.  I thought it might not
>work, but can't think of a reason.  The capacitance would read the same.
>For the tank, I put the tube on the outside because it was easier, and
>well, it never really occured to me to put it inside.
>
>  
>
I am allowing the water to enter the round tube, because this increases
the surface area
and makes it more sensitive...

>Hmmm, motorcycle fuel gauge...
>
>I was originally going to put a small magnet on a float inside the tube,
>and have a few reed switches outside.  That would work for a pond level
>indicator (reed switches are easier to deal with than hall effects), but
>you need to figure out how to stop the magnet spinning.
>  
>
That's a problem, because the fuel sloshes around too much.

--Bob

>Tony
>
>
>
>{Original Message removed}

2006\04\13@144025 by Peter

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On Thu, 13 Apr 2006, Tony Smith wrote:

{Quote hidden}

If you put a magnet float in the water and a metal wire outside the
magnet will be drawn near the metal wire. Add two reed switches near the
wire and it's done. The magnet float need to be attached to anything, it
can be a plastic flower or orb or whatnot.

Peter

2006\04\14@235615 by Tony Smith

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>...
> I was originally going to put a small magnet on a float inside the tube,
> and have a few reed switches outside.  That would work for a pond level
> indicator (reed switches are easier to deal with than hall effects), but
> you need to figure out how to stop the magnet spinning.

Mount it vertically, then it won't matter if it spins...

Cheers,

Howard Winter
St.Albans, England


But then you can only have one sensor...  well two, maybe.  For the pond
you need two sensors, (high & low level) else you get chatter.

And I noticed my local electronic shop (Jaycar in Oz) has heatshrink with
glue inside it, just what you need for a waterproof setup like this.  Only
in black though.

Tony

2006\04\15@002526 by Tony Smith

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>Hmmm, motorcycle fuel gauge...
>
>I was originally going to put a small magnet on a float inside the tube,
>and have a few reed switches outside.  That would work for a pond level
>indicator (reed switches are easier to deal with than hall effects), but
>you need to figure out how to stop the magnet spinning.
>

That's a problem, because the fuel sloshes around too much.

--Bob


Sloshing fuel can be overcome with averaging, I guess.  It doesn't move
about much overall anyway.  Just ignore reading during braking &
acceleration, where you're not really interested in the fuel level anyway.

Can't be worse than the average motorcycle fuel gauge, which has 3 levels,
full, not quite empty, and empty.  These exist only in your mind, of
course.  The holy grail isn't the cup Jesus drank from, it's the accurate,
working  fuel gauge on the bike he rode.

Standard procedure is to ride the bike until it stops.  At this point
either the main tank is empty, so you switch to the reserve, or you'd
forgotten to switch it back last time you refuelled, so you get to push
and swear at it.

Once on the reserve, you now have usually 3 litres on fuel, and (in my
case) that's 50-100km depending on the bike, enthusiam, and hills that you
can coast down with the engine off.

Some Harleys have fuel guages (floats, I think), but they often have 2
separate tanks, so the guage only measures one, and yes, you do have to
fill both of them.  Some have a light that comes on at reserve, but you'd
already figured that when the bike stopped.  Unless it doesn't have a
reserve, and the indicator bulb is blown...

Did Ford have a capacitive fuel guage at one point?  So do some
helicopters, don't they?

Tony

2006\04\15@071507 by Vasile Surducan

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On 4/9/06, Bob Axtell <.....engineerKILLspamspam.....cotse.net> wrote:
{Quote hidden}

A fountain automation it can't be without a PIC. Telemetry, ultrasonic
range finder, laser beams...using top DSP or ARM cores...
:)
Maybe a simple mercury sealed switch (floating on the water surface)
connected directly (or using a relay) into your low power pump circuit
? No PIC, allowing a long distance to pump and safe histeresys. The
smallest I've seen looks like a watch bulb.

greetings,
Vasile



Lotsa talent here. I have piles of PICs, can always
{Quote hidden}

> -

2006\04\15@083117 by Howard Winter

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Tony,

On Sat, 15 Apr 2006 13:56:08 +1000 (EST), Tony Smith wrote:

> I previously said:

>> Mount it vertically, then it won't matter if it spins...
>
> But then you can only have one sensor...  well two, maybe.  For the pond
> you need two sensors, (high & low level) else you get chatter.

No, you'll find that reed switches have quite a sharp operating point when you're moving the magnet along the
axis at a constant radial distance - much sharper than if you're moving it radially.  And there's quite high
hysteresis in both cases, so I don't think you'd get chatter unless the water level is waving up and down half
an inch or so.  Try a "dry" test on a piece of paper and plot the operating/release points, and I think you'll
see what I mean.

> And I noticed my local electronic shop (Jaycar in Oz) has heatshrink with
> glue inside it, just what you need for a waterproof setup like this.  Only
> in black though.

I've only seen it in black (and it's darned expensive!).  You could put glue of your own at both ends of
ordinary heat-shrink, but I'm not sure what type would stick to it.

Incidentally, I don't know how big your fountain is, or what size of sensor you're looking for, but these:
http://www.rapidelectronics.co.uk/rkmain.asp?PAGEID=80010&CTL_CAT_CODE=&STK_PROD_CODE=M36677&XPAGENO=1  are
pretty small, and cheap!  Only problem I can see is if the length of the mounting stem isn't long enough for
your water depth.

Cheers,


Howard Winter
St.Albans, England


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