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'[EE] Well Depth Monitor - Winter Project'
2007\10\09@091058 by Rolf

face picon face
Hi All.

I am looking for some preliminary direction for a winter hobby project.
My Father-In-Law has two wells on his property. One has a plentiful
supply of water, but the water is very very 'hard'. The other well has a
lower supply, but the quality is far better. It is easy to switch
between the two wells for the house's water supply. If the good well
runs dry he has to go through a complicated process to re-prime the
well's pump when the water level returns. This is especially complicated
in winter when it can be very cold. His current routine is to check the
well's level at least once a week. For his convenience, and my interest,
I plan to build a device that will measure the depth of water in the
well in such a way that it can be monitored from his PC, and do all the
bells-and-whistles thing including tracking the water level over time, etc.

I have researched ways to measure the water depth, and currently I am
considering implementing two of three candidate methods, but that is the
subject of a different thread.... my concern right now is for the data
transfer required.

The well is located about 10 meters from the house, and about 30 meters
from his office with his PC. The house is a log cabin with a concrete
foundation/basement. The well is 10 meters deep and 1 meter in inside
diameter. The well is capped with a concrete lid that has a square
concrete 'manhole cover' for inspection. There are photo's of the well
from the outside here:
http://www.flickr.com/photos/12903637@N08/1524116316/ and the inside of
the well here: http://www.flickr.com/photos/12903637@N08/1524133462/

I was hoping to use some form of radio transmitter (prefereably a
transceiver) to transmit the data to a receiver in the house. The reason
for a transceiver is because the computer is only on about 1/4 of the
day, so I would want to store a number of readings while the PC is off,
and then upload them in bulk when the PC comes online (as well as then
uploading updates regularly every 15min or so). I was hoping to use a
cheapish pre-built module. Specifically, I was considering something
like Vitaly's or SparkFun's BlueTooth modules.

My question for this e-mail is as follows: What can I expect from a
Class 1 BlueTooth module in terms of reliable range where the module is
installed under the 3inch concrete lid outside in temperatures of close
to freezing with about 3 feet of snow piled on top (the inside of the
well never gets much below freezing regardless of the outside temperature)?

I am (and my father-in-law is) reluctant to have to drill a hole through
the lid, but, we agree that would be preferable to trying to de-ice a
35kg man-hole cover in 20-below temperatures (Celcius or Fahrenheit)
when you are 60-something. If I need to install an antenna through the
lid it can be done though.

A further option, though less sexy, would be to use a wired mechanism.
Although this would mean not having to have batteries in the well unit
(there is no power source in the well), it would also require digging a
trench to the house, and opening up the vulnerability to inducing
lightning-strike damage to the PC, etc.... I would need to install a
conduit, have a much more significant 'impact' on the well itself, etc.
I was hoping to just be able to install a box on the inside of the well,
and for that to be enough.

Any advice, suggestions, etc. welcomed.

Thanks

Rolf

2007\10\09@100247 by Timothy J. Weber

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Rolf wrote:
> I was hoping to use some form of radio transmitter (prefereably a
> transceiver) to transmit the data to a receiver in the house. The reason
> for a transceiver is because the computer is only on about 1/4 of the
> day, so I would want to store a number of readings while the PC is off,
> and then upload them in bulk when the PC comes online (as well as then
> uploading updates regularly every 15min or so). I was hoping to use a
> cheapish pre-built module. Specifically, I was considering something
> like Vitaly's or SparkFun's BlueTooth modules.

I like MaxStream's XBee for sensors like this.  Longer typical range
than Bluetooth, and lower power because it's meant for frequent
connect/disconnect, while Bluetooth likes to be always on - or at least
those are the arguments I've heard, I haven't worked with Bluetooth.

Modules are what, $22 or $32 depending on which power level you want.
Dead easy to set up - in fact, you might not need an external
microcontroller at all for the application you're describing.
--
Timothy J. Weber
http://timothyweber.org

2007\10\09@102634 by Paul & Lynn Tyrer

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Have you considered a 1 -wire network. I guess what you could do is string a
load of temperature sensors and monitor the difference in temperature.
Assuming though that the water would be a different temperature to the air
in the well cavity. This could be connected to a PIC to monitor them and
then download to a pc when connected. The 1 Wire run could easily do the
distance.
Hope this helps.

Paul

{Original Message removed}

2007\10\09@105559 by Carl Denk

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For the wire to the house, it's possible to bury the wire (cable) 6"
below ground level with just a spade(shovel), or might be able to find
someone that will plow in (a narrow vibrating knife blade, hollow for
cable to be passed through and buried around 8". Check local cable or
Dish supplier for their contractors. For my gas well with a PIC
monitoring pressures and temperature 200' away from house, I have a 3/4"
plastic conduit with 120 VAC 3 wires (hot, neutral, and ground) plus a
fiber optic cable for the PIC RS-485 communications to a PLC. The fiber
optic gets converted to RS-485 in the house with a B&B Electronics
convertor. Most cable and Dish cables are only buried around 6", and
there are not many problems. The 120 VAC or higher needs to meet your
local electrical code which will be buried below frost level which for
Northern Ohio is around 42". For that rent a little trencher, probably
less than $100 for 4 hours.

Rolf wrote:
{Quote hidden}

2007\10\09@111652 by 556RECON
picon face
Paul & Lynn Tyrer wrote:

>Have you considered a 1 -wire network. I guess what you could do is string a
>load of temperature sensors and monitor the difference in temperature.
>Assuming though that the water would be a different temperature to the air
>in the well cavity. This could be connected to a PIC to monitor them and
>then download to a pc when connected. The 1 Wire run could easily do the
>distance.
>Hope this helps.
>
>Paul
>  
>
We worked on a project such as this.
We found that without the air circulating in the well the air and water
temp. were the same at least 10 FT above the water.  But at that time we
used a digital water temp. thermometer for water temp. for fishing. it
would only read in whole numbers and not fractional degrees.

We ended up using a metal tape measure 50 FT long. It had a float on one
end and a weight on the other and went over the top of a bearing on a
shaft.  There was a pointer for reference.

The well was inside the basement of a house.  The person used it in a
closed loop to cool his house in the summer.

I have more details if anyone is interested.

Recon

2007\10\09@113909 by Brendan Gillatt

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Rolf wrote:
> A further option, though less sexy, would be to use a wired mechanism.
> Although this would mean not having to have batteries in the well unit
> (there is no power source in the well), it would also require digging a
> trench to the house, and opening up the vulnerability to inducing
> lightning-strike damage to the PC, etc.... I would need to install a
> conduit, have a much more significant 'impact' on the well itself, etc.
> I was hoping to just be able to install a box on the inside of the well,
> and for that to be enough.

For the kind of power required for bluetooth modules, you may as well
use solar panels. If he can stand measuring the depth only once a day
(say, after he's retrieved water), they'd be ideal.

- --
Brendan Gillatt
brendan {at} brendangillatt {dot} co {dot} uk
http://www.brendangillatt.co.uk
PGP Key: pgp.mit.edu:11371/pks/lookup?op=get&search=0xBACD7433
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2007\10\09@122910 by Carl Denk

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The National Semi LM1830 water sensor chip has been around a long time
(there are probably better now days). A ground electrode, and a snsing
electrode. When water bridges between the 2 electrodes, the LM1830
switches a TTL level circuit. Would need one chip per level, output
going to a PIC, say with 8 inputs, you could sense 8 levels.

What about an ultrasonic level reading in that well diameter. A future
project I'm thinking about is a gasoline tank, 30" dia,. horizontal
length. The sensor would have to mount in a 2" i.d. pipe threaded into
the top of the tank.

Also what about a pressure sensor at bottom of well (or at pump), and a
PIC with an ADC port. Probably like this best.

556RECON wrote:
{Quote hidden}

2007\10\09@125817 by Paul & Lynn Tyrer

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Quote
We ended up using a metal tape measure 50 FT long. It had a float on one
end and a weight on the other and went over the top of a bearing on a
shaft.  There was a pointer for reference.

The well was inside the basement of a house.  The person used it in a
closed loop to cool his house in the summer.

I have more details if anyone is interested.



I would love to see more info on this, if i may. On a similar project note i
have a old Sensus water meter attached to the well input, i have a hall
effect switch attached to the outside and i have been able to pulse a led
each time the meter spins. 50 spins = 1 US gallon. I have to figure a way to
count the pulses offline so to speak. I went this way as opposed to water
level in the well as i knew how deep it was and its a 3 feet diameter hand
dug well. The water table doesnt change here rapidly so i could buy myself a
few days.
Would it be possible to use a piece of metal such as a tape measure and
measure the resistance of a float attached to it. Less resistance would
equal more water in the well.

Paul




{Original Message removed}

2007\10\09@130149 by Alan B. Pearce

face picon face
>The National Semi LM1830 water sensor chip has been around a long time
>(there are probably better now days). A ground electrode, and a snsing
>electrode. When water bridges between the 2 electrodes, the LM1830
>switches a TTL level circuit. Would need one chip per level, output
>going to a PIC, say with 8 inputs, you could sense 8 levels.

If starting down this route, why not look at the chips that Microchip have
that will do capacitive touch sensing? There are a bunch of 4 app notes in
the AN110x range about them.

Then use a pair of insulated wires down into the water, and measure the
change in capacitance between them with water level. Would take some playing
to calibrate it initially, but then it could be set up so the PIC takes a
reading every 10 minutes or so (could maybe be a watchdog timeout time?) and
saves it. Then readout on the radio link when called up.

2007\10\09@134827 by Rolf

face picon face
Rolf wrote:
> Hi All.
>  
[snipped]

> Any advice, suggestions, etc. welcomed.
>
> Thanks
>
> Rolf
>
>  


Hi again all.

To answer some other details I (intentionally) left out in my original
mail...

I have found three ways that appear feasible for actually measuring the
water depth:

1. using the capacitive nature of two conductors with the water as a
dielectric. It will change capacitance as the water rises. Measured by
timing the RC constant (or a frequency based on it).
2. Using a pressure sensor (there are multiple ways to do that....)
3. Using an ultra-sonic range finder.

I plan to implement two of the three methods, and then use them to
correlate against each other. My notes on each method are as follows:

1. Pro - simple, cheap, effective. Con - needs calibration, changes with
mineral content of water, temperature, time, and has potential to
pollute the water maybe.
2. Pro - reliable. Con - relatively expensive, and mechanically complex.
Need to measure relative pressure between bottom of well, and atmosphere
for accuracy
3. Pro - easy to install, relatively cheap. Con - it's precision is
worst when it is needed most (when the well is nearly empty - the range
is longest), needs calibration for temperature, etc. Does not like water....

I know I need to investigate some more, but, I was really hoping someone
would speak up with the experience to know whether I have a realistic
chance of getting the BlueTooth, or perhaps ZigBee (although, I was
hoping to use a COTS Class1 USB BlueTooth - Serial dongle on the PC side
- I can't see a ZigBee equivalent...) system to work under 3feet of snow
and 3 inches of concrete.

Thanks in advance

Rolf

2007\10\09@141619 by Bob Blick

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--- Rolf <spam_OUTlearrTakeThisOuTspamrogers.com> wrote:

> 2. Using a pressure sensor (there are multiple ways
> to do that....)

It's not that hard - the least expensive sensors
measure "gage" pressure of air and that's what you
want.

Mount the sensor and your electronics above water, and
run fishtank hose to the bottom of the well. Install a
tee in the hose, also above water, and connect it to
an air pump(a fishtank pump will work if your well is
not too deep). Run the pump every once in a while to
keep the hose free of water.

It's a method I've used successfully for 20 years.

Cheerful regards,

Bob

2007\10\09@154418 by Timothy J. Weber

face picon face
Rolf wrote:
> I know I need to investigate some more, but, I was really hoping someone
> would speak up with the experience to know whether I have a realistic
> chance of getting the BlueTooth, or perhaps ZigBee (although, I was
> hoping to use a COTS Class1 USB BlueTooth - Serial dongle on the PC side
> - I can't see a ZigBee equivalent...)

The MaxStream eval kit contains ZigBee/Serial and ZigBee/USB adapters.

Or, one XBee + your favorite TTL/Serial or TTL/USB dongle works too,
though it does require a bit of fiddling to make it permanent.
--
Timothy J. Weber
http://timothyweber.org

2007\10\09@170047 by Al Shinn

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Rolf,
Nothing about transmitters but some thoughts:

I can view the first photo but not the second.

No electricity in the well? Where is the the pump? I am wondering if you
can measure something about the pressure in the pipe before the pump  in
the house? Wouldn't work with a jet pump at the bottom of the well
unless there was a check valve in the house but the priming issue makes
it sound like there is a pump in the house that "sucks" the water up, so
you could just measure the "suction" while the pump is off for an
accurate water level, all done from inside.
Of course you NEED a pump at the bottom if the well is more than ~10
meters deep.

I bet you could sneak a wire for an antenna past the manhole cover
without drilling - or copper tape, etc.

Could you resonate the air cavity above the water to measure the level?
Ommmmm.



A weighted tube to the bottom of the well, open on the bottom, filled
with air (or water, etc), attached to a pressure guage at the top  of
the well? The tube could even come into the house

An insulated cover over the man hole so he won't have to de-ice it to
inspect the water level? (I know, not at all sexy or PIC or EE or
anything remotely like that)

--

Looking forward,
Al Shinn



2007\10\09@170414 by M. Adam Davis

face picon face
A few points:

1.  You're transmitting very little data.  Don't use a transceiver -
just a transmitter.  Transmit about every 10-20 minutes, and during
each transmission send the last 48 hours worth of data.  Send it twice
with some data correction information, and you'll have a plenty
reliable system.  This will also drastically lower the cost and power
consumption of the device.  A pair of D cells could run it for a year
depending on sensor consumption and time between level checks.

2. Yeah, you're going to have trouble sending any signal through
concrete and snow.  Looks like there's rebar in the concrete too.  The
best thing to do is overengineer it and try it out.  Keep in mind that
lower frequencies penetrate better, so I'd look more in the 400mHz
range and slower than up in the 900 or 2.4GHz range (ie, bluetooth,
zigbee, and wifi will be poor).  You could go very low frequency if
you enjoy designing radios.

3. Antenna design will be very important here.

4. For an interesting hack, use a pulley system with counterweights
and floats, and attach it to a generator to power the system.  It only
needs to operate if the water level is going up or down - otherwise
it's the same.  The transmitter sends a pulse of a certain frequency
going up, and a different frequency going down for each inch up or
down.  A capacitor stores energy generated inbetween pulses for use
during the pulse.  Given the huge power that can be generated from
that much water moving up and down, this should provide plenty of
energy, but it is very mechanical...

5. Rather than worrying about when the computer is on, build a
receiver that attaches to the computer and has its own display that's
always on.  That way he doesn't even need to power up the computer,
and you can have an alarm.  Let this device do the logging, and keep
the power and parts in the well cheap.

6. If the issue is drilling a hole in the concrete, you can put the
receiver on the outside of the cap to maximize coupling, and then run
cable to the house.  But at that point, is making a hole that big a
deal?  Depends on on your county environmental health organization -
could be that you'll have trouble if they ever inspect it (usually at
sale or transfer).

...

Well, I'd better stop there, or I'll start solving problems you don't have...

-Adam

On 10/9/07, Rolf <.....learrKILLspamspam@spam@rogers.com> wrote:
{Quote hidden}

> -

2007\10\09@182632 by Rolf

face picon face
Hi Adam

Those are all very good ideas. Transmitting a few day's data is a nice
twist. As for the lower frequencies, I have some experience with Linx
tech's chips at 434Mhz. I can apply that experience. I have been
thinking too much about bi-directional communication, and, I should
think more laterally it seems.

You have given me lots to think about.

Thanks

Rolf



M. Adam Davis wrote:
{Quote hidden}

2007\10\09@185410 by Dave Lag

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Rolf wrote:
{Quote hidden}

A nice submersible pump in the "good" well to cure the priming issues.
- been there/done that  :)
D

2007\10\09@224730 by John La Rooy

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On 10/10/07, 556RECON <.....556reconKILLspamspam.....charter.net> wrote:
{Quote hidden}

I think the only way to do it with thermistors would be to self heat them
a little. I bet the thermistor in air would heat a lot more than the one in
water

John La Rooy

2007\10\10@003408 by Peter P.

picon face
As others have posted, level measurement is not easy. Your 3ft well will contain
about 80 liters per vertical 10 cm (~60 gal/foot ?). So you probably want to
measure to the nearest 5cm which is 5mbar H2O. That is not so easy to measure
with a low cost gauge. The best way is probably the
float-cable-pulley-counterweight method using an encoder on the pulley (reeds
90 deg. out of phase and magnet on pulley). One problem with this is parallax,
if the float moves from underneath the pulley an error appears. So this must
be prevented. A zero switch is the only calibration required. This is the reset
(or power) switch. One brings the cable-float to the designated calibration
point (probably the highest level marked) and then turns on the unit.

Data transmission is best done one way. For this the transmitter needs to send
a clock or other datum. So there should be a real time clock in the well
electronics. 433 MHz will go your distance without trouble, using a rubber
ducky antenna. Using a simple serial protocol with FEC or redundancy you could
send a packet with the hour (minutes are not needed!) followed by 24 hourly
readings using simple serial encoding. The readings, being in increments of
5cm, will all fit in one integer representable on one byte, just like the hour.
The clock needs no calibration as the receiving computer determines the exact
time of the transmission and calibrates the offset out. So a packet sent out
will be like 25*3 = 75 characters at 1200Bauds or about 0.75 seconds of
transmission with some start and stop times.

The well electronics could be mounted on the manhole, using a single 1/3"
penetration for the rubber ducky antenna to hold everything inside on the other
side. Using 32768 kHz clock for minimal consumption and a 3.3V 433MHz module
that will be on for 1 second per hour a single lithium cell (freeze proof!)
should last for 1-3 years. All one would need would be a PIC with at least 25
bytes of ram.

For packaging, remember that everything in the well will be wet excepting in
winter when it will be frosted.

It looks like a fun project. Good luck.

Peter P.


2007\10\10@013652 by Brooke Clarke

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Hi Rolf:

If the concern is you don't want to pump the well dry then just add a switch
between the pump and it's power source that's normally on when the switch is
floating and turns off when it's hanging by it's cord.  These used to use
Mercury (some still do) but there are also Mercury free versions.

A Neon lamp in series with a resistor can be placed across the float switch and
will turn on when the switch is preventing the pump from running thus giving an
indication of why the pump is not running (time to switch to the other well).

I think this is by far the most reliable of all the options I've seen here.

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam

2007\10\10@060046 by Dario Greggio

face picon face
Rolf wrote:

> Those are all very good ideas. Transmitting a few day's data is a nice
> twist. As for the lower frequencies, I have some experience with Linx
> tech's chips at 434Mhz. I can apply that experience. I have been
> thinking too much about bi-directional communication, and, I should
> think more laterally it seems.

In Zigbee, "dormant" devices only wake up when a Master ask them data,
at which moment they'll send out all the buffered data :)

So, you can store measurements for one day or more, and when PC wakes
up, it will download those data.

PS: didn't chime in before, but I'd try TRW24 devices from Sparkfun.
And, if range is not enough, one could use another of them as a
"repeater" - only a simple PIC is needed to act as a repeater.

--
Ciao, Dario

2007\10\10@063522 by Marco Genovesi

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>> 2. Using a pressure sensor (there are multiple ways to do >> that....)



In this free Datalogger project a pressure sensor is used for water flow mesurement, however it is based on water-level variations, so it is applicable also for a well).

http://academic.hws.edu/geo/logger/Housing/Housing.html

As explained in the text, with the differential pressure sensor the possible error due to atmospheric pressure variations is removed.


good luck!
Marco





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2007\10\10@081510 by Carl Denk

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I think then you need to turn on the backup pump also. Otherwise I concur.

Brooke Clarke wrote:
> Hi Rolf:
>
> If the concern is you don't want to pump the well dry then just add a switch
> between the pump and it's power source that's normally on when the switch is
> floating and turns off when it's hanging by it's cord.  These used to use
> Mercury (some still do) but there are also Mercury free versions.
>
> A Neon lamp in series with a resistor can be placed across the float switch and
> will turn on when the switch is preventing the pump from running thus giving an
> indication of why the pump is not running (time to switch to the other well).
>
> I think this is by far the most reliable of all the options I've seen here.
>
>  

2007\10\10@100627 by Charles Rogers

picon face
Subject: Re: [EE] Well Depth Monitor - Winter Project


{Quote hidden}

Rolf:

Have you considered using depth finder similiar to that used on
fish locators?

CR

2007\10\10@105348 by Don Rahmlow

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I've had good success measuring simple resistance using basic cheap
comparators. Also requires some upfront calibration based on water's mineral
content and temp, but entirely reliable. I use shift register and SPI to
reduce PIC input to single I/O pin.

Don

{Original Message removed}

2007\10\10@110012 by Rolf

face picon face
Charles Rogers wrote:
{Quote hidden}

No, I have not considered that. Doing some reading though suggests that
to accomplish this I would need to 'float' the transducer at the water
surface, and measure the depth that way. It is certainly worth
considering, but, would mean having to deal with waterproofing issues,
etc. Would have to assume it would be more complex to get right, and
maintain. It also involves 'moving parts' as the system floats up and
down on the water.

The two main reasons I don't like the 'sonar' approaches (either the
method you suggest, or the idea of putting a sensor at the top of the
well bouncing off the water surface is that I would have to do 'tuning'
of the system in it's installed location, and that is a number of hours
away from home. I basically need to have a way to test it at my home and
then get it installed easily later. I worry that there will be issues I
can't test on-site....

Rolf

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