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-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf
Of Rolf
Sent: 09 October 2007 14:11
To: Microcontroller discussion list - Public.
Subject: [EE] Well Depth Monitor - Winter Project


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

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