REMOTE TEMPERATURE READINGS

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FURNEYCP
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REMOTE TEMPERATURE READINGS

Post by FURNEYCP » Wed Nov 19, 2008 5:57 am

iIwould like to build a system that consists of several remote temperature sensors that are sent wireless, to a receiver attached to my computer, that would read each sensor in rotation, say every 5 minutes or so, and record them in a data file. From this file I would plot each vs. time to form multiple graphs on a single chart. The object of this project would be help balance my home heating system, so the all area heat evenly , rather than one heating faster or slower than the others.

I have a Honeywell programable thermostat. This controls the temperature pretty well, but upon a change in set point, for different times of the day, which takes place automatically each day, the temperatures become unbalanced in the different location in our home, for several hours, until the new temperatures become established. This happens both on rising and falling temperature. By adjusting the the rate of air flow to each room via splitters and register settings, I think I can cause each room to change temperature more easily.

jimandy
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Post by jimandy » Wed Nov 19, 2008 6:54 am

I understand your dilemma. I have just moved into a three level house with a thermostat for each floor. In considering the problem I thought about the fact that when a lower unit is heating, the hot air will rise through the stairwells toward the upper floors, and vice versa when the weather is warm and the units are cooling. The temperatures flowing through this convection process create a real challenge for designing an algorithm for balanced temperatures throughout the house and to have each unit run with the most efficient duty cycle. My old house, also a three level one, had just one humongous unit and balance was easy to maintain by just letting the fan run continuously.
"if it's not another it's one thing."

Bigglez
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Re: REMOTE TEMPERATURE READINGS

Post by Bigglez » Wed Nov 19, 2008 10:42 am

FURNEYCP wrote:I would like to build a system that consists of several remote temperature sensors that are sent wireless, to a receiver attached to my computer, that would read each sensor in rotation, say every 5 minutes or so, and record them in a data file.
There are three parts to your project (1) Sensors,
(2) wireless interface, and (3) PC based datalogger
and display. To make it simple could you live without
the wireless part?

What if you have a temperature logger that recorded
the temp at one location over (say) 24Hours and then
you dump it to your computer and use an existing
software tool (like MS Excel) to crunch the numbers?

The temp logger could be battery operated and easy
to use. If it was based on an existing hardware
platform (such as Arduino) all you need to add is a
temp sensor and custom software/firmware.

For one tenth degree F resolution a reading would
need about four bytes of BCD data. Times twelve
readings per hour times twenty four hours is just
over one kilobyte of memory space (1152bytes).
Very easy to store in EEPROM (non-volatile storage).

The same module can be moved from room to room,
or multiple modules constructed for simultaneous
measurements on the same day.

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haklesup
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Post by haklesup » Wed Nov 19, 2008 2:42 pm

OK, here's a hacker way to do it. (hacker meaning using premade modules and re purposing them rather than a ground up design)

Locate a typical wall thermostat like the honeywell you are trying to augment in each of the zones you would like to control. Rather than wiring its control relay to the furnace, you could wire it to a wireless module. Perhaps one removed from a mini RC car hand control with left, right, and forward controls. Use the board from the RC car as a reciever.

This method does not send the actual temperature to the central controller (your PC) but instead a 1 or 0 indicating if the zone is above or below the setpoint. A bit more limiting in principal but needing a simpler wireless link. Additionally it allows the user to adjust the local zone in a natural way by changing a thermostat rather than changing a program on a remote PC.

Even a door unlock module for a car (aftermarket, upgrade) typically has 2-4 channels. You could get a kit with 3 key fobs and one reciever. Likewise garage door opener controller

Engineer1138
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Post by Engineer1138 » Thu Nov 20, 2008 9:42 am

And here's the "easy" way to do it :-)

Get a cheap cast off PC that will run XP or Win95 and a WiFi card. That's your wireless interface and sensor logger and it will either be free or about $25 if you shop carefully.

Buy a cheap USB-analog interface card and a few temp sensors, or get a few Dallas TempButtons. Dallas/Maxim has PC software on their website to read the TempButtons.

Write a simple program to read the temp button and ship the data out over the WiFi card. Bonus points if you install a webserver so your remote reader can access the data with just a browser.

[edit]
Let me clarify that since I'm not using their standard terminology. By TempButton, I mean the Dallas iButton that has a temperature reading feature.

FURNEYCP
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TEMPERATURE CONTROL PROBLEM

Post by FURNEYCP » Fri Nov 21, 2008 5:44 am

I have printed all the replys and down loaed the description of the Arduino D. which I had not heard about before. I didn't print the data sheet yet. What ever the solution to my problem, I must record all the temperatures vs. time at the same time as the problem is "dynamic. " That is there is a rate of change to evaluate. For you math nerds, its a differential equation that must be solved, at least numerically.

We don't have open stairwells although I did in the last house i owned and I know exactly what your talking about. My office was in the basement and was cold all the time, summer & winter.

It would be very difficult to run wires to each themostat as they woul have to go through the walls; wireless would be much better.

Engineer1138
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Post by Engineer1138 » Fri Nov 21, 2008 3:19 pm

I hesitate to sound like I'm soliciting here but are you interested in purchasing a solution? I'm in the process of developing a Bluetooth-connected temperature sensor. It's not "hobbyist-level" pricing but it should do what you need. If you are, PM me since commercial posts are really outside this BBS's charter.

If not, I think your best bet with minimal cost & time invested would be an Arduino BT -- that's the Arduino with onboard Bluetooth. I think they are about $100 each.

Bigglez
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Re: TEMPERATURE CONTROL PROBLEM

Post by Bigglez » Fri Nov 21, 2008 3:39 pm

FURNEYCP wrote:It would be very difficult to run wires to each themostat as they woul have to go through the walls; wireless would be much better.
So this is a permanent project, not a "science
experiment" to collect data one or two times?

For a science experiment I wouldn't worry too
much about running CAT3 or CAT5 wires through
doors and corridors in my home. These go a
central datalogger.

Another scheme is logging at each node with a
bunch of SD memory cards or even EEPROM
DIP chips that you take to the central station
for reading into your PC.

"Wireless" is a whole new can of worms...

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