thermal sensor

[mdaisl]

Hey folks, i'm new to electronics and trying to get started on my first project. I want to
make a circuit to monitor temperature. ex: if temp. drops below say 40 degree f, then,
sound an alarm. Way out there would be to not sound an alarm but to make a telephone
call with a message like "PLANTS ARE FREEZING"

Once again, i'm new don't even know what parts to buy.
Really appreciate any help.

mda

[JonHylands]

If you want to use a micro-controller, you can simply use an analog temperature sensor, and feet it into an A/D converter to get temperature in degrees C.

Go to www.digikey.com and type in LM19CIZ-ND in the product search window.

You could probably do the first part with one of those sensors, and an analog comparator, but someone else will have to supply the details.

- Jon

[Militoy]

National Semiconductor has a nice little handbook on temperature sensors that you may find helpful. There are several application circuits shown in it that may give you some ideas - even if you don't use one of their parts in your design.
http://www.national.com/appinfo/tempsensors/files/temphb.pdf

[Admin]

if in the future you plan for it to make a call, might be best to use a PC for the sensing and calling.

a quick google search gave me these usb temperature loggers:
http://www.measurementcomputing.com/cbicatalog/directory.asp?dept_id=559&top_id=557&dept_name=temperature&WT.srch=1&CID=2&t=3

http://www.downtown.com.au/new1213.htm

and this one claims it can call your cell phone:
http://www.sysman.no/sensors.htm
"Alarm to any mobile via SysManSMS Server"

[mdaisl]

thanks for the info. the handbook @ national semiconductor is a great start. found a sensor and receiver
already built at one of the box stores that does everything i want to do except make a phone call for
only 15.00 but, i want to learn how to build it myself.
mda

[JonHylands]

It turns out that making a robot be able to call someone isn't all that hard anymore - its just a case of a couple hundred bucks.

http://www.sparkfun.com/commerce/product_info.php?products_id=279
http://www.sparkfun.com/commerce/product_info.php?products_id=281

- Jon

[Militoy]

Thanks for the link, Jon. I have a few future projects in mind, which may make use of this kind of product. The “robot phone” idea is useful, but not so new – as anyone who has received those annoying automated telemarketing calls knows all too well. My family used to have an alarm system installed at our remote cabin in the mountains overlooking Tucson, AZ. The system was X-10 based, and tied into all kinds of functions in the cabin – as well as the telephone. It wasn’t unusual to get a call from “Herman” in the middle of the night, if the power failed, or some other alarm function tripped. Herman would read off statuses of Power grid; Inside and outside lighting; Window and door security; Smoke/fire alarm; Inside and outside temperatures; Furnace fuel supply; and let you listen to sounds inside the cabin for 15 seconds. Herman was destroyed with the cabin in the Bullock Fire of 2002 – and we haven’t built a new cabin on the site yet. When we do, I will build a better, smarter, faster version of Herman; “We have the technology…”

[Admin]

if this isnt going to be a mobile robot, what about just having it send a text message (or voice) to your cell through the internet?