Did you know you can turn your Nokia smartphone into a fully functional digital thermometer for less than $3 total? Here's what I did.

First, you need to build a temperature-dependant square wave generator. I used good old NE555 timer for that purpose. See the circuit below:


As you can see, I put a 10k thermistor as R2 to provide temperature-frequency dependence.

Than, connect generator's output to MIC+ and MIC- pins of the Nokia pop-port connector. The simplest way to get a connector itself is to buy a cheap Nokia headset. Make sure that it is possible to take of the connector's case before you buy. You can search for pinout at http://pinouts.ru.

Unfortunately, there is no +5V available from the Nokia pop-port, so the thermometer needs to be powered from an external source. I chose a plastic whiteboard marker tube as a case for my temperature probe and Duracell MN11 6V battery fits perfectly into it. I also put a micro switch to be able to start temperature measurement on demand.



When your Digital Thermometer is assembled, you need a piece of software to be able to calculate frequency of the square wave, convert it to a temperature and finally display. I used mShell scripting tool to write this small thermometer app:


You need mShell engine as well to be able to run the script: http://www.m-shell.net/Download.aspx.

Here is the Digital Thermometer Module assembled and working, measuring room temperature on my Nokia 6680:


For more accurate frequency-to-temperature conversion you will need to calibrate the logarithmic equation by yourself. I'll leave that one for you as homework

I will try to make it store in a file the values of temperatures every 30 minutes.

if you can help me, thank you very much.

so long

No problem, just let me know if you need help.
File management is well described in mShell specification.

Im study mshell library, for develop somes scripts, and when cooy dm in my nokia n73, and when run, nothing appear on screen.

alredy installed,copy, btradar, dEditor....


thanks

Sorry but I've never tried that on any other phone than 6680. It should definitely work, but the script may require some tuning. Unfortunately I don't have N73 phone to debug. But it is quite simple, so just get familiar with mShell and debug the script yourself.