PicAxe Thermometer

[erco]

This guy did a great job on his giant thermometer using an 08M. I want to build one with an M2 chip using readinternaltemp. Even if it requires custom calibration, it would make a great minimalist project. Temperatures change slowly, so the PicAxe could nap a lot to save battery power.

 

[hippy]

I want to build one with an M2 chip using readinternaltemp. Even if it requires custom calibration, it would make a great minimalist project.

Sounds like a plan, and you can make yourself the forum's READINTERNALTEMP expert along the way !

This is the application note you want if you haven't got it already -

http://ww1.microchip.com/downloads/en/AppNotes/01333A.pdf

Figure 4 is the key, what a 'READADC of the temperature indicator' would give, though you'll be using a 10-bit result as if READADC10.

After that, it's just a case of dealing with it as any other READADC10 reading needing to be adjusted to what it actually means.

Start with the IT_RAW readings for READINTERNALTEMP at known temperatures and build up from there. I think it's IT_RAWH that gives higher / wider range readings than IT_RAWL but requires a supply of at least 4V ...

READINTERNALTEMP IT_RAWH, 0, w0

Have fun !

 

[erco]

Great info, hippy. 4V is fine, as I'll need 5-6V for the servo. A small solar cell might be able to charge a battery and power the whole thing.

Much better than a big plastic thermometer from the dollar store.

 

[Janne]

Hi

Will be interesting to see, what kind of accuracy is possible from the internal temperature sensor. Would appreciate if you will post your findings once you're done with your project.

 

[westaust55]

In the October 2012 issue of Nuts & Volts magazine, Ron Hackett has an article entitled "MEASURING A PICAXE PROCESSOR’S INTERNAL TEMPERATURE".
This dicusses the need to calibrate for each PICAXE chip (no two garanteed to be the same).