Can we communicate a PT100 with a PICAXE?

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paste

New Member
Hello, I need to know if you can read the values of a PT100 through a PICAXE, have asked me this in college and I have to deliver this scheme, anyone could help me?. I would also like to know if you can export the temperature record from the PICAXE to a Excel.

Thank you very much!:)
 
C

Chavaquiah

Senior Member
A datasheet would help... A LOT! :p

Anyway, are those just thermistors? (I'm asking, not stating.)

If they are just variable resistance sensors you should be able to use them with any Picaxe with READADC. See page 29 of Manual 3 for an example circuit. You would need to use some formula to transform voltage read into temperature. A datasheet woul be required here.

As for exporting to Excel, just do a search on this forum (keyword EXCEL). There are very helpful discussions. Like this one: http://www.picaxeforum.co.uk/showthread.php?t=14876
 
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B

BeanieBots

Moderator
Although the PT100 is regarded as an "industry standard" for measuring temperature, it's resistance does not change a great deal with temperature. The PICAXE ADC input is in effective a voltmeter with a range of 0v to Suppy (typically 5v). Hence, you will not get much range or resolution without the aid of offset and amplification. If it is essential to use the PT100, then I would suggest the help of a few op-amps. Otherwise, I would suggest the use of the DS18B20 temperature sensor which is ideal for use with PICAXE.

For exporting data, there are many options which have been well covered here.
 
D

Dippy

Moderator
I haven't got time to search through the hundreds of PT100 sensor data sheets and my CB has failed.

General.
How are you going to deal with the linearising required? (Unless your device already has a processor?)

Have a look at this:
http://www.maxim-ic.com/app-notes/index.mvp/id/3450

If you are simply transferring data using the PICAXE then this may be easier once the data is on your PC/Excel.
But study BB's point about using op-amps to improve the dynamic range of the sensor to give better results.
 
M

MPep

Senior Member
Dippy said:
I haven't got time to search through the hundreds of PT100 sensor data sheets and my CB has failed.
Click to expand...
As you, I don't have time for doing someone else's work.

And your CB (crystal ball) has failed AGAIN?!?!?!?!????
Always appears to be on the blink when someone doesn't post enough details in the initial enquiry.
Whether that is on purpose or 'pure fluke' I'll leave for other readers to ponder over.
 
M

MartinM57

Moderator
What's the real requirement Paste? Is it to read some temperature somewhere or to interface to a PT100?

The former is easy - the "standard" temp sensor for a PICAXE is a DS18B20 and there are even specific PICAXE commands to read it.

PT100 was the device of the day many years ago, but there are better alternatives. PT100 interfacing is (much?) more complex than a DS18B20 and will require external circuitry - e.g. see http://ww1.microchip.com/downloads/en/AppNotes/00687b.pdf and further info at http://ww1.microchip.com/downloads/en/AppNotes/01154a.pdf

But required temp range, accuracy and resolution are key details to give us before a solution evolves further...
 
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Dippy

Moderator
MPep,
It was a cheap one I bought from Ebay and I didn't forsee the problems.

Paste,
As said several times above , give us more details so that suggestions can be given.
Post the criteria and what you have done so far.


Is this a college project for which you (and we) will get marks?
 
fernando_g

fernando_g

Senior Member
Posted by Dippy: "I haven't got time to search through the hundreds of PT100 sensor data sheets and my CB has failed."

Are you related to Paul the Octopus?

Now to the original poster's question: Yes you can communicate a PT100 to a PICAXE, but some front-end analog processing will be required.
 
D

Dippy

Moderator
I've not heard of the P the Oct. :confused:

- paste seems to have gone.
He was probably hoping for a complete solution (code and circuit) in the intervening days...
 
D

Dippy

Moderator
Ah, I see. Well done Ec. Have you moved to Alta Vista from Google now?

If I had been PtO then I'd have known the exact PT100 sensor, the exact PICAXE and predicted who would have designed the circuit and written the code.
It would have been much easier to predict who wouldn't have spent hours doing it for someone's college project :)
 
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