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MM_Wombat
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Joined: 12/12/2011
Location: Australia
Posts: 139

Posted: 10:36pm 19 Feb 2015

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Hi All,

I was wondering if a Micromite would work with a thermocouple sensor, or would I need to amplify the output of the thermocouple with a transistor.

I think the maximum voltage the thermocouple generates is around 14 mV at its highest temperature.

Got one leftover from a soldering iron, that I killed the ceramic heater in.

I wanted to use it to sense the temperature in my 3D printers print head and output the temperature to 3, 7 segment leds.

MM_WombatEdited by MM_Wombat 2015-02-21

Keep plugging away, it is fun learning
But can be expensive (if you keep blowing things up).

Maximite, ColourMaximite, MM+

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9073

Posted: 10:51pm 19 Feb 2015

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I use AD595 thermocouple amp chips available from eBay for about five bucks each.
What's good about these chips, is that they just output a precision voltage proportional to the temperature of the thermocouple, so you can read that with any analog pin as a voltage. There is no need to translate anything in code, you just read an analog voltage reference for your temperature - dead easy.

EDIT: Here is the voltage output chart from the PDF:

Edited by Grogster 2015-02-21

Smoke makes things work. When the smoke gets out, it stops!

twofingers
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Joined: 02/06/2014
Location: Germany
Posts: 1138

Posted: 12:35am 20 Feb 2015

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Hi MM_Wombat,

if it's about K-Type thermocouples then you could take a look at Peters code.

Alternativly are there converter chips from MAXIM (MAX31850=1-Wire, MAX31855=SPI).

There are also cheap temperatur controler from china (ebay, ...).

Regards
Michael

MM_Wombat
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Joined: 12/12/2011
Location: Australia
Posts: 139

Posted: 10:21pm 20 Feb 2015

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how do I know which type I have?

It has red and blue sheaths over the wires coming out the back.

Which according to the chart at the bottom of this WEBSITE means I have Type T, I assume.

MM_Wombat

Keep plugging away, it is fun learning
But can be expensive (if you keep blowing things up).

Maximite, ColourMaximite, MM+

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9073

Posted: 10:46pm 20 Feb 2015

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You don't.

USUALLY the blue wire is the COLD JUNCTION, and the red wire is the HOT JUNCTION.
That does not tell you what type it is though. I've never used T-type thermocouples, so not sure what their spec is.

It is most likely to be a K-type, as these are the most common.

If you have a milli-volt meter, put it across the thermocouple at a known stable temperature, then look for a match on the voltage-vs-temperature charts.

It's difficult to be sure what is going on, without a datasheet.

Smoke makes things work. When the smoke gets out, it stops!

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