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Topic: K type thermocouple (Read 12 times) previous topic - next topic

scottthehandy8

Can anyone tell me if I can hook-p a type k thermocouple to an arduino uno?

retrolefty


Can anyone tell me if I can hook-p a type k thermocouple to an arduino uno?


Not without external circuitry to handle getting cold reference junction information. The best way to utilize thermocouples is to use the purpose designed ICs made for them.


Lefty

Jack Christensen

MCP79411/12 RTC ... "One Million Ohms" ATtiny kit ... available at http://www.tindie.com/stores/JChristensen/

MarkT

Thermocouple output voltages are tiny (microvolts per degree) - far too small to use directly with Arduino analog inputs.  Themocouple ICs handle both the compensation for the cold-junction temperature and the precision amplification needed to produce usable voltage levels - some include an ADC as well so only need digital interfacing.
[ I won't respond to messages, use the forum please ]

RPCoyle

Go with what Jack pointed out. Its self contained and uses a digital readout. Google MAX31855... there are lots more at possibly better prices... if you don't mind waiting for a slow boat from China.

There are several  scripts ready to go. Just remember that the digital inputs from the Arduino have to be 3.3 volts, not 5 volts.

kg4wsv

Quote
Google MAX31855


The older MAX6674 and MAX6675 both work with K types, they work at 5V, and there is working arduino libraries (at least, there's a library for one that can be modified for the other).

I think someone even has a shield available.

-j

RPCoyle

Quote

The older MAX6674 and MAX6675 both work with K types, they work at 5V, and there is working arduino libraries (at least, there's a library for one that can be modified for the other).

I think someone even has a shield available.



I have not seen one ,  but you can buy adapters to 8 Pin SOIC to DIP8 Adapters. They are a pain to solder, but they do work.

http://www.futurlec.com/SMD_Adapters.shtml

CrossRoads

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

rochettejessy

ok now my simple question is, what if i just want to read to the nearest 100c... do i need an amp?

CrossRoads

Take a look at the AD595 datasheet, see what level of input it is expecting from the thermocouple.
The '328P can take in 1.1V/1024 as the lowest reading, about 1mV. Probably not reliably, will need a couple of mV for a reliable reading.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

Chagrin


Take a look at the AD595 datasheet, see what level of input it is expecting from the thermocouple.
The '328P can take in 1.1V/1024 as the lowest reading, about 1mV. Probably not reliably, will need a couple of mV for a reliable reading.


Looks like type K's are around 4mV per 100C. It should work.

http://srdata.nist.gov/its90/download/type_k.tab


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