How to translate SPI data to programming parameters

Projects Programming
1

I am such a noob I don't even know if I asked the question properly. I want to control a small oven used for curing powder coated items.

Due to the 400^F, it appeared I have to use a thermocouple. I have a DIY 5v relay controlled outlet to control a hot plate heating source.

Assuming I can use digitalWrite to a pin to go HIGH to signal the relay? (the relay board -Sparkfun 'Beefy' - has a transistor to increase the mA from the digital pin to the relay coil)

In the sketch, I would like to turn the oven on at temperature X and turn it off at temperature Y.

I could use the < and > "comparison operators" but I don't know what format the data from the thermocouple will be in - i.e., less than or greater than what?

Will the data be in degrees or some digital format?

Would also like to display the temperatures on a parallel LCD - think I have that one worked out but any suggestions would be most welcome.

Any suggestions or recommendations along with any info on resources where I could learn a little more would be greatly appreciated.

Hope this makes a little sense.

Thanks

2

One piece you need is a thermocouple interface. This will amplify the tiny (microvolts) signal from the thermocouple and convert it into usable data.

This adafruit product for $17.50 will do that: Thermocouple Amplifier MAX31855 breakout board (MAX6675 upgrade) : ID 269 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits

They also have a tutorial that will explain how to wire everything and they even provide a library for reading the temperature. Overview | MAX31855 Thermocouple | Adafruit Learning System

3

Thanks, John,

I had the info on that interface(which I should get tomorrow with the TC) in my message and then deleted it. The "usable data" is in SPI protocol and therein lies my problem - will I get a temperature I can use or will I get some digital format?

Guess the question was not too clear.

4

If you use the library that adafruit provides you will get a floating-point number that represents the temperature in °C or °F (depending which function you call). If you use SPI directly you will get an integer number that represents the temperature in 1/4°C (divide by 4 to get °C).

5

Thanks again, John.

If I understand correctly, I should be able to use either of those formats with a "lesser than or greater than" in the sketch.

Should get the TC and ADC (MAX31855) from Adafruit tomorrow and will play with it.

Will advise (or come up with a whole bunch of new questions) :~

Thanks for the help - really appreciate it.

6

John, got it all working with the serial monitor giving me a Celsius temperature that will work for me.

Now trying to get it to work with a LCD