# "Homemade" thermometer



## teps71 (Oct 23, 2010)

I cook several pieces of meat at the same time. So rather than have multiple digital thermometers or another ET-73, I decided to build my own. This is version one. eBay is your friend, but I've got some cash in the thermocouples. Using a programmable logic controller and a thermocouple input card I picked up from eBay I put together this "temp monitor" for lack of a better term. Four inputs, one labeled CAB for the cabinet and three "zones" for three different pieces of meat. The word "CAB" above the temp will flash if the temp falls below 200 or above 250. The Z1, Z2 and Z3 will flash once the target temp is hit. Only two thermocouples were connected when the pic was taken:








This is the backside - thermocouple connectors and power input. The box will accomodate 6 inputs, but the thermocouple card will only allow for 4:







Hitting F1 will set the target temp for Zone 1, F2 for 2, F3 for 3. Temps adjust up and down in 5 degree increments with the up and down arrow keys. F4 returns to the main screen:







Right arrow takes you to the timer screen. Left arrow takes you back to the main screen:







Under the hood:







The Programmable Logic Controller or PLC is a very feature rich device that allows for programming modules, inputs, outputs, etc. They are often used in manufacturing/factory environments to run whole machines. Future expansion may include a stack light, horn or something else to alert to over/under temps or target temps getting hit. The Micro 300 HMI is pretty basic, but a 21" touchscreen could be added. With an ethernet module, the possibilities are endless. Have the PLC send a text with status updates, when temps are hit, that sort of thing. A web page that shows all the info on one screen? Anything is possible.

Yeah, I've got too much time on my hands...


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## smokingohiobutcher (Oct 23, 2010)

Cool  gizmo!  you must be very edjumacated!!! 

Ever thought about selling one of these units?

SOB


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## meateater (Oct 23, 2010)

You lost me at homemade!  I still like charcoal. I hope ya make a bunch and stamped USA.


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## rdknb (Oct 23, 2010)

very cool although I have no idea of what you were saying lol


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## rowdyrawhide (Oct 23, 2010)

You lost me along the line here to, although I was able to make to "thermocouple"   
	

	
	
		
		



		
		
	


	





    

Nice work though.


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## tom37 (Oct 23, 2010)

Very cool workings there.

But I would make it about as far as cutting the whole in the lid and I would be stumped.

It looks great and like you said, having a light or horn on the stack would be pretty darn cool.


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## solaryellow (Oct 23, 2010)

I like it! How much do you have into it? 

What was the challenge with the thermocouples?


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## teps71 (Oct 24, 2010)

I have way too much in this! Some parts I had, some I sourced from eBay and some I had to buy new (thermocouples and box). Any commercial venture would be cost prohibitive. Nobody is going to dish out $700 for a device that only monitors temps.

The challenge in the thermocouples was coughing up the $65 per from Pyromation.com. These have some crazy accuracy like +/- .12% at 0C. Good up to 400 degrees. As you can see from the display above these were within .2 a degree of each other.







The yellow cap is protecting the probe point. The probe length is 4" and it has a 6' cord that is teflon coating over stainless braid. Should pretty well last a lifetime.


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## jirodriguez (Oct 24, 2010)

Teps71 said:


> I have way too much in this! Some parts I had, some I sourced from eBay and some I had to buy new (thermocouples and box). Any commercial venture would be cost prohibitive. Nobody is going to dish out $700 for a device that only monitors temps.


.... you have obviously never talked to an oil refinery purchaser, $700 for a device that monitors just temps for them is like you or I spending a nickle on a piece of candy. But very cool concept! I would never have the know how to make one, but it is a cool concept.


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## jcb68 (Nov 3, 2010)

I would love one of these for myself. Can you lay-out a parts & price list? That would be great.


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