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My first Arduino (Seeeduino actually) attempt w/ a thermocouple.

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Dacr0n

Member
Okay... so I've got a Seeeduino board on the way and a couple different thermocouples. My goal for right now is to be able to hook the TC up and read the temps VIA my laptop... Is that possible? Eventually, I want to integrate the signal from the TC into a more complex set of instructions that is part of a PID control script.

I am in the process of learning the C language to please bear with me. :)

Another thing on my mind was if I could just hook the TC straight to the board or am I going to need a TC amplifier chip?


Thanks in advance!

 

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Sceadwian

Banned
Silly AVR things? Don't be posting fighting words Mr RB =)
Seeeeduino is just an Arduino clone. Atmega168 @ 16mhz
 

Dacr0n

Member
I have no idea if its PIC or AVR..

Whats the difference anyways?


Any thoughts about my previous questions?
 

Leftyretro

New Member
While thermocouples are cheap and rugged they are somewhat complex and expensive to interface to micro-controllers. There needs to be amplification, cold junction compensation and finally linearization. Unless you require the high temperature range of a TC you are probably better off looking at other temperature sensors.

Lefty
 

Sceadwian

Banned
Thermistors are extremely easy to interface to micro controllers.
 

Dacr0n

Member
Okay well I have a few NTC thermistors. I guess I can start with that...

How does this look?


The one I have is the 1,000Ω @ 200C.


Is there any preferred way to hook the thermistor up to the board or do i just hook it straight up to an analog input?
 

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Leftyretro

New Member
Okay well I have a few NTC thermistors. I guess I can start with that...

How does this look?


The one I have is the 1,000Ω @ 200C.


Is there any preferred way to hook the thermistor up to the board or do i just hook it straight up to an analog input?
It will not function wired straight to a analog input pin. You must have it as part of a voltage divider network such that there will be a DC voltage that changes proportionally with the TC's temperature. It will have to be designed such that the voltage developed is limited to a 0 to 5vdc output for direct wiring to most microcontroller chips A/D input. You then have to deal with linearization if using other then a pretty narrow temperature range, depending of the temperature curve of the specific thermistor.

Lefty
 

Dacr0n

Member
Okay. Thanks for that info lefty.

I am not too concerned with linearization because I'm just going to be working with a fairly narrow temp. So temp curves and linear feedback shouldn't pose much of an issue for this project (kind of a continuation of my previous project).

So what you're refering to is roughly something like this lefty?



In reference to fig (A), Where my thermistor would take place of R1 or R2 in this circuit?

and the output to the arduino could either be B or C and ideally between 0-5 volts?
 

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Leftyretro

New Member
Well a NTC (negative temp coefficient) would have to be installed in the upper leg of the divider so that the resulting divider voltage would rise with increasing temp. If if was a PTC (positive temp coefficient) device it would have to go in the lower leg. Not sure about your source voltage values and 100vdc is very dangerous around 5 volt logic devices. Perhaps someone here has a validated circuit that is know to work correctly and safely with a micro? What total temp range are you looking to cover?

Lefty
 
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