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IR Temperature Controller for SMD Skillet Reflow

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This instructable will help if your trying to get into making your own circuit boards using SMD (surface mount device) re-flow. After hand soldering a bunch of boards I became really interested myself.

In this instructable I'm going to talk mostly about using the Melexis MLX90614 IR (infrared radiation) sensor. Also, while building a sensor interface board, I'll also take care of driving a Crydom SSR (solid state relay).

There is already a bunch of web info on re-flowing boards using either a skillet or toaster oven. Both of the following links are good:

http://www.circuitsathome.com/production/on-reflow-soldering

http://www.sparkfun.com/commerce/advanced_search_result.php?keywords=reflow&x=0&y=0&search_section=tutorials

What I thought was missing was information on instrumenting the skillet. This  instructable should take care of that.

Note, Parallax already makes, and sells, a Melexis IR interface board. However, I don't think it has any digital outputs (I could be wrong since I never owned  one). There is no way to remotely mount their sensor either - their design has the sensor solder right onto an interface board.
 
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Step 1: Construct a method to hold the sensor.

Build a simple counterweight so that the IR sensor can be suspended above the skillet. I pulled four wires through the cup and copper spiral.

Step 2: Build the interface board.

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The little PIC-12F609 circuit is really simple. The interface to the Melexis sensor is SMBus (System Management Bus). Luckily, Melexis had a good App Note on their web site. It took a bit of work to port the code over to the CCS compiler.

I also had trouble with the CCS compiler serial output code. I ended up writing my own which I think is better. My version uses one of the PIC timers. In contrast, the CCS compiler generates RS232 code using only software timers.

Anyway, all the source code is attached and, I think, well documented.

Here is a link to the Melexis web site for datasheets and app notes:
http://www.melexis.com/Sensor_ICs_Infrared_and_Optical/Infrared/MLX90614_615.aspx

The Melexis app note on the SMBus was indispensable.

Tom Cantrell had a nice write-up in issue 219 of Circuit Cellar. The original article may be purchased on their web site for $1.50. Tom's article was the inspiration which got me moving.




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R3mus2 years ago
I know this is a bit strange of a question, but where did you get that table? Its the kinds I see at school, and around the workplace, but I can never figure out where to buy one.
jimk3038 (author)  R3mus2 years ago
No problem.

Attached are a couple of images. Hope this answers your question.

Jim
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ledartist3 years ago
Great Instructable. Great to see that graph.

I use a hot plate to solder my boards as well, but I never calculated the temperature ramp. I suspect my hot plate doesn't go up that quickly either, but the little smoke always makes me nervous...
jimk3038 (author)  ledartist3 years ago
Thanks for the nice comments.

Someday I'm going to sort out how to interface my Cen-Tech IR thermometer. Have a look at this: http://www.instructables.com/id/Cen-Tech-Infrared-Thermometer-Mount/

As always, there is more info on my web site: ph-elec.com

Thanks,
Jim
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