Computing stuff tied to the physical world

Reflow revisited

In Hardware on May 9, 2010 at 00:01

As mentioned yesterday, I’m restarting the reflow oven/grill project because my old setup with an NTC resistor is causing some mechanical problems with the connection of the NTC and because I want to end up with a setup which will be easier for others to replicate.

My intention is to start this project from scratch, using a JeeNode and a Thermo Plug as sensors, and then adding a JeeLink, an FS20 remote-controlled power switch, and of course a grill to create a fully automated and self-contained reflow station for soldering SMDs on printed circuit boards.

I’ll be replicating some of the first experiments, but there will be no need to calibrate NTC readings.

I’m also going to use JeeMon to illustrate how to design and implement the software for this from scratch. I expect to extend and improve JeeMon itself along the way, since it’s still very much in its infancy.

In case this is all new to you: reflow soldering is a technique whereby you apply solder paste to a PCB, carefully add all the components on top, and then bake that whole enchillada according to a preset temperature / time profile. The end result is a finished circuit. Here are some pictures from a few months ago.

Here is the intial setup:

Dsc 1413

From left to right: a 4.5V 3x AAA battery pack, the JeeNode, the Thermo Plug, and a 1-meter thermocouple sensor. This consists of two metal wires of different types, joined at the end. The end is where sensing takes place, because every junction of two different metals generates a tiny electric potential related to temperature.

Yesterday’s post contained the very simple sketch I’m using for this first step.

Tomorrow, I’ll describe the software setup and the first steps needed to read out the data sent by this sketch.

Update – switched to a slightly simpler setup, as shown in the updated picture.