Jon's Place

Friday, March 23, 2007

Reflow Oven

For the past few days, I've been working on building a simple reflow oven for soldering surface mount boards like the one in the previous post. That one was soldered in my friend Julian's reflow oven, but I have to drive thirty minutes to get to his place, and given the quantity of boards I'm planning on building over the next few months, having my own oven will definitely be worthwhile.

Julian's oven was built from a Circuit Cellar contest entry. He used a PIC 16F876, and had a nice PCB printed from APCircuits. I decided ahead of time that since I'm undergoing the switch from PICs to AVRs, that I would use an ATmega168 based controller board instead of a PIC.

I also, after talking to my brother, realized that I could use a much cheaper parallel LCD panel ($7.30 from Digikey) instead of a much more expensive (but easier to interface to) serial LCD panel. Turns out you can interface to one of these LCD panels using 7 wires. Much thanks to Dave for his excellent LCD driver code.

So, I did a Digikey order, and got a bunch of stuff, including a 20 amp solid state relay, a K-type thermocouple, and an AD595 thermocouple op-amp chip. The thermocouple is basically a temperature probe, and the op-amp provides a 0-5 volt analog signal based on the temperature at the tip of the probe. I also picked up a nice Black & Decker toaster oven at Canadian Tire.

I put together a controller board, which at this point isn't finished - I don't have the AD595 wired in, nor do I have the connection for the relay. But the ATmega88 (which is a smaller memory size version of the ATmega168) is running, driving the LCD panel, and flashing a status LED.

Next up, I have to add in support for the relay, and then the thermocouple. Then I need to take apart the side/back of the oven, and cut into the wiring so I can control the oven using the relay. Once that is done, I take Julian's C code for the PIC, alter it to run on my ATmega88, and I'm all set...


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