Wednesday, November 27, 2013

Toast-R-Reflow: First success

I got the power board installed in the oven without too much difficulty.

This is a picture of the mounting for the power board. I drilled 4 holes in the outer sheet metal enclosure. There was a blank spot near the top (the piece is shown here upside down) where there were no ventilation holes (you don't want to be able to accidentally poke something through a vent and touch a high-voltage PCB trace) and mounted the board there. I got lazy and just shoved the 3 low-voltage wires through a vent slot nearby. I had planned on mounting a grommet, but I got lazy.

This is a view with the top put into position enough to actually attach the wires. The hot line got re-crimped with a new QD connector because the original one was the .178" size and it wouldn't fit the terminals I had mounted on the board.

If the heatsinks look a little funky, it's because it's the prototype board. I didn't properly place holes for the pins on the heatsink to sit in, and the triacs aren't perfectly positioned. The boards that are in the store now are better, but these will do for now for me.

As for the thermocouple, I just ran that through the side of the door. This lets me position it nearby the board every time I get ready. I might come up with a better solution later.

The first board that was processed by the oven was an EV Sim Mark II SMD board.

I used a template and some ChipQuik paste. It was an absolute mess. I am fairly certain that I'm not using the template right. I wound up with sort of "blobs" on the pads and in the area surrounding each. I decided to give it my best shot.

And it worked!

Every part you see there except for the through-hole components and the two parts I had to rework (the protection diode was backwards - the label was very hard to read, and the power jack has a boss that doesn't match up with the hole where it's supposed to land. I had to lop it off with an Xacto knife and resolder it), every part was "nudged" into a blob of paste and the oven took it from there. Most of the parts weren't even completely straight, but the magic of surface tension fixed that.

What's more, I was able to program the controller without mounting the through-hole ISP socket. I got a Pogo ISP adapter from SparkFun, and this was my first opportunity to use that as well, and it also worked perfectly. I went ahead and mounted the through-hole socket anyway, because this is going to wind up in the store, but at least for my own projects, I may not bother anymore.

I'm going to try to do the other two EV Sim II boards that I got in that OSH Park order tomorrow. If those work as well as this one did, then the next step will be for the oven to reflow its own permanent controller board. And that will happen as soon as those boards come back from OSH Park.

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