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Reflow Fred Style! :-) 
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Just received the solid state relay and PCB that I needed to get this show properly on the road! I guess that's my job for today, then. Nothing left to wait for.

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Thu May 03, 2012 11:00 am
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This time I got the solder paste quantity right, and preheated the oven so as to allow the solder to dry for a minute or so before reflowing it. A manual profile, if you will :-)

Image

A little more context at the same scale: http://stuff.fredcooke.com/toaster.oven ... .board.jpg

Now to wire it up and write some firmware to measure it, and then control it.

Fred.

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Thu May 03, 2012 12:37 pm
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nicely done mate. A very professional looking finish! :-)


Fri May 04, 2012 12:43 am
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Thanks! Shame i can't get a reading... I think my chinese thermocouple isn't one...

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Fri May 04, 2012 12:49 am
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LOL :-)


Fri May 04, 2012 7:18 am
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Doh! My fault, circuit was incomplete. It turns out that you really do need that 1 megaohm resistor to ground from -ve in...

Just ran a trial test, door was ajar, though, so will be slower to heat up and faster to come down. Going to go away and have lunch and shower and kill the log once it's pretty much room temp again.

Then I'll run it again once cool, and with the door closed, and with a push button for marking the log by slamming one of the other inputs.

Fred.

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Fri May 04, 2012 2:22 pm
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Some strange patterned noise on it, and the door was slightly open the whole time, but a good first run. Will have a shower, upgrade circuit with filters and log marker and rerun from cold. Peak occurs after 6 minutes. Peak temp is about 270C and solder melted at about 220C. The step near the end is the door opening and the probe hitting the floor :-) The test board is looking worse for wear after 3 times up to 230 or so. It's going brown and the solder plated pads are going dull :-)

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More data as it comes to hand!

Fred.

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Fri May 04, 2012 3:32 pm
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It turns out that I didn't fail to notice the door open the first time, rather, I fitted the ally panel to tightly/perfectly/imperfectly and the expansion forces it open with higher temps, woops. Hence the wobbles in this just after the solder melts and i fumble the door while going for the button. Peak temp 300C (I changed K temps in OLV to be C temps) and solder melting around 210 or 215C at about 4:30s time. Total log time ~55minutes and final temperature 37C. Next step, trim the panel a bit so that it's not too big, and properly fit the thermocouple to it so it doesn't move around, and add the solid state relay to control it. Then it's time to write some controller code. Great progress. To achieve the smooth numbers I added filtering to the input of the MCU and to the input of the tcouple amp. Worked perfectly.

Image

Image

More as it comes to hand :-)

EDIT: The little hiccup in the blue line is from an imperfect graft of two screenies into one to get the two sets of numbers.

Fred.

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Fri May 04, 2012 6:45 pm
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plate is 192mm
clearance "cold" is about 1.3mm +/- 0.3mm
expansion of ally is 23.1 µm·m−1·K−1
change in temp is about 230K

(0.192*230*23.1) / 1000 = 1.020096mm

So, I *should* have enough clearance, but in reality, I don't. Likely the back wall is buckling inwards to create this situation. If I shave another 2mm off, then it should be OK.

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Fri May 04, 2012 7:09 pm
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It's all about fans. :-)

more pics of setup?


Fri May 04, 2012 7:49 pm
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