Spatter Analysis

Let's see, yesterday I was not in, b/c I had presentations over at COE all afternoon.  The COSMICi group's presentation is scheduled for this afternoon at 4:30 pm in room A223, and I will leave here to go to it at about 4:00 pm.  Actually, I need to leave a little bit earlier, to get the rubrics ready.

Monday, Darryl and David came in and we talked a little about the bad DAC problem, and probed its output pin (pin 7) directly with the multimeter to verify that the problem was not in the pin-pad connection (if it had been, I don't know if that would have made it any easier to fix, but I thought we should at least check).

Probably, what we need to do at this point is just to shift DACs #3-6 up to positions 2-5, replace the comparator outputs from DAC #2 with Vcc, and modify the firmware to skip DAC #2 when configuring the voltage ladder.  We will only have 5 levels, but we rarely cross all 6 as it is.  We can space the levels out to cover the same range.  It is less information than we had originally, sure, but not too bad.  I just hope we don't lose another one!

In case the problem was caused by water drips from the cooling system, we will hereby institute a policy of only running the fan (not the thermoelectric plate) to eliminate condensation.  If it turns out that the plate absolutely has to be used, we will minimize the chance of drips by only running for a few minutes at a time for short tests.  No more long overnight runs with aggressive cooling until we get a better cooling system.

 We also peered at the board with the magnifying glass, and there is clear residue, probably from evaporated water dripped down from the cooling plate.  Dr. Ordonez suggested during his visit last week that we turn the system upside-down, but we will still need some mechanical support to do that.  Also, that is not a permanent solution b/c we don't really want water dripping onto the carpet & people in the classroom in CLC.  If a cold plate is still used in the new design, then either the cold side has to be sealed from contact with the air, or else there has to be some kind of tray to catch the drips.

In other news:  I am giving a graduate seminar in the ECE department at 4:15 pm next Tuesday (in A337) to survey issues in hardware-software codesign (controlling custom hardware from C) that are exemplified by the work that was done in this project on the FEDM board.  All COSMICi computer engineering students (and all Senior Design students in general) should attend.