Feeling much more confident in my own soldering skills, I took the design of the previous evolution to the next logical stage. Featuring 8 phototransistors and 7 LEDs, these boards represent the refinement of the previous design. Feeling good about my SMD soldering abilities, I went with TSSOP ICs and 1206 and 0805 components otherwise. Ribbon cable connectors were still used, though this would be the last iteration to do so.

Unfortunately, an unseen problem with the previous module’s LED driver configuration made its way to this prototype as well. The ULN2003A current-sink driver I was using had it’s ground connected to the load resistor for the LEDs to save space on the board layout. Unfortunately, this meant that when any LED was turned on the ground for the ULN2003 was lifted, and all of the other LEDs would glow very dimly. This wasn’t noticed in the previous iteration which was very sensitive to ambient lighting issues, but the precision of this prototype made the problem clear as day.

Ponoko was again used to manufacture a laser cut enclosure seen in the pictures below. This enclosure design would prove to be the biggest design leap in this iteration.

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