All of the major components of our Lego Sorting Machine have reached the proof of concept stage, so the mission for the last two months has been replacing prototype hardware components with parts that are production ready. After the recent completion of the camera and light-box overhaul, it was time to focus on the belt buckle.

Do it again! But better this time...

Our conveyor belt controller (the "Belt Buckle") previously consisted of two arduinos in box, with some hot glue and a small bread board. It worked well enough for our R&D porpoises, but we're getting closer to being production ready. The porpoises have begun to demand better pay and higher quality tools.

The first thing we needed were the output circuits for the air valves. In a previous post, I wrote about a circuit that would allow the arduino to safely power the air valves. We had decided to support up to 16 air valves for this version of the belt buckle, meaning I would need to manually solder 16 MOSFETS, 16x resistors and diodes, and three wires per MOSFET.

I made one of them for the R&D porpoises to play around with, and it worked perfectly. However it took about 2 hours of work to cut, bend, mount, and solder all of the bits for each unit. I didn't much care to devote ~30 hours of work to making 15 more of these, so I outsourced the work to my good friend Aliexpress.com.

I lost an afternoon scouring the endless menagerie of dubious and chintzy items that Ali has to offer. Endless rows of knick-knacks, cheapsakes, futurisms, and oddities fought for my attention like journalists chasing an acquitted politician. I pushed and squeezed through the chaotic bustle of discount coupons and flashing sale banners, doing my best to ignore the cat calls of cyberspace salesmen peddling their meatspace commodities.

My determination paid off. Over the clamor of the busy market streets; through the haze of smoke and dust I heard them calling. I pushed faster and more rudely through the surging masses of digital delights until I found them.

Tucked away in one of a million small corners of Aliexpress, I found a lovely little board with 4 MOSFET outputs each, and they work beautifully. To save space in the Belt Buckle enclosure I drilled some extra holes and stacked them up using some standoffs, like this:

We now have 16 MOSFET outputs, ready to go. I terminated the outputs onto 1/4' audio jacks, as you can see here:

Once the airjets are operational they will plug in here. I don't have any fancy labels yet so I used my God-like photoshop skills to make a picture which shows the port numbers:

Supply and Demand

Previously, the belt buckle was powered by the USB connection. A couple of hacked together power adapters were used for the camera LEDs and the belt encoder. We now have a 12VDC,  10 amp power supply that runs both arduinos, the air valves, the belt encoder, and the MOSFET boards:

Finally we installed a nice looking power plug with an illuminated on/off switch. The only thing yet to be done is mount a metal plate over the terminals on the back of the switch, so we don't have any exposed 120 volt conductors.  

Here is a picture of it fully assembled and ready for action!