Devlog 1 - Smart Bin

why: recycling bins get contaminated easily, and one bad load can get the whole bin rejected and landfilled. every recycling project i’ve seen is an app telling you which bin to use. i wanted the bin to just do it.

schematic

• 34 components, 26 nets: pi header, load cell (hx711), battery sense (mcp3208), servo rail, led driver, break-beam
• hx711 runs at 3.3 v so both signals are pi-safe, which deletes 4 level-shifting parts
• servo has its own ground meeting pi ground at one 0r link. a shared return browns out the pi and corrupts the sd card
• caught a real bug: led on gpio18 and servo on gpio12 are both pwm0

board

• 65 × 45 mm, 2 layers, pi zero hat footprint. fully routed, ground plane poured. gerbers exported.

cad

• 7 parts on a base plate: pan, hub, idler, servo mount, bearing block, pi mount, plate.

• it couldn’t move. pivot sat 16 mm above the plate, but the pan is 180 mm wide, so at 45° the edges swing 65 mm down and cut through it. raised the pivot to 70 mm

• also measured my actual mg996r instead of trusting the spec (it was actually 39.9 not 40.7 mm, shaft 10.95 off centre not 10.35)

FYI i accidently cadded on fusion and forgot to lapse (there goes like 4 hours of my life) and i imported to onshape so u can see it