Are our components enough?

[u/Shadow_StrikerX]

Hey guys! We are currently developing our senior high school capstone research project called Eco-nnect. The goal of the project is to build an automated reverse vending machine that accepts plastic bottles and tin cans in exchange for Wi-Fi access/time.

Before we finalize our wiring and assembly, we’d love to get some feedback from people who have built similar embedded systems or reverse vending machines.

Here is our current component list:

Component List & Specs:

Main Controller: Orange Pi One + 16GB Sandisk Class 10 MicroSD Card

Sensors:

Plastic Detection: LJC12A3-5-Z/BX Capacitive Proximity Sensor (NPN)

Metal/Can Detection: LJ12A3-4-Z/BX Inductive Proximity Sensor (NPN)

Object Passage/Counting: E18-D80NK Adjustable IR Obstacle Sensor

Signal Isolation & Interfacing: PC817 4-Channel Optocoupler Isolation Board

Display: LCD 2004 (or 1602) Board with I2C Module

Actuator/Mechanism: MG996R High-Torque Metal Gear Servo Motor

Power Supply & Distribution:

12V 5A DC Power Adapter

LM2596 DC-DC Buck Converter (12V to 5V step-down)

Female 12V DC Barrel Jack Adapter (5.5mm x 2.1mm)

Relay: 5V 1-Channel Relay Module

Network & Cabling: CAT6 Ethernet Cable + Assorted Jumper Wires (M-M, M-F, F-F)

Question:

Sensor Logic & Logic Levels:

Both the inductive and capacitive sensors usually run on 6V–36V (we plan to power them via 12V). Since their NPN outputs will send 12V signals, we are using the PC817 Optocoupler board to safely step down the signal to 3.3V for the Orange Pi GPIO pins. Is this setup solid, or is there a better way to route this?

For the capacitive sensor (plastic), how sensitive is it in practice? Have you experienced false positives with nearby enclosure materials (e.g., acrylic or wood)?

Mechanism / Sorting:

Is a single MG996R servo sufficient for a trapdoor/sorting flap mechanism, or should we consider stepper motors or dual servos if the flap gets weighed down?

Missing / Recommended Components:

Is there anything essential we forgot (e.g., flyback diodes, extra decoupling capacitors, terminal blocks, specific fusable protection)?

Any feedback, wiring layout advice, or hardware pitfalls you encountered while doing a similar setup would be an awesome help for our team! Thanks in advance!