Sean Outram

About

Experience

Portfolio

Blog

Designing the sequencer hardware


The basic design

  • Should be based around the Pico W
  • Should have built in methods for displaying basic information
  • Use an external 240VAC -> 5VDC board (for safety and ease)
  • Have 3 Control channels
  • Expose UART pins for the wait sign

General wiring Diagram

My general idea for how the sequencer works is like:

            Power in
               |
            Control Board
        /     ^             \
    Power Board            Relay

The challenges

240v

Working out how to handle this was a challenge. This included things like:

  • Designing the PCB to handle it
  • Safeguards for if something goes wrong.

I solved these issues by:

  • using 3mm traces for anything that should take 240V
  • having a ground plane on the PCB so the circuit will ground via the cable instead of the rest of the circuitry
  • Putting a fuse inline before the 3 light channel outputs

Size

The art of compacting a 4 layer PCB's is intense. I eventually ended up with a long but thin PCB