I’m not putting a WiFi router into a phone charger (Part 3)

Sourcing Electronics

Sourcing components for prototyping is usually straightforward; your CAD software will generate you a CSV BOM, you upload it to Digikey, and parts show up at your front door. I’ve gone through Mouser, Digikey, LCSC, Aliexpress, and my friend Mia to get parts for this build. You arrive at a costly prototype when you add up the combined shipping costs, parts costs, and duties.

Graphical Guide to Sourcing Electronics

Power Board Design

Boards with no components
Flyback Design

Transformer Isolation

Half decent looking transformer

PCB Isolation

The transformer isn’t the only item requiring decent isolation; the PCB should also be designed to allow acceptable creepage and clearance.

  1. Clearance is the shortest distance in air between two conductive parts.
  2. Creepage distance is the shortest distance along the surface of solid insulating material between two conductive parts.
IPC2221A
High side to low side isolation

Line Bypass Capacitor

As for other safety components, let's talk about some key players.

CY3

Fusing

Fuse F1
NTC1
D1

In Conclusion

This certainly wasn’t my ideal post, but things are rocky right now. I plan to build some costly prototypes in the coming months, test and wait until things shake out on the chip shortage front.

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