Laptop2usb

laptop2usb

The premises

• In tech-oriented public spaces there's constant shortage of wallplug USB chargers
• The notebooks' powerbricks generally outlive the notebooks themself, so with enough effort you may get one for free

How do I?

You fasten the PCB to a powerbrick.

The device takes anything between 17-20V, converts it into 5V, and splits into multiple USB and screw terminal ports. All of these ports are polyfuse-protected.

Status

I'm yet to check a couple of things, and will do rev.2:

• The converter gets super hot right now - is this OK? Calculate and document thermal resistance stuff. Verify converter efficiency.
• Is the 10 mOhm current-limiting resistor even working?
• The future is now - add USB C?
• Maximum current it can handle (it was designed for 8A max, but I doubt it'll survive that for long)
• Are USB ports wired properly? Do android/iOS/raspberry PIs utilize it well enough?
• Now check the first letters of the list

Trivia

I ordered the prototype from JLCPcb, with passive elements surface mounted. Their online tool automatically assigns the elements from BOM into the part numbers from their store. Apparently it parsed the shunt 10mOhm resistor as 10 Mega Ohms.

With 10MegaOhms in the power path, the LM25085 somehow managed to produce 4V output with enough current to shine an onboard LED. Now that's dedication.

EDIT: it's been 2 years and one of my friends at work did literally the same kind of mistake when ordering PCBA from circuithub. I managed to catch that mistake quite fast, and implement a fix. I guess the lesson is, that those silly side-projects are really not in vain.