Hacking together a USB-C charger for a cheap Chromebook

The era of USB-C has come. The other day I threw all other cables into a box, and bought a set of USB-C to USB-C, Lightning, and microUSB cables. USB-C chargers around the house, USB-C PD power bank, even a nice small USB-C dock that works with the Nintendo Switch if the charger can do the right voltage. It's glorious.

Only one thing won't charge with USB-C, my awfully cheap ($190 for 4GB of RAM) Samsung Chromebook 3, a machine I use when I want the extra security of the Chrome OS platform. Instead, this laptop charges from an old-school 12V barrel connector, forcing me to carry around an extra brick. 😢

side view of the laptop with round charging connector

USB traditionally delivers 5V of power, but with the introduction of the USB Power Delivery standard, devices can negotiate higher voltages with capable power bricks. Indeed, 12V is an option, and at least a couple of my chargers support it.

USB charger with 12V marking amongst others

It should be possible to hack together a USB-C charger for my cheap Chromebook!

What we need is called a "USB-C PD trigger", a little board that negotiates a specific PD voltage with a charger. There are a few variants, including ones with a button to select the voltage, but the most common one is a tiny board with a female USB-C connector called ZYPDS.

They are so cheap that I suspect the reason the laptops don't come with them is that 1) it requires a charger that can deliver that specific voltage, and people are already confused enough by USB-C and 2) the USB-C charger side is probably more expensive.

They usually support 15V/20V (selected by soldering a bridge), and while I suspect 15V would have worked too, I found one on eBay claiming 9V/12V. It has the same model name, but a different PCB color. Perfect!

an order for a blue 9V/12V ZYPDS for $4.42

This thing is small enough to fit in a cable (or even in the laptop, but I wanted to keep this as uninvasive as possible) so I also got a short cable with a barrel connector, and some heat shrink tubing.

When it arrived it was already configured for 12V, and delivered more or less on the spot.

multimeter connected to the ZYPDS showing 12.17V

The only tricky thing was figuring out the polarity of the cable and the connector. I learned that the polarity of the connector is the marking on the charger that looks a little like ⊖--C●--⊕, and commonly the outer surface of the barrel is the negative. I figured out which wire connected to the outer surface with the multimeter continuity mode.

multimeter connected to the barrel connector and a wire from the cable

A mediocre soldering job later I had a short adaptor from USB-C to a barrel connector.

ZYPDS with two wires soldered to the connector pads

And it successfully charges the laptop!

the adaptor connected to a charging laptop

The only snag was that the barrel connector I got wasn't a perfect fit for the laptop, so it would lose connection if not pulled downwards. Knowing the setup worked, I just cut the stock charger and used its connector instead. It was more annoying to solder because it's a concentric cable, but it works perfectly.

With the heat shrink tubing on it doesn't even look that bad, and definitely beats carrying an extra charger around! (By the way, heat shrink tubing is amazing.)

the adaptor charging a laptop

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