Home › Builds › Run 12 V things from a USB-C charger: PD trigger board, watt meter, 12 V lamp and a USB step-down

Run 12 V things from a USB-C charger: PD trigger board, watt meter, 12 V lamp and a USB step-down

Bench build · Module builds · Beginner · about 15 minutes

Turns a USB-C phone charger that offers 12 V into a 12 V supply with a meter. A USB-C PD charger gives 5 V until something asks for more. A trigger board asks for 12 V and switches its output on once the charger agrees. Check the charger’s label first: most 20–30 W phone chargers offer 12 V, but many laptop chargers jump from 9 V straight to 15 V and refuse 12 V (then ask for 15 V and add a buck module set to 12 V). An inline watt meter shows volts, amps and watts, then the 12 V runs a lamp (or a router, an LED strip, a fan), and a USB step-down module makes 5 V for a phone at the same time. Three boards, no soldering beyond screw terminals.

Run 12 V things from a USB-C charger: PD trigger board, watt meter, 12 V lamp and a USB step-down: the finished build running on the simulator's bench

Build it in the labGuided build, test sheet and fault finding, free in your browser.

zencircuitlab.com/l/run-12v-things-usb

Parts list

Test procedure

Each test has an expected value and a pass range, like a factory test sheet:

  1. Output voltage
  2. Lamp current
  3. USB output
  4. Power drawn from the charger

How it works

What it does: Turns a USB-C phone charger that offers 12 V into a 12 V supply with a meter.

Build it (guided or ready-made), then run its test procedure below. Every test has an expected value and a pass range, just like a factory test sheet.

Background

USB-C PD (2015 onwards) made laptop chargers into adjustable power supplies; trigger boards cost less than a meal.

More builds: module builds