$10 ResMed CPAP DIY Power Adapter – 3D Printable + Electronics Guide

This project allows you to power a ResMed AirSense 10 CPAP machine using a DIY adapter that delivers the required 24V power and the correct 3.3V signal pin voltage. This setup is useful if you're building a portable power solution, using a USB-C PD battery bank, or a 12v/24v car battery port or any DC power supply  (ideally 90Watts)

The adapter includes:

A custom 3D-printed enclosure

A boost converter for 24V

A buck converter for 3.3V signal generation

A 2.7Kohm resistor on the signal pin to "unlock" full CPAP functionality

Electronics

ResMed machines require:

24V DC on the inner barrel

GND on the outer barrel

3.3V DC on the center pin (sense pin) to confirm the power supply is genuine

Without the signal pin at 3.3V + 2.7k residtor the device will not work thanks to ResMed “proprietary” design -you will need the below cable 

https://www.aliexpress.com/item/1005007383388995.html

and will need a connector to bring in the power source

https://www.aliexpress.com/item/1005008525467502.html

 Power Components

1. Boost Converter (to 24V)

Converts the input voltage (e.g., from USB-C or battery) to a stable 24V output -  you will need to adjust the potentiometer so the output delivers 24V

Used to power the CPAP device

https://www.aliexpress.com/item/1005006053916223.html

 2. Buck Converter (to 3.3V)

Converts the input voltage to 3.3V to power the signal pin - you will need to adjust the potentiometer so the output delivers 3.3V

This ensures the machine recognizes the power source as valid

https://www.aliexpress.com/item/1005008604867476.html

Signal Pin Setup

To simulate the original ResMed power supply, a 3.3V signal must be applied to the center pin of the barrel connector.

I used:

3.3V from the buck converter

A 2.7kΩ resistor between the 3.3V output and the center pin

This works because the ResMed just checks for the presence of 3.3V — no data or voltage divider is needed in this case.

Optionally(if you are powering it using a car/truck) add a 50v/100nF capacitor from center pin to GND for noise filtering and  and a 50v/100uf on the input between the + and GND

Wiring Summary

All grounds must be common between 24V and 3.3V sources.