This cable will let you get rid of all those wall adapters you have stashed in the plastic bin in the basement. Instead of multiple wall warts with different power and current capabilities, this cable will convert any USB Type C power adapter with Power Delivery (PD) support into a DC power port, at up to 5 Amps output!
Inside the cable is a PD sink negotiation chip. When plugged into a proper PD Type C adapter that can provide 9V it will chat with the PD source chip in the power supply and tell it "Hey please change your output to 9V thankyouverymuch!", and ta-da, you get 9V out on the DC barrel jack.
Do check the side of the adapter you are plugging into to make sure it is a PD source - the voltage and current capabilities will be listed on your adapter. We have a demo image up top for what it will look like if it can support the desired output.
Note it is not a boost or buck converter - if the power supply only can do 5V or 20V it will not magically convert it to 9V. Voltage output will often be 0.25V to 0.5V higher than the rated voltage so that at high current draw the voltage drop across the cable will still keep it at about the desired voltage at the tip.
This cable includes an EMARK chip, required by the USB C specification but sometimes left out. That means you can use this for high current (5A) charging / power delivery. These are also especially souped-up USB Power Delivery cables, meaning they're suitable for a swath of demanding devices, like laptops.
This cable is 1.2 meters (or 1.8m, for the 28V version) long, so you get just the right amount of length for your project. Also comes with a velcro tie to keep it nicely coiled and neat. Tip is 5.5mm outer diameter, 2.5mm inner diameter with center positive voltage, but it's springy so it works just fine for 2.1mm as well.
Please note: If your USB PD power supply does not explicitly have 28V out, the 28V cable will provide 20V or some other lower voltage.