Based on the Particle.io Photon. Opto-isolated to protect your computer in case of FET failure. Design to switch the low voltage output of the power supply to your modem, I terminated in a DC barrel connector male and female, to go inline to the cable modem.
This project was built out of what I had on hand. The PHT8N06LT FETs used (which are now obsolete), IRLL024N and STN3NF06L look to be alternatives for this part. Tested @ 12V / 1A, should work to 24V and 2A (but test the FET for heat generation and voltage drop). Should also work at 5V (see schematic for notes).
PCB was CNC'd on an Othermill and the copper was Tin coated.
ALL files, including schematic, BOM and source code is included in this project. You assume all risk associated with building or using this project.