Cable Modem Automatic Power Cycler

thingiverse

When our Netgear CM2050V started flaking out and lost internet connection daily, our ISP just kept advising us to power cycle the modem. Despite a strong signal from the ISP, the cable modem would not reconnect by itself without a power cycle.We found that inconvenient, so I designed this electronic gizmo to automatically power cycle the cable modem if the connection is lost for a (configurable) time period, using a LED on the front of the cable modem to determine if the connection was lost.The 3D-printable photocell clip in this design is specific to the CM2050V cable modem. Our modem is located in a dark closet so I don't need to worry about light leakage from other sources, but the clip is in black PLA to limit light intrusion as much as possible.Parts I used for the electronics (see photo) were as follows:Male power plug (matches the one on the cable modem's 12V power adapter)Female power connector (matches the one on the cable modem)Arduino Nano (available from Amazon)5V Relay Module with Photoisolator (such as item B095YD3732 from Amazon)5V regulator (I used an LM340T5)15uF capacitor (other values will work too)Photocell22Kohm resistor (or similar)Piezo beeperSmall breadboard to solder loose parts ontoSmall enclosure to hold the electronics (I used a metal case from a dead 5-port ethernet switch and designed a 3D-printed faceplate which covers the cutout for the ethernet ports; a case is NOT included in this design).Miscellaneous wire, solder, and Kapton tape to wrap around PCB'sSchematic diagram attached, and Arduino nano code is in the attached .ino file.The circuit draws about 25mA from the cable modem's 12V power adapter when the relay is not activated, and 125mA when the relay is activated (but the cable modem will be off). Instead of using the 12V power from my cable modem's power adapter, 5V power can instead be supplied to the circuit above via the USB connector on the nano board (this is what I did for testing, with no voltage regulator needed).The relay module was jumper-configurable for high or low input to activate the relay. I set it for high to match my arduino code.Instead of interrupting the 12V DC input to the cable modem, one could use the relay to interrupt the A/C power to the power adapter, but I didn't want to mess with higher voltages, and I liked being able to power the circuit from the existing 12V power adapter.You may need to tweak the photocell input voltages depending on your photocell and brightness of the connection LED on your cable modem.You will also want to tweak the time delays in the Arduino code for your preference (default is to wait 30 minutes for the cable modem to establish a connection after power up, wait 5 minutes after the connection is lost before power cycling, and turn off the modem power for 15 seconds).After all this, I solved the Netgear CM2050V lost connection issue by simply doing a Factory Reset. :-) But, I still have this gizmo attached and waiting for a connection loss.