KX4OM Plug PiG

Plug PiG

If you've built the NoGa PiG, I don't have to tell you how useful it is. No more blown fuses to your QRP rigs and accessories. Everything I connect to my battery on the workbench or in the field is protected by this handy unit, which is typically built in an altoids tin. Since I occasionally operate QRP mobile, and I sometimes use the DC socket one of those hefty emergency battery units that are used to jump start a car, I thought it would be nice to have PiG protection anywhere, any time.

Like the original NoGa PiG, the Plug PiG uses a 3Amp-rated shunt reverse power diode, an LM311 used as a voltage comparator, and a Polyswitch RXE135 resettable fuse. The Polyswitch device is rated at 1.35 Amps hold current, 2.7 Amps trip current and 40 Amps maximum current on overload or short circuit conditions.

In reengineering the PiG functionality for a much smaller case, I decided to leave out a few features. I didn't need the optional keyer and audio noise suppression, since this was to be power protection only, and since it's designed strictly for battery-powered use, I could leave out the overvoltage protection features. First, I traced out the existing PC board of the cell phone charger/DC adapter. I created a schematic of the needed funtionality in EAGLE Cad, and next I laid out the components to fit the required footprint of the PC board. Then it was a matter of stuffing the board and testing the short circuit and undervoltage features of the unit, following the instructions from the original NoGa PiG. One other addition I made is a "Power Good" LED to let me know that the socket I'm plugged into actually has power to it.

Below are several photos of the unit as I proceeded through the design and construction. Click on the images to enlarge them.


Original Board & New Board Plug PiG Design Stuffed Board & AssemblyPower Check Under-Voltage Test New Board Installed