Utility Plug

The Utility Plug is a small board to interface a port to an RJ-12 jack.

The kit includes the following extra components, to handle a variety of simple interfacing and signal-conditioning scenarios:

  • 2x 100 Ω, 1 kΩ, and 10 kΩ resistors (1/6 watt)
  • 2x 1N4004 diodes, for AC to DC conversion and to drive inductive loads
  • 2x 2N4401 transistors which can switch up to 500 mA @ 40V

These extra components make it possible to adjust signal levels, provide input protection, limit the current going through attached LEDs or lights, and generate more current than the ATMega I/O pins can generate by themselves.

Also included in the kit is a 1-meter length of 6-wire white cable, with an RJ-12 plug already crimped on.

The RJ-12 jack on this plug can also be used with RJ-11 cables (commercial or home-made) with only 4 of the 6 wires connected. In this case PWR and IRQ will not be connected, only AIO, DIO, +3V, and GND.


For a simple connection, with all the port pins wired through to the RJ-12 jack, short out the 4 small jumpers on the plug by adding a dab of solder to them.

For other circuit options, please refer to the schematic below.

Header Pinouts

The 1-meter cable uses the following color codes:

  • +3V = RED
  • PWR = BLUE

Design Info

Dimensions: 21.1 x 34.0 mm
CadSoft EAGLE design files: see below.
This plug can be operated at 5V as well as 3.3V.

This board uses the conventions of a JeePlug and can be used with the ports on a JeeNode. It can also be used with other boards and MCU’s, if you hook it up properly and adapt the interface code for it.

How to Get It

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