Opto-coupler Plug

The Opto-coupler Plug is a small board containing a dual opto-coupler. It can be used to detect the presence of low DC voltages (a few dozen volts) and currents (milliamps) without creating a direct electrical connection to any other circuits.

The two independent input channels use separate built-in LED’s which must be driven with ~ 3 .. 55 mA of current. Two 1 kΩ series resistors are included, which match ~ 3 .. 12 V DC sources. Select other resistor values for higher or lower voltages.

The current v2 board can also be configured as a dual opto-coupled output interface, where each channel acts as a (polarized) switch, based on the built-in photo transistor. The output current is limited to 60 mA max. Note: the solder jumpers need to be shorted out to use this as an output board.

This combination of dual opto-coupler chip and connector style is aimed at low-voltage use. Higher voltages (such as AC mains) are not supported - you should only attempt this if you know what you’re doing, and at your own risk!

The terminal blocks used on this plug are detachable and use a standard 3.5 mm grid. The two inputs have separate connectors.

The pins are laid out as two independent pairs. Each pair is an electrically isolated LED with no connection to the rest of the circuit. LEDs are polarized and should be properly connected to power +/-.


The V2 board can be populated as either an input plug or an output plug. The choice determines how the IC socket should be soldered on, as well as where to use resistors and set the solder jumpers:

Header Pinouts

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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