Description : This is a board designed for opto - isolation . This board is helpful for connecting digital systems ( like a 5V microcontroller ) to a high - voltage or noisy system . This board electrically isolates a controller from the high - power system by use of an opto - isolator IC . This IC has two LEDs and two photodiodes built - in . allows the low - voltage side to control a high voltage side . We often use this board to allow a microcontroller control servos or other motors that use a higher voltage than the TTL logic on the ( 3 . 3V or 5V ) micro , and may cause electromagnetic interferance with our system as the motors turn on and off . This board will isolate the systems , creating a type of electrical noise barrier between devices . This breakout board uses the ILD213T optoisolator and discrete transistors to correct the logic . Comes with two channels . Great for use in noisy circuits where signal lines require electrical isolation . A normal LED opto - isolator will invert the logic of a signal . We threw some transistors on this compact board to correct the inversion . What you put into the IN pins , will be replicated on the the OUT pins , but at the higher voltage ( HV ). Size : 15mm * 12mm * 5mm Material : Plastic Color : Red Package Includes : 1x Module with 2 Pin Headers (2 Pack)