This is a peripheral board with 4 relais, rated at 5A/250V each. The board has a ML10 output connector for connection with the AT2313 Project board. It has also 4 LED’s for indication which relais is switched on.
The circuit is simple, it consists of no more then an ML10 connector, a ULN2803A, which contains eight open collector darlington transistors, four of them amplifies the signals that come from the microcontroller. The IC has build in protection diodes, so no external diodes for driving the relais are needed. There are also four LED’s with current limiting resistors to indicate if a relais is energized, each output of the relais goes to a 2-pole screw connector.
Schematic Circuit and PCB Layout
Below you see the picture of the curcuit
For more detail: Relais Driver Board