A simple relay drive board, allowing Arduino to control 24V monostable relays. It is designed to use with 24VDC realys with coil power ca. 480mW. Current load for each Arduino channel is less than 2.5mA. Each channel is controlled with the high state.
Relay coil wire pair shall be connected to one pair of ARK connectors (COIL_1, COIL_2, etc.)
Arduino circuit(5V) and operating circuit (24V) are fully separated with the PC817 optocouplers. GND and AGND shall not be short-circuited.
There is no need for using the Rx-3 resistors (11kOhm) and LED-x (low-current LED, 2mA), they are just for the indication purpose and the circuit works just fine without them.
PCB still under development. It is right now 107mm x 95mm, 107mm x 108.5mm would be easier to mount in standard PCB din holders. Mounting holes should be moved.
|Qty||Value||Device||Package||Parts||Description||MF||MPN||Aliexpress or Ebay link|
|15||ARK300/2||Wire mounting connectors|
|8||1.5kOhm||Rx-1 1.5kOhm Resistors, lowering the current load from arduino|
|8||18kOhm||Rx-2 18kOhm Resistors, limiting the current draw of the transistor|
|8||11kOhm||Rx-3 11kOhm Resistors, limiting the current draw of the LED|
|8||PC817||Ox Optocouplers, separating the arduino from the 24V circuits|
|8||BC337||Tx NPN Transistors, driving the relaye|
|8||1N4007||Dx Diode, discharging the relay's diode after turning of the relay|
|8||2mA LED||LEDx Low current LED, 2mA, indicating the state of the relay|
|1||PCB Board||PCB board|