1 2 4 8 16 Channel DC 5V Relay Module with Optocoupler Low Level Trigger Expansion Board for arduino Raspberry Pi 1 Channel : The new 5V Relay Module Can be used as microcontroller development board module can be used as home appliance control 5 V-12V to TTL control signal The control signal DC or AC, 220V AC load can be controlled. There is a normally open and one normally closed contact A power indicator light A control indicator, pull off, disconnect does not shine Transistor drive to increase the relay coil control pins high impedance. The control pin has a pull-down circuit to prevent malfunction relay vacant 2 Channel : The new 5V Relay Module Can be used as microcontroller development board module can be used as home appliance control 5 V-12V to TTL control signal The control signal DC or AC, 220V AC load can be controlled. There is a normally open and one normally closed contact A power indicator light A control indicator, pull off, disconnect does not shine Transistor drive to increase the relay coil control pins high impedance. The control pin has a pull-down circuit to prevent malfunction relay vacant 4 Channel : The new 5V Relay Module Can be used as microcontroller development board module can be used as home appliance control 5 V-12V to TTL control signal The control signal DC or AC, 220V AC load can be controlled. There is a normally open and one normally closed contact A power indicator light A control indicator, pull off, disconnect does not shine Transistor drive to increase the relay coil control pins high impedance. The control pin has a pull-down circuit to prevent malfunction relay vacant. 8 Channel : The new 5V Relay Module Can be used as microcontroller development board module can be used as home appliance control 5 V-12V to TTL control signal The control signal DC or AC, 220V AC load can be controlled. There is a normally open and one normally closed contact A power indicator light A control indicator, pull off, disconnect does not shine Transistor drive to increase the relay coil control pins high impedance.