The relay output is can only drive small loads of up to 100 mA @ 5 V so normally there is a need for an external realy. In that case. the power to drive the relay comes from outside the AKKR8 sensor board. Please use the following diagram for wiring:
The relay can be from 5V to 24V Coil, and the power supply needs to match the voltage of the relay coil. Please bear in mind that the AKKR8 sensor can not be connected to a power supply exceeding 5V ±10%. It is recommended that a fuse is present in this loop, and should be a 50mA to 100mA quick-blow fuse as required by the relay coil resistance.