Review on Lystin 8 Channel DC 5V Relay Module Control Board with Optocoupler: Ideal for Arduino, Raspberry Pi, and STM32 by Brian Trotter

Please note that when using this device you must route a LOW signal from your microprocessor to turn on the relay. Outputting a HIGH signal from your microcontroller turns the relay off. Your output pin connected to the control input of the relay should be able to draw 13 milliamps. Note that turning on all eight relays may cause your microcontroller to draw more current than it can safely handle. Check your specs. Since the voltage drop is very small, the reduction in current does not usually cause large power dissipation (heating). this is usually the culprit behind such device overload situations. However, to be on the safe side, check how high the maximum simultaneous output current consumption is.