Review on 🔌 SunFounder 5V 8 Channel Relay Shield Module: Compatible with Arduino R3, Raspberry Pi 3, 2 Model B & B+ by Doug Hawkins

It looks like the manufacturer made a mistake in the product description. I was concerned about my RPi's reverse current because the description says it's 15-20mA. According to the internet, most Raspberry Pi boards are only rated for 16mA per GPIO pin (and only 50mA for all pins). It looks like both my boards (2 and 4 relays) use 2.2kΩ resistors on either side of the optocoupler. I have measured that 1.65-1.85mA is being fed back into my Pi when the GPIO pin goes low. I would recommend using a separate 5V power supply if you are activating 4+ relays at once or if you are using the USB ports. to power peripheral devices. Each relay's coils appear to draw 70mA, and some RPis can only handle around 300mA (and possibly less, depending on your Pi and power supply). I also measure the 3.6V potential between the relay board and the GPIO pin when the pin goes low. .