Review on ELEGOO Optocoupler Module for Arduino and Raspberry Pi - Channel-Enhanced for Optimal Performance by Jeff Westra

Great relay boards, I just need to get my dog to stop opening Amazon packages first. I think she's so excited she forgets to sniff it first to see if it's a pack of treats or toys for her. As soon as she rips open the envelope or box and takes out what's inside, she seems to stop and sniff it, and if it's not her treat or toy, she stops. . Long story short, both of my 8 channel relay cards worked fine. I tested them, all 8 channels worked as expected. Before you write negative reviews about these relay boards, remember that they are activated LOW, not HIGH as you would normally expect. In fact, all relay boards of this type START ACTIVE LOW whether it is a single channel or a 16 channel relay board. Also, I've seen some negative reviews about contacts failing at less than 10 amps and less than 30 volts DC. You need to protect the contacts when the load to be switched is inductive and not just resistive. You can use a 1/2 watt 100 ohm resistor in series with a 0.1uF non-polarized capacitor rated at 1000 volts across your relay pin to help bleed and ground arcing on those pins extinguish to protect them from welding. I hope this will be helpful to you. If you're not very knowledgeable about electronics, read as much as you can to have more fun and less frustration.