I got a project using arduino and 8 channels relay to switch on lights, now I got a problem of some channels can switch on all the time, but sometimes fail to switch off. If I repeat the process of switch on and off, sometimes it will switch off successfully. No ‘click’ sound is heard while I try to switch off but the led on the relay is off. Any idea on this? Thanks.
Attached is the way how I connect the arduino and relay: