Understanding the difference between 4-pin and 5-pin relays is crucial for any electrical project! 💡 4-Pin Relay (SPST): Simple ON/OFF switching for one load. It has Common (30), Coil Ground (85), Coil Power (86), and Normally Open (87) contacts. 5-Pin Relay (SPDT): Switches between two loads, like high/low beam headlights. The key difference is the extra "Normally Closed" (N.C.) contact (87a). Knowing how to connect the N/O and N/C pins helps with various applications, from lights to alarms an