Relay not being triggered / ESP32 + external 5v : r/arduino
esp8266 - Powering up an ESP32 with IO extender (MCP23017) and two of 8 channel relays from an external 5 V, 10 A power supply - Electrical Engineering Stack Exchange
Raspberry Pi: 8 Channel Relay + External Power Supply Tutorial and Example - YouTube
Relay Control not Working External Power Supply! - General Electronics - Arduino Forum