Overview A compact 5V relay module built around the ESP-01S (ESP8266) WiFi module, designed for smart home and IoT switching applications. Control mains or low-voltage loads remotely over your WiFi network - no hub or proprietary cloud service required when running open firmware. Compatible with popular open-source firmware including Tasmota and ESPHome, making it a natural fit for Home Assistant and MQTT-based automation setups. The onboard relay is driven via an optocoupler for isolation between the ESP8266 logic and the relay coil circuit. Specifications Module supply voltage DC 5V Relay load - AC 10A @ 250VAC / 10A @ 125VAC Relay load - DC 10A @ 30VDC / 10A @ 28VDC Relay contacts NO, NC, and COM - suitable for both normally-open and normally-closed wiring Relay model SRD-5VDC-SL-C (or JQC-3FF-S-Z equivalent) WiFi module ESP-01S (ESP8266, 1MB flash) WiFi standard 802.11 b/g/n, 2.4GHz Relay control GPIO0 (via onboard optocoupler) Common Use Cases Smart lighting control (lamps, LED strips via SSR) Remotely switched power outlets Pump or irrigation control Garage door or gate triggers Home automation with Home Assistant / MQTT Firmware & Programming Notes The ESP-01S ships with basic AT firmware. To use Tasmota or ESPHome you'll need to flash via a USB-to-UART adapter (3.3V logic - a CP2104 works well). To enter flash mode, hold GPIO0 low at power-on. Tasmota's Generic (18) template or a custom ESPHome config with output: GPIO0 for the relay are the typical starting points. Note: If switching mains voltages, ensure the module is enclosed safely and that wiring is performed by a licensed electrician where required by local regulations.
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