M5Stack U140 Solid State Relay Unit is a DC to DC Single-phase controller kit with an ESP32C3 controller board and solid-state relay. This relay unit supports Modbus networking and fundamental control modes of operation. The controller kit adopts semiconductor switching elements and is contactless. This controller kit offers several advantages, like extremely long life, low switching noise, high switching speed, and no switching spark. The controller kit is designed for humidity or explosion-proof requirements, harsh environments with corrosion, and frequent turn-on/off requirements.