Description: A adapter module for ESP-01 Wi-Fi module. 3.3V voltage regulator circuit and onboard level conversion circuit can make 5V microcontroller easy to use with ESP-01 Wi-Fi module. Also, the item can be used with Arduino UNO R3 or compatible board. Here is schenmatic: http://img.banggood.com/file/products/20160408023336ESP-01%20Adapter%20module%20Schenmatic.pdf Features: Working voltage: 4.5~5.5V (On-board 3.3V LDO Regulator) Working current: 0-240mA Interface logic voltage: 3.3V / 5V compatible(On-board level shift circuit)