Our crowtail add a new sensor about environmental monitoring that called Crowtail- HTU21D HumIdity &Temperature sensor, which is a low-cost, easy to use, highly accurate, digital humidity and temperature sensor. And the work voltage range about this sensor is 1.5V-3.6V, so we need to use the AMS1117 to achieve step-down when we want it work with our crowduino which has a 5V voltage output. The sensor outputs the calibrated digital signal in standard I2C format. Diversified output mode, wide operating voltage range, while high temperature accuracy and humidity accuracy. HTU21 series module designed for low-power/small-volume application design, with good quality, fast response speed, anti-interference ability, cost-effective advantages, very low power consumption. It’s ideal for environmental sensing and data logging and perfect for a weather stations or humidor control systems. All you need is connect the specific crowtail port into the arduino/crowduino by using a crowtail cable.