SainSmart LM317 Adjustable Voltage Regulator Step Down Power Supply Module With LED Meter Input: DC 0V ~ 30V / AC 0V ~ 22V Output: DC 1.25V ~ 28V Output current: 2A Max. Circuit board size: 69 x 50 x 27mm ( L x W x H ) Due to the digital voltage display module operating voltage is 3V- only when the voltage is higher than 3V to display properly