D-PLANET [2-Pack] LM2596s Buck Converter DC to DC Step-Down Voltage Regulator Power Module 36V 24V 12V to 5V 2A Voltage Stabilizer with LED Display 

Product Features Parameters: Input Voltage: DC 4-40V, error ±0.1V( note: digital display dose not work when input voltage is under 4v) Output Voltage: DC 1.25V - 37V Output Current: 3A(MAX) It is recommended to use under 2A (NOTE: When using high power, add a heat sink to the power supply chip) Size: 6.6x3.9x1.8CM Weight: 22g Fuction: Built in over-temperature protection function Built in current limit function Built in output short-circuit protection function How to use 1.Press the button in a short time( 1 second) so that “in” LED lighted, the voltmeter shows the value of input voltage 2.Press the button in a short time( 1 second) again so that “out” LED lighted, the voltmeter shows the value of output voltage 3.Rotate the top screw of potentiometer clockwise to boost the value of the output voltage, anti clockwise to reduce it. 4.long press the button between 1 and 4 seconds to turn off the voltmeter. How to adjust accuracy of input/output voltage (for the person who need a highly accurate value of number） 1.long press the button for more than 4 seconds, then release, voltmeter and “in” LED flash in synchronization entering into the input voltage calibration mode. 2.Press the button in a short time( 1 second) to adjust the value(range from -0.5~0.5v, positive means to  rises units, negative means to minus units)( Due to a unit is less than 0.1V, so you have to continuously press 1 to 5 times to see the voltmeter change 0.1V) 3.long press the button for more than 2 seconds and then release to enter the output voltage calibration mode. 4.After calibration, long press the button for more than 2 seconds all parameters will be saved automatically and back to the voltage display.