This is an LM2596 DC-DC buck converter step-down power module with high-precision potentiometer for adjusting output voltage, capable of driving a load up to 3A with high efficiency. When the output current required is greater than 2.5A(10W) an external heatsink is suggested. Use on board switch to change display measurement between the input or output voltage, and a LED indicate which value(IN/OUT) is being measured. This setting is stored even after power off. Voltmeter can be turned off, just keep the switch pressed for 1 second and leave it. Adjust Input and output voltage measurement error offset – long press switch for 4 seconds or more, the digital display flashes, then short press the button to change the value of output (values range from -0.5 to 0.5, the unit is V), a positive number indicates an upward calibration, negative downward calibration. Now press the button again for adjust input offset in same manner.