Step Down LM2596 DC-DC Power Module LED Display Power Supply 3A Adjustable Step-Down Converter 4.0~40 V Voltage Regulator 1, with a voltmeter display, voltmeter error 0.1V, range 4 ~ 40V. (Note: the input voltage is lower than 4V, the onboard voltmeter does not work and does not display) 2. The large volume 5*5 touches the button to switch the measurement input or output voltage, and an indicator light indicates which voltage is being measured. The first time the default digital tube displays the input voltage, and the input indicator IN is on; when the button is touched, the digital tube displays the output voltage, and the output indicator OUT is on. And keep it after the setting, even if it is powered off and then turned on. 3, the voltmeter can be turned off, long press the switch for more than 1 second and less than 4 seconds, you can turn off the hand. Once the voltmeter is turned off, simply press the switch to turn on the voltmeter. 4, with terminal block, no soldering iron can also be used easily, and retain the wire bond point (the input voltage must be more than 1v higher than the voltage to be output) 5, using 150KHz internal oscillation frequency, belonging to the second generation of switching voltage regulator, low power consumption, high efficiency 6, the input end with diode protection, reverse connection will not burn out the module 7, with overheat protection and short circuit protection (more than 15W, please strengthen the heat) How to adjust the accuracy? Output voltage (Input voltage)calibration steps Step 1, Adjust the right button so that "OUT" ("IN")LED lighted, the voltmeter shows the value of output voltage; Press the right button for more than 2 seconds, release, voltmeter and "OUT" ( "IN")LED flashes in synchronization so that you enter the output voltage calibration mode. Step 2, Press the right button (normal speed), the voltage value is adding up a unit; Press the left button, minus a unit; Due to a unit is less than 0.1V, the minimum voltage display to 0.1V, so you need to continuously press 1-5 times to see the voltmeter change 0.1V, how many times voltmeter change 0.1V by pressing the key, depending on the current display voltage, the higher the voltage, the fewer the number of press. Step 3, press the right button for more than 2 seconds, release, to exit the output voltage calibration mode. All parameters set to automatically power down to save. Specifications: specification: Input voltage: 2.5V~40V Output voltage: 1.25V~37V (adjustable) Output current: 3A (maximum) Conversion efficiency: 92% (maximum) Output ripple: