5A DC-DC adjustable step-down module with a voltmeter One: Product Description This product is a 180 KHz fixed frequency PWM buck (step-down) DC/DC module,capable of driving a 5A load with high efficiency, low ripple and excellent line and load regulation.The module with a voltage meter to display the input voltage and output voltage, and the voltage can be corrected through the button to improve the accuracy of the voltmeter. Features: 1. LED power indicator. 2. Button to switch measurement of the input or output voltage, and LED indicates the current measurement of the input or output voltage; The nixie tube can be turned off by another button. Mentioned states are able to be memorized, is not lost even if the power is disconnected. (On-board marked "IN" LED is turned on, the nixie tube display input voltage value, "OUT" LED bright display is the output voltage value). 3. Special launch, the voltmeter calibration function, will never exist voltmeter inaccurate Voltmeter calibration method: (1) Output voltage calibration steps Step 1, adjust the right button so that "OUT" LED lighted, the voltmeter shows the value of output voltage; Press the right button for more than 2 seconds, release, voltmeter and "OUT" 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. (2) Input voltage calibration steps Step 1, adjust the right button so that "IN" LED lighted, the voltmeter shows the value of input voltage; press the right button for more than 2 seconds, release, voltmeter and "IN" LED flashes in synchronization so that you enter the input voltage calibration mode. Steps 2 and 3, consistent with the output voltage calibration method. Two: Performance parameters 1.Input voltage range:4~38VDC(Note:input voltage not exceeding 38V) 2.Output voltage range:1.25-36VDC adjustable 3.Output current: 0-5A 4.Output power: 75W 5.voltmeter range: 4 to 40V, error ±0.1V 6.Operating frequency: 180KHz 7.High efficiency up to 96% 8.Built in thermal shutdown function 9.Built in current limit function 10.Built in output short protection function 11.Input reverse polarity protection: None (if required, high current diode in series with the input). 12.L x W x H =6.6*3.9*1.8CM  Three: application The DC/DC buck module applications the input voltage is higher than the output voltage of the buck field, such as battery, power transformer, DIY adjustable regulated power supply, LCD Monitor and LCD TV,portable instrument power supply,telecom/networking equipment,24V vehicle notebook power supply,industrial equipment buck.12V buck to 3.3V, 12V buck to 5V,  24V buck to 5V,24V buck to 12V,  36V buck to 24V etc.