Features:The LCD can display input and output voltage, output current and output power. The module has reverse input protection. (please try not to connect input reversely. There is + - marks on board that you can check before wiring) It can step-up and step-down, output voltage is adjustable within 0.5-30V, limit current is adjustable within 0.2-4A. Output has flow back protection, do not need to add flow back protecting diode when it is used to charge battery. Use button to control output ON/OFF state, and can set default as ON or OFF when powered. It uses step up/down chips as main controller, external 60V 75A MOS tube as switch tube, double 60V 5A SS56 schottky as rectifier, withstand 60V voltage, better tjam XL6009/LM2577 immature solutions. The output ripple is small, and have the LC filter. Specification:Type: 4A non-isolated step up/down constant current power supply moduleInput Voltage: 5.5-30 VDC (at 5V input, it can also step up down voltage, but the voltage current measurement is inaccurate; when lower than 4.7V, under-voltage protection)Output Voltage: 0.5-30VDC adjustableOutput Current: 0.2-3A adjustable, enhance heat dissipation can be up to 4A (please enhance heat dissipation when module temperature is over 65) with constant current indicator light, output power do not exceed 35W; for low voltage output, current do not exceed 4A, otherwise it will burn out.Voltage Display Resolution: 0.05VCurrent Display Resolution: 0.005AConversion Efficiency: About 88%Soft Start: Yes (it may fail when big power load module start)Reverse Input Protection: YesOutput Flow Back Protection: YesShort Circuit Protection: YesFrequency: 180KHZ Weight:48g / 1.7oz (approx.) Package list:1 * Module4 * Plastic Supports1 * Heat SinkOperation Instructions:1. The module has IN/OUT, ON/OFF two buttons:IN/OUT button switches input voltage and output voltage display, long press to switch output current output power display;ON/OFF button control output ON or OFF, long press can set default output state is ON or OFF when powered next time.2. CC is current setting potentiometer, clockwise rotation can increase setting current, when the load current reaches setting current, it enters constant current state, and CC constant current indicator light (red) lights up;CV voltage setting potentiometer on the right can be rotated clockwise to increase output voltage.ON indicator light shows output state, which lights up when output voltage, otherwise lights off.Current Adjustment:1, Used as a normal step up/down module with over current protection. (1) Adjust CV constant voltage potentiometer till output voltage changes to the required voltage value.(2) Use multimeter 10A current to measure output short circuit current (connect two test probes directly to output), and adjust the CC constant current potentiometer till output becomes the expected over-current protection value.(for example, multimeter displays the current value is 2A, so when you use the module, the maximum current can only be up to 2A; when current reaches 2A, the red CV CC indicator light is on, otherwise the light is off)Note: Due to the current sampling resistance at output, there will be 0~0.2V voltage drop when connected to load, and for large current, there will be voltage drop on input and output wires, which is normal. 2. Used as a battery charger.Module without constant current function can't be used to charge the battery, because the empty battery and charger has big voltage difference, the charging current will be too large, causing battery damage. At beginning charge the battery with constant current, and switch back to constant voltage after charging to a certain degree.(1) Make sure battery's float charging voltage and charging current;(for example, a 3.7V/2200mAh li-ion battery has float charging voltage of 4.2V, maximum charging current of 1C, that is 2200mA)(2) When there is no load, multimeter measures the output voltage, adjust the constant-voltage potentiometer to make the output voltage to reach float charging voltage;(if charge a 3.7V li-ion battery, adjust the output voltage to 4.2V)(3) Use multimeter 10A current to measure output short circuit current (connect two test probes directly to output), and adjust the CC constant current potentiometer till output becomes the expected charging current value.(4) Connected to the battery and start charging.(step 1, 2, 3 are: input is connected to power source, output is disconnected, not connected to battery)3. Used as high-power LED constant current driver module(1) Make sure the LED's working current and maximum working voltage;(2) When there is no load, multimeter measures the output voltage, adjust the constant-voltage potentiometer to make the output voltage to reach maximum working voltage of the LED.(3) Use multimeter 10A current to measure output short circuit current, and adjust the CC constant current potentiometer till output becomes the expected LED working current.(4) Connected to the LED