DC-DC 5.5-30V to 0.5-30V Automatic Step up Down Converter Boost Buck Voltage Regulator Module Features: The module has reverse input protection. (please try not to connect input reversely. There is + - marks on board that you can check before wiring) 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. The output ripple is small, and have the LC filter. Specification: Type: 4A non-isolated step up/down constant current power supply module Output 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; Current Display Resolution: 0.005A Conversion Efficiency: About 88% Soft Start: Yes (it may fail when big power load module start) Reverse Input Protection: Yes Output Flow Back Protection: Yes Short Circuit Protection: Yes Frequency: 180KHZ Weight: 48g / 1.7oz (approx.) Package list: 1 * Module 4 * Plastic Supports 1 * Heat Sink Operation Instructions: Current Adjustment: 1, Used as a normal step up/down module with over current protection. (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) 2. Used as a battery charger. (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 (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, test. (step 1, 2, 3 are: input is connected to power source, output is disconnected, not connected to the LED) Note: When this module is used more than 3A, 35W, please enhance heat dissipation! Module's input IN- cannot be short circuit with output OUT-, otherwise constant current function fails. Please make sure that the power supply's power is always greater than the required power of output load! Module has output short circuit protection, after short circuit protection, module automatically shut down output, which can be recovered if module is powered on again. If your power supply does not have output current limit protection, it is suggested to connect a fuse at input in series, in order to improve safety coefficient.