Use: 1. Vehicle power supply simply Input the module powered cigarette holder termination point on the car you can adjustment potentiometer The output voltage can let you adjust (because it is a step-down module the output voltage is lower than the input 1.5~3V) in 3~27V; As many devices powered your phone MP3 MP4 PSP charging so very simple and convenient. 2. Step-down charger: As the module has constant pressure limiting function so can be used in addition to adjustable power supply the Can also be used as charging module to use: just set the output current limit (replacement R1R2 resistance can change the output current) Can of lead-acid batteries lithium batteries the charging voltage can be adjusted by the buyers themselves 3. Power for your electronic devices when your device needs 3~22V power supply when but you are now in the hands only 12V or 24V battery you can use this module directly to buck 3~22V solve your problems. 4. System foreline powered when you do a project when Input supply voltage is below the voltage you need (3-25V) the module will be your best choice Instructions for use: 1. Adjustment of the output current limit point: IC will automatically adjustment R1 R2 voltage at both ends it does not exceed 0.3 V achieve the purpose of limiting 2. Mobilize the potentiometer can change the output voltage to be adjusted gradually because sometimes when the situation fast or slow be sure to load transfer otherwise it will damage the module. Shun raised lowered against the minimum adjustable to 3V. Note: 1. In order to improve efficiency reduce loss minimize the length of Input and output leads and try to use thick lines. 2. Do not exceed Input voltage of 27V otherwise easily damage the module. 3. The module does not reverse polarity protection do not reverse input polarity or in series with the input of a recoverable overcurrent protection device.