Thisis because even I had the same problem. So all u need is a high voltage (12v) transistor and the other parts : arduino, 12v adapter and relay. Now connect the vcc of relay to 12v adapter. Now connect the one end of the transister (refer to data sheet) to 12 adapter connect the middle pin of transistor to one of the pwm pin of arduino . Linds Replacement AC Adapters meet or exceed the laptop manufacturer's original specifications. Each features a power-on LED and universal switching 100 - 240 volt AC input voltage. The unit has a 48 inch long attached output cable and is supplied with a 60 inch long AC input cord. Tips are available for most laptop models. Thegoal of this Instructable is to make a functional, Ardunio digitally controlled, power supply. We tested the supply and controller so that you can grab your old laptop wall wart (output voltage between 14 and 20V), connect it to the supply's Vin line and digitally specify what output voltage you want in the range between 0 and 12 V. Assuming you already have an Ardunio and a laptop charger Usually a regular security camera uses around 1A (Ampere) to work properly even using the infrared illumination, so make sure to buy an appropriate power supply. Please, just don't confuse the voltage with the current. You need the correct voltage (12V) and enough current (1A). You can find both information when buying your security camera kit Theknob can be adjusted more evenly, and it can reach 13V ~ 14V by rotating 50%. 2. Increase the off gear to turn off the power without pulling the plug. 3.Add a polarity converter cable, which make it compatible with more devices，doubles its range of application. Can be applied to almost all commonly used electronic devices. You can jrOTw4.

can you use a 12v adapter for a 14v device