If you have some spare white LED's & want to do something with those then it's excellent to build a lighting system with low heating and low power consumption with bright light.It doesn't requires any type of heat sink.
Step 1: Materials Required
* 24 white high intensity led(You can use any no of it but then you have to consider the power consumption of it and according to it use resistors with suitable wattage)
* PCB (if available) otherwise protyping board
* Old USB type mobile charger
* Any USB cable
Step 2: Led Matrix
Just create a 3x8 led matrix as shown. All LEDs are connected in parallel.
Step 3: Connect the USB Cable
Just connect the positive and negative power supply wires of the usb cable with the anode and cathode of any one of the LED ( since all led are connected in parallel) respectively.
Step 4: Charger
Connect the usb cable with the mobile phone charger. That's it !!! nothing else to do.
Step 5: Completed Led Light.
Just connect the mobile charger with the mains and enjoy cheap lighting solution with low power consumption. It doesn't requires any type of heat sink.