LED Strip Power

I have a small project where I need to place some lighting inside a cabinet which will consist of three small strips of LEDs. I know the easiest way would be to just buy something off the shelf, but I have access to some power units and would like to make my own.

A 12v 5M strip of LEDs runs at 5A, I'm looking at using strips no longer than 1M reducing the current down to 1A max per strip. I will need to use 3 of these.

Working in IT I have access to lots of PSU for laptops. The majority will be Dell 90W units that cannot be used for users due to broken sockets or the outer insulation broken, these are all around 19.5V output.

I would like to create a small circuit that could supply power to the 3 LED strips. Initially I had thought about using the L78 12V voltage regulator, as these are rated at max 1.5A I could use three off the main PSU creating 3 separate Outputs.

The more research I've done into this is that they will produce a lot of heat due to the voltage drop of around 7 Volts, actual heat generated I'm not sure of unless I actually try one so don't know how much of an issue it would be.

Does anyone else have any thoughts on the best way to get over this issue using a laptop PSU?

Many thanks in advance for your replies.


There have been many similar questions on reducing voltages. Using linear regulators waste a lot of energy in the form of heat.

Your best plan would be to get a switching regulator that would be able to reduce to 12v but be much more efficient.

These are very easily obtained from most hobby electronics suppliers.