How do i use the linear voltage regulator?

Question

Hello guys, a few days ago I asked a question about a project i was doing.

And now i have another question about it.

I want to power a raspberry pi3 and an lcd screen from a battery

I am going wit a NiMh battery because I read they are safe to use. Then i searched for a couple voltage regulaotr i for 5V 3A for the pi and one 12V 1A for the screen.

But how do i wire them in parallel and what caps do i need?.

I made a simple drawing of how i would wire them up if got them.

Please tell me if this would work

The black rectangles are the voltage regulators.

shabaz · Accepted Answer

Hi Vincent,

To determine the capacitor requirement, the information will be in the specific device datasheets, i.e. MC7812 and LM323 datasheets, they contain this detail (just google 'MC7812 datasheet' etc and go to the manufacturer site).

However, this circuit will not work, because the lower linear regulator in the diagram will be dissipating around (15-5)*3 = 30W. That's a large amount of heat (imagine a lightbulb). Instead a DC-DC converter can be used, they are more efficient.

The top linear regulator in the diagram will be dissipating (15-12)*1 = 3W which will require a heat sink. No large battery or cell is entirely safe, it is advisable to have a fuse or other protection device in-line in case of shorts.