What you have will work but is inefficient, and will dissipate a lot of heat. If
you use a 7805 in a TO3 case and a large heatsink, you'd be better off when
running off the car battery. However, running from a gelcell, you are wasting
power. A SMPS would be your best bet. The Linear Tech
(http://www.linear-tech.com) website has a program that will allow you to enter
your specifications and will select the proper device. National also has a few
good devices too. Overheating can also be caused by the regulator(s)
oscillating. A 0.1uf cap across each 78xx will stabilize them.
Rick

Jim wrote:

> Hi
>
> I have a lcd tv and a dvd player I want to run on a 12v battery.
> Like from my van battery or a 12v gellcell.
> The dvd runs on a 12v wall wart rated at 1a.
> The lcd tv runs on 6v@ 1a.
> I have built a simple circuit using a 7812 & 7805 and it works fine
> the tv works good on the 5v and draws .7a But these regulators get so hot
> they must be wasting alot of energy are there better regulators I could use
> in this app? the gellcell's I have are rated 12v @ 5ah/20h And I don't think
> it will last very long driving these loads.
>
> Thanks for any input
>
> James M
>
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