Help with very simple circuit

[butler20]

Hi im wondering if someone could please help me with a basic circuit? im making a boombox that runs off a battery. I would like to connect together the amp, volt/battery meter, the charging input and a light that turns on only when i plug in charger. Any help would be greatly apreciated. Thanks

Battery: SLA 12v, 7.2 Amps
Amplifier: 12v, 2 Amps
Led volt/battery meter: 4.5 ~ 30V, <60mA
light: 12V 100mA

[JMACgyver]

[attachment=0]

boombox.gif (8.04 KiB) Viewed 5994 times

[/attachment]Hello,

Ok, this is what I came up with. It *should* work, but I make no guarantees as to its suitability and safety. You must assume all risk.
</legalese>

Some important notes about the circuit:
Meter is on when AMP or CHARGER is in use.
AMP can be used while charging. (maybe)
LAMP is not polarized.
is better to charge BATT with AMP off.
The Charging port is your normal standard coaxial DC JACK with switch

How I believe it works:
Basically, all the positive lines stay connected.
The current flows from the BATT's negative terminal, thru the NC switch built-in to the DCJACK, around to the both the METER and AMP(boombox).
The LAMP while shorted by the DCJACK should have no current running thru it because the current would rather go thru to SWITCHed terminals of the DCJACK which have lower resistance.

When the Charger is connected, the NC switch opens, and current now flows to the BATT, one side of the LAMP, *thru* the LAMP (which now lights) to the METER and the AMP, then the juice runs back to the positive side of everything.

At least, that's how i interpret this to work. I recommend trying this on breadboard with substitute/lower risk parts.

Hope this helps!
--Electro--
aka The Other David

[butler20]

thanks very much for your help! I will give it try