voltage change help

electronicsguru · Post by **electronicsguru** » Sat Dec 17, 2005 3:46 pm

i am working on a custom project...

i need a way to drop 12v down to 9v safely. I know u can buy those adapters for cars that do it for cd players, but I need something small that can be contained in a project box.

What I have is a radioshack audio amplifier, that takes 9V in. This will be in a comm trailer that if broken into will give a verbal warning via this amplifier connected to 2 external powerhorn speakers and an voice recorder. This kit is ran off of a 12 V battery on a trickle charger.

With a few components, can I safely drop 12 to 9? I wouldnt imagine this would be too hard considering the amp isnt obviously drawing that much current.

Thanks,

dave

tvsjr · Post by **tvsjr** » Sat Dec 17, 2005 3:54 pm

Err, electronics guru? Yeah.

One 7809 regulator (or one of its ilk) should do just fine. Mind the data sheet and add the filtering components that they usually suggest.

thebigphish · Post by **thebigphish** » Sat Dec 17, 2005 9:15 pm

dbcomm · Post by **dbcomm** » Sat Dec 17, 2005 11:36 pm

You could (or have somebody) build a buck converter. Simple device that will step down the DC dependent on capacitor value.

gr8amp · Post by **gr8amp** » Sun Dec 18, 2005 4:31 pm

dbcomm wrote:You could (or have somebody) build a buck converter. Simple device that will step down the DC dependent on capacitor value.

The output voltage of the buck converter is dependant on the duty cycle of the switching waveform, not the value of the cap shown in that schematic. There is also a lot more too a buck converter than the "ideal" circuit shown.

Building a buck converter isnt nearly as simple as tossing a few caps on a linear regulator and calling it a day. Both work, but the linear regulator is the really the simplest solution. Cheap, easy to use, and work great...