DC 12 volts to DC 9 volts??????

Guest
What would be the simplest was to knock a 12 volt lantern battery down
to 9 volts?
 
sky_diver_@excite.com wrote:

What would be the simplest was to knock a 12 volt lantern battery down
to 9 volts?
Click to expand...
The *simplest* way would be a linear voltage regulator like a 7809.

http://www.onsemi.com/site/products/summary/0,4450,MC7809A,00.html

It won't regulate the 9V output as the battery gets exhausted though. A
switching regulator is more complicated but is better in this respect.

Graham
 
<sky_diver_@excite.com> wrote in message
news:1123955560.772858.15910@g47g2000cwa.googlegroups.com...
What would be the simplest was to knock a 12 volt lantern battery down
to 9 volts?

Four 1N400x diodes in series with the battery, that is 4 x 0.7V = 2.8V drop.
Click to expand...
 
<sky_diver_@excite.com> wrote in message
news:1123957170.951186.251690@g43g2000cwa.googlegroups.com...
thanks

Before you do this, make sure tthe 12V is really 12, and not something like
Click to expand...
14.5, which is what you would get in a car.12V power supplies sold for use
with 2 way radios are set to 13.8. Even 8 new dry cells would be about
12.8. I vote for an LDO series regulator.

Tam
 
"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message
news:ZamdnZ2dnZ2FJ-KCnZ2dnV_dY9-dnZ2dRVn-0J2dnZ0@comcast.com...
sky_diver_@excite.com> wrote in message
news:1123957170.951186.251690@g43g2000cwa.googlegroups.com...
thanks

Before you do this, make sure tthe 12V is really 12, and not something
like 14.5, which is what you would get in a car.12V power supplies sold
for use with 2 way radios are set to 13.8. Even 8 new dry cells would be
about 12.8. I vote for an LDO series regulator.

Tam

If it is a lantern battery as stated, the maximum voltage using 8 internal
Click to expand...
Alkaline cells would be 12.48V.
A fresh Alkaline cell usually gives 1.56V so 8 x 1.56V would give 12.48V.
This would give 9.68V after the diodes, still acceptable.
But I agree that a voltage regulator, preferably a low dropout regulator
could be better in some cases.

M.S.
 
On Sat, 13 Aug 2005 14:50:33 -0400, Tam/WB2TT wrote:

sky_diver_@excite.com> wrote in message
news:1123957170.951186.251690@g43g2000cwa.googlegroups.com...
thanks

Before you do this, make sure tthe 12V is really 12, and not something like
14.5, which is what you would get in a car.12V power supplies sold for use
with 2 way radios are set to 13.8. Even 8 new dry cells would be about
12.8. I vote for an LDO series regulator.

Tam
Click to expand...
The original post was referring to a 12V lantern battery.

Still, if the OP needs a regulated 9 V output, then the diode method might
not be good enough, and some type of regulator might be required. 7809?

But if the OP just needs 9V, more or less, then the diodes should work
fine.

--Mac
 
On Sat, 13 Aug 2005 10:52:40 -0700, sky_diver_ wrote:

What would be the simplest was to knock a 12 volt lantern battery down
to 9 volts?
Click to expand...
How much current do you need? How well regulated does the 9V have to be?

Or, if you don't know, then what are you going to do with the 9V?

--Mac
 
"Mac" <foo@bar.net> wrote in message
news:pan.2005.08.13.20.16.23.727906@bar.net...
On Sat, 13 Aug 2005 14:50:33 -0400, Tam/WB2TT wrote:


sky_diver_@excite.com> wrote in message
news:1123957170.951186.251690@g43g2000cwa.googlegroups.com...
thanks

Before you do this, make sure tthe 12V is really 12, and not something
like
14.5, which is what you would get in a car.12V power supplies sold for
use
with 2 way radios are set to 13.8. Even 8 new dry cells would be about
12.8. I vote for an LDO series regulator.

Tam

The original post was referring to a 12V lantern battery.
Click to expand...
Yeah, I saw that the first time I read this, then forgot. Problem with a
constant voltage drop is that if 12V gives you 9, then 10V gives you 7,
whereas with the LDO anything over about 9.5V will still give you 9 out.
Check out national.com.

Tam

Still, if the OP needs a regulated 9 V output, then the diode method might
not be good enough, and some type of regulator might be required. 7809?

But if the OP just needs 9V, more or less, then the diodes should work
fine.

--Mac
Click to expand...
 
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