adapting 12vdc to 9vdc

C

Chas

Guest
I plan to use a ''boombox" in my vehicle because the existing sound device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug from
the 12v cig lighter to a power plug on the boombox? I imagine I will need
some sort of voltage reducer. Anyone got any ideas on how one could build
such a reducer. I am fearing such a device may induce noise.
.. . . . .I am of an understanding that 1.5v batterys are acutally 1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8 of the
AA's and tap off 6.
any help would be greatly appreciated.. . . chas
 
You don't want to use a resistor, because if you turn up the volume, the
change in current drawn as the sound gets louder and softer will "modulate"
the voltage.

You need a properly regulated supply to step the voltage down to 9V. I don't
know who makes one, especially of the capacity needed for a boombox.
 
On Jan 18, 4:55 pm, "Chas" <footboar...@bresnan.net> wrote:
I plan to use a ''boombox" in my vehicle because the existing sound device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug from
the 12v cig lighter to a power plug on the boombox?  I imagine I will need
some sort of voltage reducer.  Anyone got any ideas on how one could build
such a reducer.  I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally 1.2v.  Is
this correct?  If so, I could run the 12v car voltage to 10 AA batterys and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8 of the
AA's and tap off 6.
any help would be greatly appreciated.. . .  chas
Click to expand...
AA batteries (regular carbon or nickel metal hydride) are 1.4 to
1.5V, NICAD AA batteries are 1.2V. So you need to drop 14V to 9V.
14V because that is the actual voltage of a car system whenever the
engine is running,12V is the nominal battery voltage when the engine
is not running.

You need to determine the current drain of the device in order to
figure out what value of resistor you need to put in series with the
14V to drop it to 9V. You need to drop 5V, the value of the resistor
needed is R=V/I where V=9, I=current drain in amps.
 
On Wednesday, January 18, 2012 2:55:09 PM UTC-8, Chas wrote:
I plan to use a ''boombox" in my vehicle because the existing sound device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug from
the 12v cig lighter to a power plug on the boombox?
Click to expand...
Well, yes there are plugs that would be safe. They're commonly
used for cellphones and such, and they contain a fuse and suitable
stepdown power supply. First, you need the power ratings of
the boombox (probably 9V at 1A will suffice to fill a small car
with tunes), and of the lighter socket.

The car power may have spikes up to 50V, so the conversion does
offer some challenges. If the 'boom box' has AC power option,
an off-the-shelf inverter to make 120VAC will be the easiest option.
 
If memory serves me (and it doesn't always), at the specified specific
gravity of a lead/acid cell for automotive use is the nominal voltage is2.2
volts.

Thus a fully charged 6 cell battery is nominally 13.2 volts.

But, of course, in the automotive world the battery is only used for
starting unless the engine is off. When engine is running the voltage
available to the vehicle's electrical system is determined by the alternator
and its associated regulation system.

A decent voltmeter is a handy way to check your own particular situation.

Charlie

<hrhofmann@att.net> wrote in message
news:5881c6c9-8bf9-4bba-98aa-83239d776dd2@e8g2000yqd.googlegroups.com...
On Jan 18, 4:55 pm, "Chas" <footboar...@bresnan.net> wrote:
I plan to use a ''boombox" in my vehicle because the existing sound device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug from
the 12v cig lighter to a power plug on the boombox? I imagine I will need
some sort of voltage reducer. Anyone got any ideas on how one could build
such a reducer. I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally 1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8 of
the
AA's and tap off 6.
any help would be greatly appreciated.. . . chas
Click to expand...
AA batteries (regular carbon or nickel metal hydride) are 1.4 to
1.5V, NICAD AA batteries are 1.2V. So you need to drop 14V to 9V.
14V because that is the actual voltage of a car system whenever the
engine is running,12V is the nominal battery voltage when the engine
is not running.

You need to determine the current drain of the device in order to
figure out what value of resistor you need to put in series with the
14V to drop it to 9V. You need to drop 5V, the value of the resistor
needed is R=V/I where V=9, I=current drain in amps.
 
On 1/19/2012 6:55 AM, Chas wrote:
I plan to use a ''boombox" in my vehicle because the existing sound device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug from
the 12v cig lighter to a power plug on the boombox? I imagine I will need
some sort of voltage reducer. Anyone got any ideas on how one could build
such a reducer. I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally 1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8 of the
AA's and tap off 6.
any help would be greatly appreciated.. . . chas


Just search for "three terminal regulator" until you find a circuit for
Click to expand...
the 9volt one. This is a very simple circuit and easy to build, I have
had such in use for years in my vehicles. You can build it in a small
diecast box which would be strong and act as a heat sink for the regulator.

Rheilly P
 
On 1/18/2012 2:55 PM, Chas wrote:
I plan to use a ''boombox" in my vehicle because the existing sound device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug from
the 12v cig lighter to a power plug on the boombox? I imagine I will need
some sort of voltage reducer. Anyone got any ideas on how one could build
such a reducer. I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally 1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8 of the
AA's and tap off 6.
Click to expand...
Don't do that. It's wrong for a lot of reasons.
You need a regulator.
If you intend building something, make sure you understand this:
http://www.littelfuse.com/data/en/Application_Notes/an9312.pdf

Safest thing is to buy a car adapter.

any help would be greatly appreciated.. . . chas
Click to expand...
 
On 1/19/2012 1:08 PM, mike wrote:
On 1/18/2012 2:55 PM, Chas wrote:
I plan to use a ''boombox" in my vehicle because the existing sound
device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug from
the 12v cig lighter to a power plug on the boombox? I imagine I will need
some sort of voltage reducer. Anyone got any ideas on how one could build
such a reducer. I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally
1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys
and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8
of the
AA's and tap off 6.

Don't do that. It's wrong for a lot of reasons.
You need a regulator.
If you intend building something, make sure you understand this:
http://www.littelfuse.com/data/en/Application_Notes/an9312.pdf

Safest thing is to buy a car adapter.

any help would be greatly appreciated.. . . chas



Umm, looking at the OP's message that might be a tad over the top for
Click to expand...
his level ??
Sure there can be lots of transients but I reckon for domestic
applications it's not necessary to go beyond some stiff caps or a
resistor and zener or even a choke where the job is to step down ?

Rheilly P
 
On Jan 18, 9:43 pm, Rheilly Phoull <rhei...@bigslong.com> wrote:
On 1/19/2012 1:08 PM, mike wrote:







On 1/18/2012 2:55 PM, Chas wrote:
I plan to use a ''boombox" in my vehicle because the existing sound
device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug from
the 12v cig lighter to a power plug on the boombox? I imagine I will need
some sort of voltage reducer. Anyone got any ideas on how one could build
such a reducer. I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally
1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys
and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8
of the
AA's and tap off 6.

Don't do that. It's wrong for a lot of reasons.
You need a regulator.
If you intend building something, make sure you understand this:
http://www.littelfuse.com/data/en/Application_Notes/an9312.pdf

Safest thing is to buy a car adapter.

any help would be greatly appreciated.. . . chas

Umm, looking at the OP's message that might be a tad over the top for
his level ??
Sure there can be lots of transients but I reckon for domestic
applications it's not necessary to go beyond some stiff caps or a
resistor and zener or even a choke where the job is to step down ?
Click to expand...
Anything's better than trying to use a battery string as a voltage
regulator. The worst that could happen using your idea is that he
would have to buy a new boom box. Second worst is that he would have
to buy a new three-terminal regulator.
 
"Charlie" <left@thestation.com> wrote in message
If memory serves me (and it doesn't always), at the specified specific
gravity of a lead/acid cell for automotive use is the nominal voltage
is2.2 volts.
.....< snip
Thus a fully charged 6 cell battery is nominally 13.2 volts.
Charlie
Yes, that is what I always see about auto battery voltages....13+vdc.
Click to expand...
Chas
 
Would you please share your schematic for the voltage regulator?
I would be most appreciative. . . . .Also, thanks for the guidance.
chas. L7912CV-Negative

http://www.ebay.com/itm/
2-Pcs-3-Terminals-1-5A-12V-L7912CV-Negative-Voltage-Regulator-/280803733057?pt=LH_DefaultDomain_0&hash=item416134ee41
.. . . .I'm curious...my first email to your address bounced...is it valid or
is my system messed up?
****************************

"Rheilly Phoull" <rheilly@bigslong.com> wrote in message
news:ztGdnW0YCOwtMIrSnZ2dnUVZ_u2dnZ2d@westnet.com.au...
On 1/19/2012 1:08 PM, mike wrote:
On 1/18/2012 2:55 PM, Chas wrote:
I plan to use a ''boombox" in my vehicle because the existing sound
device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug
from
the 12v cig lighter to a power plug on the boombox? I imagine I will
need
some sort of voltage reducer. Anyone got any ideas on how one could
build
such a reducer. I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally
1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys
and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8
of the
AA's and tap off 6.

Don't do that. It's wrong for a lot of reasons.
You need a regulator.
If you intend building something, make sure you understand this:
http://www.littelfuse.com/data/en/Application_Notes/an9312.pdf

Safest thing is to buy a car adapter.

any help would be greatly appreciated.. . . chas



Umm, looking at the OP's message that might be a tad over the top for his
level ??
Sure there can be lots of transients but I reckon for domestic
applications it's not necessary to go beyond some stiff caps or a resistor
and zener or even a choke where the job is to step down ?

Rheilly P
Click to expand...
 
Here's another possibility...

Buy an inverter that converts 12V DC to 120V AC. Then use an AC power supply
("wall wart") suitable for the boombox. It might even have its own built-in
AC adapter.
 
I find that UseNet groups almost always suggest the most-complex and
most-difficult-to-implement solutions one can imagine.

There are three simple solutions...

1) Use rechargeable batteries. This won't be cheap, but the OP can operate
the boombox anywhere. This is an essentially fool-proof solution.

2) Find a 9V auto cord.

http://www.radioshack.com/product/index.jsp?productId=3812864

3) Buy an inverter and use the power supply that came with the boombox.

http://www.amazon.com/Wagan-EL2402-SmartAC-Power-Inverter/dp/B000YQT6RS/ref=sr_1_2?s=electronics&ie=UTF8&qid=1326975432&sr=1-2
 
Buy an inverter that converts 12V DC to 120V AC. Then use an
AC power supply ("wall wart") suitable for the boombox. It might
even have its own built-in AC adapter.

total waste of energy ...
Click to expand...
WHY?

It requires no energy -- it's plug 'n play.
 
On 1/19/2012 2:03 AM, Chas wrote:
Would you please share your schematic for the voltage regulator?
I would be most appreciative. . . . .Also, thanks for the guidance.
chas. L7912CV-Negative

http://www.ebay.com/itm/
2-Pcs-3-Terminals-1-5A-12V-L7912CV-Negative-Voltage-Regulator-/280803733057?pt=LH_DefaultDomain_0&hash=item416134ee41
. . . .I'm curious...my first email to your address bounced...is it valid or
is my system messed up?
****************************

"Rheilly Phoull"<rheilly@bigslong.com> wrote in message
news:ztGdnW0YCOwtMIrSnZ2dnUVZ_u2dnZ2d@westnet.com.au...
On 1/19/2012 1:08 PM, mike wrote:
On 1/18/2012 2:55 PM, Chas wrote:
I plan to use a ''boombox" in my vehicle because the existing sound
device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug
from
the 12v cig lighter to a power plug on the boombox? I imagine I will
need
some sort of voltage reducer. Anyone got any ideas on how one could
build
such a reducer. I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally
1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys
and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8
of the
AA's and tap off 6.

Don't do that. It's wrong for a lot of reasons.
You need a regulator.
If you intend building something, make sure you understand this:
http://www.littelfuse.com/data/en/Application_Notes/an9312.pdf

Safest thing is to buy a car adapter.

any help would be greatly appreciated.. . . chas



Umm, looking at the OP's message that might be a tad over the top for his
level ??
Sure there can be lots of transients but I reckon for domestic
applications it's not necessary to go beyond some stiff caps or a resistor
and zener or even a choke where the job is to step down ?

Rheilly P



Targus and Igo make universal car chargers. Can be had for $5 or so
Click to expand...
shipped on ebay.
The problem is that they require special tips to configure the voltage
and the cheap ones come without tips.
But if you can design a regulator, you can open 'em up and add the
required voltage setting resistor and put the right plug on the wire.
 
On 2012-01-19 11:03:09 +0100, "Chas" <footboarder@bresnan.net> said:

Would you please share your schematic for the voltage regulator?
I would be most appreciative. . . . .Also, thanks for the guidance.
chas. L7912CV-Negative

http://www.ebay.com/itm/
2-Pcs-3-Terminals-1-5A-12V-L7912CV-Negative-Voltage-Regulator-/280803733057?pt=LH_DefaultDomain_0&hash=item416134ee41
..

. . .I'm curious...my first email to your address bounced...is it valid or
is my system messed up?
****************************

"Rheilly Phoull" <rheilly@bigslong.com> wrote in message
news:ztGdnW0YCOwtMIrSnZ2dnUVZ_u2dnZ2d@westnet.com.au...
On 1/19/2012 1:08 PM, mike wrote:
On 1/18/2012 2:55 PM, Chas wrote:
I plan to use a ''boombox" in my vehicle because the existing sound
device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug
from
the 12v cig lighter to a power plug on the boombox? I imagine I will
need
some sort of voltage reducer. Anyone got any ideas on how one could
build
such a reducer. I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally
1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys
and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8
of the
AA's and tap off 6.

Don't do that. It's wrong for a lot of reasons.
You need a regulator.
If you intend building something, make sure you understand this:
http://www.littelfuse.com/data/en/Application_Notes/an9312.pdf

Safest thing is to buy a car adapter.

any help would be greatly appreciated.. . . chas



Umm, looking at the OP's message that might be a tad over the top for his
level ??
Sure there can be lots of transients but I reckon for domestic
applications it's not necessary to go beyond some stiff caps or a resistor
and zener or even a choke where the job is to step down ?

Rheilly P
Click to expand...
hi,
you must know how many amperes your boombox will draw from the battery ...
because if it draws 1 amp, and you must step down the voltage from 12v to 9v
you will have to dissipate 3W from the 78xx regulator
also a 7912 will output 12v, negative, and a 7809 will really outpout
9v positive what you need...
if it is too hot, you must then use a switching regulator
then it's cheaper generally to buy a ready made from ebay or dealextreme
hope this helps.

--
----------
Kripton

the ESR Repository @ http://kripton2035.free.fr/esr-repository.html
the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html
 
On 2012-01-19 11:20:41 +0100, "William Sommerwerck"
<grizzledgeezer@comcast.net> said:

Here's another possibility...

Buy an inverter that converts 12V DC to 120V AC. Then use an AC power supply
("wall wart") suitable for the boombox. It might even have its own built-in
AC adapter.
Click to expand...
total waste of energy ...
--
----------
Kripton

the ESR Repository @ http://kripton2035.free.fr/esr-repository.html
the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html
 
<Kripton> wrote in message news:4f182d0a$0$16304$426a74cc@news.free.fr...
On 2012-01-19 12:31:10 +0100, "William Sommerwerck"
grizzledgeezer@comcast.net> said:

Buy an inverter that converts 12V DC to 120V AC. Then use an
AC power supply ("wall wart") suitable for the boombox. It might
even have its own built-in AC adapter.

total waste of energy ...

WHY?
It requires no energy -- it's plug 'n play.

I'm not talking of human energy, but electricity energy ...
each time you convert voltage (12v->120V) then 120V->9V
you have power losses, that generate heat.
that means the energy if transformed into heat, useless and poor solution
for the planet ...
instead use a smps converter from 12vdc to 9vdc they exists
they are cheap, and the power losses are reducted to a minimum
Click to expand...
I don't blame you for wanting to be green, but the energy involved is tiny,
compared to the energy the engine uses. For example, 20HP is about 15kW. Ten
watts (at worst) to run a boom box is nothing.
 
On 2012-01-19 12:31:10 +0100, "William Sommerwerck"
<grizzledgeezer@comcast.net> said:

Buy an inverter that converts 12V DC to 120V AC. Then use an
AC power supply ("wall wart") suitable for the boombox. It might
even have its own built-in AC adapter.

total waste of energy ...

WHY?

It requires no energy -- it's plug 'n play.
Click to expand...
I'm not talking of human energy, but electricity energy ...
each time you convert voltage (12v->120V) then 120V->9V
you have power losses, that generate heat.
that means the energy if transformed into heat, useless and poor solution
for the planet ...
instead use a smps converter from 12vdc to 9vdc they exists
they are cheap, and the power losses are reducted to a minimum

--
----------
Kripton

the ESR Repository @ http://kripton2035.free.fr/esr-repository.html
the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html
 
On 1/19/2012 6:03 PM, Chas wrote:
Would you please share your schematic for the voltage regulator?
I would be most appreciative. . . . .Also, thanks for the guidance.
chas. L7912CV-Negative

http://www.ebay.com/itm/
2-Pcs-3-Terminals-1-5A-12V-L7912CV-Negative-Voltage-Regulator-/280803733057?pt=LH_DefaultDomain_0&hash=item416134ee41
. . . .I'm curious...my first email to your address bounced...is it valid or
is my system messed up?
****************************

"Rheilly Phoull"<rheilly@bigslong.com> wrote in message
news:ztGdnW0YCOwtMIrSnZ2dnUVZ_u2dnZ2d@westnet.com.au...
On 1/19/2012 1:08 PM, mike wrote:
On 1/18/2012 2:55 PM, Chas wrote:
I plan to use a ''boombox" in my vehicle because the existing sound
device
is defective and next to impossible to remove.
My boombox uses 6 AA batteries...would it be safe to just run a plug
from
the 12v cig lighter to a power plug on the boombox? I imagine I will
need
some sort of voltage reducer. Anyone got any ideas on how one could
build
such a reducer. I am fearing such a device may induce noise.
. . . . .I am of an understanding that 1.5v batterys are acutally
1.2v. Is
this correct? If so, I could run the 12v car voltage to 10 AA batterys
and
then tap off six batterys....
Else, if the AA's are truly 1.5 volts then run the 12v car power to 8
of the
AA's and tap off 6.

Don't do that. It's wrong for a lot of reasons.
You need a regulator.
If you intend building something, make sure you understand this:
http://www.littelfuse.com/data/en/Application_Notes/an9312.pdf

Safest thing is to buy a car adapter.

any help would be greatly appreciated.. . . chas



Umm, looking at the OP's message that might be a tad over the top for his
level ??
Sure there can be lots of transients but I reckon for domestic
applications it's not necessary to go beyond some stiff caps or a resistor
and zener or even a choke where the job is to step down ?

Rheilly P
Click to expand...
Try this, just use a 7809 regulator instead.
http://www.zen22142.zen.co.uk/Circuits/Power/9v2a.htm
You will also find this circuit in the Dick Smith Catalogue.
Dont forget to build it in a metal box to use as a heat sink.
Also there are such devices on ebay using switch mode devices that are
are more efficient but can introduce some noise in cheap audio
equipment. But they are cheap and save you the work.



http://www.zen22142.zen.co.uk/Circuits/Power/9v2a.htm
 
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