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.

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

On Jan 18, 4:55*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.
any help would be greatly appreciated.. . . *chas

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?

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

wrote in message
...
On Jan 18, 4:55 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.
any help would be greatly appreciated.. . . chas

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
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.

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/Ap...tes/an9312.pdf

Safest thing is to buy a car adapter.

any help would be greatly appreciated.. . . chas

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/Ap...tes/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

On Jan 18, 9:43*pm, Rheilly Phoull 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/Ap...tes/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 ?


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" 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.
Chas

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/in...ductId=3812864

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

http://www.amazon.com/Wagan-EL2402-S...75432&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 ...

WHY?

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

On 2012-01-19 11:20:41 +0100, "William Sommerwerck"
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.

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 ...
On 2012-01-19 12:31:10 +0100, "William Sommerwerck"
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

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"
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

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

the ESR Repository @ http://kripton2035.free.fr/esr-repository.html
the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html

On Wed, 18 Jan 2012 15:55:09 -0700, the renowned "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


Hey, this little device would probably have adequate capacity ;-)

http://www.nextag.com/Medela-9-Volt-...8F46D24A00A4FA



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

On 2012-01-19, Kripton Kripton wrote:
that means the energy if transformed into heat, useless and poor solution
for the planet ...

BARF! I for will not lift a finger to "save the planet." It doesn't need
saving, and if it did "reducing power losses" is not going to do the trick.

--
-----------------------------------------------------------------------------
Roger Blake (Change "invalid" to "com" for email. Google Groups killfiled.)

"Climate policy has almost nothing to do anymore with environmental
protection... the next world climate summit in Cancun is actually
an economy summit during which the distribution of the world's
resources will be negotiated." -- Ottmar Edenhofer, IPCC
-----------------------------------------------------------------------------

Hey, this little device would probably have adequate capacity. ;-)

http://www.nextag.com/Medela-9-Volt-...8F46D24A00A4FA

The question is... what is the original poster's "capacity"? ahem

On Jan 19, 6:49*pm, Roger Blake wrote:
On 2012-01-19, Kripton Kripton wrote:

that means the energy if transformed into heat, useless and poor solution
for the planet ...

BARF! *I for will not lift a finger to "save the planet." It doesn't need
saving, and if it did "reducing power losses" is not going to do the trick.

--
-----------------------------------------------------------------------------
* Roger Blake (Change "invalid" to "com" for email. Google Groups killfiled.)

* "Climate policy has almost nothing to do anymore with environmental
* *protection... the next world climate summit in Cancun is actually
* *an economy summit during which the distribution of the world's
* *resources will be negotiated." -- Ottmar Edenhofer, IPCC
-----------------------------------------------------------------------------

dimwit's .sig retained to show dimwittedness.

too bad he'll never know how ****ed up his word wrap is.

On Thu, 19 Jan 2012 10:07:50 +0800, Rheilly Phoull
wrote:

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
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
To expound on this idea, the xx1084 family of regulators would be
ideal. Specifically, the AP1084TL-U adjustable regulator. Datasheet:
http://www.diodes.com/datasheets/AP1084.pdf. It's capable of putting
out 5A and has thermal shutdown.

The parts list is simple - An AP1084TL-U, 2 ea 100µF, 25volt caps, a
120 ohm and a 750 ohm 1/4 watt resistor, the die cast box, and an
insulator - the tab of the AP1084 is at the output voltage.

PlainBill

On Jan 20, 2:26*pm, wrote:
On Thu, 19 Jan 2012 10:07:50 +0800, Rheilly Phoull









wrote:
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
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

To expound on this idea, the xx1084 family of regulators would be
ideal. *Specifically, the AP1084TL-U adjustable regulator. *Datasheet:http://www.diodes.com/datasheets/AP1084.pdf. *It's capable of putting
out 5A and has thermal shutdown.

The parts list is simple - An AP1084TL-U, 2 ea 100µF, 25volt caps, a
120 ohm and a 750 ohm 1/4 watt resistor, the die cast box, and an
insulator - the tab of the AP1084 is at the output voltage.


One problem with using this part is the risk of destroying it as soon
as you start the car: The absolute maximum supply voltage is only 12V,
and the alternator puts out more than 13VDC.

"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



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

This all reminds me of my boom box I built in the early 80s. I used car
parts and a gel cell, compatible with car charging systems, which can reach
16 volts. Picture does not show horn loaded drivers.
http://www.zekfrivolous.com/slidesan...1/PICT0055.JPG

Greg

On 1/21/2012 6:41 AM, spamtrap1888 wrote:
On Jan 20, 2:26 pm, wrote:
On Thu, 19 Jan 2012 10:07:50 +0800, Rheilly Phoull









wrote:
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
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

To expound on this idea, the xx1084 family of regulators would be
ideal. Specifically, the AP1084TL-U adjustable regulator. Datasheet:http://www.diodes.com/datasheets/AP1084.pdf. It's capable of putting
out 5A and has thermal shutdown.

The parts list is simple - An AP1084TL-U, 2 ea 100µF, 25volt caps, a
120 ohm and a 750 ohm 1/4 watt resistor, the die cast box, and an
insulator - the tab of the AP1084 is at the output voltage.


One problem with using this part is the risk of destroying it as soon
as you start the car: The absolute maximum supply voltage is only 12V,
and the alternator puts out more than 13VDC.

The 7809 has a max input of 40v from memory.

Rheilly P

On Jan 21, 1:04*am, Rheilly Phoull wrote:
On 1/21/2012 6:41 AM, spamtrap1888 wrote:







On Jan 20, 2:26 pm, wrote:
On Thu, 19 Jan 2012 10:07:50 +0800, Rheilly Phoull

*wrote:
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
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

To expound on this idea, the xx1084 family of regulators would be
ideal. *Specifically, the AP1084TL-U adjustable regulator. *Datasheet:http://www.diodes.com/datasheets/AP1084.pdf. *It's capable of putting
out 5A and has thermal shutdown.

The parts list is simple - An AP1084TL-U, 2 ea 100µF, 25volt caps, a
120 ohm and a 750 ohm 1/4 watt resistor, the die cast box, and an
insulator - the tab of the AP1084 is at the output voltage.

One problem with using this part is the risk of destroying it as soon
as you start the car: The absolute maximum supply voltage is only 12V,
and the alternator puts out more than 13VDC.

The 7809 has a max input of 40v from memory.


I'd use a 7809 myself, but the part with the low abs max Vin
recommended here was a AP1084TL-U.

On 1/21/2012 5:48 PM, spamtrap1888 wrote:
On Jan 21, 1:04 am, Rheilly wrote:
On 1/21/2012 6:41 AM, spamtrap1888 wrote:







On Jan 20, 2:26 pm, wrote:
On Thu, 19 Jan 2012 10:07:50 +0800, Rheilly Phoull

wrote:
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
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

To expound on this idea, the xx1084 family of regulators would be
ideal. Specifically, the AP1084TL-U adjustable regulator. Datasheet:http://www.diodes.com/datasheets/AP1084.pdf. It's capable of putting
out 5A and has thermal shutdown.

The parts list is simple - An AP1084TL-U, 2 ea 100µF, 25volt caps, a
120 ohm and a 750 ohm 1/4 watt resistor, the die cast box, and an
insulator - the tab of the AP1084 is at the output voltage.

One problem with using this part is the risk of destroying it as soon
as you start the car: The absolute maximum supply voltage is only 12V,
and the alternator puts out more than 13VDC.

The 7809 has a max input of 40v from memory.


I'd use a 7809 myself, but the part with the low abs max Vin
recommended here was a AP1084TL-U.

I don't understand the problem. I have been using the 7809 etc. for
years in the automotive situation without a single failure.
It's not exactly rocket science

Rheilly P

I don't understand the problem. I have been using the 7809
etc. for years in the automotive situation without a single
failure. It's not exactly rocket science.

The problem is that the OP probably knows little about electronics, and is
likely to completely botch the project. He'll return to us asking for
troubleshooting help.

No one mentioned putting a string of silicon diodes in series to lower
the voltage. Unlike a resistor, the voltage drop would be reasonable
fixed. But, no fancy parts, capacitors, etc are required. Sort of
crude, but why wouldn't it work? 7 diodes would drop approx 4.2 volts
bringing 13ish down to 9ish. Or, maybe 8 diodes to be safe. 13.8 down
to 9. Just wondering why no one mentioned the possibility. Heat
would have to be handled, but no worse than a three terminal regulator
and the heat would be spread across all 8 diodes.

Excellent idea. 1N400x rectifiers should work.

On Sat, 21 Jan 2012 01:48:39 -0800 (PST), spamtrap1888
wrote:

On Jan 21, 1:04*am, Rheilly Phoull wrote:
On 1/21/2012 6:41 AM, spamtrap1888 wrote:







On Jan 20, 2:26 pm, wrote:
On Thu, 19 Jan 2012 10:07:50 +0800, Rheilly Phoull

*wrote:
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
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

To expound on this idea, the xx1084 family of regulators would be
ideal. *Specifically, the AP1084TL-U adjustable regulator. *Datasheet:http://www.diodes.com/datasheets/AP1084.pdf. *It's capable of putting
out 5A and has thermal shutdown.

The parts list is simple - An AP1084TL-U, 2 ea 100µF, 25volt caps, a
120 ohm and a 750 ohm 1/4 watt resistor, the die cast box, and an
insulator - the tab of the AP1084 is at the output voltage.

One problem with using this part is the risk of destroying it as soon
as you start the car: The absolute maximum supply voltage is only 12V,
and the alternator puts out more than 13VDC.

The 7809 has a max input of 40v from memory.


I'd use a 7809 myself, but the part with the low abs max Vin
recommended here was a AP1084TL-U.
No one mentioned putting a string of silicon diodes in series to lower
the voltage. Unlike a resistor, the voltage drop would be reasonable
fixed. But, no fancy parts, capacitors, etc are required. Sort of
crude, but why wouldn't it work? 7 diodes would drop approx 4.2 volts
bringing 13ish down to 9ish. Or, maybe 8 diodes to be safe. 13.8 down
to 9. Just wondering why no one mentioned the possibility. Heat
would have to be handled, but no worse than a three terminal regulator
and the heat would be spread across all 8 diodes.

On Jan 21, 8:27*am, "William Sommerwerck"
wrote:
No one mentioned putting a string of silicon diodes in series to lower
the voltage. *Unlike a resistor, the voltage drop would be reasonable
fixed. *But, no fancy parts, capacitors, etc are required. *Sort of
crude, but why wouldn't it work? *7 diodes would drop approx 4.2 volts
bringing 13ish down to 9ish. Or, maybe 8 diodes to be safe. *13.8 down
to 9. *Just wondering why no one mentioned the possibility. Heat
would have to be handled, but no worse than a three terminal regulator
and the heat would be spread across all 8 diodes.

Excellent idea. 1N400x rectifiers should work.

I tried running a small 9V transistor radio years ago at work from a
12V supply. I used a zener and a series resistor. Even with such a
small radio the pair got much too hot. The OP plans to power a boom
box. At the least he'll need to use a three terminal regulator or a
series pass transistor with the zener in the base circuit. Whatever it
turns out to be may need a heat sink, must be properly polarized,
fused, adequately wired, (so as to not set the vehicle on fire), and
I agree with William that this project, although simple to a seasoned
technician might be beyond his capabilities. Lenny

On Sat, 21 Jan 2012 05:27:16 -0800, "William Sommerwerck"
wrote:

No one mentioned putting a string of silicon diodes in series to lower
the voltage. Unlike a resistor, the voltage drop would be reasonable
fixed. But, no fancy parts, capacitors, etc are required. Sort of
crude, but why wouldn't it work? 7 diodes would drop approx 4.2 volts
bringing 13ish down to 9ish. Or, maybe 8 diodes to be safe. 13.8 down
to 9. Just wondering why no one mentioned the possibility. Heat
would have to be handled, but no worse than a three terminal regulator
and the heat would be spread across all 8 diodes.

Excellent idea. 1N400x rectifiers should work.

Exactly! I have a bunch of 1N4003's in my junk box that I used for
any project needing a general purpose diode that can handle some
power.

On 2012-01-21 18:55:59 +0100, said:

On Sat, 21 Jan 2012 05:27:16 -0800, "William Sommerwerck"
wrote:

No one mentioned putting a string of silicon diodes in series to lower
the voltage. Unlike a resistor, the voltage drop would be reasonable
fixed. But, no fancy parts, capacitors, etc are required. Sort of
crude, but why wouldn't it work? 7 diodes would drop approx 4.2 volts
bringing 13ish down to 9ish. Or, maybe 8 diodes to be safe. 13.8 down
to 9. Just wondering why no one mentioned the possibility. Heat
would have to be handled, but no worse than a three terminal regulator
and the heat would be spread across all 8 diodes.

Excellent idea. 1N400x rectifiers should work.

Exactly! I have a bunch of 1N4003's in my junk box that I used for
any project needing a general purpose diode that can handle some
power.

you mention it : the voltage of a car battery varies ...
from 14v to 12v or less
does the boom box handle 10v to 8v ? or not ?
that's why a regulator is needed, except if a regulation is made inside
the boom box ?
who knows...
--
----------
Kripton

the ESR Repository @ http://kripton2035.free.fr/esr-repository.html
the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html

On Sat, 21 Jan 2012 21:23:33 +0800, the renowned Rheilly Phoull
wrote:



I don't understand the problem. I have been using the 7809 etc. for
years in the automotive situation without a single failure.
It's not exactly rocket science

Rheilly P

It's not rocket science, but there are some subtleties:-

http://www.vishay.com/docs/88490/tvs.pdf

A few parts (series 1N400x, series power resistor, parallel TVS) will
protect the regulator against +/-100V transients and reverse wiring.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

forward voltage drop of a diode varies with current through the diode.

"Yes, but..." It's much closer to being constant, than it is with a
resistor.

wrote in
:

On Sat, 21 Jan 2012 01:48:39 -0800 (PST), spamtrap1888
wrote:

On Jan 21, 1:04*am, Rheilly Phoull wrote:
On 1/21/2012 6:41 AM, spamtrap1888 wrote:







On Jan 20, 2:26 pm, wrote:
On Thu, 19 Jan 2012 10:07:50 +0800, Rheilly Phoull

*wrote:
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 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

To expound on this idea, the xx1084 family of regulators would be
ideal. *Specifically, the AP1084TL-U adjustable regulator.
*Datasheet:http://www.diodes.com/datasheets/AP1084.pdf. *It's
capable of putting out 5A and has thermal shutdown.

The parts list is simple - An AP1084TL-U, 2 ea 100µF, 25volt
caps, a 120 ohm and a 750 ohm 1/4 watt resistor, the die cast
box, and an insulator - the tab of the AP1084 is at the output
voltage.

One problem with using this part is the risk of destroying it as
soon as you start the car: The absolute maximum supply voltage is
only 12V, and the alternator puts out more than 13VDC.

The 7809 has a max input of 40v from memory.


I'd use a 7809 myself, but the part with the low abs max Vin
recommended here was a AP1084TL-U.
No one mentioned putting a string of silicon diodes in series to lower
the voltage. Unlike a resistor, the voltage drop would be reasonable
fixed. But, no fancy parts, capacitors, etc are required. Sort of
crude, but why wouldn't it work? 7 diodes would drop approx 4.2 volts
bringing 13ish down to 9ish. Or, maybe 8 diodes to be safe. 13.8 down
to 9. Just wondering why no one mentioned the possibility. Heat
would have to be handled, but no worse than a three terminal regulator
and the heat would be spread across all 8 diodes.


forward voltage drop of a diode varies with current through the diode.

--
Jim Yanik
jyanik
at
localnet
dot com

Kripton wrote in :

On 2012-01-21 18:55:59 +0100, said:

On Sat, 21 Jan 2012 05:27:16 -0800, "William Sommerwerck"
wrote:

No one mentioned putting a string of silicon diodes in series to lower
the voltage. Unlike a resistor, the voltage drop would be reasonable
fixed. But, no fancy parts, capacitors, etc are required. Sort of
crude, but why wouldn't it work? 7 diodes would drop approx 4.2 volts
bringing 13ish down to 9ish. Or, maybe 8 diodes to be safe. 13.8 down
to 9. Just wondering why no one mentioned the possibility. Heat
would have to be handled, but no worse than a three terminal regulator
and the heat would be spread across all 8 diodes.

Excellent idea. 1N400x rectifiers should work.

Exactly! I have a bunch of 1N4003's in my junk box that I used for
any project needing a general purpose diode that can handle some
power.

you mention it : the voltage of a car battery varies ...
from 14v to 12v or less
does the boom box handle 10v to 8v ? or not ?
that's why a regulator is needed, except if a regulation is made inside
the boom box ?
who knows...

you also need FILTERING to reduce ripple(and noise);
auto alternators do NOT output straight DC,but pulsating DC.

A regulator IC will reject a lot of ripple and noise.
a string of diodes will not.

but hey,it's your boom box.(and ears)


--
Jim Yanik
jyanik
at
localnet
dot com

On Sat, 21 Jan 2012 16:50:58 -0600, the renowned Jim Yanik
wrote:

Kripton wrote in :

On 2012-01-21 18:55:59 +0100, said:

On Sat, 21 Jan 2012 05:27:16 -0800, "William Sommerwerck"
wrote:

No one mentioned putting a string of silicon diodes in series to lower
the voltage. Unlike a resistor, the voltage drop would be reasonable
fixed. But, no fancy parts, capacitors, etc are required. Sort of
crude, but why wouldn't it work? 7 diodes would drop approx 4.2 volts
bringing 13ish down to 9ish. Or, maybe 8 diodes to be safe. 13.8 down
to 9. Just wondering why no one mentioned the possibility. Heat
would have to be handled, but no worse than a three terminal regulator
and the heat would be spread across all 8 diodes.

Excellent idea. 1N400x rectifiers should work.

Exactly! I have a bunch of 1N4003's in my junk box that I used for
any project needing a general purpose diode that can handle some
power.

you mention it : the voltage of a car battery varies ...
from 14v to 12v or less
does the boom box handle 10v to 8v ? or not ?
that's why a regulator is needed, except if a regulation is made inside
the boom box ?
who knows...

you also need FILTERING to reduce ripple(and noise);
auto alternators do NOT output straight DC,but pulsating DC.

A regulator IC will reject a lot of ripple and noise.
a string of diodes will not.

Actually, it makes it worse (percentage-wise).


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

wrote:

On Thu, 19 Jan 2012 10:07:50 +0800, Rheilly Phoull
wrote:


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
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

To expound on this idea, the xx1084 family of regulators would be
ideal. Specifically, the AP1084TL-U adjustable regulator. Datasheet:
http://www.diodes.com/datasheets/AP1084.pdf. It's capable of putting
out 5A and has thermal shutdown.

The parts list is simple - An AP1084TL-U, 2 ea 100µF, 25volt caps, a
120 ohm and a 750 ohm 1/4 watt resistor, the die cast box, and an
insulator - the tab of the AP1084 is at the output voltage.

PlainBill

How about jest a 5 volt zener diode in series and a a small capacitor
after it to filter out noise?

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.

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


http://www.ebay.com/itm/180763839264 is an adjustble 3A buck
regulator for less than $5. It's a switch mode power supply, so it won't
generate a lot of waste heat.


--
You can't have a sense of humor, if you have no sense.

On 2012-01-27 03:38:55 +0100, "Michael A. Terrell"
said:


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


http://www.ebay.com/itm/180763839264 is an adjustble 3A buck
regulator for less than $5. It's a switch mode power supply, so it won't
generate a lot of waste heat.

and more searching on ebay for "LM2596" gives you the same board for
$2.5 shipped ...
and agree it does not generate waste heat !
but they don't seems to search for a smart solution...
--
----------
Kripton

the ESR Repository @ http://kripton2035.free.fr/esr-repository.html
the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html