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12V DC to 1.5V DC needed
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3T39
electronics forum addict


Joined: 31 May 2005
Posts: 79

PostPosted: Fri Jul 14, 2006 10:02 pm    Post subject: 12V DC to 1.5V DC needed Reply with quote

Hello, All!


Could anyone please suggest a fairly simple circuit to convert the 12V DC of
a motor car down to 1.5V DC needed by my MP3 Player ?
Any help appreciated.



With best regards, 3T39. E-mail: rubbishrat@hotmail.com
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Arfa Daily
electronics forum Guru


Joined: 06 May 2005
Posts: 588

PostPosted: Fri Jul 14, 2006 10:05 pm    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

"3T39" <rubbishrat@hotmail.com> wrote in message
news:44b81477$0$5221$db0fefd9@news.zen.co.uk...
Quote:
Hello, All!


Could anyone please suggest a fairly simple circuit to convert the 12V DC
of a motor car down to 1.5V DC needed by my MP3 Player ?
Any help appreciated.



With best regards, 3T39. E-mail: rubbishrat@hotmail.com


Resistor and NiMHi cell perhaps ? Only 1.2v, and not terribly kind to the
battery, but simple, cheap and should work ok

Arfa
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Ralph Mowery
electronics forum Guru Wannabe


Joined: 13 Aug 2005
Posts: 137

PostPosted: Fri Jul 14, 2006 10:31 pm    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

"3T39" <rubbishrat@hotmail.com> wrote in message
news:44b81477$0$5221$db0fefd9@news.zen.co.uk...
Quote:
Hello, All!


Could anyone please suggest a fairly simple circuit to convert the 12V DC
of a motor car down to 1.5V DC needed by my MP3 Player ?
Any help appreciated.


Depends on the needed current. The lm317 is a simple regulator you set the

voltage with a couple of resistors. Here is another one.

http://www.irf.com/product-info/datasheets/hirel/om183sc.pdf
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3T39
electronics forum addict


Joined: 31 May 2005
Posts: 79

PostPosted: Fri Jul 14, 2006 10:38 pm    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

Hello, Arfa!
You wrote on Fri, 14 Jul 2006 22:05:09 GMT:


AD> "3T39" <rubbishrat@hotmail.com> wrote in message
AD> news:44b81477$0$5221$db0fefd9@news.zen.co.uk...
??>> Hello, All!
??>>
??>> Could anyone please suggest a fairly simple circuit to convert the 12V
??>> DC of a motor car down to 1.5V DC needed by my MP3 Player ? Any help
??>> appreciated.
??>>
??>> With best regards, 3T39. E-mail: rubbishrat@hotmail.com
??>>
AD> Resistor and NiMHi cell perhaps ? Only 1.2v, and not terribly kind to
AD> the battery, but simple, cheap and should work ok


Hhmm, A bit brutal Arfa, I see what you mean but I was hoping for a tad
more sophistication :^)
but thanks anyway.

With best regards, 3T39. E-mail: rubbishrat@hotmail.com
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Jim Land
electronics forum beginner


Joined: 06 Jun 2006
Posts: 46

PostPosted: Fri Jul 14, 2006 11:09 pm    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

"3T39" <rubbishrat@hotmail.com> wrote in
news:44b81477$0$5221$db0fefd9@news.zen.co.uk:

Quote:
Could anyone please suggest a fairly simple circuit to convert the 12V
DC of a motor car down to 1.5V DC needed by my MP3 Player ?


A simple circuit will do it: a linear voltage regulator, a couple of
resistors, a capacitor, a diode.

For further info, try sci.electronics.basics
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Jim Land
electronics forum beginner


Joined: 06 Jun 2006
Posts: 46

PostPosted: Fri Jul 14, 2006 11:26 pm    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

Jim Land <RrrrFfffTttt(NO)@(SPAM)hotmail.com> wrote in
news:Xns9800B8C3B9BC5RrrrFfffTttt4396hotm@216.168.3.44:

Quote:
"3T39" <rubbishrat@hotmail.com> wrote in
news:44b81477$0$5221$db0fefd9@news.zen.co.uk:

Could anyone please suggest a fairly simple circuit to convert the 12V
DC of a motor car down to 1.5V DC needed by my MP3 Player ?


A simple circuit will do it: a linear voltage regulator, a couple of
resistors, a capacitor, a diode.

For further info, try sci.electronics.basics


Wait! You don't need to build your own circuit. You can *buy* a device
that does exactly what you want.

http://www.google.com/search?q=Griffin+PowerJolt+iPod
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Eeyore
electronics forum Guru


Joined: 22 Jun 2006
Posts: 642

PostPosted: Fri Jul 14, 2006 11:36 pm    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

3T39 wrote:

Quote:
Hello, All!

Could anyone please suggest a fairly simple circuit to convert the 12V DC of
a motor car down to 1.5V DC needed by my MP3 Player ?
Any help appreciated.

Cheap adaptor on ebay ?

Graham
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Franc Zabkar
electronics forum Guru


Joined: 01 May 2005
Posts: 616

PostPosted: Fri Jul 14, 2006 11:40 pm    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

On Fri, 14 Jul 2006 23:02:06 +0100, "3T39" <rubbishrat@hotmail.com>
put finger to keyboard and composed:

Quote:
Hello, All!


Could anyone please suggest a fairly simple circuit to convert the 12V DC of
a motor car down to 1.5V DC needed by my MP3 Player ?
Any help appreciated.



With best regards, 3T39. E-mail: rubbishrat@hotmail.com

Get an old mobile phone car adapter and modify the output for 1.5V. A
lot of the switchmode types use an MC34063 IC which should be able to
go down as low as 1.25V by changing one or both feedback resistors.
Use a zener diode to crowbar the output in case of overvoltage.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
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Michael Black
electronics forum Guru Wannabe


Joined: 24 Mar 2005
Posts: 251

PostPosted: Sat Jul 15, 2006 2:23 am    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

Franc Zabkar (fzabkar@iinternode.on.net) writes:
Quote:
On Fri, 14 Jul 2006 23:02:06 +0100, "3T39" <rubbishrat@hotmail.com
put finger to keyboard and composed:

Hello, All!


Could anyone please suggest a fairly simple circuit to convert the 12V DC of
a motor car down to 1.5V DC needed by my MP3 Player ?
Any help appreciated.



With best regards, 3T39. E-mail: rubbishrat@hotmail.com

Get an old mobile phone car adapter and modify the output for 1.5V. A
lot of the switchmode types use an MC34063 IC which should be able to
go down as low as 1.25V by changing one or both feedback resistors.
Use a zener diode to crowbar the output in case of overvoltage.

That seems a bit like overkill.


Getting the needed voltage is really easy, given the low voltage
and the likely low current consumption of the device. (A dropping
resistor and a 1.5V zener would do it, though likely the forward
voltage drop of 2 silicon diodes would provide the "zener" and easier
to find to boot.)

But since he wants to run it off a car battery, it gets complicated.
You really need to ensure that no voltage spikes are going to get itno
the MP3 player from the +12v line on the car.

I suspect your suggestion would work well, under the assumption that they
would have done good filtering on that car adaptor. But it's overkill
in terms of current capacity, and it seems odd to start fiddling with
a switching supply to get a miniscule current at 1.5V. If someone does
that, they might as well just leave the adaptor as is, and drop the output
via a resistor and zener, leaving the adaptor to take care of the voltage
spikes.

The easiest solution would be to get an A battery, and run the MP3 player
off that. Those had enough current capacity that it would likely be a long
time before it needed replacing (and the thumbscrews on the terminal make
the replacing easy). But I have no clue where one can buy A batteries
these days, or even if they are still being made.

So one could use a D cell, and just live with the occasional replacement,
which is bound to be far less frequent than the AAA inside the MP3 player.

Michael
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Puckdropper
electronics forum addict


Joined: 13 Sep 2005
Posts: 73

PostPosted: Sat Jul 15, 2006 4:42 am    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

"3T39" <rubbishrat@hotmail.com> wrote in
news:44b81477$0$5221$db0fefd9@news.zen.co.uk:

Quote:
Hello, All!


Could anyone please suggest a fairly simple circuit to convert the 12V
DC of a motor car down to 1.5V DC needed by my MP3 Player ?
Any help appreciated.



With best regards, 3T39. E-mail: rubbishrat@hotmail.com

You may find it cheaper and easier to go with rechargable batteries.
I've found most AA NiMH batteries do a good job, and my charger will
charge any number of them I put in. (Great for a device that uses three
batteries.)

(Just throwing this out as an alternative. There's plenty of other good
suggestions already posted.)

Puckdropper

--
Wise is the man who attempts to answer his question before asking it.

To email me directly, send a message to puckdropper (at) fastmail.fm
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Arfa Daily
electronics forum Guru


Joined: 06 May 2005
Posts: 588

PostPosted: Sat Jul 15, 2006 11:51 am    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

"3T39" <rubbishrat@hotmail.com> wrote in message
news:44b81ce2$0$5222$db0fefd9@news.zen.co.uk...
Quote:
Hello, Arfa!
You wrote on Fri, 14 Jul 2006 22:05:09 GMT:


AD> "3T39" <rubbishrat@hotmail.com> wrote in message
AD> news:44b81477$0$5221$db0fefd9@news.zen.co.uk...
??>> Hello, All!
??
??>> Could anyone please suggest a fairly simple circuit to convert the
12V
??>> DC of a motor car down to 1.5V DC needed by my MP3 Player ? Any help
??>> appreciated.
??
??>> With best regards, 3T39. E-mail: rubbishrat@hotmail.com
??
AD> Resistor and NiMHi cell perhaps ? Only 1.2v, and not terribly kind to
AD> the battery, but simple, cheap and should work ok


Hhmm, A bit brutal Arfa, I see what you mean but I was hoping for a tad
more sophistication :^)
but thanks anyway.

With best regards, 3T39. E-mail: rubbishrat@hotmail.com

Agreed, but you did say that you wanted it simple. All of the solutions
offered further down, which make use of a linear regulator, such as the
LM317, are very inefficient in terms of heat produced. My thinking with
using the NiMH cell, was that the series resistor could be dimensioned to
give a very light trickle charge to the cell, of only a few mA. This sort of
scheme is common in cordless phones, for instance, and doesn't seem to do
the battery packs too much harm - you generally get 2 - 3 years reasonable
service from them. The current to run the MP3 player would then be provided
basically by the cell. When the player was out of use, the cell would
continue to be gently charged, ready for your next journey. Simple and
reasonably efficient ?? There is an added advantage in that the cell
provides a fairly low impedance, so will tend to absorb any transients on
the line from the vehicle's electrical system. To be sure, you could always
'complicate' the circuit, by adding a C of say 0.1uF across the cell.
Between that, and the relatively high value of the charging resistor, just
about all spikes should be slugged to the point of no consequence.

Arfa
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3T39
electronics forum addict


Joined: 31 May 2005
Posts: 79

PostPosted: Sun Jul 16, 2006 1:19 pm    Post subject: Re: 12V DC to 1.5V DC needed Reply with quote

Hello, Arfa!
You wrote on Sat, 15 Jul 2006 11:51:39 GMT:


AD> "3T39" <rubbishrat@hotmail.com> wrote in message
AD> news:44b81ce2$0$5222$db0fefd9@news.zen.co.uk...
??>> Hello, Arfa!
??>> You wrote on Fri, 14 Jul 2006 22:05:09 GMT:
??>>
AD>>> "3T39" <rubbishrat@hotmail.com> wrote in message
AD>>> news:44b81477$0$5221$db0fefd9@news.zen.co.uk...
??>>>> Hello, All!
??>>>>
??>>>> Could anyone please suggest a fairly simple circuit to convert the
??>> 12V
??>>>> DC of a motor car down to 1.5V DC needed by my MP3 Player ? Any help
??>>>> appreciated.
??>>>>
??>>>> With best regards, 3T39. E-mail: rubbishrat@hotmail.com
??>>>>
AD>>> Resistor and NiMHi cell perhaps ? Only 1.2v, and not terribly kind to
AD>>> the battery, but simple, cheap and should work ok
??>>
??>> Hhmm, A bit brutal Arfa, I see what you mean but I was hoping for a
??>> tad more sophistication :^) but thanks anyway.
??>>
??>> With best regards, 3T39. E-mail: rubbishrat@hotmail.com

AD> Agreed, but you did say that you wanted it simple. All of the solutions
AD> offered further down, which make use of a linear regulator, such as the
AD> LM317, are very inefficient in terms of heat produced. My thinking with
AD> using the NiMH cell, was that the series resistor could be dimensioned
AD> to give a very light trickle charge to the cell, of only a few mA. This
AD> sort of scheme is common in cordless phones, for instance, and doesn't
AD> seem to do the battery packs too much harm - you generally get 2 - 3
AD> years reasonable service from them. The current to run the MP3 player
AD> would then be provided basically by the cell. When the player was out
AD> of use, the cell would continue to be gently charged, ready for your
AD> next journey. Simple and reasonably efficient ?? There is an added
AD> advantage in that the cell provides a fairly low impedance, so will
AD> tend to absorb any transients on the line from the vehicle's electrical
AD> system. To be sure, you could always 'complicate' the circuit, by
AD> adding a C of say 0.1uF across the cell. Between that, and the
AD> relatively high value of the charging resistor, just about all spikes
AD> should be slugged to the point of no consequence.

Yes I did say simple Arfa, and I understand what you say. You're quite right
about it, and I'm thinking now I might give this a try, I thought around
800R 0.25W what do you think?
Can I mention your name if I set the car on fire? :^)


Also I'd like to thank everyone who took the time to write down your
thoughts on this
Much appreciated !



With best regards, 3T39. E-mail: rubbishrat@hotmail.com
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