12v power supply

D

don

Guest
I've got a walkman type mp3 player that I want to connect up to my car's
power supply.

I bought a $20 cigarette lighter adaptor, but there is too much
interference from the car's motor/electrics (loud whirring in speakers
in time with eng revs).

I rang a couple of car radio installers but they reckon there is nothing
"off the shelf" (suppressors etc) to fix that prob?

Some time ago someone in here posted about a power supply gizmo he made
to overcome that prob.

I thought I had saved the post, but can't find it :(

Anyone save the post or know how to do it?

Thanks.
 
On Tue, 09 Sep 2003 11:12:52 +1000, don wrote:

I thought I had saved the post, but can't find it :(

Anyone save the post or know how to do it?
Click to expand...
Try searching http://groups.google.com/

--

Noah
Linux. The leading OS of the future.
 
"don" <don@theparty.com> wrote in message
news:3F5D2914.3772EBD0@theparty.com...
I've got a walkman type mp3 player that I want to connect up to my car's
power supply.

I bought a $20 cigarette lighter adaptor, but there is too much
interference from the car's motor/electrics (loud whirring in speakers
in time with eng revs).

I rang a couple of car radio installers but they reckon there is nothing
"off the shelf" (suppressors etc) to fix that prob?

Some time ago someone in here posted about a power supply gizmo he made
to overcome that prob
I once went through a similar exercise. I found that the cigarette lighter
Click to expand...
adapter I had, used a switchmode type power supply, and was quite badly
filtered, letting through both engine noise and inducing it's own high
frequency noise. The solution I came up with was as follows: (hopefully
ascii art will be readable, stupid outlook express won't let me have a fixed
pitch font)
+12V--->|---L------L------7805-->|-----------
C | C C
G-----------------------------------------------
To explain - first thing it goes through is a diode, I found this necessary,
presumably to stop the capacitor discharging back through the car electrics.
Then it goes through a T circuit with two coils and a capacitor. For the
coils, I wound a lot of turns of fairly thick enamel wire on a ferrite
former. (you don't want much DC resistance). The capacitor was a couple of
4700uF 25V electro's in parallel. The device I wanted to power required
4.5V at 500mA. As a result a 7805 had enough current capability (I had a
small heatsink on it, it didn't get very hot). I probably could have got
away with the straight 5V output, but decided to put a diode in series with
it's output to drop the voltage by another .6V to give an output voltage of
4.4V. Finally I had a .1uF capacitor just to give a bit more high frequency
filtering. Because I mounted the above in the engine bay and ran it to a DC
plug in the cabin, I added another .1uF cap at the DC plug. The end result
was a nice quiet noise free power rail. I found that every filtering item
was necessary, cutting out any particular item would result in a bit of
noise back on the line again.
If you need a different voltage, you can add extra diodes to the output to
drop it further - eg 2 more would make the output 3.2V which would be fine
for 3V items. If you need a higher voltage you can use a resistor divider
between the output and ground pins of the 7805 and the ground rail to
increase the voltage to anything up to about 10V. For the diodes, 1N4004's
or any other 1A rectifier diode will do. With suitable heatsinking on the
7805, the above should handle up to 1A, which is more than enough for most
small devices like CD/mp3 players.
In my application, the whole bundle was about the size of a fist - I mounted
it in the engine bay, and fitted a DC jack into the centre console, so I
could plug my CD player into it.

I thought I had saved the post, but can't find it :(

Anyone save the post or know how to do it?

Thanks.
Click to expand...
 
On Tue, 09 Sep 2003 11:12:52 +1000, don <don@theparty.com> wrote:

I've got a walkman type mp3 player that I want to connect up to my car's
power supply.

I bought a $20 cigarette lighter adaptor, but there is too much
interference from the car's motor/electrics (loud whirring in speakers
in time with eng revs).
Click to expand...
A whirring sound is the alternator and it should have a
condensor/capacitor from it's B+ to ground. From memory they are
0.5uf.

There is such a thing as a line filter for cars, simply a choke and
cap arrangement usually.
Just dug out the Jaycar catalogue and they have them ready made.

Al

2003 insult page awaits your contribution
http://kwakakid.cjb.net/insult.html
 
On Tue, 09 Sep 2003 11:12:52 +1000, don <don@theparty.com> wrote:

I've got a walkman type mp3 player that I want to connect up to my car's
power supply.

I bought a $20 cigarette lighter adaptor, but there is too much
interference from the car's motor/electrics (loud whirring in speakers
in time with eng revs).

I rang a couple of car radio installers but they reckon there is nothing
"off the shelf" (suppressors etc) to fix that prob?
Click to expand...
Funny, I've purchased one from a car audio shop many years ago.
 
thanks

Noah wrote:

On Tue, 09 Sep 2003 11:12:52 +1000, don wrote:


I thought I had saved the post, but can't find it :(

Anyone save the post or know how to do it?


Try searching http://groups.google.com/

--

Noah
Linux. The leading OS of the future.
Click to expand...
 
Justin Thyme wrote:

"don" <don@theparty.com> wrote in message
news:3F5D2914.3772EBD0@theparty.com...
I've got a walkman type mp3 player that I want to connect up to my car's
power supply.

I bought a $20 cigarette lighter adaptor, but there is too much
interference from the car's motor/electrics (loud whirring in speakers
in time with eng revs).

I rang a couple of car radio installers but they reckon there is nothing
"off the shelf" (suppressors etc) to fix that prob?

Some time ago someone in here posted about a power supply gizmo he made
to overcome that prob
I once went through a similar exercise. I found that the cigarette lighter
adapter I had, used a switchmode type power supply, and was quite badly
filtered, letting through both engine noise and inducing it's own high
frequency noise. The solution I came up with was as follows: (hopefully
ascii art will be readable, stupid outlook express won't let me have a fixed
pitch font)
+12V--->|---L------L------7805-->|-----------
C | C C
G-----------------------------------------------
To explain - first thing it goes through is a diode, I found this necessary,
presumably to stop the capacitor discharging back through the car electrics.
Then it goes through a T circuit with two coils and a capacitor. For the
coils, I wound a lot of turns of fairly thick enamel wire on a ferrite
former. (you don't want much DC resistance). The capacitor was a couple of
4700uF 25V electro's in parallel. The device I wanted to power required
4.5V at 500mA. As a result a 7805 had enough current capability (I had a
small heatsink on it, it didn't get very hot). I probably could have got
away with the straight 5V output, but decided to put a diode in series with
it's output to drop the voltage by another .6V to give an output voltage of
4.4V. Finally I had a .1uF capacitor just to give a bit more high frequency
filtering. Because I mounted the above in the engine bay and ran it to a DC
plug in the cabin, I added another .1uF cap at the DC plug. The end result
was a nice quiet noise free power rail. I found that every filtering item
was necessary, cutting out any particular item would result in a bit of
noise back on the line again.
If you need a different voltage, you can add extra diodes to the output to
drop it further - eg 2 more would make the output 3.2V which would be fine
for 3V items. If you need a higher voltage you can use a resistor divider
between the output and ground pins of the 7805 and the ground rail to
increase the voltage to anything up to about 10V. For the diodes, 1N4004's
or any other 1A rectifier diode will do. With suitable heatsinking on the
7805, the above should handle up to 1A, which is more than enough for most
small devices like CD/mp3 players.
In my application, the whole bundle was about the size of a fist - I mounted
it in the engine bay, and fitted a DC jack into the centre console, so I
could plug my CD player into it.


I thought I had saved the post, but can't find it :(

Anyone save the post or know how to do it?

Thanks.
Click to expand...
err, got it all except for the bit after "I once went through a similar
exercise", lol.

A bit too advanced for me, but I've copied it to cd just in case.

Many thanks for your trouble :)
 
Albm&ctd wrote:

On Tue, 09 Sep 2003 11:12:52 +1000, don <don@theparty.com> wrote:

I've got a walkman type mp3 player that I want to connect up to my car's
power supply.

I bought a $20 cigarette lighter adaptor, but there is too much
interference from the car's motor/electrics (loud whirring in speakers
in time with eng revs).

A whirring sound is the alternator and it should have a
condensor/capacitor from it's B+ to ground. From memory they are
0.5uf.

There is such a thing as a line filter for cars, simply a choke and
cap arrangement usually.
Just dug out the Jaycar catalogue and they have them ready made.

Al

2003 insult page awaits your contribution
http://kwakakid.cjb.net/insult.html
Click to expand...
thanks for response. Al.

The car is only a few years old and has the usual suppressor.

I'll try one of the Jaycar line filters.

Thanks for the tip.
 
David, Sauer wrote:

On Tue, 09 Sep 2003 11:12:52 +1000, don <don@theparty.com> wrote:

I've got a walkman type mp3 player that I want to connect up to my car's
power supply.

I bought a $20 cigarette lighter adaptor, but there is too much
interference from the car's motor/electrics (loud whirring in speakers
in time with eng revs).

I rang a couple of car radio installers but they reckon there is nothing
"off the shelf" (suppressors etc) to fix that prob?

Funny, I've purchased one from a car audio shop many years ago.
Click to expand...
If you are talking about the "usual" suppressors, then yes thay have been
around a long time and my car has one fitted.

The info I was after was specific to when the "usual" suppressors don't do
the job. Sorry, I didnt make that clear.

Thanks for your response.
 
"don" <don@theparty.com> wrote in message
news:3F5EFA73.6B3265D4@theparty.com...
<snip>
err, got it all except for the bit after "I once went through a similar
exercise", lol.

A bit too advanced for me, but I've copied it to cd just in case.

Many thanks for your trouble :)
Sorry mate, i kinda assumed that since it's aus.electronics you would have
Click to expand...
had a bit of experience in electronics at the component level. No prob's,
i'll give you a quick summary in non-techie terms.
I found that the ciggie lighter adapter was totally useless for this type of
stuff, too much noise. I hunted around and couldn't find any off-the-shelf
kind of solution that was at a price I was prepared to pay for it. So in
the end, I grabbed a few electronic components and made one myself. All up
I reckon the bits cost about $10, maybe $15. Less than the amount I wasted
on the ciggie adapter, and far less than any off-the-shelf solutions I saw
in shops, and it worked a treat.
 
Justin Thyme wrote:

"don" <don@theparty.com> wrote in message
news:3F5EFA73.6B3265D4@theparty.com...
snip
err, got it all except for the bit after "I once went through a similar
exercise", lol.

A bit too advanced for me, but I've copied it to cd just in case.

Many thanks for your trouble :)
Sorry mate, i kinda assumed that since it's aus.electronics you would have
had a bit of experience in electronics at the component level. No prob's,
i'll give you a quick summary in non-techie terms.
I found that the ciggie lighter adapter was totally useless for this type of
stuff, too much noise. I hunted around and couldn't find any off-the-shelf
kind of solution that was at a price I was prepared to pay for it. So in
the end, I grabbed a few electronic components and made one myself. All up
I reckon the bits cost about $10, maybe $15. Less than the amount I wasted
on the ciggie adapter, and far less than any off-the-shelf solutions I saw
in shops, and it worked a treat.
Click to expand...
Actually I stumbled in here a year or so ago with a question about a wounded
monitor. Got it answered, fixed the monitor and have browsed back every now and
then. Its an interesting ng, even for an electonics dud :)

The reason I saved (somewhere) the post that I referred to, is that it was very
straight forward...buy this, solder that, connect the other, kind of stuff.

I'll harrass Jaycar in the morning. If I don't do any good, I'll decipher your
solution and give it a go.

Thanks again.
 
how about a large cap (10,000uF) and a +12V Regulator with low voltage drop
out ?

"don" <don@theparty.com> wrote in message
news:3F5EF973.BC88F81A@theparty.com...
thanks

Noah wrote:

On Tue, 09 Sep 2003 11:12:52 +1000, don wrote:


I thought I had saved the post, but can't find it :(

Anyone save the post or know how to do it?


Try searching http://groups.google.com/

--

Noah
Linux. The leading OS of the future.
Click to expand...
 
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