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Old 22nd February 2006, 07:43 AM   #1
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Default Stepping 12v down to 5v

What different ways is there to step down the 12v of a car battery power down to 5v that i could use for a small amp that i have?
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Old 22nd February 2006, 07:58 AM   #2
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You could use an off-the-shelf DC/DC Converter: Example.

Cheers,

Bruno
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Old 22nd February 2006, 08:51 AM   #3
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Default Re: Stepping 12v down to 5v

Quote:
Originally posted by silentblackhat
What different ways is there to step down the 12v of a car battery power down to 5v that i could use for a small amp that i have?
What sort of amplifier.
Preamp or power amp.

Or more correct question is:
How much current does your amp need, at 5V DC?

---------------------------

Buying a DC/DC converter for supplying less than like 0.5 A
is not necessary. I would say it is the wrong idea, in 9/10 cases.

A simple 5V/1A (or 5V/100mA) three pin regulator IC is all that is needed.

1 pin is for 12 Volt input, 1 pin is for 5 Volt output
1 pin is connected to 0 Volt (Ground)

Such an IC costs only a few pennies.

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Old 22nd February 2006, 11:50 AM   #4
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The problem with liniar regulators is power loss.

At 5V out 0.5A you use (12-5)*0.5= 3.5W in heat while you supply only 2.5W out of the regulator.

Switching is great but difficult unless you know what you a doing or buy a DC/DC module.

Try looking up "Buck converter"

That is the topology most common in DC/DC converters. It generates a lower output voltage (compared to input) with little loss.

\Jens
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Old 22nd February 2006, 01:35 PM   #5
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I'll second that. Try looking at this link: http://cache.national.com/ds/LM/LM2596.pdf
The LM2596 comes in four flavors: 3.3V, 5V, 12V & Adjustable versions. In their simplest form, they require only 2 caps, one diode and one coil. That's why they are called SimpleSwitchers.

Don't know how to design one? No big deal, the entire designe procedure and some examples are included, you only need to plug in your parameters, and spit out your answers. There are even ready-made coils for your particular app, or you can roll your own from any #26 Powdered-Iron toroid (colored yellow).

I'm not the world's best designer / prototyper, but I have designed, fabricated and tested a SimpleSwitcher-based buck regulator in just a little over an hour. Including soldering.

Steve
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Old 22nd February 2006, 02:28 PM   #6
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well its not really a big amp or an amp at all but it does have a very small amp in it. i am making a circuit in my car that has a chip on it that u cna record a sound to and have it played back(like those picture frames from radio shack that u can record a message to and it plays back when u press the playback button, but imnot making a picture frame) so it wont use much at all. i might just get a 5v battery,and add a relay to have it switch that 5v battery on to pwoer the small amp. every time i use it, it will only be on for about 5-6 seconds. not much power at all
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Old 22nd February 2006, 02:40 PM   #7
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For such a low power application, a 7805 regulator IC would be a much more ecologic solution (no more batteries). It's cheap and very easy to implement since it only has 3 pins.
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Old 22nd February 2006, 04:25 PM   #8
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Quote:
Originally posted by JensRasmussen
The problem with liniar regulators is power loss.

At 5V out 0.5A you use (12-5)*0.5= 3.5W in heat while you supply only 2.5W out of the regulator.
This is no problem for this very low power amplifier
fead from a 12 Volt Car battery.
Mostly when using, will be no loss, as you have car running.
Car batteries have a capacity of more than 50 VAh.

Would have been an issue, if was a lower capacity battery.
Like NiMH or small lead battery. (SLA)

I say, like poster here above:
buy a 7805, 5 Volt 1 Ampere regulator, for 1 buck.
You might not even have to use a piece of aluminium to put it on (for cooling).
But do it anyway.
For example 40 x 50 mm aluminium plate of 0.5 mm thickness.

-------------------

Save the more complicated, more expensive solutions for others to chose.
And for situations where is a call for it.


You can do shopping using a little Fiat car.
You dont have to buy a Chevrolet truck, Rolls Royce or a technically advanced Jaguar.

You might even be able to use your bicycle!
.... or walk ...



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Old 22nd February 2006, 04:36 PM   #9
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I'd use a 5v regulator and throw the power away as heat.
Just as others have said.

The regulator will help reduce electrical noise too.
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Old 22nd February 2006, 05:27 PM   #10
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I have an update. i went to radio shack to get some parts for my circuit im making(that im integrating the voice chip in) and i saw that radio shack has the same type of recording thing i need andi t runs on a 9v battery. i think i will get the thing from radio shack instead of ordering the chip off of the net
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