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car mp3 player: pwr supp

Y

YNos

Member
hello all, am new to the group here, looks interesting...
anyway- I am making a in-car, x86 mp3player. <linux, IRman, 200mhz, 64mb RAM> i see all the plans for them say to use an inverter<13.8dcto110ac>, was thinking....why(or how hard is it> that someone hasent made a dc13.8todc12&5 converter. was wondering if anyone has a schematic<or kit>
to do so.
i am thinking of usin cajun, or qnx
anyone have any input<what distro, config, so on> plz post.
thanks,
YNos😕
 
For 5V, you can use one of maxim's ic that'll do 5V @ 5A, which is plenty enough to run a hard drive, mobo, and play mp3's (assuming your cpu speed is no faster than p166mmx). I forgot the part #, but it's a chip that requires very little external parts.

As for the 12V, you might have some problems here because in order to get regulated 12V, your going to need at least 14VDC because of the voltage drops across the internal diodes. A general LM7812 would work, but it only supplies 1A and requires around 13-13.5V to supply the full 12V, which means it'll give you 12V only when the engine is on. Maxim might also have a 12V regulator that'll run with supply voltage as low as 9V (i think, not too sure about it).

Anyways, check their website.
 
I actually did this, using the Maxim MAX787 switchmode regulator. What a wonderful part. 🙂 Pretty low heat, too. I used an ordinary 12V regulator for the +12v line without problems. The drop might have brought the voltage down below +12, but it was still enough for a stable system.
You can just omit the -5V supply, and if you don't need VGA video, omit -12V, too.

[edit] The 12V regulator hookup is simple enough, but check out the MAX787 datasheet for the schematic on that one.
 
could you link to a schematic, and give a partlist? are all these available from mouser?
thnx
YNos
 
The schematic for the 787 is on the first page of the datasheet, here.
You don't need much for the 12V reg. You should be able to find most of those parts from Mouser. The diode is kind of exotic, but not so much you couldn't find one.
 
killbat,

that's the part I'm talking about, MAX787. I built a PS for my car using that and the schematic in the datasheet. Works like a charm. It runs cooler than other regulators, but you still need at least a 1"x2" heatsink for it. I also remember using a 12V regulator (2 of them), one to power the motherboard and the other to power the hard drive. Those ran really hot and could only get them to run at ~12V if the engine was on.
 
thanx all, i have ordered the parts, and will post when i can tell you all weather it was a good outcome or not.
YNos
 
Hmmm... you should be able to thow a bunch of these in series to get up to the amperage required for a AMD. I am gonna try that. Now I got something to o tommorow.
 
damn, you think the parts could come any slower<or does that fall in the same catergory as a watched pot?>
 
hey, still waiting for the parts to come, anyone know if there are smaller mobo's that are designed for 12v, or 13.8v?
the board that i am using is not very small, maybe i can use something smaller?
 
Three easy ways to build car MP3 player.

1) Buy Car CD/MP3 player.

2) Buy Rio Volt. Hook to amp in car stereo.

3) Buy HD based MP3 player, like Creative Nomad. Hook to amp in car stereo.


All three of these options will probably sound better, will certainly be smaller, and will most likely be cheaper than what you're doing now. But if you must build your machine into your car, good luck, and may your tunes sound good.
 
this is more of a knowlege project than a hurry up and get it done project, am hoping to learn more from it than how to spend money.
am using hardware i have here, was just wondering about the pc104/sbc.
 
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