possible new psu for 60watt setups

**vash** · 08-11-2002, 02:10 AM

What are some inexpensive good ways of regulating the cars positive voltage so that it always is at 12volts 5 amps

I aks this because i want to use the DC-DC power board that comes with this case for my Via Epia motherboard:

http://www.casetronic.com/Product/PC...7/CS-2677.html

This case comes with an external AC adapter which powers the DC-DC power board that is within the case. If I could regulate the positive power from the cars batter to 12v 5 amps I could power the DC-DC power board, by using this method of powering my carputer i could take it out of my car and inside my house and just plug in the external ac adapter and also use my carputer as a houseputer.

**ShinkunoNamida** · 08-11-2002, 03:09 AM

This has been discussed in depth. Pretty much you make a circuit, have someone make it for you, or try to find one in a store.

You might find a laptop adapter or something.

The important part is to make sure it's regulated

**vash** · 08-12-2002, 05:15 AM

are there any design specs for a Do it your self project.... I would like to build the smallest circuit possible.... maybe it could work so that it kept the dc-dc board up and running even if the power droped to 8volts for a second from starting the car? please just post a link or two to get me started,

as i am very new to the whole mp3 car stuff.... i currently have a tiny itx via epia 5000, i have an lcd .. havent got that working completely, i also have an ir2pc module... i have that working on another machine but not mine cause i think my serial port is bad... and the lcd i either have wired wrong or something... although i followed the wiring diagram exactly. so once i get the lcd and serial port working all i will need for my project is the psu. thank you for all your help...

**THEMP3KID** · 08-12-2002, 07:04 AM

www.sproggy.com but, you would have found that by searching.. :P

**vash** · 08-12-2002, 08:22 AM

I have read MANY MANY threads... i already know about the sproggy.... its an entire design for a psu... and i dont really want to do it that way... all i need to regulate is the +12v @5amps... to supply the dc-dc board with power, and i want to do it so that it supplies the +12v@5amps even if the car drops to say +8V for a second when i start the car.... i do not need the other voltage amounts that the sproggy has.... i would just use the sproggy entirely but it does not have an input jack for the external ac adapter that i want to use so that i can use the mp3 player in my house as well as my car.

**Casper** · 08-12-2002, 05:01 PM

mp3kid.... if your so sure that everything can be found by searching... heres one for ya... whats the exact value of pi to the point where it bocomes a rational deicmal?

Should keep yer busy for a while...

**gfoulks** · 08-12-2002, 05:12 PM

vash,
I have a DC powered system as well and am looking for something I guess like you are. I want to supply regulated power to the system with the least amount of hardware and make it a hardwire setup... No plugs please.

greg

**jpainter99** · 08-13-2002, 10:45 PM

Guys I have not looked into this in great detail yet, but I think something along the lines of this IC would work. Im not saying this will work, or this is the right way to do it, but it looks promising to me.

Check out LT1084CP-12

http://rocky.digikey.com/WebLib/Line...85%20Fixed.pdf

On a first glace looks like all you need is this chip and 3 little capacitors. The chip is less than $8 on digikey. Im toying around with the idea of this chip, a little 12V ups battery (less than $20) and some healthy diodes for battery isolation.

**Casper** · 08-14-2002, 06:32 AM

Jpainter99, this would quite possibly work to produce the voltages required, however, these low dropout regulators are constructed using linear technology (as the page header would suggest :-p) and therefore are very inefficient.

This is because if you were to draw 7.5A on the 3.3v chip, it would draw 7.5A on the 12v line input (this is my understanding of linear technology anyway), and therefore be of at BEST 27.5% efficiency. This is fairly poor when you've got a contained power system such as a car battery and alternator.

This is the reason most people on the board have chosen to use switching regulators if they choose to build their own DC-DC supply. This is because it is not only efficient, but produces good quality supply. The process is very complicated to explain, but example circuits can be found on the Maxim-IC (http://www.maxim-ic.com) and National Semiconductor (http://www.national.com) websites. Practical power supplys to make are Sproggy's, and possibly if you've got some competence with electrical circuitry, Texas Instrument ISR's (Kaboom will be selling these PSU's in the near future, but until then its over to us). Also Jeff's power supply works very well with its shutdown controller.

**jpainter99** · 08-14-2002, 10:00 AM

I see your point. It does mention that these new IC's have the quiescent current flowing to the output tho which makes them more efficient. I'll have to look into the switching as well when my power supply comes in this week.

Cheers,
Justin