12v 5 Amp Regulator

slarty · 06-29-2003, 02:40 PM

Hi All

I have an EPIA M 9000 in a C134 1Din and would like to have it regulated @ 12v 5Amp please is there a comercial regulator I can buy off the shelf or is there anyone who can build or show me how to build such a device. I have no experience with building this sort of thing. All I know is that it needs to be a separate unit to the C134 which is 1 Din.

I've read that the EPIA can be simple fused @ 5 Amp but also some others state that this may cause issues with hardware if the unit is not regulated.

Any help much appreciated

tejesh83 · 06-29-2003, 02:50 PM

I've been looking for a standalone regulator but no luck so far.

Typically, regulators take in a higher voltage then they put out. So maybe 15-18v DC in for a clean 12V out. I guess its difficult to build a 12v in 12v out regulator.

An opus power supply will give you 5A - 6.5 Peak on the 12V rail if that helps any.

slarty · 06-30-2003, 04:53 AM

Many thanks

I'd like to keep the Regulator as an Inline unit or a separate under dash mounted unit as I do not really want to strip the C134 in any form or way

I'm going to work on a DIY version if I can. If you get anywhere I'd be interested on the results

fantasy · 06-30-2003, 08:18 AM

i would be very interested in a DIY regulator as well... to put inline for a DC-DC psu

slarty · 06-30-2003, 05:56 PM

Does anyone know if this would do http://www.national.com/pf/LM/LM338.html

ADJUSTABLE voltage OUTPUT between
+1.2V ~ +32V, in TO-3 STEEL PACKAGE. Manufactured by
NATIONAL SEMICONDUCTORS Part Number LM338K/STEEL,

could it be wired in and aadjusted easily?

Trottingwolf · 06-30-2003, 07:25 PM

It sounds to me like your best bet if you dont want to buy something like a Opus PS is to use the 12V parts from a sproggy PS. It uses the LM2587T buck/boost regulator to supply about 2A at 12V with an input of about 8-24V or somewhere around there. If you really need more than 2A then you may want to look at getting a laptop power supply for a car that is 12V or a little more and regulate it down to 12V. The big problem with that last idea is the laptop PS can cost a lot of money. Check ebay they may have some cheap.

Alanh · 06-30-2003, 09:29 PM

The Nat. Semi. part is a linear regulator. A lot of the numbers in their datasheet seem to be assuming Vin-Vout is greater than or equal to 3V, so you'd need 15v in to get 12v out to be within their specs. It might work with less, but I don't know.

As noted before, what is really needed is some kind of switching power supply that can boost the voltage up to 12V if necessary and there isn't a magic bullet solution (i.e. solder a couple of inexpensive parts together) for one of those.

Where I work, we have engineers who design power supplies. Admittedly they're for applications more critical than a car computer, but they specialize in that area because it isn't easy to design good ones.

Alan

smanders · 06-30-2003, 10:38 PM

I have also done some of my own research in this area and talk to several hardware engineers that design these kinds of power supplies.

Most regulators that can supply some higher current require a minimum Voltage drop of 1.5V, most are around 3V as stated earlier. You could build a low-volt drop out regulator but when the voltage drops near 12V, it will not be regulated which could be bad. Also during starts the voltage can drop to 11V or even 10V which could do some damage. The DIY solution would be a two-stage voltage regulator. I would find one that boost voltage to 24V then use a switcher 12V regulator. One I found was LM2679. Funny now you have just built a DC-DC converter.

I have opted to just get Opus Solutions new 90W PSU whenever it becomes available.

Good Luck,
smanders

Skraggy_uk · 07-10-2003, 07:10 AM

Quote:

Originally posted by Trottingwolf
It sounds to me like your best bet if you dont want to buy something like a Opus PS is to use the 12V parts from a sproggy PS. It uses the LM2587T buck/boost regulator to supply about 2A at 12V with an input of about 8-24V or somewhere around there. If you really need more than 2A then you may want to look at getting a laptop power supply for a car that is 12V or a little more and regulate it down to 12V. The big problem with that last idea is the laptop PS can cost a lot of money. Check ebay they may have some cheap.

All the Ebay ones (and the same one found at Maplin) appear to regulate down to 15v+ @ 3.5AMP max.

I know it might prove an expensive way to do it, but could you take two of them, in parallel, running into a regulator that will regulate down to 12V? Before passing through to the unregulated powerboard?

Trottingwolf · 07-10-2003, 08:45 PM

You could do something like that, but the one problem is when you run two things in parallel sometime one will do all the work and the other will do nothing. If you look at the datasheets for the 12V regulators you are using they may tell you how to use two of them in parallel properly. Or you could just try it and check with a mulit-meter that they are both doing something.
I just looked on ebay and I see the one your talking about(hehehehe) yeah two of those, two linear regulators, might work from the start or it might take some messing with to get it to work but in the end it should. The other main problem you might have is that the linear regulators will put off a lot of heat. Over all it shouldnt be too hard to put together, it just might not be the best or most eligant solution.
Oh you may want to use switching 12V regualtors if you do this. That would cut down on the heat but would make the project more work to get right. If you have 15V in then I think you can get 12V 5A switching regulator no problem. All just depends on how complex you want it to be.

Skraggy_uk · 07-11-2003, 02:10 AM

Thats what I figured. With the cost of the two car cords modded into one box, and setup to be hardwired instead of using a lighter socket, one of the Epia based 60/70/120watt PSU's and the required Voltage regulators, I'm probably looking at about £100GBP (UK prices, or US prices plus import duty and taxes suck). For not much more I could buy an Opus.

peter3 · 07-16-2003, 05:42 PM

search for a lt1084cp-12
it's a 12v 5A regulator
just need 2 or 3 condensator's (capacitor's)

Skraggy_uk · 07-18-2003, 02:31 PM

Peter, I figured using two of the car power packs to get roughly 15v 7 amp, that could then be dropped to a regulated 12v, which would cover the under voltage situations.

Maybe a couple of those in Parallel, and the Lex 14-19v input Epia type PSU might do the job?

Bj · 07-19-2003, 04:02 AM

The only way to get 12V DC out of a 8-15V input is to step it up to a higher voltage first, and then step it down again. You can only do this with a switchmode circuit. All of the targus laptop power supplys and the morex cupid do this. The industry standard is 50V. So you step up to 50V and then take this 50V and step it down again to your required voltage and current ie 12V @ 7A.

I have been designing a similar supply to do this two stage process, and will post a schematic when I'm happy with it.

I hope this helps. You can't use linear regulators to do this process due to the voltage input required to power it.

Bj

Falken · 07-19-2003, 05:33 AM

I'm following up on a couple of potential solutions. The best so far provides an 12v DC-DC regulated 12V supply 5.4 amps. Essentially it replaces the AC/DC supply "brick".
So far, so good. Unfortunately the price for small quantities is too high at £120. Anybody interested in a group buy to try and get the prices down?