Regulating car 12v

[werner]

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[Highflyer_GP]

I think that you may need a zener diode in conjunction with a voltage regulator type of circuit to keep the threshold at +-12V. Also if I recall PC's operate at 5V so it wouldn't make much sense to step up to 220V when the PC is going to step it down to 5V anyway.

 

[DAE_JA_VOO]

Your best bet would be to ask on a forum that's dedicated to this kinda thing. The best place to ask would be MP3Car.

 

[Gunny]

It depends on the current you drawing at 1 amp you can use a LM7812 its a 12v positive regulator you can get 2 amps if you sink it realy well. LM317 is variable but then again also 1 amp stable. You'll have to use a LM7812 as a reference and then piggyback a few power transistors to build amps.

 

[ebendl]

The PC power supplies are usually switching mode power supply designs, which means they don't use a transformer (big and bulky and heavy) but rather fancy circuitry to bring the voltages down. They can usually accept a wide variation (thats why you can use your laptop adapter in the states with 110V as well as here with 220V) and is much more efficient (little power is lost, thats why you can get 18A out of it). But because of correction circuitry to keep it stable, they are very complex.

Reading this again, I don't really think that helps, but at least it explains the theory.

 

[RichardP]

Dont even try clamping 2Amps! .. get a DC-DC converter. http://en.wikipedia.org/wiki/DC_to_DC_converter

It will accept dirty DC voltages and output a regulated clean DC voltage. the typical input range is 9-18VDC and will regulate a constant 12V output.

http://www.amplicon.co.uk/dr-prod3.cfm/subsecid/51/secid/6/groupId/10749.htm

Just a refrence web site.

@Gunny - The 7812 metod wont work as the regulator needs 1.5V to operate.. and when the battery is not at full power, the regulator cant function.

Zener clamping is a good idea when you want to dump voltage (wattage) for example on an alternator... its not good for voltage regulation

 

[DragonLogos]

@Gunny - The 7812 metod wont work as the regulator needs 1.5V to operate.. and when the battery is not at full power, the regulator cant function.

Zener clamping is a good idea when you want to dump voltage (wattage) for example on an alternator... its not good for voltage regulation

WHAT!!!!!

 

[werner]

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[Gunny]

Ok been doing some reading up found it interesting enough to look into.
idealy you need about 3 amps on each voltage rail being 12v, 5v and 3.3v.
Apparently the 3.3v rail is the one that will draw the most as it powers the proccessor, memory and most functions on the mobo. So for the 12v rail you'll need to step up the voltage before regulating it as our friend richard pointed out to have a 2v minimum buffer to to operate the 12v regulating components. 7v is the lowest the car battery could drop to so stepping up to 20v should work. the other rails will be ok as 7v is 2v above 5 and 3.3v will be a non issue. Looking at what Richard said maybe the 7812 isnt the best option maybe use a 8512 i think it is, its a switched mode regulator.

 

[mancombseepgood]

Spelling please Werner

thanks for the input guys, but I am struggling to find a (reasonably priced) dc-dc convertor that can handle 200watts+

converter

I think the suggestions given are all a bit....erm....pap in die broek. Just to refresh, the ac/dc is labelled 12v 18 AMPS.

labeled

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