one more question... (computer at power supply mod) - Electronic Circuits Projects Diagrams Free

truenoteno · 16th April 2003, 07:40 AM

i want to get a computer going in my car.
Could remove the transformer from the AT computer power supply and input 12VAC instead ?
how do i get AC from DC ?

bogdanfirst · 16th April 2003, 08:22 AM

you can get 12V directly from the battery, use some caps for filter....
but for 5V and -12, -5 and 3.3 or 2.5 you need some more complicated psu. you should use a good switching...
but about the transformer, i dont know......i dont think that it will work...

truenoteno · 16th April 2003, 08:27 AM

i mean get 12v from battery, convert to AC 12 or whatever the output of the transformer was then connect to where the transformer was in the power supply, doing it this way gets the -12, -5 and all the other voltages you mentioned
why wouldn't it work ? (i don't want to waste my time on a dud project)

thanks

daviddoria · 16th April 2003, 12:31 PM

haha there's no sense in converting DC to AC back to DC. just use 12v from the battery and get 5v using some sort of voltage limiter... you can't use a step down transformer cause those are AC only.

also, be sure to use some caps (duno what value) as a filter (get the spikes out of the AC)

Mosfet · 16th April 2003, 06:01 PM

Many retailers sell DC-DC converters that are cost effective and efficient
http://www.astrodyne.com [no recommendation, I just have their catalog in front of me]
Here is what others have done:
Retired electronics teacher, two versions, poor hand-drawn schematics:
http://www.bobblick.com/techref/proj.../mp3book2.html
http://www.bobblick.com/techref/proj...p3/yammp3.html
http://www.geocities.com/SiliconVall...4/CPSschem.PDF busy version
http://home.concepts-ict.nl/~cybersa...3/sch_smps.gif similar
http://www.geocities.com/andrewmuck/PSU.htm Muck's version

Ricky · 18th April 2003, 03:36 PM

An easier solution is to use a voltage converter from dc to ac and just plug your computer psu to it. :wink:

stevez · 18th April 2003, 05:56 PM

It is my understanding that in some car electrical systems that disconnection (intentional or the cable breaks) of the battery while the car is running will send voltages to very high levels momentarily and that electronics for those applications are designed with this in mind. The 12 volts is also incredibly noisy. I've veiwed the voltage spikes from the fuel injectors as they appear at the cigarette lighter -they are significant. I'd avoid direct use of the 12 volts unless you've addressed the overvoltage and noise.

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16th April 2003, 07:40 AM	(permalink)
truenoteno	one more question... (computer at power supply mod) i want to get a computer going in my car. Could remove the transformer from the AT computer power supply and input 12VAC instead ? how do i get AC from DC ?

16th April 2003, 08:22 AM	(permalink)
bogdanfirst	you can get 12V directly from the battery, use some caps for filter.... but for 5V and -12, -5 and 3.3 or 2.5 you need some more complicated psu. you should use a good switching... but about the transformer, i dont know......i dont think that it will work...

16th April 2003, 08:27 AM	(permalink)
truenoteno	i mean get 12v from battery, convert to AC 12 or whatever the output of the transformer was then connect to where the transformer was in the power supply, doing it this way gets the -12, -5 and all the other voltages you mentioned why wouldn't it work ? (i don't want to waste my time on a dud project) thanks

16th April 2003, 12:31 PM	(permalink)
daviddoria	haha there's no sense in converting DC to AC back to DC. just use 12v from the battery and get 5v using some sort of voltage limiter... you can't use a step down transformer cause those are AC only. also, be sure to use some caps (duno what value) as a filter (get the spikes out of the AC) __________________ thanks, david

16th April 2003, 06:01 PM	(permalink)
Mosfet	Many retailers sell DC-DC converters that are cost effective and efficient http://www.astrodyne.com [no recommendation, I just have their catalog in front of me] Here is what others have done: Retired electronics teacher, two versions, poor hand-drawn schematics: http://www.bobblick.com/techref/proj.../mp3book2.html http://www.bobblick.com/techref/proj...p3/yammp3.html http://www.geocities.com/SiliconVall...4/CPSschem.PDF busy version http://home.concepts-ict.nl/~cybersa...3/sch_smps.gif similar http://www.geocities.com/andrewmuck/PSU.htm Muck's version

18th April 2003, 03:36 PM	(permalink)
Ricky	An easier solution is to use a voltage converter from dc to ac and just plug your computer psu to it. :wink:

18th April 2003, 05:56 PM	(permalink)
stevez	It is my understanding that in some car electrical systems that disconnection (intentional or the cable breaks) of the battery while the car is running will send voltages to very high levels momentarily and that electronics for those applications are designed with this in mind. The 12 volts is also incredibly noisy. I've veiwed the voltage spikes from the fuel injectors as they appear at the cigarette lighter -they are significant. I'd avoid direct use of the 12 volts unless you've addressed the overvoltage and noise. __________________ stevez