"ocran" wrote in message
ws.com:
Is there an easy method to step up the voltage? I am thinking to around
14v, when off of course. I don't car if it gets higher when the engine
is running, anything under 24v will do. But I would also like it to not
drop below 14v when cranking. Would a homebrew transformer do this? Of
couse with a diode and everything, but is it possible?

Thanks

It's going to take more than just a transformer and diode to make 14VDC from
12VDC. You'll probably want a switchmode DC-DC converter with a wide input
range (try to get one that will handle 8 volts or less, they should be
available down to 5 volts), 12 volt nominal adjustable output with wide
adjustment range, and enough current plus some overhead for your system. I
think 10 amps should do it for most systems. You may also need to do some
filtering since switchmode supplies can make a lot of electrical noise. A
DC-DC converter is not something you can homebrew without a lot of electronics
training, based on the apparent level of expertise from your post.

Good luck.

--
--------------------

Best regards,

Alan "A.J." Franzman

Email: a.j.franzman at verizon dot net

--------------------

You can buy a 14-16volt battery, but you' ll also need a new alternator with
an adjustable regulator to charge it... If you go this route, you will have
to either isolate it from the rest of your electrical system (cause your
car's computer and OEM electronics will NOT like 16v) or have a step-down
device between the battery and car electronics...

Generally though, your not gonna get any benefit from going to higher
voltage unless your into competition, as the audible difference is not going
to be perceivable...

Why exactly are you trying to do this?

n8



Is there an easy method to step up the voltage? I am thinking to around
14v, when off of course. I don't car if it gets higher when the engine
is running, anything under 24v will do. But I would also like it to not
drop below 14v when cranking. Would a homebrew transformer do this? Of
couse with a diode and everything, but is it possible?

Thanks
--
ocran

basically, i need 5v and 12v to run my machine. The 5v is easy and no
problem. The 12v is not a problem when the car is running. but when it
is off, my battery alone is only around 12.36v, thus the regulator
cannot regulate it, and my 12v turns out to be around 10v. And the hard
drive refusses to work with that low of a voltage.

That would be an awfully unstable power supply anyway. Why don't you just
buy a 12v input computer power supply?

Mark,
My overall goal is to achive +5v and +12v both at about 2 amp load, with
the input voltage of a car. By using regulators, caps, coils an diods i
have succesfully done this with virtually no noise, when the car is on,
when Vin is greater then 14v. But when the car is off, Vin dips to about
12.36v and the 12v regulator refuses to work. Thus i need never use it
when the car is off, or figure out how to step the voltage up. i have a
vicor power supply lying on my desk that steps it up to 24v, which is
nice, because it will isolate the ground, but i have to read if the
regulators can handle 24v, and if they do, how big of a radiotor i will
need.
--
ocran
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hope your not using linear regulators for the 5volts... and if this is a
complete computer you are trying to run (full size mobo and HD) than
2amps isn't enough on the 5volt rail... 10amps more like it...
--
SkinnyBoy
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ocran wrote:
*They are low dropout positive regulators. for all i know, that could
be linear. 2 amps will be plenty, i assume it will be lower then that
once it is booted. *

If its a full size HD and mobo, the HD alone will draw 2 amps from the
5volt rail when spinning up.... have you actually tried this? linear
regs are too inefficient and will get too hot... thats really all there
is to it...
--
SkinnyBoy
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yeah, it works no problem, little warm, but i have a big radiator.
--
ocran
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If thats the case, can you take pic? also, what computer are you running
off this... you are running a computer, right? what are teh specs, CPU,
memory, and what size harddrive? thanx...
--
SkinnyBoy
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Mark,
My overall goal is to achive +5v and +12v both at about 2 amp load, with
the input voltage of a car. By using regulators, caps, coils an diods i
have succesfully done this with virtually no noise, when the car is on,
when Vin is greater then 14v.

Even when the amps are drawing current and the car is idling?

yeah, i can get a pic, not at the moment, cause i have some stuff to do
but a little later today. Yes works even when the car is idleing. The
processor is 233 mhz, and 32 mb ram, with an 80 gig hdd. Here are some
pics of the second one i made:

http://tinyurl.com/g8l2

This will give you an idea of the hardware.
--
ocran
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ocran wrote:
*yeah, i can get a pic, not at the moment, cause i have some stuff to
do but a little later today. Yes works even when the car is idleing.
The processor is 233 mhz, and 32 mb ram, with an 80 gig hdd. Here are
some pics of the second one i made:

http://tinyurl.com/g8l2

This will give you an idea of the hardware. *

A P233 on its own will draw a good 4 amps on the 5 volt rail... a 80HD
will probably take 1 amp to spin up and idle at about 500ma... all adds
up.. yo'd be looking at a peak draw of about 6-8amps on the 5volt rail,
and 6 or so amps constant... Plus the character LCD screen... I think I
call your bluff.... either you are making stuff up, or you powersupply
can deliver more than 2amps per rail, or it gets too hot to touch...

Ok... I take all that back.... its not even a full sized motherboard.. I
asked that at the start... hey, and your not even using voltage
regulators... yoyur using stupid modules... forget it.. they are
probably switchmode... you need to learn to describe things better.. lol
SEEYA!!
--
SkinnyBoy
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