Text 12635, 81 rader
Skriven 2009-04-28 12:29:04 av James Bradley (1:342/77.0)
     Kommentar till en text av Maurice Kinal
Ärende: someone over the rainbar
================================
on 04-21-09 18:32: Maurice Kinal to James Bradley re: somewhere over the rainbo

 MK> any specialty stores there that might have vehicle based
 MK> monitors for sale? All the ones here are the more expensive
 MK> marine based thingies meant more for GPS etc. and are more
 MK> industrial grade than consumer based. Really nice but not
 MK> exactly within the price range I am thinking. Even the

Off the top of my head, I would reach for a de-commissioned
overhead-projector-*VGA-thingamadohicky. I'm pretty sure they use a rectifier,
(AKA: wallwart) so they shouldn't be too far away from functioning off (a
portion of) 12VDC. Second efforts, would go toward IBM Thinkpads that run off
14.?VDC, and use a generic DC plug. 

PS: I just saw a Benq Q9U3 (Best guess on the model number, however.) that
sported a 12V label, and a nini-DIN <G> plug at a Cash Con yesterday. I suspect
dialing back the "Brightness" setting would reduce the Halogen draw of power to
be battery/alternator friendly.

 MK> Xenarc's are a tad pricey but at least more within range
 MK> for testing purposes.

"Testing porpoises"... You aint land locked! <giggle> What's it going in, and
what's driving it? (IOW: Do you *need* NTSC composite output?)

 > Charging Power -> 12V |-> Inverter -> AC
 >    |
 >    |-> MB
 >    |<- "Power Good?"

 MK> I am not certain about the map above but if the AC goes down then the
 MK> battery is in complete control over anything that is wired into the
 MK> DC output of the inverter.  The MB isn't even aware of any

So far, we have a UPS. But, why the inverter?

 MK> power outages since it is wired into the pure DC output of
 MK> the inverter.  It only sees the DC and has no idea about AC

Inverters make a simulated AC sine out of DC, not the other way.

 MK> whatsoever.  Only the inverter is aware about the
 MK> difference and if the AC is on and the battery is weak
 MK> it'll charge it while still maintaining the DC, which is
 MK> all the MB cares about. It is clueless about AC and
 MK> requires either an AC -> 12VDC adapter or the current
 MK> wiring scheme, which happens to be pure 12VDC.  As of last
 MK> week AC is of no consequence to the MB ... unless of course
 MK> the AC power is off long enough to drain the battery and
 MK> then all is lost until the AC is restored and the inverter
 MK> recharges the battery.  [...]

I'll expand my block diagram of a UPS:
>AC /->Filtered, Switched to below if AC fails. Otherwise-> \->
>   \->Rectifier->12V->Inverter->Square Wave Approx. (Typ.) AC /

Remove everything South of the 12V plus the top line, and it sounds like what
you have on your bench. You could replace your AC supply with a solar panel,
and do away with the rectifier too. Automobile alternators have their own (full
wave?) rectifiers.

 MK> Furthermore, the battery could easily be in a car, boat,
 MK> whatever, and the result will be the same as long as it is
 MK> clean 12VDC straight off the battery.  However that isn't
 MK> the case at the moment and the 12VDC is clean since there
 MK> is no interference from alternators, etc.

I wonder what the AC component would be. Nothing a filter network couldn't deal
with.

 MK> enviroment without actually being mobile.  :-)

This is me, not biting that bait. <L>



... James
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