Alt-BEAM Archive
Message #05132
To: beam@sgiblab.sgi.com
From: Darrell Johnson beamtastic@yahoo.com
Date: Thu, 8 Jul 1999 14:11:34 -0700 (PDT)
Subject: [alt-beam] Re: Power Smart Head
--- Don Papp wrote:
> On Thu, 8 Jul 1999, Darrell Johnson wrote:
>
> > > 1) Live without a "lock" LED
> > >
> > > 2) Make a FLED-alike with some extra components
> >
> > ok.. First off, it's not a "lock" LED.. the FLED
> isn't even a part of
> > the PSH circuit, it's a part of the SE that I'm
> using.. All the FLED
> > does is blink when the first inverter of the 1381
> latch SE goes low...
> > This means the SE has triggered and the circuit is
> 'active' it blinks
> > whether the head is moving or locked.. The FLED
> isn't even necessary..
> > it's just some eye candy for when the head is just
> sitting there
> > waiting for someting to move.
>
> Mmm. Curious. A pseudo-lock, then?
>
> > Second off, it doesn't use very much current at
> all.. any LED you use
> > is going to use way more current..
>
> Surely an LED only on for 1/10 of a sec once per
> sec (and a single
> '14 inverter on all the time at a very slow rate)
> uses less current than a
> FLED. Perhaps not. Clearly some measuring is
> required, unless someone
> can provide some numbers.
Well I don't have anything very accurate, but it'll stay in active
mode, without light for about 45 minutes or so.. maybe longer, haven't
tested it too much yet. That's not even on a full cap charge.
>
>
> > enough,and the FLED doesnt' use *any* current
> while the SE is charging,
> > because it is not on.
>
> Truly? I thought all FLEDs ate some power even
> when they are not
> 'blinking'. Was that not part of the reason the
> FLED SE is obsolete?
It doesn't use any power, because both leads are high while the SE is
charging. It only uses power when the 1381 triggers.
>
>
>
> The FLED is lit, but is not blinking. It *is*
> shielded with
> shrink-wrap (to avoid the predicatable followup
> question) and playing with
> the Rfled value (via different values and pots)
> yielded no gainful
> results. It either blinked irregularly or not at all
> and was very dim. Not
> anything like you see in your psh.mov video file.
> Anything too low (Rfled,
> I mean) gave a nice LED light, but sucked up power
> faster than the solar
> cell provided it. Tried a couple different FLEDs
> just in case mine was
> faulty, but no go. Gave up on it. :(
It might just be your FLED then.. don't know.. a less eficcient FLED
than mine?? It won't really make a difference if it's shielded or not
though, since that was just a part of the old FLED SE requirements...
the use of the FLED in the PSH circuit has no effect on SE operation.
>
> So, it's not a LOCK led - but more of a
> pseudo-lock, or more
> accurately, perhaps a 'heartbeat'. What would you
> prefer it be referred
> to as to avoid confusion?
'heartbeat' sounds groovy, since that's basically what it is.. means
the circuit is alive.
>
> I'm still interested in whether anyone else has had
> trouble
> implementing the FLED part of the PSH cct. If so,
> then perhaps the design
> should be changed to be more tolerant. (I think my
> alternative to the
> FLED will work regardless of component tolerances,
> especially since the
> timings are not critical)
the alternative just leads to a dramatically higher parts count.. I'll
stick to using my FLEDs.... :)
good luck,
Darrell
===
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