Alt-BEAM Archive
Message #05127
To: beam@sgiblab.sgi.com
From: Don Papp donp@cronus.oanet.com
Date: Thu, 8 Jul 1999 13:59:55 -0600 (MDT)
Subject: [alt-beam] Re: Power Smart Head
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.
> 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 Was that not part of the reason the FLED SE is obsolete?
> As for the FLED I'm using.. just the standard FLED that Radio Shack
> sells... don't have any of the specs on it though..
> If your FLED is dim, try a smaller resistor in place of the 3.3k that
> will let more current through. If your FLED starts blinking before the
> 1381 triggers, you have the FLED in backwards..
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. :(
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? Though it is only eye-candy, it adds much to
the head.
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)
More elegant solutions for an alternate to the FLED are invited,
as well.
| Donald Papp
| don@oa.net
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