Alt-BEAM Archive

Message #05149



To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Thu, 8 Jul 1999 16:55:49 -0700
Subject: [alt-beam] Re: Power Smart Head


There are 2 spare 240 inverters in Darrell's version of the PS HEAD which
can be used as an oscillator to flash a LED with low duty cycle to replace
the FLED. This would require a LED, a small cap, 3 resistors and a diode
which is a lot of parts compared to the FLED.

BTW on the Darrell's original layout drawing the 2 unused inverter inputs
were not terminated to ground or +V resulting in possible high current draw
and oscillations.
I assume that was an oversight that has been corrected by now but may help
explain the aberrant FLED behaviour.

regards

Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
tel: (604)590-7493
fax: (604)590-3411

> -----Original Message-----
> From: Don Papp [SMTP:donp@cronus.oanet.com]
> Sent: Thursday, July 08, 1999 1:00 PM
> To: beam@sgiblab.sgi.com
> Subject: 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 Was that not part of the reason the FLED SE is obsolete?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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