Alt-BEAM Archive
Message #00192
To: Ben Hitchcock beh01@uow.edu.au
From: John Mitchell johnm@magnet.com
Date: Fri, 5 Feb 1999 11:18:28 -0500
Subject: [alt-beam] Re: The BEAM clock challenge
On Fri, 5 Feb 1999, Ben Hitchcock wrote:
> Great idea!
>
> I see just one problem, though: accuracy.
> [story here]
> The moral? Straight R-C timing circuits with a time period of over 1 minute
> are pretty unreliable.
> Your clock would be pretty cool, though. I guess if you had some way of
> resetting it each day (say from a normal clock that had its alarm set for
> midnight) then it would work really well.
>
> I'd love to see it when it's finished!
>
> Ben
Last I recalled, a normal 555 timer takes 80mA!
One way to make a BEAM clock is to:
- buy a LCD clock, which runs forever on a button battery
- hook up your micropower trigger to the center segment of the
rightmost hours digit. (That is, "10", "11" = off, "12" = on.)
- set alarm at 12:00
- set time to be (12:00 - count), ie 10:00 for a 2-hour time.
I have a book from Radio Shack, "Getting Started with Electronics" (?),
that has a section on interfacing with LCD calculators and such.
Basically, use an optoisolator.
- j
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