15 Aug
2006
15 Aug
'06
5:26 a.m.
Subject: Re: PDP-8 /e/f/m memory
From: "Chuck Guzis" <cclist at sydex.com>
Date: Mon, 14 Aug 2006 22:19:08 -0700
To: cctalk at classiccmp.org
On 8/14/2006 at 9:35 PM Don wrote:
I shave off the top of the DS1287s and replace the cell. It's easy to find
the battery on those as it's magnetic!
Unless you can make a battery application last A VERY LONG TIME
(not just a LONG time since those are the cases where you get
screwed because you have forgotten about the battery that
you replaced 1 or 2 years ago... *but*, if you replaced it
*10* years ago you don't mind -- as much -- when it dies
after that long of a service life) it will frustrate users.
Well, consider the Dallas battery-inside-the-chip clock-calendar circuits.
7 years sounded like forever--and it may well have been to the original
owners of the equipment. But now, they're starting to fade and finding
replacements can be a bit of a hassle. In 20 years, it'll probably be
nearly impossible. For this particular application, any keep-alive power
source needs only to
last as long the longest power-off interval. If, as Don, says a supercap
will last several months, that should be good enough--and it's a permanent
solution. Heck, I wonder if you could trickle-charge the battery with
ambient light via a solar cell. That should extend the keep-alive period
some.
I just don't like chemical reactions in my equipment--it's sort of like
bird's nest soup. It might taste good, but I don't like the idea of eating
bird spit..
Then place the battery at the ends of two wires remote from where their
failure can do harm.
Experience is a good adaquately sized Li cell is by far the easiest solution
when used with the Dallas ram controller chips.
Allison