21 Jul
2005
21 Jul
'05
12:49 a.m.
I'm trying to decide what to do about the whole
battery aspect. If the
machine isn't going to be used for long periods of time then it makes
sense not to have any batteries in it in case they leak (or whatever).
But then if it doesn't need batteries during normal running, it seems a
bit of a waste to have them there at all (and need to open up the case
to fit them each time the machine's used)
I presume they're normally used to keep some form of RAM containing
configuration data alive though (plus maybe some kind of service
On the MG1, there are 5 NiCd cells in series with a tap 3 cells from the
-ve end. The tap is used to hattery-back the real time clock chip (which
probably contains a small amount of RAM to store configuration data,
etc), all the cells are used to power the turn-on relay.
There is no service processor in an MG1 (unlike, say a Torch XXX). There is
an I/O processor, but it's not battery-backed, or anything.
processor operational) as well as providing power to
the start up relay
- so I'm not sure what the implications are there of not having them
fitted.
Unlike a XXX (again), the MG1 doesn't use the NiCds as a shunt regulator
on the real time clock supply. A XXX's clock chip can be damaged if the
thing is powered up with the NiCd battery open-circuit. I think you have
my XXX schematics, in there I show a mod to use non-rechargeable cells
with a zener diode acting as the shunt regulator.
Maybe an external NiCd pack is the way to go - there are plenty of screw
points at the rear of the case from which a suitable bracket for a
battery box could be attached. Mind you, I'm sort of at the point where
I think any machine which is to be stored for any period of time unused
should have its PSU disconnected just to stop anyone trying to randomly
power it up before doing some basic checks - in which case they'd need
to open the case anyway.
Good idea. Of course removing the NiCd cells from a XXX would ensure
this, there is no way it'll power up without them.
Personally, I'd put the AA cell holders I mentioned onto the power
distribution board. It's drilled to take them, or at least the one in my
MG1 was. Then you can clip in some normal, non-tagged NiCds if you want
to run the machine.
-tony