Re: Connectors.

Brian Smithson (brian@grot.ca41.csd.mot.com)
Mon, 2 Dec 91 19:34:55 PST

[This is a reply to mail from Fritz, but it might be of wider interest. -Brian]

Fritz asks:
> [...]
> I also have a question which you may have answered before, but I can't
> find it in my files:
> What does the manual say about the nicad battery used in the UltraLite?
> Apparently it is supplied from a separate source (hence the 9 pins!)
> on the charger. How many cells (i.e. what voltage) are used and what
> is the rating?

Here's the info on the NiCd Backup Battery:

Voltage: 3.6 V
Capacity: 850 mAH
Watt-Hours: 3.06
Battery Life/Charge: 7 days
Total Recharge Cycle: 300
Size: 7.75" X 5/8" X 5/16"
Weight: 0.213 pounds
Location: Compartment on bottom side of the
UltraLite

The AC adaptor provides 15.6, 12, and 5 volts. My guess is that the
15.6V is for the charging circuit, the 12V is to run the unit (in place
of the battery, since it's being charged), and the 5V is for the
peripheral bus.

> After reading about your battery eliminator, I might prefer the "direct
> route" via a wooden block! Since 7-pin Din plugs are available - remember
> I found some cheap ones in Germany - couldn't one use the plug to
> supply current just to the operating battery (simple supply) and not
> the silicon disk which lasts over a week, anyway (I have had the courage
> to wait over 7 days without loss of memory).

You bring up an interesting point. There is probably a way to power the
unit using a 12V power supply connected to the DC-IN plug, instead of having
to add a jack as I did. Now that I think of it, I seem to recall that
someone out there looked at the internals of the AC charger/adaptor and
found some strange stuff (a loose transistor connected to some of the pins
on the DC-IN plug comes to mind) which might be there to switch the power
over so that the battery is freed up for charging. Details of that
investigation were posted to the list. The important thing is that you
switch the unit power over to the new power supply and disconnect the battery.
You don't want your power supply trying to charge the battery!

Well, I'm not going to look into it, since I already have a solution
(albeit crude). Sounds like a good project for someone on the list.
Any takers?

-- 
-Brian Smithson
 Motorola Inc., Computer Group, Commercial Systems Division
 10700 N. De Anza Boulevard, Cupertino, CA 95014 USA, (408)366-4104
 brian@csd.mot.com, {apple | pyramid}!motcsd!brian