Re: [stella] watching the processor run

Subject: Re: [stella] watching the processor run
From: Chris Wilkson <cwilkson@xxxxxxxxxxxxxxxx>
Date: Fri, 29 May 1998 10:52:58 -0700 (PDT)
> Erm, what? The energy capacity? I think this depends on the capacity of
> the cells you use. You can't say in general "the capacity of lead-acid
> batteries is higher than that of NC ones" or vice-versa. Both are
> available in different sizes and capacities. I don't know what you're
> comparing here.

Yah, I should have said energy density.  Of course the CELL density is a
lot higher too ;)  So if the energy density is higher then the energy capacity
will be higher for cells of the same size.  Good point.

The cells I use are 2.0AH, BTW.  About the size of a "D" cell, a little longer.

> Well, in fact I tried it with the NC battery of my RC car, giving 7,2
> Volts. The 300 mA was measured with a multimeter hooked between the
> battery and the 2600. It was infact somewhat below 300 mA. So, assuming
> the battery had 1,4 Ah (I think they were sold with this capacity then),
> you can play about 4-5 hours with one charging. Note that the voltage
> will stay ABOVE 7,2 volts during most of the time, unlike
> one-way-batteries, saying 1,5 Volts on it, but going below that very
> soon.

Yes, Nicads have basically a piecewise linear voltage/charge function.
It's relatively flat until they discharge to a certain point, then they die.
Quickly.  Lead acids cells have a simple linear voltage/charge function.
So as soon as they start discharging, their voltage starts dropping.  But
this is A LOT slower than carbon/zinc or alkaline batteries.  When I ran it
for the 5 hours, I had experienced the early stages of color loss.  But it
was only noticable by looking at an o'scope.  I'm guessing I probably
could've squeezed another hour out of them.  I'll try to test it this weekend.

> Of course, you need additional batteries for the screen...

Yep.  What I'd really like to do is hook up a color LCD screen.  But that's
way too time consuming at this point.  

> There this "portable 2600 clone" comes to mind. I think it had a battery
> compartment. Does anybody know what type of cells, and how many, were
> used, and when this one would "give up", or if they did something to
> reduce the current it needed?

I don't know anything aobut it, but I suspect that they would have done some
re-engineering while they were at it.  There are a couple of places that the
2600 could save on power.  One really nice thing about nicad batteries is
the fact that 4 of them together can make up a well regulated logic power
supply.  At 300mA, that saves 1.2 watts just from the internal regulation!
The video circuitry can be cleaned up some, but there's a limit.  You're stuck
with the TIA, 6507, and RIOT.  Although you could probably use a super low
power 6502 successfully.

Hmm...I see one of my 2600 jrs undergoing some major surgery pretty soon. :)

-Chris


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