Re: [stella] Re: Watching the processor run

Subject: Re: [stella] Re: Watching the processor run
From: Chris Wilkson <cwilkson@xxxxxxxxxxxxxxxx>
Date: Tue, 2 Jun 1998 09:49:34 -0700 (PDT)
> >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 CELL density? Per what? If you need 4 lead-acid cells to reach over
> 7 volts, but 6 NC cells, the NC are more, so the cell density is higher
> (?!)

The plain density of each cell.  Meaning that lead is a hekuva lot denser than
nickel/cadmium. :D  Think: car battery...

> >The cells I use are 2.0AH, BTW.  About the size of a "D" cell, a little
> longer.
> 
> Hmmm, that gives about 4 Wh per cell for a D+ size. The NC D cells I
> recently bought have 1,2 V x 4 Ah, so that's 4,8 Wh. So I think also the
> energy density of the NC cells is higher than the one of lead-acid.
> By the way, how much do these little lead-acid cells cost? My NC cells
> costed about $4 each - but that was an occasion, normally, they would
> cost $8-$12 each.

Hmm.  Could be...the data sheets I have are pretty old.  I don't know how
much they cost.  All the cells that I have were obtained as part of a Lego(tm)
robot kit.  But I later found that the mfr of the cells is located about 15
miles from my parents house!  I'll try to find out.  That leaves current
capacity as the only clear advantage to lead-acid cells.  Ever try to weld
steel with a 2v battery?  These can do it!  Though it's probably terribly
unsafe... :P

> >>(...)
> >> 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.
> 
> Looking forward to it... but you need not damage your cells for that
> reason!

Well...I didn't get to try it.  My real job interfered. :( Don't know if it
would damage them or not.  But I have about 30 of them, so I'll try it anyway.

> >> 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.  
> 
> Arm, not for me... I've got a "Game Gear" at home (which I won at a
> Karaoke contest), with TV Tuner. If you connect the middle pin of the
> 2600's antenna outlet with the tuner's antenna, it should work. The
> other problem could be, then, that this combination isn't very handy
> anymore (4 Units- 2600, Joystick, battery, screen - and 3 cables -
> power, joystick and antenna). This is also what prevented me to do

That's COOL!  So the fix is easy...just hot glue the game gear to your 2600! ;)
Or better yet, hot glue some mounts to the game gear and to the 2600.  That
way the game gear is still detachable.  Do the same thing with the batteries.
That gets it down to 2 objects at least...

> >> 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?
> >

> >Hmm...I see one of my 2600 jrs undergoing some major surgery pretty soon. :)
> 
> That leaves the question at which voltage range these three chips would
> be able to work without regulation.

I dunno.  Most 5v chips today spec 5v +/- 10%. (Ie. 4.5v to 5.5V)  But a lot
of older chips need better than 5% regulation.  But Nicads are well regulated.
Any battery is really.  Just think of them as big honking capacitors.  There
won't be any random noise or anything.  It will look like a regulated dc
supply.  It's just that the dc voltage drops over time.  But with Nicads, as
you point out, the voltage is almost constant.  So it starts out between 4.7V
and 5V and stays there for quite a while.  Good stuff.

-Chris

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