Mike,
Button cells are available in larger sizes too. Some of the gear I
have uses a CR2450 which has 620 mAh of storage. I have a problem
with some of the rechargeables especially the NiCad nightmares I've
seen in the Peavey equipment. I replace them with cell phone
batteries mounted in a remote location away from all boards and
switches.
Letting the current settle will help a lot getting to the 2uA state
in these ram chips.
Fran
--- In
korgpolyex@yahoogroups.com, "korgpolyex800"
<korgpolyex800@...> wrote:
>
> Hi Atom,
>
> I will see if I can measure the current but at low current draws the
> meter may not be entirely accurate. I'll give it a go though.
>
> According to the datasheet, if I take CS1 high or CS2 low before the
> power supply drops from 5V to battery 3V, then the current draw will
> be 2uA (typical) up to 100uA (max). But the datasheet seems a bit
non
> specific about the timing of the chip select lines being at correct
> levels prior to the supply dropping to 3V.
>
> So I have a couple of theories as to why the battery is going flat
> fast. First, the CS2 chip select line was not being pulled down to
0V.
> I've placed a 10K pull down on that line. I am hoping that this,
easy
> to install, extra resistor will fix the problem.
>
> Second, perhaps the timing of the shutdown of power from 5V to 3V
(on
> battery) is critical. If that is the case, then I can see a
situation
> where the chip select lines could be in the wrong state when the
power
> down occurs. In that circumstance, the battery will pull alot more
> current while on battery. As I said though, the datasheet is doesn't
> explain the timing very well. Nevertheless, if the one pull down
> resistor doesn't fix the problem then I'll add a capacitor on the 3V
> battery side of the power supply to the two static RAMs. This will
> ensure that the chip select lines settle into their correct state
long
> before the memory power supply falls from 5 to 3V.
>
> So I don't think this is a big problem, it is just going to take a
> while to work out exactly what has to be done. I am hoping that the
> single 10K ohm pull down resistor is all that is needed.
>
> Zoinky makes a good point though. The button cell most certainly can
> be replaced by two AA batteries. I like the button cell because it's
> guaranteed not to leak all over the insides of your precious
synth's.
>
> I cringe thinking about the number of Poly's that have been sitting
in
> storage with batteries slowly decomposing all of the PCB's. I bought
> one on ebay specifically because the case, joystick etc was in
perfect
> condition while the insides were completely acid wrecked.
>
> I think the button cell should be OK in the long run. It is just
going
> to take a few months to be certain that it is set up just right.
And I
> wanted to warn everyone before they lose their patches.
>
> Mike.
>
> --- In korgpolyex@yahoogroups.com, Atom Smasher <atom@> wrote:
> >
> > On Tue, 27 May 2008, korgpolyex800 wrote:
> >
> > > So, I had a look at the design and think I might have missed a
> pull down
> > > resistor that would reduce the current by about half. I've
added the
> > > pull down onto both of the HAWK-800 kits and I guess in about
six
> weeks
> > > I'll know if it made any difference at all.
> > =================
> >
> > do you have a multi-meter? measure how much current is moving
> through the
> > battery...
> >
> >
> > > A single 6264 static RAM in standby mode uses between 2 and
50uA.
> > ==============
> >
> > that's a big range... what determines the actual current?
> >
> >
> > > The longer term solution is now being looked at. There are two
> ways to
> > > go about this. One way would be to use a rechargeable battery
> scenario.
> > > The other, would be to write patches into flash memory. I'll
post
> again
> > > as soon as I come up with a solution.
> > ================
> >
> > a slightly larger rechargeable battery (1/3 AA) would have a
better
> > amp-hour rating, and would last longer than a 2032. i've seen
gear with
> > original 10-15 year old lithium batteries running strong.
> >
> >
> > --
> > ...atom
> >
> > ________________________
> > http://atom.smasher.org/
> > 762A 3B98 A3C3 96C9 C6B7 582A B88D 52E4 D9F5 7808
> > -------------------------------------------------
> >
> > "In peace, sons bury their fathers.
> > In war, fathers bury their sons."
> > -- Herodotus
> >
>