A few cautionary notes regarding replacing external power
supplies with home-brew battery packs --
A lot of devices expect the external supply to provide CONSTANT
voltage, and will not tolerate any significant droop in the
voltage level. This can mean that, for example, a 3V device
would switch off when the big sled full of D cells drops from
3.08 with super fresh batteries to, say, 2.95 -- even though 90%
of the power is still there. It will depend on the device. The
Edirol R-1 shuts off after about 1hr of recording when powered
externally by 2 fresh D cells! This is half the record-time with
2 internal AAs. And like a lot of devices, since it's not an
"expected" loss of power, there is no provision to save the
current recording before shut-down.
The engineered approach to this is to provide a regulated supply
with constant voltage, so that the device never sees anything
below the nominal 3V. This, of course, requires starting with
higher voltage, since the regulator introduces its own voltage
drop. Also, the regulator will consume a little power on its
own.
The hacker approach is to wire the battery sled directly into
the device's battery compartment. Most devices expect the
internal battery voltage to droop tremendously before
considering the battery to be "dead." In some cases, a power
jack can be built into the battery compartment cover, and
solder-tacked onto the nub and spring battery contacts.
It's also worth noting that the "wallwart" style power supplies
often provide a rough, half-rectified ripply DC that's a few
volts above the nominal supply. The device expects this, and
provides its own lightweight regulation to get it down to the
nominal level. This means that if you measure the voltage output
of a 3V wallwart, it might well read 4.5V on a meter, although
on an oscilloscope you'd see that it's actually wobbling between
3V and 4.5V. This would not necessarily mean it's safe to
provide a CLEAN 4.5VDC to the external power input.
Personally, I favor hacking the case and wiring right into the
internal battery contacts. If done carefully, it can be undone.
If you need to switch back and forth, you can build a "fake
battery" to make pressure contact like real batteries, and
possibly even simulate a decent cover (with a power jack in it).
This can then be removed and the device is back to normal.
ac
Allen Cobb
http://acobb.com
http://shakespeare.acobb.com
http://timbreproductions.com
-----Original Message-----
From:
Behalf Of oryoki2000
Sent: Wednesday, September 14, 2005 9:56 AM
To:
Subject: [Nature Recordists] Re: M-Audio MicroTrack 24/96 power
We live in a world filled with low-power gadgets
(cell phones, PDAs, music players and more).
So there is no shortage of external battery boxes
to keep them running.
Here are a few more USB battery power units that
will power the M-Audio Microtrack 24/96. When
selecting a cable to connect them, remember
that the Microtrack 24/96 has a mini-USB
connector, while these external batteries utilize
a standard-size USB connector.
--oryoki
USB power from four AA batteries $3
http://www.dealsonic.com/usbbapabapof.html
USB power from AA batteries plus adapters for other
low power devices like cell phone, PDA $17
http://www.semsons.com/semsons-inc/unbaexwiusbp.html
USB power plus AA recharger in one portable unit $22
http://www.semsons.com/semsons-inc/pocpowban.html
3600 mAh Lithium-Ion battery with USB $30
http://www.usbgeek.com/prod_detail.php?prod_id=3D0255
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----~->
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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