Power consumption and rectification

Bas Wijnen wijnen at debian.org
Thu Nov 5 18:14:44 EST 2009


I have measured the power consumption of the device, by removing the
battery and tapping the usb cable, insering a current and voltage meter
in it.  I found the following:

- When the device is on, with the display enabled, it uses 123 mA.
- When the device is on, with the display disabled, it uses 37 mA.
- When the device is off, it uses 4.5 mA.

The device used 4.7 V during the measurement.  The battery that came
with it says 4.2 V, 850 mAh.

This leads to the following times:
- on with display: 6.2 hours.
- on without display: 20.5 hours.
- off: 7.0 days.

"on without display" is the state where it's waiting for a connection in
usb boot mode (with the auo display, which is off by default).  No
devices are enabled.  In particular, this is probably not a good
estimate for how long it can be used to play sound files.

Also, these times are computed from what the battery says it can do; I
expect actual values to be slightly lower (and much lower when the
battery gets older, of course).

This measurement leads to a short rectification:

On Sat, Oct 31, 2009 at 10:19:29AM +0100, Bas Wijnen wrote:
> - Warning: when booting Iris in its current state, the lcd will switch
>   on and display nonsense.  Leaving it on for a minute or so makes the
>   device unbootable for some time (probably until it cooled down).  I
>   don't know if this is harmful for the device, so don't try.

There is no problem.  The device was sometimes on and sometimes off when
I replugged it.  If it became unbootable, it was off.  Pressing the
power button made it work again.  I'm pretty sure there is no damage at
all, even if the display is left like this for a longer time (not that
that's very useful...).

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