[Tinyos-help] ask about energy consumption

[Zainul M Charbiwala]

It is hard to tell whether the batteries for each node had the same
capacity to begin with. Assuming they were fresh batteries with equal
capacity, they would all die at pretty much the same time. This is
what you see and its because:

1. Transmit cost and receive cost on the CC2420 are about the same so
it doesn't really matter  whether you are closer to the sink. The node
that transmits more often will tend to die a little faster (which
contradicts your observations) because even though the Tx power is
lesser than Rx, while the Tx block is active, Rx is also active (so
that is is ready for the ACK), resulting in almost double the
consumption during transmissions.

2. If you're not using LPL, then all the nodes are burning pretty much
the same amount and the high constant Rx cost overshadows any
differences you would see in Tx costs.

3. Battery drain is highly non-linear, batteries have manufacturing
variations and they are quite environmentally sensitive. Along with
this, tiny variations in node components will cause an unequal power
consumption. For example, the LED bias resistors may be unequal (they
are 10% tolerance on MicaZ) which may cause different current draws.


Hope that helps, at least partially.

Zainul.


On Wed, Jun 17, 2009 at 12:19 AM, ma. pratama<spidol_permanen at yahoo.com> wrote:
> Hi all...i recently try to run multihop program from crossbow with 3 node
> and 1 sink (im using Micaz mote and MIB520 board programmer). and after 16
> hour nonstop,  node 3 ( the longest from the sink) started to run out of
> energy to transmitted the packet. and then after a several minutes, node 2
> started to ran out energy too. And finally, node 1(closest to the sink) lost
> its power too.. i wonder why node 3 lost its power first?? from information
> i read the node that close to sink will lost the power first because it
> receive and transmitted the data to the sink?? please correct me if im
> wrong.
>
> Anyone know why it happen like that??
>
>
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