On Wed, 24 Jan 2007 09:07:16 GMT, "John"
wrote:


As a % of time the buzzer isn't running very often and the
rest of the receiver may be using on a few uA. Since I have
one that uses 2 x C cells and they have lasted a little over
a year already, it is already clear it uses significantly
less than 1mA on average.

I stand by my point - the bell unit is acting as a radio receiver all the
time - ready to ring if it receives the correct input. It is bound to use a
significant amount of power. I would only consider having a mains powered
one - as many have a 13 amp plug through facility you are not even losing a
socket.
Battery quality is also an obvious factor.



Define "significant amount of power". Since the batteries
in mine are plain old Duracell alkalines rated for 7800mAh,
http://www.duracell.com/oem/Pdf/others/ATB-full.pdf
and since it's already ran for over a year (but let's round
down to 1 year for simplicities' sake), 24/7 constantly,
that's already an absolute maximum possible avg. current of

7800 / [24 * 365] = 0.9mA

.... and it only goes lower every day it continues to run off
same pair of cells. It may be that those Duracells can
produce more than 7800mAh at such a slow drain rate, but not
enough to make much of a difference in the calculations,
we're still looking at a sub-1mA range considering those
cells aren't dead yet and may not be any day soon.

I would agree that battery quality is an obvious factor but
why would someone put low quality batteries in (anything?)
except perhaps for those generic NiMH if the device didn't
need run any longer than those can provide before another
recharge cycle is acceptible - definitely not the case in
this context with a door buzzer.