Re: Current consumption of LCD kitchen timer?

On 13/05/2025 21:18, Carlos E.R. wrote:

On 2025-05-12 11:55, Pamela wrote:

On 20:45  11 May 2025, john larkin said:

On Sun, 11 May 2025 17:51:56 +0100, Pamela
<pamela.private.mailbox@gmail.com> wrote:

On 17:15  10 May 2025, john larkin said:

 ...
 

When I'm cooking the radio is on, the big extractor fan whirring away
and the tap gets left running (yes!). So beeps from the timer add only
a little more noise.
>
That extra minute of beeping is useful when cooking something like
pasta (or maybe a hard boiled egg) and you want to cook for just a bit
longer.
>
The question is ... is this truly wasteful on the battery or does it
make little difference?

 I think it doesn't make a difference.
 And it is not that trivial to measure, because cmos circuitry only draws current at the instant of switching. So, use a scope. Otherwise, I would try to measure it.

I suspect a piezo buzzer doesn't emit repeated sets of beeps without an
external chip, so the spec sheet may not contain the consumption info.

The piezo sounder will be at least 1mA current draw and might be 5-10mA. That is about 100-1000x the standby current for a digital clock chip with a bare metal LCD display.
At 1mA a 2400mAh battery lasts 2400 hours  = 100 days
At 10uA the same battery lasts 240000 hours = 10000 days ~ 22 years (which vastly exceeds the battery shelf life self  discharge time)
So yes it does shorten battery life each time it beeps for a whole minute but probably not by enough to even notice unless you set a 1s delay and keep on resetting it so as to draw 1mA for the sounder. (almost continuously).
Even if the sounder takes 10mA a 2400mAh battery could run it for 10 days continuously (long enough to drive you bonkers).
--
Martin Brown