Re: Current consumption of LCD kitchen timer?

On Mon, 12 May 2025 10:55:50 +0100, Pamela
<pamela.private.mailbox@gmail.com> 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:

On Sat, 10 May 2025 10:56:01 -0500, John S <Sophi.2@invalid.org>

On 5/10/2025 9:58 AM, john larkin wrote:

On Sat, 10 May 2025 14:37:40 +0100, Pamela
<pamela.private.mailbox@gmail.com> wrote:

>
>
I'm interested to know the current drawn by a kitchen LCD
digital timer.
>
(1) How much current does the timer draw when counting time?
>
(2) How much current is drawn when the piezo buzzer is sounding?
(Averaging out beeps and silent bits.)
>
My guesses are 2mA and 25mA, respectively. Is that about right?
>
>
I mean a timer similar to this one, running off a 1.5V battery.
https://www.amazon.com/Digital-Kitchen-Timer/dp/B00GOPICNM

 
That suggests a product line: a series of batteries (AA, AAA, 9v)
that measure current wirelessly, or datalog.

>
Hey! I like that idea!

 
A small PCB could have a tiny lithium battery and a uP with an
internal ADC. A diode would make a logarithmic current-to-voltage
converter from picoamps to milliamps. May as well report
temperature too.
 
Someone could sketch a schematic to discuss. It needs the right uP
and some code. And some mechanical design.
 
Might not handle high peak currents, amps.
 
Of course the electronics could be in a box with a tiny flex
running to the dummy battery. Or just squeeze the flex between the
battery and a contact. Or just sell the flex, with banana plugs on
the other end to go into a DVM. That's too easy.

>
I asked about current consumption because, when the time is up, I
leave my kitchen timer beeping until it cuts out. That's usually a
minute of beeping.

 
That sounds anoying. I use a mechanical timer with "extended ring"
and sometimes want to drown it.
>

If this is done a couple of times a day, would the AAA battery run
out in an appreciably shorter time?

 
Wild guess 50 mA. A good (not Amazon) AAA is good for about an
amp-hour, which is 20 hours of beeping. At 2 minutes/day, it 's good
for roughly 600 days. Replace the batteries every year.
 
What are you cooking? My biscuits are critical. One minute over or
under wrecks them. I set the timer to 15 minutes and start inspecting
from there.

>
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?

Use good batteries and replace them once a year. I do all mine in
January. Food is too important to take chances.

>
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.

No, the piezo is usually a passive polarized ceramic strip, and the
driver is in the main timer chip.

When I get a new microwave, the first thing I do is open it up and
destroy the piezo. I don 't need a loud annoying BEEP BEEP to know
when the microwave is done. We kinda autistic engineers are triggered
by loud noises like that.

And I have a pretty good timer in my head, which some people do. I
usually know what time it is, within a minute or two. Quantitative
instinct.