Current consumption of LCD kitchen timer?...

[john larkin]

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.

 

[Pamela]

On 15:20 12 May 2025, john larkin said:

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.

It\'s said good cooks often have a very accurate sense of time. However
I am poor at that, which is why I need something to time even an extra
minute. Most people could guess a minute reasonably well but I often
lose track!

 

[john larkin]

On Mon, 12 May 2025 15:57:51 +0100, Pamela
<pamela.private.mailbox@gmail.com> wrote:

On 15:20 12 May 2025, john larkin said:
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.

It\'s said good cooks often have a very accurate sense of time. However
I am poor at that, which is why I need something to time even an extra
minute. Most people could guess a minute reasonably well but I often
lose track!

Imagine some line cook who has a dozen orders in his head, all
overlapping, some well done and some medium rare.

Do you design electronics? That benefits from quantitative instincts,
and I think helps develop them.

But people are very different, and there\'s always Spice.

LT Spice, not the other sorts of \"spice\".

 

[Joe Gwinn]

On Mon, 12 May 2025 15:57:51 +0100, Pamela
<pamela.private.mailbox@gmail.com> wrote:

On 15:20 12 May 2025, john larkin said:
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.

It\'s said good cooks often have a very accurate sense of time. However
I am poor at that, which is why I need something to time even an extra
minute. Most people could guess a minute reasonably well but I often
lose track!

Same here. My solution is to have a timer in count-up mode running
next to the stove, so I can glance at it as needed. I still get
distracted, but the effect is reduced.

Joe

 

[Liz Tuddenham]

Pamela <pamela.private.mailbox@gmail.com> wrote:

It\'s said good cooks often have a very accurate sense of time. However
I am poor at that, which is why I need something to time even an extra
minute. Most people could guess a minute reasonably well but I often
lose track!

I am fairly poor at timing because I tend to use the cooking time to do
something else, then get engrossed in that and forget what the time is.
Luckily I do have a good sense of smell, so sometimes I can catch things
before they are too badly incinerated.

If I am cooking several batches like a production line, I tend to fill
in the time by washing up the utensils and cleaning down the surfaces
ready for the next batch, so I am right beside the cooker and don\'t
forget.


--
~ Liz Tuddenham ~
(Remove the \".invalid\"s and add \".co.uk\" to reply)
www.poppyrecords.co.uk

 

[Sam Plusnet]

On 12/05/2025 15:20, john larkin wrote:

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.

You are the exact opposite of my wife, who\'s signature phrase is:

\"Good heavens! It can\'t be that time.\"


--
Sam Plusnet

 

[Sam Plusnet]

On 11/05/2025 21:57, john larkin wrote:

On Sun, 11 May 2025 16:32:03 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2025-05-11 12:51, Pamela 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
wrote:
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 the question 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.

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


I admire your patience. That would drive me nuts. I doubt that the
beeper requires much current--piezo sounders are pretty efficient at
turning battery power into annoying noises.

Cheers

Phil Hobbs

Whoever invented the piezo buzzer should be welded into a prison cell,
with a dozen piezo buzzers.

How about a few of those birthday cards which play a \'tune\' when opened
- for special occasions?

--
Sam Plusnet

 

[john larkin]

On Mon, 12 May 2025 19:53:14 +0100, Sam Plusnet <not@home.com> wrote:

On 12/05/2025 15:20, john larkin wrote:
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.

You are the exact opposite of my wife, who\'s signature phrase is:

\"Good heavens! It can\'t be that time.\"

I once had a gf who was always between 1 hour and 2 hours late.
I\'ve never had a watch but I\'m basically never late.

My wife tends to put things on a burner or into an oven and go away.
I like her, so I keep an eye on things when I can.

I tend to design control systems by fiddling in Spice, instead of
using hard stuff like control theory. I can usually guess R and C
values pretty close, and iterate from there. Bad guesses can fail to
converge, the \"lost in space\" effect.

 

[Martin Brown]

On 12/05/2025 15:05, Pamela wrote:

On 12:10 12 May 2025, Martin Brown said:
On 10/05/2025 14:37, Pamela 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

Second one might be about right perhaps 10mA is more likely but I\'d
be very surprised if the display operating and timing current was
more than 20uA (and it could easily be lower).

Bare metal LCDs take almost no current at all (but have to be driven
with an AC signal). They are no different at the core to LCD digital
watches with an alarm function probably even using the same chips and
a slightly beefier piezo sounder.

If beeping consumes 10mA then, in theory, you would get 100 hours of
beeping from single AA alkaline (1,000 mAh).

That\'s 6,000 one-minute \"overruns\", under optimal conditions. Let\'s say
it\'s only 1,500 in real life conditions.

In conclusion, if overruning beeping is done twice a day, then the
battery would last a couple of years.

That\'s seems slightly optimisitic because I usually change the battery
about once a year or so when I don\'t let the beeping run on. (However, the
abttery is changed largely because the display has started to dim.)

LED contrast is *very* sensitive to battery voltage - the chip is
already using an antiphase pair of signals and possibly a voltage
doubler to drive the LCDs. 3.3v to 5v being a typical drive voltage.

At such tiny currents the battery has essentially its shelf life and
will supply 10-20uA almost forever but at gradually lower voltages. Once
the voltage is below a certain point the clock still runs but you can
only see the display by holding it at just the right angle.

One big annoyance with such LCD displays is that they really won\'t
accept rechargeable cells because the fully charged voltage is too low
to run the display with an acceptable contrast.

--
Martin Brown

 

[john larkin]

On Mon, 12 May 2025 19:54:57 +0100, Sam Plusnet <not@home.com> wrote:

On 11/05/2025 21:57, john larkin wrote:
On Sun, 11 May 2025 16:32:03 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2025-05-11 12:51, Pamela 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
wrote:
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 the question 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.

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


I admire your patience. That would drive me nuts. I doubt that the
beeper requires much current--piezo sounders are pretty efficient at
turning battery power into annoying noises.

Cheers

Phil Hobbs

Whoever invented the piezo buzzer should be welded into a prison cell,
with a dozen piezo buzzers.

How about a few of those birthday cards which play a \'tune\' when opened
- for special occasions?

That would be sadistic.

 

[Carlos E.R.]

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.

--
Cheers, Carlos.

 

[Martin Brown]

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