Re: Current consumption of LCD kitchen timer?

On 5/10/25 9:15 AM, john larkin wrote:

On Sat, 10 May 2025 10:56:01 -0500, John S <Sophi.2@invalid.org>
wrote:
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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.
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(1) How much current does the timer draw when counting time?
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(2) How much current is drawn when the piezo buzzer is sounding?
(Averaging out beeps and silent bits.)
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My guesses are 2mA and 25mA, respectively. Is that about right?
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I mean a timer similar to this one, running off a 1.5V battery.
https://www.amazon.com/Digital-Kitchen-Timer/dp/B00GOPICNM

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

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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.
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Someone could sketch a schematic to discuss. It needs the right uP and
some code. And some mechanical design.
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Might not handle high peak currents, amps.
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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.
>

 There are a few products already available to easily do such measurements, such as:
 https://www.joulescope.com

 This can also provide the time integral of consumption to be able to predict battery life. It can be especially tricky where devices have microamp quiescent currents together with multi-milliamp bursts when active.
 If a meter shunt is large enough to measure the sleep current it can have too large a voltage burden when the device springs to life - accurate measurement of microvolts across the sense resistor is required.
 I have measured sleep currents with an ordinary DVM fairly successfully by putting a large electrolytic across the terminals to avoid the large drop during the active times.