Current consumption of LCD kitchen timer?

At least 100x too high for the basic clock consumption. According to

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.

There are a few products already available to easily do such measurements, such as:

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.

Unfortunately these devices are very power hungry. A three phase supply is recommended.

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?

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

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.

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

I think that the equipment to measure probably costs more that a years supply of batteries.....

Dave

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

Does a piezo run off 1.5V ?

This sounds like alien technology.

Some do. But the kitchen timers I’ve seen have small auto transformer (tapped inductor about size of quarter watt resistor) to make the buzzer much louder.

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 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.

That was my guess based on the single alkaline cell the timer uses.

However I hadn't considered a voltage converter inside. I reckoned the timer would use only the bare minumum circuitry like a counter IC and display driver.

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

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.)

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

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!