A CR2032 has 235 mAh, which I believe Casio watches use, and their batteries last 5-7 years. So, if we divide that out, that’s something like 5-6 microamps (235 mAh / 5 years / 365 years / 24 hours * 1000 = 5.36… microamps). Converting this to watts @ 3v: 15-18 microwatts.
If you remove RF from the equation (Bluetooth, WiFi, etc) and custom build the chip, you can get some very low power draws. If all you’re doing is sampling temps or something, you could send an update periodically over serial or something and fit under 100microwatts or so. You could probably even do RF if you have a large enough cap and send once it charges.
This is a very important spec to include…this battery can deliver 0.03mA of power, which is incredibly little.
0.03mA of current. That times the 3 volts = 0.1 mW of power.
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Should be plenty for watches and IOT devices.
Not really actually…not from a single cell at least
Why not?
A CR2032 has 235 mAh, which I believe Casio watches use, and their batteries last 5-7 years. So, if we divide that out, that’s something like 5-6 microamps (235 mAh / 5 years / 365 years / 24 hours * 1000 = 5.36… microamps). Converting this to watts @ 3v: 15-18 microwatts.
I think that math is correct (this question reaches a similar conclusion), and it leaves some headroom as well.
If you remove RF from the equation (Bluetooth, WiFi, etc) and custom build the chip, you can get some very low power draws. If all you’re doing is sampling temps or something, you could send an update periodically over serial or something and fit under 100microwatts or so. You could probably even do RF if you have a large enough cap and send once it charges.
Google says a Casio watch needs .004mA so not quite enough.
Did you typo or did he? .03 is significantly bigger than .004
0.03 is 7.5x more than 0.004 tho?
You are right! I didn’t count the 0’s!
That’s definitely in the ballpark though. Surely they could cut 25% power draw to support a 50 year battery.
I wonder how much we really need for a clock (555 eq) to work?
https://www.ti.com/lit/gpn/LM555
2mA minimum, and that’s just q current. It’s gonna be much higher when you’re actually using it for a clock.
I’m sure the casio’s main power sink is the display. I bet the refresh rate could be reduced for better battery life.
Isnt the refresh rate just 1 Hz?