[SOLVED] CR2032 for small LED light?

[jackyzhangsh]

Hi,

We are trying to design a small keychain-like system. One requirement is that there needs to be small light indicators when some buttons are pressed. It should look like the picture below:

The question is that is the small light in the picture a LED light? What current does it require? We are looking at CR2032 buttons and typically this cell has a continuous drain of only 0.2mA. Though it also specifies a pulse current of 15mA, how long can that pulse last?
So is it possible for us to use CR2032 for such a small light?


Jack

 

[betwixt]

You can run a small high brightness LED like that at about 2mA for a long time, maybe 10 hours or more before the battery gives out. If all you need is a few seconds it should last a long time.

Consider that most "keyring" LED lights use nothing more than a CR2032 and a white LED straight across it. They actually rely on the cell not being able to produce enough current to damage the LED but they still work for many hours if left switched on.

Brian.

 

[jackyzhangsh]

betwixt,

But the spec of CR2032 says that the continuous is only 0.19mA. If the LED draws 2mA, it is 10x larger, and does it damage the cell after running for like several hours (it seems outrageously long for a 10x-larger current)?


Jack

 

[tpetar]

Yes low current 2mA LED should be used, if you use high bright LED at 25mA-35mA this will discharge battery faster.

CR2032 have capacity around 240mAh to 2,00V. Nominal voltage is 3V, Lithium.

CR2032 datasheet :
http://data.energizer.com/PDFs/cr2032.pdf
http://cr2032.co/datasheets/maxell-cr2032-datasheet.pdf

 

[jackyzhangsh]

tpetar,

2mA is low for LED indeed. However, it is still 10 times of the 0.2mA continuous specification. I wonder if it is too large to discharge it for several seconds?

Many CR2032 gives 15mA as its peak pulse current. However, how long can the "pulse" last? Should it be a few mSec's, or even a few seconds or minutes?



Jack

 

[tpetar]

No my friend 2mA LED light nice, CR2032 from my epirience can handle 2mA LED for many years in blinking operation. You can try to use two batteries one for 2mA and one with 25mA LEDs, CR2032 is not expensive, make sacrifice with 2 batteries for knowledge. :grin: Also use LED appropriate resistor.

 

[jackyzhangsh]

tpetar,

I believe its fine. Will ask factories about the actual ability.

Bob