On 30/05/2011 09:36, V G wrote:
> Hey all,
>
> This is regarding my optical guitar tuner idea, where a circuit will be
> powered from CR2032 coin cells. The circuit will be drawing (I'm guessing=
)
> around 30-50mA due to 2-4 LEDs pulsing at sound frequencies.
>
> I know that CR2032s are designed for around a 1mA continuous draw, and up=
 to
> 10mA pulse draw, but people make LED keychains out of these things all th=
e
> time and those LEDs draw 20mA or so continuously. I want to power the tun=
er
> with these cells, but I don't want the performance of the batteries to
> degrade as much due to the relatively high current draw. Therefore, I'll =
be
> putting these batteries in parallel (about 3 or 4 of them in parallel).
>
> Is this okay? What kinds of issues will there be? Will there be issues of
> the batteries charging into each other? Things like that?

You can put a small resistor in series with the battery, and a large=20
capacitor on the other side to reduce the pulse current on the battery.
I would say it's right on the limit, and as Russell mentioned specs=20
between makers vary quite widely, but I would suggest you try it and see.
2 LEDs if pulsed at 20mA at a 1/10 duty cycle will be 4mA which the=20
CR2032 datasheets I looked at suggested is possible (assuming you are=20
not running continuously all day long)
The energizer datasheet has a graph for a 1:14 duty cycle at 23mA. The=20
6.8mA graph is for 2 seconds on at a time.

--=20
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