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'[EE] Battery draining problem'
2006\01\15@112150 by Shay

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I made a little box for my son which has a bunch of different types of
switches and some LED's.  It's also got a pot and a little buzzer so he
can turn the volume up and down.  He really likes it but after a day the
battery dies.  I've got a 9 volt hooked up to everything.  I have
battery hooked directly up to the switches and then the switches are
connected to the led's with a resistor in between.

So am I missing some key part that would help from draining the
battery?  LED's shouldn't drain a 9 volt battery that quickly and the
buzzer is almost never on.  Really, only 1 or 2 led's are lit at any
given time and they're really low volt led's.

Thanks for any help,
Shay

2006\01\15@173427 by Jinx

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> So am I missing some key part that would help from draining
> the battery?  LED's shouldn't drain a 9 volt battery that quickly
> and the buzzer is almost never on.  Really, only 1 or 2 led's
> are lit at any given time and they're really low volt led's.

Shay, a typical zinc-carbon PP3-type 9V battery is probably 150-
200mAh capacity. 2 LEDs, 5mA each = 15-20 hours

BTW you did mean to say the LEDs are "low current" rather than
"low volt" ? A 1" piece of wire is very "low volt" but would take
rather a lot of mA to "drive" it ;-))

There are several ways around your problem, some quick 'n' easy,
some not

- super-ultrabright LEDs and a higher value resistor

- make a battery from AAs, which have higher mAh than a PP3

- reduce voltage to PIC range and flash LEDs (you could also
make a gated oscillator from CMOS)

etc etc etc


2006\01\15@201416 by William Chops Westfield

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On Jan 15, 2006, at 8:23 AM, Shay wrote:

> LED's shouldn't drain a 9 volt battery that quickly and the
> buzzer is almost never on.  Really, only 1 or 2 led's are lit at any
> given time and they're really low volt led's.

A typical 9V battery has about 500mAH of energy, so if you're
driving 20mA into LEDs, you can only expect a life of about 25 hours.
LEDs are low current compared to incandescents, but they're not all
that low power on an absolute scale...

BillW

2006\01\15@220817 by kravnus wolf

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Out of curiosity, check the ampere comsumption when it
is
idle and when it is used. Maybe some bad connection?

John

--- William Chops Westfield <spam_OUTwestfwTakeThisOuTspammac.com> wrote:

{Quote hidden}

> --

2006\01\16@100721 by alan smith

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I'd suspect the buzzer...probably a current hog, and did you just put the pot in series with it...so all that "energy" is simply converted to heat?

kravnus wolf <.....kravnusKILLspamspam@spam@yahoo.com> wrote:  Out of curiosity, check the ampere comsumption when it
is
idle and when it is used. Maybe some bad connection?

John

--- William Chops Westfield wrote:

{Quote hidden}

> -

2006\01\16@100913 by alan smith

picon face
I'd suspect the buzzer...probably a current hog, and did you just put the pot in series with it...so all that "energy" is simply converted to heat?

kravnus wolf <kravnusspamKILLspamyahoo.com> wrote:  Out of curiosity, check the ampere comsumption when it
is
idle and when it is used. Maybe some bad connection?

John

--- William Chops Westfield wrote:

{Quote hidden}

> -

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