Kiitoksia paljon.  I didn't consider those factors in my design. (-:  =
Whoops.  Anyway, time for a new project.

Thanks also to all who took their valuable time to help me. I'm really =
learning a lot.

-----Original Message-----
From: pic microcontroller discussion list =
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Harold Hallikainen
Sent: Friday, June 04, 2004 22:38
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC:] First Project Finished! But... it used up all my bat =
tree

Running LEDs off a 9V battery is gonna give you pretty short battery =
life.
Looking at
http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_Alka=
line_Hdbk_03-04_v1.pdf
a 9V battery is rated at 570mAH. Note also that the cut off voltage is
4.8V.  Your cutoff voltage is probably higher when considering the
regulator drop out voltage, etc.

If you have 20 LEDs and run 5mA each, that's 100mA when all are lit,
which, at best, would give you 5.7 hours operation. Looking at the
discharge curves, a 100mA load would be equivalent to a 90 ohm resistor.
With a 5.4V cutoff, you can expect about 8 hours of operation. Increase
the time a bit since not all LEDs are on all the time, but decrease the
time as your average LED current increases (peak current times duty =
cycle
if multiplexed).

This, of course, is why watches use LCD instead of LED.

Harold


> Hi Guys.
>
> I finished my first project!  Finally.  I got the idea from Mike =
Predeko's
> book for the LED clock.  But I couldn't find the right parts to put
> together the multiplexing for all the LED's, so I decided to work with
> what I have available and made a binary clock:  20 small 3mm LED's =
that
> show the hours, minutes, and seconds in bcd binary.
>
> The design so far is simply a 9v battery, a 5v voltage regulator, a =
PIC
> 16f877, a 32.768 kHz crystal + 2 22pf caps, resistors and LED's, and =
one
> resistor tied to MCLR.
>
> The programming was fun.  Building and soldering the rat's nest out of
> wires on the back of the board wasn't.  (-:  (Took 3 weeks.)
>
> I left it running for a test last night and it sucked all the juice =
out of
> my 9 volt battery in just a few hours.
>
> Would someone give me hints as to how to figure out what the problem =
is
> why it is using so much power?
>
> Thanks in advance.
> Lindy
>
>
>
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