Lindy,

 You may want to consider multiplexing the LED's so that only 1 is on
 at a time.  But it will appear as though they are all on at once because
 of our 'persistence of vision'.  Most commercial clocks do this.  If you
 have a LED ( 7 segment) digital clock around, shake it in front of you
 and watch the digits.  They will all appear to spread apart because they
 are multiplexed.   This allow the numbers to appear to us as though they
 are all on at the same time, but in reality only one is on at a time, and
 therefore, you have only one LED current to be concerned about.
 You could set your LED current to about 10-15 ma, and save a lot of
 battery power.   If you don't have a need for reading this clock across
 the room, you could set the current even lower.

                                                Regards,

                                                  Jim


> I connected my multimeter from +5 on the battery to the circuit and it
> reads about 75 mAmps.  I'm quite new to this, but that seems like a
> lot.
>
> Since all the LED's are connected to a common ground in my circuit
> (already soldered), can I add a resistor between the cathode of the
> LED's to the battery ground?
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Fred Hillhouse Sent:
> Friday, June 04, 2004 21:11
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC:] First Project Finished! But... it used up all my
> bat tree
>
> Although many LED clocks have 9V batteries in them, usually the LEDs
> are off if the AC power fails for some reason. The 9V battery only
> powers the 'time keeping' circuit, not the 'time displaying' circuit.
>
> You may want to consider a 9V wall wart instead.
>
>
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Lindy Mayfield
> Sent: Friday, June 04, 2004 2:48 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [PIC:] First Project Finished! But... it used up all my bat
> tree
>
>
> 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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