Demonstration Board using Watch Crystal and Four LEDs

Half of a Radio Shack 276-159B printed circuit board holds the PIC and LEDs  
used in most CheaPIC programs.  Looking from the top, the PIC socket is 
positioned lright as far as possible with pin 1 at the upper right, 
( demobdt.jpg ).  Notice that the PIC is upside down. This is the position 
you will view the LEDs such that bit 0 is at the right.  A watch crystal is
attached to pins 16 and 15 with 33pf caps from the bottom edge pads of these
pins to the bottom edge pad of pin 14, (Vdd).

Also notice resistors from RB0-RB4, (pins 6-9), going to outer pads which also 
connect to the anodes of the LEDs.  The LEDs are lined up along the top 
left edge.  A 'U' shaped piece of  bare wire forms a ground bus and is 
connected between pin 5, (Vss), and the outer pad which used to be connected
to pin 9 but has been cut free.  The cathodes of the LEDs are connected to this 
bus.  The 'U' shaped wire extends through the board and is bent over and 
soldered to the adjacent 'L' shaped pad, giving a number of connecting
points for ground wires.

Power comes from a two pin connector at the left.  You use this as a power 
switch by pushing in wires from the batteries.  The wires go to the two 
pads closest to that end. Red jumper wires lead from the + pad to pin 14, 
(Vdd), and pin 4, (MCLR). I drilled small holes in the center left end and 
wrapped thin wire around the power leads coming in as a strain relief.

Heavy wire is soldered as pins to the outer pads of pins 13, (RB7), 12, (RB6), 
and 11, (RB5).  I used pieces of wire from a leads of a large resistor. When
a ground wire is touched to these wires, it simulates a pushbutton switch.

The outer pad of RA3 has a wire attached.  This and a ground wire leading 
wires attached to a piezoelectric speaker.  A 100 ohm resistor is in series 
with one of the speaker leads.  Speaker wires are coupled to demo board wire 
with small wirenuts. This makes it easy to disconnect the speaker when not 
used.  The speaker is a piezoelectric unit from Radio Shack,(demobdl.jpg).

The size of the LED resistors depends of the type of LEDs used.  Normal LEDs 
would require maybe 10 ma each, up to 40 ma if all were on at once.  I 
choose to use low-current red LEDs from Radio Shack, (276-310, 2 for $1).  
2.2K resistors seem to drop about 1 volt giving a current of about 1/2 ma with 
reasonable brightness.  Four would draw only 2 ma.

Why all this concern for low current?  I use 3 AA batteries for a power 
source.  With a constant draw of 10 ma these would last about 3 months.  If 
the current goes up to 100 ma that time goes down to 9 days.  One of the 
projects is a clock which runs for long periods of time.  In that case, every 
little bit of current saving helps a lot.

You could use a 3 cell battery holder or simply stack the cells in a triangle 
shape, wrap with electrical tape and solder on wires.  Scrape the battery 
terminals before soldering.

'demobdb.jpg' shows the bottom of the board. Notice at the upper right that 
extensions to the outer pads on PIC pins 5-9 have been cut away.  This 
leaves pads free for LED resitors and pad for the ground bus.