BY RON NEWTON
It was a dark and stormy night. Two small children were walking down the
dimly lit sidewalk. The full harvest moon was peeking out every now and
then through the small breaks in the clouds. A dog was howling on an eerie
note. Spooks, goblins, and vampires could be seen on the other side of the
street. The children slowly walked up to door with bags in their small hands.
As they crept up closer, on the wall there was a strange picture of a skull or
was it a lady sitting at her mirror? As they draw nearer, all of a sudden there
is a great flash of light and Shazam! A lightning bolt from the picture flashes
with a great clap of thunder!
Halloween is one of America’s (and my) favorite holidays. It has become progressively more and more
popular with parties, and probably is in second for
outdoor displays next to Christmas.
This project was designed to be flexible and reusable
for other holidays, and the basic unit can be put together
for less than $15 plus the board. No surface soldering is
required, so this is an easy first time project. Depending
on what type of display you use, the price can increase.
Plain LEDs are cheap. I used high output white LEDs
which sell for $.89 ea. If you want 100 lumens per LED,
the price can jump to $8 ea, and you will need to add
drivers. For those who want lighting for a stage
production, simply can use photo triacs (Sony S211602F)
and drive up to 16 amps 220 volts for each bulb.
If you don’t want sound, leave out the sound chip and
save money. The board can be triggered using a
momentary switch. The one described in this article uses a
Parallax Passive Infrared detector (PIR) for detecting the
■ FIGURE 1. The printed circuit board.
presence of a person. The PIR is also available at
RadioShack for $9.99. My project ended up costing about
$40. This doesn’t have to be a one-time project. I have put
in programming pads, so if you have a PIC 2 programmer
you can program the light output for Christmas,
Valentine’s Day, birthdays, etc. Changing the DIP switch
will allow you to code many different programs. The voice
chip can be reprogrammed by the DIP switch giving you
many choices of different tunes. If you use the PIR, it can be
utilized in a lot of other projects as it is a plug-in module.
The heart of the board is a Microchip PIC16F690. It
also controls the sound module. The board will provide 30
milliamps for each of the 16 LEDs using a multiplexing
technique. The eight outputs are divided into two sections
of four outputs ( 42 = 16). The LEDs are set up in four
groups of four with their anodes tied together. The first
cathode of each group is daisychained together. Same
with the second, third, and fourth LED. By applying a
positive voltage to group one and grounding LED one, it
will light; grounding LED two, it will light; and so on.
The PIC is triggered by shorting the two terminals
labeled S2. There is also a jack to plug in the PIR which
will detect a person’s presence using infrared sensing.
Both S2 and the PIR provide a positive voltage to trigger
the PIC. I added a three-position DIP switch so that you
can program nine different modes (32 = 9). The switch
also controls if the voice chip is being used for recording
or playing. If you’re not using the PIR and if S2 is kept
shorted (using a shorting bar), the unit can cycle at 30
seconds, one minute, two minute, and four minute cycles,