prevent spurious outputs. Both
the badges and candles
interface with a PIC12F508 for
control. When the detector
detects a 36 kHz signal, it pulls
its output low.
Wand
When the momentary
switch is pressed, it applies
power to the chip. The program
is about as simple as you can
get. It has two peripheral
registers for timing and uses a
series of NOPs to lock down
the 36 kHz frequency. It
produces a square wave output
on all five outputs. Each
PIC12F508 has an internal
oscillator which is trimmed at
the factory. Once it’s
programmed, no adjustment for
frequency is necessary. The two
registers provide a 70 millisecond pulse. This prevents the
person from holding down the
button and cheating. They have to re-push the
button. The wand uses two AAA batteries for
power.
Candle
The candles also use two AAA batteries, have
an on/off switch for power, and are triggered via a
Vishay TSOP2436 infrared receiver. A yellow LED
flickers using a random number generator when
the IR beam hits the IR detector. It can be turned
off again if the IR beam is again detected. There is
a built-in delay to prevent false signaling. The IR
receiver draws 3 ma; this is why a power switch is
needed.
Badge
■ Schematic.
■ FIGURE 1.
The badges are powered by a three volt
lithium battery and also have an on/off switch. They use
the same Vishay detector. If an IR beam is detected, it will
light the red LED and emit a squeal from the piezo buzzer.
For each hit, the buzzer counts the score. The score
counter can be reset by pressing the reset switch. When it
reaches 10, the badge will stop counting and will need to
be reset.
Construction: Wands and Candles
The wands are made out of 14” pieces of 3/4”
hardwood dowels. (See Figure 1.) Do not use pine or
poplar as it will split. (The plans and dimensions are
located on the N&V website.) Locate the center of the
dowel. Using a center drill, center drill both ends. Drill the
5/8” hole first to 5. 5”. Remove the 5/8” drill and using an
extended 1/4” drill, drill halfway through the remaining
portion of the wand. The drill will center in the 5/8” hole.
Reverse the dowel and using the extended 1/4” drill, drill
the dowel completely through. The candles are made the
same way, only they are 8” in length. You will find that the
main problem is the drilling of a continuous 1/4” hole as
