Nuts & Volts

Build the Pocket Marquee Badge
together with solder. Use standard
anti-static precautions when handling
the ICs prior to their being soldered
onto the PCB (grounded wrist strap
and grounded anti-static work surface).
Solder resistors, capacitors, and
battery holder first, ICs second, and
LEDs last. Before soldering the battery
holder in place, make sure that the +
on the holder is oriented properly with
the + on the circuit board silkscreen. If
the holder is installed backwards,
something is going to get damaged!
When installing the LEDs, be sure
to align the anode and cathode leads
with the proper pads on the circuit
board. Note that the anode lead on the
LEDs is longer than the cathode.
Another way to distinguish between the
anode and cathode is to use the diode
test function on your DMM. When the
LED is lit, the positive lead is connected
to the anode. Bend LED leads at
right angles to the body and trim excess
lead length, as shown in Figure 4.
After component assembly is
complete, inspect all of the solder connections
for shorts, cold solder joints,
etc. Next, install the battery with the
negative side down towards the
circuit board. If the LEDs don’t start
sequencing on their own, briefly push
the on/off switch. After the circuit is
functioning normally, remove the battery
and attach the pin-back. You may
want to apply a protective coating of
spray varnish to the completed assembly.
If so, don’t forget to first mask off
the switch and battery with tape.
PARTS LIST
The parts listed here are appropriately sized to fit on the
printed circuit board used in the author’s prototype and also available as listed
below. Obviously, if you decide to hand-wire your Pocket Marquee Badge, you have
more latitude in choosing what parts to use. Please note that all parts listed below
are supplied from Mouser, unless noted otherwise.
ITEM DESCRIPTION PART NO.
❑ B1 Renata CR1225 3V Lithium coin cell 614-CR1225
❑ C1, C2, C3 0.1 μF 1206 SMT capacitor 140-CC502B104K
❑ D1-D16 Agilent HLMP-K150 red LED 512-HLMPK150
❑ R1 56K 1206 SMT resistor 263-56K
❑ R2 1.6M 1206 SMT resistor 263-1.6M
❑ R3 1.3K 1206 SMT resistor 263-1.3K
❑ R4 1M 1206 SMT resistor 263-1M
❑ S1 Mountain Switch 101-0364 tactile 101-0364
pushbutton switch
❑ U1 74HC163M 512-MM74HC163M
❑ U2 74HC154M 512-MM74HC154WM
❑ U3 74HC132M 512-MM74HC132M
❑ Battery holder Renata SMTU1225-1 614-SMTU1225-1
❑ Pin-back adhesive backed available at fabric stores.
❑ Etched, drilled circuit board with solder-mask, and silkscreen available from Doug
Malone, P.O. Box 1542, Battle Ground, WA 98604 for $12 plus $4 shipping/handling.
items are becoming more and more
popular. However, the Pocket
Marquee Badge is special for two
reasons: you can use your creativity
to customize the tag to suit your
needs and you build it yourself! NV
Additional Thoughts
An obvious alternative to the logic
IC design described in this article is to
use a microcontroller, such as a PIC.
The use of a microcontroller would
make the generation of much more
interesting and complex patterns of
moving lights possible. However, most
— if not all — of these patterns would
involve more than one LED lit at a
time. This results in increased current
drain and shortened battery life. If this
is an acceptable trade-off, then this
may be an avenue for you to explore.
LED jewelry and other novelty
April 2006 47