Fig. G: LEDs press-fit into holes. Fig. H: Bend the LEDs’
negative leads to meet. Fig. I: Glue the battery’s negative
side to the cap so the negative leads are touching it.
Fig. J: Coil wire around a small screwdriver to make a
2d. Make your spring. First strip the enamel coating
off your magnet wire by folding a piece of sandpaper
in half and running about 3" of wire between the
grit. Sand the wire until you see the bare copper, but
don’t over-sand or the wire might break.
Tightly wrap the wire around a small screwdriver
or the ink cartridge of a ballpoint pen, leaving about
½" uncoiled at the end (Figure J). Coil the wire 5
times around, and cut off the spring.
2e. Bend the positive LED leads to meet each other,
then tape them together by wrapping a piece of aluminum insulation tape around both leads. Tape your
spring to the battery with aluminum tape (Figure K).
Adjust the spring to sit as close as possible to the
positive leads without touching them. Pliers come
2f. Stick a piece of double-sided foam tape onto the
battery (Figure L), then stick it to your yo-yo (Figure
M) and you’re done!
Q: Why don’t the LEDs light when I throw my yo-yo?
A: Move the spring closer to the positive leads. Check
the polarity of the LEDs (+ to + and – to –).
spring. Fig. K: With conductive tape, tape the positive
leads to each other, and tape the spring to the battery.
Fig. L: Double-stick tape on battery. Fig. M: Finished cap
in place. Fig. N: Initial design: 2 springs, twice the trouble.
Q: Why do the LEDs stay on after throwing?
A: Move the spring slightly farther back, away from
the positive leads.
This is my second prototype and I’m already thinking of newer designs. Using multicolor LEDs like the
retail version would be a nice addition.
To keep the yo-yo spinning smoothly, make sure
all the parts are centered to the rotational axis. Less
mass on the caps will also lessen the wobble caused
by any off-axis components.
In my first design (Figure N) the LEDs stayed lit
after just one throw. Since copper wire isn’t the
springiest, and there was too much wire, it pulled
itself toward the leads too much. Also, using 2
springs caused twice the problems!
DIY LED side caps video:
More on LED side caps:
MAKE engineering intern Eric Chu throws yo-yos and builds
robots. He is the creator of Chu Pads, friction pads for bringing yo-yos back up, and is developing silicone response pads.