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Unit 10: Electricity Page 25
Here’s what you do: Troubleshooting: There are a few
problem areas to watch out for
1. Find a piece of squishy foam. when building this sensor. First,
Like a sponge. You want make sure the hole in your foam is
something that will spring big enough to stick a finger (or
back into shape after you thumb) easily through. The foam
squeeze and release it. keeps the foil apart until stepped
2. Cut a small (1/2” diameter) on, then it squishes together to
hole through the middle of allow the foil to make contact
the sponge with a pair of through the hole.
scissors.
The second potential problem is if
3. Lay a small piece of the switch doesn’t turn the buzzer
aluminum foil over each side
off. If this happens, it means
of the hole. The foil needs to
you’re bypassing the switch
be smaller than the sponge
entirely and keeping the circuit in
but larger than the hole.
the constant ON position. Check
4. Lay a paper clip on top of the the two foil squares - are they
foil, one per side. touching around the outside
edges? Lastly, make sure your
5. Wrap the whole thing
foam is the kind that pops back
securely with tape.
into shape when released. (Thin
6. Set aside. sponges can work in a pinch.)
7. Using alligator wires,
What’s happening? You’ve made
batteries in a holder, and an
a switch, only this one is triggered
LED, create a simple circuit
by squeezing it. If you’re using the
that makes your LED light up
special black foam without the
(see Lesson 1 for
hole, it works because the foam
instructions).
conducts more electricity when
8. Remove one of the alligator
squished together, and less when
wires from the LED and
it’s at the normal shape.
insert a third wire to the LED.
9. Attach the remaining two First, the special black foam is
alligator wires to the paper conducting some (but not enough)
clips, one to each side. electricity when you squeeze it. It’s
just the nature of the black foam
10. Squeeze the foam.
included with the materials kit.
Your LED should light up!
Second, when you squeeze it,
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