Elenco Snaptricity® - Manual (Page 75)

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Buzzer Project #65
Educational Corner:
Electric Paths
FOR ADVANCED USERS -
ADULT SUPERVISION RECOMMENDED
As in the preceding relay circuits, the current through
the electromagnet makes a magnetic field that attracts
the nut-snap, which breaks the circuit to the lamp.
However in this circuit attracting the nut-snap also
breaks the circuit to the electromagnet, which then
releases the nut-snap. This creates a feedback loop
which raises and releases the nut-snap in a repeating
cycle. The buzzing sound you hear is from raising and
releasing the nut-snap many times a second.
Description
Set the slide switch (S5) to position B to turn on the
circuit. The lamp (L4) should be on; adjust the position
of the grommet until you hear a buzzing sound. If the
lamp is off, make sure the 4-snap is touching the lamp
snap at C6 without being snapped there. Make sure the
4-snap lays centered on the snap at C6 (vibration tends
to move it off-center).
This circuit requires precise adjustment; if it doesn’t
work then make sure the grommet and 4-snap are
positioned as described above and start over. If you still
can’t get it to work, rotate the 1-snap at location A4 by
90 degrees, this may make the 4-snap move more
easily.
Operation
Build the circuit shown. At base grid location B6-B8, 3-
snaps are on levels 1, 3 and 4. Snap the 4-snap onto
the 1-snap at A4, then place it so it lays on the snap at
C6 (DO NOT SNAP IT ON). Place the nut-snap on the
4-snap so it will be under the electromagnet (M3). This
circuit works best with new alkaline batteries.
Place the rubber grommet on the iron core rod and
push the rod into the electromagnet until it is just barely
above the nut-snap without touching it (0.025 inches).
Assembly
Snappy says: this circuit also works if you replace
the lamp with the meter, use the 1mA scale.
Since the circuit is sometimes on and sometimes
off, the meter pointer will be vibrating.
Note spring
direction of
1-snap