Data Sheet

FOR ADVANCED USERS -
ADULT SUPERVISION RECOMMENDED
Note spring
direction of
1-snap
Project 78
Build Your Own Buzzer
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 attract-
ing the nut-snap also breaks the circuit to the
electromagnet, which then releases the nut-snap.
This creates a feedback loop which raises and re-
leases the nut-snap in a repeating cycle. The
buzzing sound you hear is from raising and re-
leasing the nut-snap many times a second.
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). Snap
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).
Turn on the slide switch (S1). 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.
Project 79
Build Your Own
Vibrating Circuit
Use the preceding circuit, but replace the lamp (L4) with the meter
(M5), set to the 5V scale. Since the circuit is sometimes on and
sometimes off, the meter pointer will be vibrating.
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