FOR ADVANCED USERS - ADULT SUPERVISION RECOMMENDED
Note spring
direction of
1-snap
Project 77
Build Your Own Relay
Build the circuit shown. Three 3-snaps are stacked together
at base grid location E4-E6. Snap the 4-snap onto the 1-
snap at grid location D2, then place it so it lays on the snap
at F4 (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).
Turn on the slide switch (S1). The lamp (L4) should be on
(if off, make sure the 4-snap is touching the 2-snap at F4
without being snapped there).
Push the press switch (S2) to turn on the electromagnet.
This should raise the 4-snap slightly and turn off the lamp
(adjust the position of the grommet on the rod if it does not).
If you still can’t get it to work, rotate the 1-snap at location
D2 to the proper spring direction as shown, this may make
the 4-snap move more easily.
The current through the electromagnet
makes a magnetic field that attracts the
nut-snap, which breaks the circuit to the
lamp.
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