Data Sheet

Project 76
Relay Circuit
Build the circuit, place the glow fan on the motor (M1), and set the meter
(M5) to the 1A setting. Turn on the slide switch (S1); the three lamps (L4)
light and the meter measures the current.
Push the press switch (S2) to activate the relay (S3). The lamps turn off
and the motor (M1) spins the fan.
1A
Name an appliance in your home that uses a relay to switch lights or mo-
tors on and off.
Project 75 Relay Memory
Build the circuit and turn on
the slide switch (S1). Noth-
ing happens. Now push the
press switch (S2). The lamp
(L4) comes on and stays on
even after you release the
press switch (the circuit “re-
members” that you pushed
the press switch). Turn off
the slide switch to turn off
the lamp.
Why is the lamp off until you push the press switch?
Why does the lamp stay on after you release the
press switch? (Look at the explanation of how the
relay works in project 8, and note that when the relay
is on contacts 1 and 3 on the relay symbol in the draw-
ing are connected.)
!
WARNING: Moving parts. Do not
touch the fan during operation.
!
WARNING:
Do not lean
over the motor.
+
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