Manual

Assembly:
1. Place base grid supports on base grid A.
2. Place parts on grid B, and install into
base grid supports on grid A.
3. Install remaining parts on grid A.
Turn on the slide switch (S1); the white
LED should be on, but there should be no
sound. If there is sound, move the circuit
away from room lights.
Hold a mirror so that light from the white
LED (D6) is reflected to the phototransistor
(Q4); an alarm sounds when you succeed.
The color LED (D8) is intentionally
installed backwards and will not light.
MIRROR
Use as per instructions
Use the preceding circuit,
but make sure everything
is securely snapped.
Carefully place the circuit
upside down on the floor or
a table, then slide the
mirror under it, as shown.
When the mirror reflects
light from the white LED
(D6) to the phototransistor
(Q4); an alarm sounds
indicating success.
Project 140
Floor Mirror Circuit
-72-
Project 139 Free Mirror Circuit
When installed backwards,
the color LED’s color
changing microcircuit acts
like a small electric speed
bump. It is used here to
regulate the voltage to the
NPN transistor (Q2), so that
room lights do not easily
trigger the alarm.