Velcro tape, ¾", 7" long
Copper or brass foil, 36 gauge (0.005") or thinner,
1" wide, 6" long available from hobby or craft stores
Insulated wire, 18 gauge, 10" lengths ( 2)
Headers, 2-pin ( 2) or male breakaway header cut into
Solderless breadboard such as part #276-001 from
RadioShack ( radioshack.com), $20
Jumper wire kit RadioShack #276-173
Batteries, AA ( 4)
Battery holder, 4xAA
Dual op-amp IC, MCP6002 part #MCP6002-I/P-ND
from Digi-Key ( digikey.com)
Resistors, ¼W: 220Ω ( 1), 10kΩ ( 1), 100kΩ ( 1),
1MΩ ( 1) 3.3MΩ ( 2)
Capacitors: 10nF ( 1), 0.1μF ( 2)
Diodes, 1N4001 ( 3) RadioShack #276-1653
DISCLAIMER: The Truth Meter reveals changes in
arousal, but it’s not really a “lie detector.” Even polygraph
tests, which measure GSR, heart rate, blood pressure, etc.,
are not admissible as evidence in many courts.
Photography by Sam Murphy
1. MAKE THE 2 SENSORS
1a. Cut some ¾" velcro tape into a 3½" piece
of loop (soft) side and a ¾" square of hook
(rough) side (Figure C). D
1b. Peel off the tape backing, and align and
stick the hook velcro, back to back, at one end
of the loop velcro.
1c. Cut a 10" length of 18-gauge wire and strip
½" off one end. Lay the stripped end of the
wire perpendicularly across the end of the
loop velcro’s sticky side so that its stripped
portion hangs off the edge (Figure D).
1d. Lay a 1"× 3" strip of copper or brass foil
over the sticky portion of the loop velcro and
wire. Press together firmly and evenly and
trim off the excess foil (Figure E).
1e. Fold the stripped portion of the wire back
over the foil and solder it in place. Try to
create a smooth, flat surface with the solder
that won’t dig into your finger.
Repeat 1a–1e for the second sensor.
1f. Strip ¼" of the sensor wire ends and
solder them to a 2-pin header so they can
be inserted into the breadboard (Figure F).
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