Materials List: The Invisible Radar Triangle:
Similarity & Scaling for Models

Each group needs:

  • 1 infrared sensor, specifically, the Sharp GP2Y0A02YK0F IR package for $14.50 at Acroname (includes an infrared sensor, JST 3-pin connector and three pre-crimped wires; this infrared sensor takes a continuous distance reading and returns a corresponding analog voltage with a range of 20 to 150 cm [7.87 to 59.05 in])
  • 4 AA battery holder with cover and switch, such as item #W32971 for $1.95 at Pitsco
  • 3 AA alkaline batteries, such as item #W51046, two batteries for $2.93 at Pitsco
  • 2 plastic wire-connectors, such as item #53213, 25 for $2.69, at Lowes
  • 2 4-40 x ¾" Hillman combo round-head standard machine screws with nuts, such as item #62045, 12 for $1.18 at Lowes
  • 2-inches of 18 AWG shield wire, such as item #W12741, a 55-foot spool for $5.95, at Pitsco
  • 2 alligator clips, such as item #44564, two-pack for $1.96 at Lowes
  • ~3 inches of electrical tape (or, give each team a roll so teams do not have to wait for tape), such as item #19456, 10-roll pack for $4.97 at Lowes
  • precision screwdriver set, for assembling the sensor modules, such as item #W944S, a Performance Tool 6-piece screwdriver set for $2.49 from O'Reilly Auto Parts at
  • mini multimeter, such as item #W31912 for $23.95 (includes 9V battery, test leads and probe) at Pitsco
  • digital protractor, such as item #79017 for $24.98 at Lowes
  • 25-foot metric and SAE tape measure, such as item #317494 for $10.98 at Lowes
  • 1 toy airplane, such as a balsa wood glider, item #W50364 with a 12-inch wingspan for $3.95 at Pitsco
  • 3 balloon sticks with cups or 3 wooden craft sticks, to support toy airplane, such as Knextion balloon sticks with (cone-shaped) cups, 12 for $12.59 from Amazon at
  • foam core board, such as 20 x 30-in x 3/16-in thick polystyrene core board, 10-pack for $31.03 at Walmart
  • modeling clay (one-pound package), to use as desired, perhaps to secure the stick holding the airplane, such as item #W37660 for $3.50 at Pitsco
  • 5 zip ties, such as item #292689, 500-pack of 8-inch nylon cable ties for $14.84 at Lowes
  • 4 rubber bands, such as item #W33567, 2300 size #16 rubber bands for $5.95 at Walmart
  • 4 3-oz plastic cups, such as 100-pack for $8.16 at Walmart
  • gallon-size plastic zip lock bag, to contain materials needed to assemble and calibrate the sensor
  • classroom object such as a box, book or the wall, to help in calibrating the sensor by measuring the distance between the sensor and the object
  • Assembling the Sensor Handout
  • Calibrating the Infrared Range Sensor Worksheet
  • The Invisible Radar Triangle Worksheet
  • The Invisible Radar Triangle-Scale Model Rubric
  • The Invisible Radar Triangle Quiz, one per student
  • notebook (or lined paper), for documenting design plans, one per student
  • TI-84 graphing calculator

To share with the entire class:

  • computer and projector to show a PowerPoint® file, The Invisible Radar Triangle Presentation
  • Phillips screwdriver, for assembling the sensor
  • electric drill with 9/64 drill bit, for assembling the sensor
  • wire strippers, for assembling the sensor
  • white glue, for students to use as desired, perhaps to assemble the airplane or glue plastic cups together to look like a radar system
  • fishing line, such as a 225-yd roll of 25-lb clear monofilament fishing line for $3.10 by Eagle Claw at
  • clear scotch tape, to tape down the tape measure