Up next in How to Do Fun Tech & Science Projects (52 videos)
School science fair coming up? Don't worry: We've got step-by-step instructions to dozens of science projects in this Howcast video series, including how to build an erupting volcano, how to make glow-in-the-dark art, how to make a weather barometer, how to make disappearing ink, how to make 3-D glasses, and how to make a marshmallow gun.
You Will Need
- A laser pointer
- Some Duct tape
- A few small mirrors
- An L.M.741 microchip
- A 220-ohm resistor
- A photocell
- An inexpensive digital camera
- An extra small screwdriver
- A wire coat hanger
- Some thin, insulated wire
- A printed circuit board
- A 9 volt battery
- A 9 volt battery clip
- Soldering equipment
- A pair of wire cutters
- A soap caddy with drainage holes
- A voltage relay
Build the circuit
Build the circuit. Center the microchip on the circuit board. Pop in the voltage regulator. Connect the battery clip leads to the regulator. Run 2 more leads out from the regulator. Pop in the resistor and the photo cell. Link the chip to the photo cell. Pop in the relay. Link the chip to it as well. Link the other side of the relay to "power."
Disassemble the digital camera so you can access the board connected to the camera’s trigger button.
Solder wires to terminals
Look for the two tiny terminals that lead to the trigger button. Solder wires to each of these terminals and feed them through the trigger button hole.
Reassemble the camera
Reassemble the camera. If you can’t get it back together easily, use duct tape to keep it closed. Just don’t tape over the lens.
Position circuit inside soap caddy
Position the circuit inside the soap caddy so the photocell is exposed behind one of the holes.
Connect battery to circuit
Connect the battery to the circuit, and use tape to secure the whole assemblage inside the box.
Attach wires to voltage relay
Slip the two wires coming from the camera through another hole, and attach them to either side of the voltage relay.
Cut & tape coat hangers
Cut the coat hanger into several pieces. Tape one piece to the laser pointer and the others to the back of the mirrors.
Place the camera in an inconspicuous location with the lens pointing at the object you want to protect and secure it in place.
Position laser pointer
Position the laser pointer in another inconspicuous place and secure it too.
Place the mirrors to create a perimeter around the object you’re protecting, adjusting them until the laser hits the photocell.
Test the system
Now break the beam to test the system… And get ready to confront the perpetrator with your irrefutable evidence.