Fooling a Motion Sensor

MacGyver and Jack use a large blanket to hold up in front of them in as they move slowly down a hallway. The idea is to trick the motion sensor so that they can steal something.

There are several different types of motion sensors. If you have one in your house for your security system, it’s probably a PIR—Passive InfraRed sensor. This basically works by detecting the infrared radiation that your body emits because of its temperature. For this type, you can just block the IR light coming from your body—at least in theory.

Other types include a microwave sensor. This emits microwave light that reflects off things. If the thing is moving, there will be a slight shift in the reflected frequency—it is this change in frequency that tells the sensor something is moving. Yes, this is the Doppler Effect.

But could the sheet method actually work? Yup. This was tested by the MythBusters.

Hanging boot to fool painting sensor

They need a painting off the wall. It has a sensor that detects if the painting is lifted up. MacGyver hangs a boot on the sensor to mimic the weight of the painting.

It’s basically a version of Indian Jones stealing the idol at the beginning of Raiders of the Lost Ark.

Chair to block a door

What happens when you jam a chair under a door handle? Sometimes this will indeed prevent the door from opening. As the door starts to open, the chair rotates to a more upward position. However, the door handle stops the back of the chair from moving upwards. This means that that bottom of the chair pushes MORE into the floor. The basic model of friction says that the frictional force is proportional to this force pushing into the floor.

This trick can sometimes work.

Zip line from a curtain

MacGyver takes a curtain and cuts it into strips. Then he uses these strips to make a rope. The rope makes a zip line to send the stolen (borrowed) painting over the fence so they can escape into the pool.

Turpentine and packing peanuts

Yeah, mixing stuff together and then lighting it on fire can make a big mess. Let’s just leave it at that.