One of the most useful sensors for automating a haunted house is a motion sensor. This sensor lets you activate your special effects only when a new group of people arrives. That way the surprise won't be ruined by people seeing or hearing the effects before they get close enough.

In this project, I am going to show you several ways that you can use a motion sensor to automate your Halloween setup.

Step 1: How Passive Infrared (PIR) Motion Sensors Work

For a good in-depth tutorial of all things related to PIR motion sensors you can check out this page by adafruit: 
I will attempt to give a brief summary here.

Passive Infrared (PIR) motion sensors work by detecting the movement of heat. They detect heat with a pair of pyroelectric elements that turn the incoming heat into a small electrical signal. The pyroelectric elements are wired in the opposite polarity to each other. So the signals normally cancel each other out. But when a heat source moves in front of the sensor, it creates a series of positive and negative pulses that are detected by the microprocessor. The PIR sensor then outputs a HIGH signal to indicate that motion was detected. This signal can then be used to trigger other circuits such as lights, alarms or cameras. 
<p>Also for ac switching couldn't you just use a solid state relay connecting the switch line of the SSR to the output of the arduino? </p>
Yes, you can easily use a solid state relay. But they are a lot more expensive than a regular relay (about $20 more). I was just using the cheaper option.
<p>Does the sensor receive variable input data. As in different voltage readouts for a heat source as it gets closer and farther away?</p>
No. This type of sensor just outputs a HIGH signal when it detects motion and a LOW signal when it doesn't detect motion.

About This Instructable


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Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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