The special effects in a haunted house need to be well timed. The best way to do this is to use sensors to detect where your guests are in the haunted house. So I am doing a series of projects that demonstrate a variety of sensors that you can use to automate your haunted house. Last week I showed how to make a simple DIY pressure plate switch.
This week, I am going to show you how to make a proximity sensor and how you can implement it to activate special effects.
Step 1: Materials
33 ohm Resistor
10 kohm Resistor
Black Heat Shrink Tubing (the same diameter as the phototransistor)
Step 2: How an Infrared Proximity Sensor Works
This isn't exact because the amount of reflected light also depends on the physical properties of the reflecting surface (sometimes called its reflectivity). However, it works well enough to use to activate special effects in a haunted house.
I chose to use infrared light for this sensor because it is invisible to the human eye. So your guests won't notice it. Also it won't experience as much interference from the lighting in the room.