Recommendation for Motion Sensor

Purpose: Part of the child lock system (To prevent a child/pet from entering the dryer when it’s operating).

Types of Motion Sensors

• Passive Infrared (PIR)
• Detects body heat (infrared energy) ++ Tripped when object blocks too many grid zones and infrared levels change rapidly Microwave Sends out MW pulses and measures reflection off moving object Covers a larger area than PIR Vulnerable to electrical interference More expensive than PIR Dual Tech Utilizes sensors of different areas of the spectrum One sensor must be passive, and one active Not as likely to cause false alarms Area Reflective Type Emits infrared rays from an LED Measures the distance to an object and detects if it’s in a designated area Ultrasonic Sends pulses of ultrasonic waves Measure reflection of moving object Can’t detect around an obstacle (ie clothes) Vibration Detects vibration

Recommendation: PIR sensor. This motion sensor is affordable ($10 for one on the Adafruit website), requires little energy because it’s passive (5-12 V), and lasts for a long time. Passive PIR sensors are the most commonly used motion sensors in home security Though the PIR sensor has a lesser quality of detection, we believe its affordability outweighs given that the subjects of the detection are likely a large child or pet, making the chance of a missed detection less likely.

However, the PIR sensor has a few downfalls. Since it detects change in infrared, this sensor cannot detect cold-blooded animals (such as snakes, lizards, and other reptiles). As our first sensor, we will prioritize the case if a child is trapped inside It would be able to detect a passed out child with the movement of their breathing Furthermore, it would not be able to detect an inanimate object such as food or leaves. This situation would most likely be up to the user when they lock the dryer Possible problems to test for: Movement of warm clothes setting off a false alarm Entering warm air setting off a false alarm High heat in dryer making it more difficult to detect a child

Specific model on Adafruit: Link: https://www.adafruit.com/product/189 Price: $10 Adjustable delay before firing (2-4 seconds) Adjustable sensitivity 1 foot cable for easy repositioning Runs on 5-12V (Could be adjusted to 3V with extra work) Sensing range: ~20ft in a 120 degree cone Another possibility: 5 for $10 on Amazon, https://www.amazon.com/DIYmall-HC-SR501-Motion-Sensor-Module/dp/B012ZZ4LPM/ref=sr_1_2?ie=UTF8&qid=1499904095&sr=8-2&keywords=pir Adafruit also includes a tutorial on how to build a system to light an LED when the motion sensor is activated: https://learn.adafruit.com/trinket-powered-room-conference-occupancy-display?view=all

Configuration:

Next steps: Wiring the sensor in the dryer. Coding the motion sensor. Determining the system Emergency stop button on inside and outside Microcontroller Display Locking mechanism (magnetic?) After testing, look into a dual motion sensor