How do Motion-Activated lights work?
Hey friends, Happy Wednesday!
I’m creating a draft of this newsletter in April, as I’ll be on vacation around the time you receive this email.
I’m including an extended summary of how a gadget works in my newsletter, from which you can understand the essence in less than 3 minutes. Let’s look at how motion-activated lights work this week. I aim to write my newsletter issues in a way one can follow them while traveling on a bus, having a coffee, waiting for food, etc. Let's jump in!
Tweet of the week
I’m sharing a cool fact about gadgets every day on Twitter. And here is one of them for you.
How do Motion-activated lights work?
Introduction
Have you ever walked on a street with the lights outside an apartment automatically turning on as you walk across? These are motion sensor-activated lights that detect a person in the vicinity. But, how do they do that? These technologies are also used when you walk through a corridor and you have the lights on. Let’s see how they work.
Most of the lights have a small contraption within them using Infrared motion detector technology which makes this possible.
Image Source: CP Electronics
Working Principle
Humans and animals emit Infrared radiation always. They exist in the electromagnetic spectrum and can be detected but cannot be seen with the naked eye. Our body temperature is different from the environment’s temperature. The higher our body temperature, the higher the infrared radiation.
Thus considering this science, we developed Passive Infrared (PIR) sensors like Pyroelectric sensors that detect changes in infrared radiation emitted by objects in their field of view. When a person or object moves within the sensor’s range, it detects the change in infrared heat patterns and triggers the lights to turn on.
The electronics connected to the sensor is programmed to detect quick changes in the amount of infrared energy it receives. When someone walks by, the infrared energy in the area changes rapidly, allowing the sensor to easily detect it.
Additional Info for Geeks
How do Pyroelectric sensors detect changes in Infrared radiation?
Material Selection: Pyroelectric sensors are made of special materials known as pyroelectric crystals or ceramics. These materials possess a unique property where their polarization (the alignment of positive and negative charges within the material) changes when the temperature of the material changes.
Polarization and Electric Charge: The pyroelectric material is initially electrically neutral, with an equal distribution of positive and negative charges within its crystal lattice. When the temperature of the material changes, it causes the atoms or molecules within the material to move and disrupt the balance of charges.
Temperature Change Detection: When an object enters the field of view of the pyroelectric sensor and emits infrared radiation, the temperature of the sensor’s surface changes. This temperature change affects the polarization of the pyroelectric material, causing a redistribution of the positive and negative charges.
Electric Signal Generation: The redistribution of charges generates an electric potential across the pyroelectric material, generating an electrical signal. This signal is proportional to the rate of change of temperature and, hence, to the presence and movement of objects within the sensor’s range.
Signal Processing: The electrical signal generated by the pyroelectric sensor is then processed by an associated electronic circuit. This circuit amplifies and analyzes the signal to determine the presence, direction, and speed of motion. It also sets the sensitivity and triggering thresholds for activating or deactivating the connected devices, such as lights or alarms.
Side note: Pyroelectric sensors are responsive to changes in temperature and not the absolute temperature itself. This means that they can detect differences in infrared radiation emitted by objects as they move across the sensor’s field of view, rather than measuring the temperature of the objects directly.
Question of the week
We looked at how Infrared energy is used for detecting a motion. What other kinds of sensors/methods can you think of, that would activate the lights automatically? Feel free to reply to this email with your thoughts, and we can have a discussion.
Gadget of the week
Healthcare Camera: Dr. Clobo is a smartphone-connected ear scope equipped with 8 LED lights and a high-definition camera. It allows you to easily examine hard-to-see parts of your body, such as your ears, nose, teeth, skin, and throat. The camera captures a clear, zoomed-in video feed and streams it to your phone in real time. Unlike other devices, Dr. Clobo is Wi-Fi connected and does not need Bluetooth.
Thank you for reading!
Have a nice rest of the week, and take care!
Until next Wednesday,
Chendur
