Motion sensing light

Nowadays we have seen multiple automated machines and gadgets. The human desire to accomplish more with less has extended into the security systems, where devices like motion-sensing light bulbs provide high levels of security while taking up little space and using less power than convention lighting systems. The technology behind this is old and most of us aware of the infrared light detection mechanism to detect motion. If you are not aware of this, don’t worry you are at the right place. Before going to dig up the engineering of this gadget, let’s introduce it.

What is a Motion-sensing light?

A Motion-sensing light is turned ON as soon as the motion sensor detects you. Most of the motion sensors in this gadget are using infrared for detection mechanisms.

Before understanding this mechanism first of all let me tell you that motion sensing can be achieved by using other techniques also like ultrasound, microwave, or photosensor. All of these are techniques are using active sensors. They emit some kind of energy (sound, microwave, or light) into the environment to detect a change of some sort. The motion sensors of most of the lights (including other security systems) are using passive sensors that detect infrared energy. These sensors are therefore known as PIR (Passive Infrared) or Pyro-electric sensors. Infrared energy detected by this passive sensor and it turned ON the Motion-sensing light.

We have a brief about the motion-sensing technology of this instrument. Now it’s time to see the engineering behind this gadget.

Engineering inside it:

A Motion-sensing light includes below important hardware units:

  1. Power adapter
  2. Sensor
  3. Light bulb

Power adapter:

It is the primary unit of this gadget. The power adapter converts the input AC power to DC power and delivers it to the Sensor and Light bulb module of this gadget. The adapter circuit has several diodes, resistors, capacitors, transistors, and a high-frequency transformer. Its working is similar to an adapter circuit of LED or Smart bulbs but output current or load handling capacity is good to drive both modules (Sensor and Light bulb).


We have already discussed the type of sensor inside the Motion-sensing light bulb. It is a PIR sensor. These sensors are a little bit completed than other automation sensors because multiple variables affect the sensor performance.