The base of the NPN transistor used for controlling the output relay is connected to the output pin 3 of the IC via a 1K resistor. An LED is also connected through its current limiting resistor at the output of the IC. A relay with its driver circuit is connected between pin 2 and the capacitor’s positive terminal. One resistor of the voltage divider circuit is connected via a 1uF capacitor to the output pin 3 through the 100k resistor. The output of the voltage divider circuit is connected to pin 6 of the IC. In the circuit, pins 2 and 6 are connected, and also pins 4 and 8 are connected. The complete motion detector circuit using a 555 timer is given below. In this project, we are using an active IR sensor module as it is readily available, affordable, and easy to use.ĥ55 Timer Motion Detector Circuit Diagram LED looks exactly like a normal LED but it emits IR instead of the visible colors that we are familiar with. Photodiode is the key component that detects the bounced back radiations. Two main components of an IR sensor module are IR LED and photodiode. This photodiode in this case can only detect Infrared light and not visible light. On the other hand, we have IR modules that send an IR pulse continuously and when it bounces back from an object, the module can detect it by using a photodiode. The PIR sensor does not emit any IR radiation but only detects the radiations and thus it is called “passive”. All the hot objects generate these IR radiations and by detecting these radiations, we can sense the motion. Infrared comes in the place of the electromagnetic spectrum which is not visible to naked eyes. IR stands for infrared radiations/light and it is the most common way of detecting motion. Components Required to Build a Motion Detector CircuitĪ list of components required to build a motion detector circuit is given below: This is the application of that circuit, we will also demonstrate the circuit by designing it on a piece of perf-board. In our previous tutorial, we learned about the 555-timer as a latching circuit. Since this circuit uses a digital timer IC, so the operation of the circuit is fast and accurate with even faster detection speeds. The 555 timer IC is used as a switch here. So, in this tutorial, we are going to use an IR sensor with a NE555 Timer IC to detect motion and switch the AC load according to that. It is also very common in manufacturing industries, like on conveyor belts where the presence/position of a particular object has to be detected. These circuits are mainly used to drive AC load (like lights, fans) in home automation or IoT projects. Motion sensor circuits are there on the Internet for quite a while now.
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