How to create a motion sensor

Today we bring you an article from a blog user who asked for it through the suggestions section. The aim of this tutorial is to explain how to build a motion sensor.. This device can detect all kinds of events occurring in its environment.

How it works is based on the change of state that occurs when an object cuts the wave path between two sensors.. The received signal is passed through a signal comparator which, in the case of finding any difference between the sensor signals, causes a warning element to be activated (loudspeaker, siren, light bulb, etc.).

A circuit that follows the above operation is as follows:

Circuit of a motion sensor.

Circuit of a motion sensor 2.

In the circuit of the image, we can see that everything starts with two LDR resistors (its value varies depending on the received brightness). The signal from these two components are first passed through a operational integrated circuit 741 which acts as a comparator of the two signals and returns a signal if the two signals are different. Subsequently, the signal is calibrated with a set of resistors and is made to reach a 555 timer which after 10 seconds activates the buzzer.

Another option is to use a device that sends laser beams to a photoresistor that varies with heat. A typical laser sold at a flea market can be used. When a person cuts the path of the light beam, the value of the photoresistance will change and the alarm will go off.

The outline of this example is as follows:

Diagram of a motion sensor.

As you can see the assembly is not very complicated if you have a minimum knowledge of electronics. The circuits must be built on an integrated circuit board. To learn how to do this you can go through the following tutorial: How to make a printed circuit board.

32 thoughts on “Cómo crear sensor de movimiento”

  1. Martin Aleman

    In the first diagram there are no R's and C's values. In the second one I don't know what is the CL or DL (it doesn't look good), but which component is it?

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