How to make a motion sensor yourself?

Movement sensors are now sold in almost all household appliances stores. The motion sensor for lighting is used in everyday life, for example in the entrances. Of course, did you pay attention to the lamps that light up when you approach them? This is one example of the use of motion sensors in everyday life, and there are still many such examples. The motion or motion sensor is used in home and industrial alarms, they are in robotization and automation schemes, motor speed measurement, etc. But in addition to industrial use, the motion sensor can also be used in everyday life. Moreover, if you make a motion sensor yourself, then knowing the scheme of its operation, you can use such a device to turn on or turn off any household appliances.

Let's look at the main parts of the product. The first thing you need to start with is to make a motion sensor yourself, this is to ensure its power supply. The power source should be safe first, have small dimensions as small as possible, and be designed for long-term operation under load. A standard power supply for charging batteries or any other with an output voltage of five volts is well suited for this purpose. It's easy enough to make the motion sensor yourself, it does not require scarce or expensive parts.

Now we select a photocell, for our purposes any one will do, its area does not matter, a little later we will know why. Photocell cathode Connect to the positive terminal of the power supply. Now the current is limited by the photocell, the rated current must flow through it, otherwise it will just burn out. According to Ohm's law, we calculate the resistance value, and solder it to the anode terminal of the photocell.

Now the tuning resistance is 10 kOhm, one of the leads is sealed to minus the supply, the second to the free end of the current-limiting resistance. Now we collect the circuit of the emitter follower using a transistor with an npn junction. Its base is soldered to the free end of the tuning resistance. The collector is directly soldered to the positive terminal of the power supply, and into the emitter circuit we switch on a small power relay with a rated voltage of five volts. The second end of the relay coil is soldered to the negative terminal of the source. The relay contacts are assembled according to the self-picking scheme, that is, when the first trigger of the motion sensor is activated, the relay will be tightened and provide its own power with its contacts. Free relay contacts go to the load, for example, lighting or tape recorder, it all depends on your imagination. As you can see, it's easy to make the motion sensor yourself. The main thing in this case is not to overload the contacts, because the relay used in the circuit is of low power. But as a load, we can use one more relay, with more powerful contacts, which will provide you with the load you want.

To reset the device to its original state, it is enough to interrupt its power for a short time. Turn on the power circuit of a small switch with self-reset. As a source of radiation, you can use a laser pointer, providing it with constant power from our source. Now it is clear why the area of the photocell did not play any role, the emission of the pointer monochrome and the light beam will not change in area.