Many sensors in a smart home perform similar functions and we are even talking not just about different sensor manufacturers, or about different types of connections with these sensors, but in general about the types themselves, that is, for example, there is a presence sensor or a motion sensor, that is, they are basically both that and the other determines the presence of a person, and in in this case, of course, you can decide which one to use, one is more expensive, the other is cheaper, one has its advantages, the other has its advantages, and of course you can always think and choose the right sensor, or the right type of sensor.

Presence sensors, they are of course the most usually expensive, sophisticated, they have the ability to detect a person there.

They are also different, there are also cheaper ones, which are historical and quite ancient devices, they simply determine where a person is moving and accordingly they will show, if he is not moving, then they will not show, but at the same time they can react to any other devices, to any objects, air conditioning, fan, doors, curtains happen in different ways and of course also react, and if the motion sensor is passive infrared, first of all, it runs on a battery, unlike the presence sensor, and its consumption is very low, but it also determines just exactly if a person moves, then it reacts to it, if there are any other objects, then it will certainly not react to them, well, there are also interference, for example, it can react to some sunlight or a heating radiator, but by and large they mainly react to humans, but they can also work on pets.

Therefore, it is necessary to select specifically according to the situation, for example, a motion sensor, it also sees only within the room, but it can also look through the walls of the presence sensor and it can certainly be put behind some obstacles, and fixed to the ceiling, and then it will show from there, that is, it is also convenient and of course it is alternative.

Also, for example, there are opening sensors that can be placed on the door they will respond to the opening of the door, in such a way that just the reed switch will open due to the fact that the magnet moved away from it, or moved closer, but you can also put a vibration sensor that will in principle also respond to the opening of the door, butanother, that is, it can, if for example a window is installed, then the opening sensor will respond only when the sash moves away from the frame, and if the vibration sensor, then it can, for example, measure that if the window is rejected, then it can work accordingly, if it is just opened, then it can work that it was opened, but it will not be able to determine whether it is open now or not, that is, they also have slightly different functions, but they are very similar and the vibration sensor can determine that the glass was broken, or the door or window was just hit there, but the opening sensor will not be able to do this, but for example if you use it for the following purposes if you open a nightstand or locker, then they are basically suitable, because it is not so important whether the door is open or not, it is important that the event itself has occurred, that is, the vibration sensor can even in this case, in some cases, it will be more convenient, and in some cases, for example, the opening sensor will be convenient.

When measuring, for example, air quality on CO2, you can also use different versions of devices, you can buy a sensor that measures only CO2 and it works quite well, and they have different features there, of course, there are homemade ones, there are branded ones, but if you look cheaper, then there are such universal sensors that measure just air quality, there it is CO2 that is not the main parameter and in general it can react to any different gases in the air, and it is possible to react to some kind of dust, and therefore there is also an alternative here that you can just buy just a CO2 measuring device, but you can buy devices that have different sensors installed, several at once, but either they make cheap sensors, CO2 is called, but there is actually a universal sensor that measures everything in a row and of course there is no question of accuracy, that is, it can simply show a huge content of CO2, although in fact this is not the case.

There is also a rather interesting way to measure temperature.

Many devices have a built-in thermometer.

It mainly tracks the operation of the device itself, whether it overheats or not.

In some devices, a correction is made in connection with this, if they are heated enough to work more precisely, they measure this temperature accordingly, it is also visible in the smart home system during integration, mainly if it is a zigbee device, it can transmit this information through integration through, for example, Zigbee2MQTT, it can also be used, and there is even a calibration function, and you can basically make it show the real temperature, for example, I have the vibration sensor, it is also the current temperature, of course, there is an overestimated degree of 5, but in principle, if such a calibration is done, it is simply lowered in fact, or in the smart home system it is already processed, reduced, then you can not put a separate temperature/humidity sensor, for example, but simply use this information from the already installed sensor, this is convenient and of course this way you can save quite a lot.

Or, of course, you can just buy a homemade sensor, but this is also essentially a temperature and humidity sensor, and in general there is no alternative here.

The humidity itself probably will not measure in another way, that is, only the humidity sensor can probably measure humidity, but there is also a device, for example, if there is a humidifier, then in principle it can also be a sensor already built in, and it makes no sense to buy a separate device that measures humidity, you can just also if it integrates normally and transmits this information, then how to measure.

But you can always of course find another way, for example, it is clear that if water was consumed in the bathroom, for example, then you can simply assume that there were expenses, for example, on the sensor, on the water meter, determine how much water was consumed and just from this calculation make the assumption that the humidity is high and you need to turn on the fan, if the light is on there for more than five minutes, then the bathroom is used for water and, accordingly, the humidity is high, that is, even in principle, it is not necessary to measure there, that is, there are such ways of obtaining information from other sensors, it is also possible.

An interesting way to still get information about air pressure, then in general, of course, you can just buy an Aqara temperature/humidity/pressure sensor, and it will show the current pressure, or you can actually just use an external weather Internet server to get this information, and also in the smart home system Home Assistant, there is also already built-in weather informers, that is, it essentially shows pressure in the current location there and there is not much point in buying a sensor that can do this, this is also, as it were, actually an alternative.

For example, there are still separate light sensors, they sell, but either there may be an Aqara motion sensor, which has a built-in light sensor, or a Tuya presence sensor, it also has a built-in light sensor, but you can still do it, for example, I have a webcam, there are actually several of them, there are also quite cheap ones.

300 rubles, that is, they basically shoot in a room and just by them you can see that when shooting I take a frame once a minute and I save this frame as a jpg file and by the size of this file it is easy to determine what the illumination of the room is, you don't even need to open it, disassemble it with some libraries, that is, you can just look at the size and understand that if there is an acceptable dependence on compression, depending on the size of the image, if you allow 10 kilobytes, then the room is dark because due to compression, the picture becomes very small, if the brightness is high, then the detail is higher and, accordingly, there can be let's say 100 kilobytes, and due to this, you can easily determine that such illumination is low, then you need to turn on the light if the illumination is high, then the light should be turned off, or not turned on, that is, this is also a way to get around for example, and the smart home system to transmit information about what is light, but you can also track it by time, for example, that first you can determine what day of the week is by time and you can also understand what the weather is and, accordingly, if it is clear on the street, then it means in principle this is summer, then the brightness is high, of course, not necessarily.

For example, I make it even easier to share, I do not use the light sensor in the room to control the brightness of the dashboard, I actually just based on the time and position of the switches, that is, if the light switches are turned on, then accordingly there is a certain brightness in the room, and no matter what time of day, the brightness will always be the same, less, so depending on this, after a certain time, if the sunset has already come, then I have to turn on the light switch or remotely, it doesn't matter if I turn it off anyway, the information is transmitted to the smart home system, then I understand that the room has such and such illumination, that is, I basically don't need to measure anything else, I I immediately adjust the parameters of the dashbodra illumination so that it is comfortably visible, that is, if I would use the light sensor there, it costs of course, but firstly it has a delay, and secondly it does not always see correctly what is happening, it needs to be placed correctly, for example, if some lamp does not work properly.

if it falls directly on it, then it just won't show this brightness, or it might fall on it, and it will underestimate and work incorrectly, in other words, this is also an alternative way to get information in the smart home system.

Automation in a smart home should be useful and create additional comfort, but sometimes everything goes wrong… The reasons for this, and how to configure everything, see on my channel.