Now-a-days parents are getting too busy with their works and tend to forget about the child and babies. After a facing a small accident by the child and later parents notice it, will not affect much as they couldn’t able to stop the accident. To overcome from this small mishap to the kids called child monitoring system where, a PIR sensor is placed in the living of the child. Once the child starts to move in the living room from the placed where the child is placed then the sensor will alert the alarm. This sign will help the parents to monitor the baby and look after. This will prevent the child from many dangerous situations. In this article we will study about the PIR sensor circuit working and how it really monitors the child from all sorts of dangerous situations.
Child Monitoring System Working
The child monitoring system mainly includes what is a PIR sensor, working, circuit diagram with working, advantages, disadvantages and its applications.
What is a PIR Sensor?
Pyroelectric (“Passive”) Infrared (PIR) sensors allow to sense motion. This sensor is used to detect whether a human has moved out or in of the sensor range. They are inexpensive, low-power, small, easy to use and don’t wear out. For that reason they are commonly found in gadgets and appliances used in homes or businesses.
PIR is made by a pyroelectric sensor which detects the levels of infrared radiation. Every PIR sensor emits some low level radiation, and for the hotter things the more radiation is emitted. This sensor motion detector will basically split in two halves. The reason for that is that we are looking to detect motion, i.e. Change not average IR levels. Here the two halves are wired up so that they cancel each other out. Suppose if one half sees more or less IR radiation than the other, the output will be high or low.
This sensor will have a bunch of capacitors, resistors, inductors and also supporting circuitry. It is inexpensive chip. To emit a digital output pulse from the analog sensor the chip takes the output of the sensor and does some minor processing on it
It is to detect when a person has entered or left the area, or has approached, PIR sensors are great. PIR sensors are basically requires low power. It is of low cost, have a wide lens range, are easy to interface with and pretty rugged. The drawback of the PIR sensor won’t tell number of people is around or how close they are to the sensor, the lens is often fixed to a certain sweep and distance and they are also sometimes set off by house pets.
How Does it Work?
PIR sensor is a little more complex than other sensors this is because there are multiple variables that affect the sensors input and output.
As we have discussed above that the PIR sensor itself has two slots in it, each of the slots is made of a special material which will be sensitive to IR. In the ideal case of sensor, both slots detect the same amount of IR, the ambient amount radiated from the room, outdoors or walls. Let say a warm body like an animal or child passes by, then the change of pulses is detected by as follows.
It first intercepts the one half of the PIR sensor, which causes a positive differential change between the two halves.
When the warm body leaves the sensing area, the reverse happens, whereby the sensor generates a negative differential change.
Circuit Diagram Working
PIR sensors operate at 3-9V DC. Depending on the surrounding conditions PIRs takes some time to get stable itself. So one can find, LED turn OFF and ON randomly for about 10-60 seconds.
Whenever the child moves which is said as motion is found then LED blinking. The jumper is placed between middle PIN and outer corner PIN. This is called as “Non-repeatable trigger” or “non-retriggering” and the jumper is said to be in L position. LED will blink continuously in this position until there is motion.
After connecting this jumper between middle PIN and inner corner PIN, till there is any motion LED will stay ON all the time. This one is called “Repeatable trigger” or “retriggering” and jumper said to be in H position.
To set the time, distance range and delay, here two potentiometers are used. The LED will get ON when output is HIGH during the time delay. In the case of Non repeatable triggering, after the time delay the OUTPUT will automatically become low.
In the case of Repeatable triggering, after time delay the OUTPUT will also become lower, but in case if there is a continuous child monitoring system activity; even after the time delay the OUTPUT will remain HIGH. There will be Distance Adjustment potentiometer which can be turned in clockwise rotation, and increasing the sensing distance like about 7 meters, whereas on the other hand, the sensing distance decreases to about 3 meters.
By turning the time delay potentiometer in the clockwise direction the sensor delay lengthened to 600S, 10 minutes, and if turned to the opposite side, it shortens the delay by 0.3 second. Basically PIR sensor detects infrared up to 8 to 14 micrometers of wavelength and will have the range of 3-15 meters with a field of view less than 180 degrees. This range may also vary depending upon different models. Some ceiling of PIR sensors can be covered at 360 degrees.
The IR sensor will be is housed in a hermetically sealed metal which is used to improve noise or temperature or humidity immunity. There is also a window which is made by IR- Transmissive material it is coated silicon because it protects the sensing element. Back of the window there are the two balanced sensors.
Pyroelectric infrared sensors and IRA series will exhibit high sensitivity and reliable performance.
- High immunity to external noise
- Higher in cost-performance
- Custom design is available
- High stability with temperature changes
- Slight movement can be detectable.
- High sensitivity and excellent S/N ratio
- Household and also used for other appliances
- Lighting appliances
From the above discussed circuit diagram it is clearly understood that how the PIR sensor will work in different modes. It is so simple circuit and can be implemented in many places where you need to find the movement of any living being. In this article it is used especially for the baby monitoring system.
Here in a room many PIR sensors can be used and also can be placed around the house too for the better monitoring of the child. When it detects the movement of the child where he/she is not supposed to go then if in case the child moves into that place, then the PIR sensor will alert the alarm and this will indicate to the parent that the child is moving in the restricted place. This will definitely help from happening any accident. One sensor may not cover the entire room so it’s better to have multiple sensors.
Child monitoring system is easily installed at home without any supervision of the technical person. Once it’s installed one can have a peace of mind rather keeping an eye all the time and getting disturbed from the regular work.
- Application of this device is good for security reasons.
- Military people can also make use of it, especially during night time.
- Some of the other places where the PIR sensor can be used are parking area, supermarket, library, hospital, grocery stores, garden and many such public places
- In this globalization world save electricity is the important fact and PIR sensor looks after it effectively.
- It can make use of these detectors in equipments as well as appliances
- It is a good source of saving energy
- Evaluation of moving object becomes easy due to the intensity of infrared lights.
- You can also adjust it according to the outside changing temperature.
- You don’t have to get dependent on exterior sources of energy as electricity gets produced from infrared lights.
- Spotlight of IR light is possible because of lenses present in PIR sensor.
- It responds aptly to living beings (human, animals) motion and can get adjusted to body temperature.
- It can make use of it on DVDs or television sets or VCRs.
- PIR sensors have a property of only receiving infrared light and cannot emit it like other types of infrared sensors.
- They can be expensive to purchase, calibrate and install.
- The chances of not covering the entire room. So multiple sensors have to use
- The chances of triggering the motion detector then you don’t want to
- If the outside detector is placed or mounted too close to a light that stays on at night then it will be triggered continuously by bugs.
- The sets shutoff of this sensor will be too short i.e. <30 seconds
By the reliability of a motion sensor can be affected by rapid environment changes and direct sunlight
- Some of the things like direct wind from the cooler/ air conditioner, fire places or heater can affect because it actually detects the change in the IR energy. To specifically the heat energy emitted by a normal human skin temperature.
It can be concluded that the above article on To Build Child Monitoring System Circuit and Its Working Principle is understood clearly about its basic function, working principle, advantages, disadvantages and applications. If in case any of the point is not clear or to implement electrical projects, please feel free to ask by commenting in the below section.