Infrared motion sensor sr 501. Motion sensor connection diagrams
Motion sensors are devices that respond to moving rather than stationary objects. This is how they differ from presence sensors configured to be triggered by the disappearance of moving objects in the controlled area.
In other words, a device that controls movement should work when a person is inside the observed space, when he moves or freezes, but at least just moves his fingers. At the same time, presence control devices are triggered when people have completely left the room or a completely frozen person remains in it, not making any movements.
Principles of operation of motion sensors
Both groups of these sensors can work based on:
capturing sound vibrations with sensitive acoustic systems;
perception of thermal radiation caused by the human body by infrared receivers passive action;
overlapping invisible to the human eye infrared rays directed from the emitter to the receiver active method.
There are other ways to detect a moving person, but they, like the acoustic method, are rarely used. And in home appliances Most often, motion sensors are used that work with electromagnetic oscillations of waves located in the infrared spectrum. They are described in .
For IR sensor receivers general principle work.
Motion sensors and presence sensors capture infrared radiation that spreads in all directions from any objects located in the field of view. Thermal rays, as in a conventional optical system, for example, a camera, fall on a segmented lens that works according to the Fresnel principle.
This glass or optical plastics construction is created with large quantity concentric sectors / segments, each of which forms a narrow beam of parallel thermal rays on the IR sensor.
It is also called the term "PIR sensor" because it has a pyroelectric effect - it creates electric field proportional to the received heat flux. The received signal is processed by electronic devices.
For most sensor designs, the pyrodetector works with analog values. An example is .
It has small dimensions, works on the basis of a microcircuit, has three terminals for connecting power and load wires, and two adjusting potentiometers. When triggered, it produces a control electrical signal with a voltage of 3.3 volts and a current of several milliamps.
Recently, blocks have been introduced that perform double conversion and command processing based on .
This allows the use of microprocessor devices and computer technologies for further signal conversion and the formation of various control algorithms for automatic devices.
Both analog electronic and digital sensors are connected to power supplies and have output devices that switch the load in the primary network.
One of the principles is laid down in the electronics operation algorithm:
motion detection;
stay trips.
When a person appears in the field of action of the sensor, by his presence he makes changes to the heat balance environment, and all his movements are recorded through the Fresnel lens as a camera lens. Electronic units are triggered and give an electrical signal to the control contact.
This completes the functions of the sensor itself, although the process of switching actuators has not yet been completed, and the power of the control signal of the motion sensor for switching lighting fixtures, turning on a sound siren, sending SMS to a mobile phone, or performing other tasks is not enough.
This signal must be amplified and transmitted to a powerful contact for switching the load.
The motion sensor HC-SR501 discussed above cannot perform these functions on its own. To implement them, you can assemble a simple transistor switch on.
The VCC and GND terminals of the motion sensor and the key are powered by =4.5÷20 volts from an additional source, and the control signal from the sensor's OUT pin is fed to the amplifier terminal of the same name. The appropriate voltage load is connected to the output circuit.
If you use this scheme to turn on your mobile phone, you can receive SMS on your mobile phone, which will be a signal about the appearance of unexpected guests in the security zone.
In most ready-made modules for lighting circuits with motion sensors, its amplifier and power contact are built-in, switching the load circuit. The designs of such blocks, powered by a network of ≈220 volts, have three terminals for connecting wires directly on the case, two of which supply power (phase L and zero N) and the third L "together with zero N is used to switch lamps.
Active Motion Sensors
Devices that work on the principle of channel control between the IR emitter and receiver have approximately the same algorithm, are tuned to a common frequency, like the remote control remote control TV or wireless computer mouse with their receivers. They can have an autonomous power supply independent of the stationary electrical network.
In this case, one of the layouts of the modules of the direct or rotary method of forming a path using mirrors is performed.
Sensor connection diagrams
Wiring diagram for easy connection shown in the picture.
With this connection, the operating mode of the lamp fully corresponds to the algorithm laid down electronic circuit, and is adjusted by adjustment potentiometers.
On the simple designs sensors, two regulators are installed:
1. LUX - the level of illumination, upon reaching which the sensor is triggered (for example, there is no need to use electric light in sunny weather). For regulation, its highest value is initially set;
2. TIME - the duration of the timer, or, in other words, the length of time in which the lamp will be on after motion is detected. Usually, a minimum value is set, because with each new movement, the sensor will constantly restart.
Usually these two adjustment parameters are enough to adjust the control of household lamps. There are two more potentiometers:
1. SENS - sensitivity or range. It is used to reduce the control zone in cases where it is not possible to limit it by changing the orientation of the motion sensor;
2. MIC - the acoustic noise level of the built-in microphone, at which the sensor is triggered. But in living conditions this function is not needed - the sensor will be triggered by extraneous sounds of passing cars, children's exclamations ...
Scheme of connecting a luminaire to two sensors
This method is used in places where it becomes necessary to control lighting from two remote points with limited visibility for one sensor.
The terminals of the same name are connected in parallel to each other and output to the power supply network and the lighting device. When the output contact of any sensor is triggered, the lamp lights up.
Wiring diagram via switch
This method is used when a motion sensor block is added to an existing lamp with a switch. When the switch is turned on, the circuit operates completely as it is configured by the electronics. And when the contact is open, the phase is removed from the power supply and the motion sensor is disabled.
Practice has shown that among apartment owners, when leaving the premises, the habit of automatically turning off the light with a switch has been preserved. After that, when a person enters the room, the motion sensor is disabled. To exclude such situations, the switch contacts are shunted, which makes the transition to the previous circuit.
In this circuit, the switched on switch completely bypasses the output contact of the motion sensor. It is used when a person is in a fixed position for a long time, and the shutter speed of the timer is short and you have to make extra distracting movements to turn on the lamp.
Scheme for connecting powerful loads by electromagnetic devices
A motion sensor block with low power contacts can be used for very high power lighting fixtures. For this, an intermediate device is used - a relay or contactor of the appropriate ratings. Its winding is connected to the low-power contact of the sensor, and the power contact switches the load of the lighting system.
In this circuit, as in all others, it is necessary to accurately calculate the switched powers and select power contacts for them. After being put into operation, the load currents must be measured and compared again with the power of the contacts. For reliable long-term operation of the system, it is necessary to create a power reserve.
Such a circuit with electromagnetic devices is able to work reliably and for a long time. But, it has two significant drawbacks:
1. increased noise level and emerging electromagnetic interference accompanying the process of moving the armature during switching;
2. constant wear of the contact system due to discharges that occur when the circuit breaks, which requires periodic preventive maintenance.
Triac and trinistor circuits are deprived of these shortcomings.
Scheme for connecting powerful loads with semiconductor devices
In this case, there are no all kinds of noise and interference. But for the operation of a semiconductor device, it is necessary to convert the control signal of the motion sensor into a harmonic that coincides in frequency with the mains voltage. To do this, a special matching scheme is created, which issues alternating current on the .
When the matching circuit is operating, the triac is open. and the lamps are on. When there is no control signal, the triac is closed and the lighting controlled by it is turned off.
The disadvantage of this scheme is the complexity of the design of the matching signal of the electronic device.
Selecting the installation location and sensor orientation method
Depending on its design, the motion sensor can have a different viewing angle to control the space from a few degrees to a circular view, which is usually used for ceiling mounting.
These angles are distributed in the horizontal and vertical planes, determine the observation area, and are indicated in the documentation.
Sensors designed for wall mounting usually have a view of about 110÷120 or 180 degrees horizontally and 15÷20 vertically.
Outside this space, no movements are detected by the sensors. Therefore, when installing a motion sensor, it is important not only to select them according to the viewing characteristics, but also to adjust them after installation to correct the direction. Designs with a movable viewing body facilitate adjustment, while for other devices it is necessary to think over and perform the initial installation very carefully.
Ceiling sensors typically have a 360 degree horizontal field of view that extends in a cone from top to bottom. His zone of control is much larger, but it can also have blind space in the corners of rooms.
Influence of foreign objects on the operation of sensors
When installing and configuring a motion sensor, it is important to take into account the conditions for their placement, assess the impact on their reliability of nearby objects and various sources energy. Thermal heaters, swaying tree branches, passing cars, elevators going up/down, and other objects can cause the devices to cause frequent false alarms.
When there is no way to get rid of them, then the sensitivity of the device is coarsened with a potentiometer or the interference zone is shielded.
Infrared motion sensor (PIR Motion sensor) HC-SR501 (DSN-FIR800) used to detect movement of objects in the controlled area that emit infrared radiation (heat). The principle of operation of the sensor is based on pyroelectricity.
Pyroelectricity is the property of generating a certain electric field when a material is irradiated with infrared (thermal) rays. A Fresnel lens is installed above the sensing element, which is used to increase the viewing radius and amplify the incoming infrared signal.
Modules HC-SR501 is a module consisting of a 500BP IR sensor, a Fresnel lens, and a BISS0001 microcircuit control module. The module operation mode is set by a jumper (mode H or mode L).
Operating modes
The module operation mode is set by a jumper. There are two modes - H mode and L mode. In the photo, the module is set to H mode.
- H mode- in this mode, when the sensor is triggered several times in a row, its output (at OUT) remains at a high logic level. Red jumper.
- L mode- in this mode, a separate pulse appears at the output each time the sensor is triggered. Yellow jumper.
Note:
On this instance, there is no block for the jumper, but there are contacts on the board for sealing the jumper, and option H is already closed by a printed conductor.
To select L mode, you must remove the factory jumper (as shown in the picture).
Key Features of HC-SR501
- Color: white green
- Dimensions: 3.2 cm x 2.4 cm x 1.8 cm (approx.)
- Infrared sensor control board
- Sensitivity and delay time can be adjusted
- Working voltage: DC 4.5V-20V
- Current:<60 mA
- Output voltage: high / low signal level: 3.3V TTL output
- Detection range: 3 - 7M (can be adjusted)
- Detection range:<140 °
- Delay time: 5-200S (can be adjusted, default 5s -3%)
- Time blockade: 2.5S (default)
- Trigger: L: Non-repeatable trigger H: Repeat trigger (default)
- Operating Temperature: -20 - 80°C
- Trigger method: L unique trigger / H repeat trigger
Contacts:
OUT(output signal) – contact for data exchange between the sensor and the microcontroller;
VCC- supply voltage (4.5 - 20v);
GND- general contact. 
Infrared motion sensor HC-SR501 it is not recommended to use in places with sudden temperature changes (a sharp burst of infrared radiation) from heating, it will be perceived as the appearance of a moving object, which may cause false alarms.
The HC-SR501 module is often used in burglar alarms, as well as in smart homes to control lighting when a person enters the room.
In the struggle for the life of incandescent lamps on the landing, I tried a fairly large number of schemes for their protection. These were both simple diodes and soft start circuits, and acoustic sensors. Not all have proven themselves on the positive side. Going to the Aliexpress website, I came across a pyroelectric sensor HC-SR501. At a price of less than one dollar, the sensor has a number of positive qualities, namely: power supply from 5 to 20 volts, motion detection zone from 3 to 7 meters, turn-off delay from 5 to 300 seconds. (I don’t see the point in giving a full description here, since this information is more than enough). Externally, the sensor looks like this:
Just what you need to illuminate the landing, where people do not walk so often and the constant glow of the lamp is useless.
The photo below shows the connection points for the common wire (GND), the trigger signal output (Output) and the power bus (+ Power). The board has two variable resistances: one regulates the response zone (Sensitivity Adjust), the other the turn-off delay (Time Delay Adjust).
In addition, there is a jumper for switching modes. H and L. In mode L the sensor, having fixed the movement, outputs a high-level signal. Regardless of whether there is further movement in the detection area or not, after a set delay time (for example, 30 seconds), the output signal will be turned off.
In mode H the output signal will disappear only after the delay time has elapsed from the moment of the last motion detection in the detection zone. That is, they passed through the movement zone - it will turn off after 30 seconds, stay and move in the detection zone for 10 minutes and leave it - it will turn off after 30 seconds. While you are in the detection zone, the sensor will not turn off.
Just what you need to illuminate the landing, where people do not walk so often and the constant glow of the lamp is useless. Having studied the datasheet and materials on the network, I discarded the Arduino use cases as excessively costly and sketched the following circuit.
Functionally, the device consists of three nodes:
- the HC-SR501 sensor itself;
- an actuator consisting of a resistor R3, a transistor VT1, a diode D1 and a relay P1, where R3 and VT1 serve as a link between the sensor and the relay. Without them, the load capacity of the sensor is so low that only an LED can be connected directly;
- transformerless power supply, where R1 is needed to reduce the inrush current (often it can be neglected), capacitor C1 with a rating of 0.47 - 0.68 uF with an operating voltage of at least 250 volts provides an output current of up to 0.05 A, R2 is necessary for discharging capacitor C1 after disconnecting the device from the network.
Why a diode bridge is known to everyone. The filter capacitor should be selected with an operating voltage of at least 25 volts. Well, finally, the zener diode sets the voltage at the output of the power supply at 12 volts. The choice of a zener diode specifically for 12 volts is due, on the one hand, to the supply range of the sensor from 3 to 20 volts, on the other hand, the operating voltage of the relay is 12 volts.
Separately, it is worth mentioning the transistor. This is practically any NPN transistor structure - 2N3094, BC547, KT3102, KT815, KT817, etc. etc.
A relay with almost any coil resistance, a switching voltage of 250 volts and a current of 3 amperes, which will make it possible to safely switch a load of several hundred watts.
