The P918 is a pyroelectric infrared sensor that integrates a digital intelligent control circuit and a human body detection sensitive element in an electromagnetic shielding cover. The human body sensing sensor couples the sensed body motion signal to the digital smart integrated circuit chip through a very high impedance differential input circuit. The digital smart integrated circuit converts the signal into a 15-bit ADC digital signal when the PIR signal exceeds the selected digital valve. The value will have a timed REL level output.
Digital signal processing, low voltage, low power consumption, and work instantly after startup.
Two-way differential very high impedance sensor input
Second-order Butterworth bandpass filter with built-in infrared sensor to shield input interference at other frequencies
Sensitivity, timing time, illumination sensor Schmitt REL output.
3. Performance parameter
1.Maximum Ratings (Any electrical stress that exceeds the parameters in the table below may cause permanent damage to the device.)
Parameter symbol Minimum Maximum unit Note
Voltage Voo -0.3 3.6 V
Operating temperature Tst -20 85
pin limit Into -100 100 mA
storage temperature Tst -40 125
2.Working conditions (T=25 °C, V DD = 3V, unless otherwise specified)
Parameter symbol Minimum Typical Maximum unit Note
Voltage VDD 2.7 3 3.3 V
Operating temperature IDD 12 15 20
Sensitivity threshold VSENS 120 530 V
Output low frequency LOL 10 mA VOL < 1V
Output high frequency LOH -10 mA VOH > VDD-1V)
REL low level output lock time TOL 2.3 S Not adjustable
REL high output lock time TOH 2.3 4793 S
Voltage input range 0 VDD V Adjustment range between 0V and 1/4VDD
Input bias current -1 1
Input low voltage VIL 0.2 VDD V OEN voltage high to low threshold level
Input high voltage VIH 0.4VDD V OEN voltage low to high threshold level
Input Current LI -1 1 Ã VSS < VIN < VDD
Oscillator and filter
Low pass filter cutoff frequency 7 Hz
High pass filter cutoff frequency 0.44 Hz
Oscillator frequency on the chip FCLK 64 KHz
3. Output voltage waveform
4.Output trigger mode
When the pyroelectric infrared signal received by the probe exceeds the trigger threshold inside the probe, a count pulse is generated internally. When the probe receives such a signal again, it will consider that it has received the second pulse. Once it receives 2 pulses within 4 seconds, the probe will generate an alarm signal and the REL pin will trigger high. . In addition, as long as the received signal amplitude exceeds 5 times the trigger threshold, only one pulse is required to trigger the output of REL. The figure below shows an example of a trigger logic diagram. For multiple trigger situations, the hold time of the output REL is counted from the last valid pulse.
5. Extended time ONTIME
The voltage applied to the ONTIME terminal determines the delay time for the REL to maintain the high level output signal after the sensor is triggered. Each time the trigger signal is received, the delay time is restarted. Due to the dispersion of the internal oscillator frequency, the delay time. There will be a certain margin of error.
6. Sensitivity setting
The voltage at the SENS input sets the sensitivity threshold, which is used to detect the strength of the PIR signal at the PIRIN and NPIRIN inputs. When grounding is the minimum threshold of voltage, the sensitivity is the highest. Any voltage above VDD/2 will select the maximum threshold, which is the lowest sensitive setting for PIR signal detection, ie the sensing distance may be minimal. It should be pointed out that the infrared sensor sensing distance is not linear with the SENS input voltage, and its distance is different from the signal-to-noise ratio of the sensor itself, the imaging object distance of the Fresnel lens, the background temperature of the moving human body, the ambient temperature, the environmental humidity, and the electromagnetic interference. Such factors form a complex multivariate relationship, that is, the output cannot be judged by a single indicator. In actual use, the result of the debugging is subject to change. The smaller the SENS pin voltage is, the higher the sensitivity is, the farther the sensing distance is. The S918-H has a total of 32 sensing distances, and the closest sensing distance can reach centimeter level. In actual use, the resistance division method can be used to achieve the adjustment sensitivity.
4.Transmission spectrum of window material
6. Size angle bitmap ˆmm)
7. Application circuit
When there are stains on the window, it will affect the detection performance, so please pay attention.
The lens is made of a weak material (polyethylene). When a load or impact is applied to the lens, malfunction and performance deterioration may occur due to deformation and damage, so avoid the above.
Failure to apply static electricity of ±200V or more may cause damage. Therefore, please pay attention to the operation, avoid touching the terminal directly by hand.
When soldering a wire, solder the soldering iron at a temperature of 350 ° C or less and soldering within 3 seconds. When soldering through a solder bath, performance may deteriorate, so avoid it.
Please avoid cleaning the sensor. Otherwise, the cleaning liquid may intrude into the inside of the lens, which may cause deterioration in performance.
When using the cable wiring, it is recommended to use shielded wires to minimize the influence of interference.