Smart infrared forehead temperature gun chip/PCBA solution development
The intelligent infrared forehead thermometer can measure the body temperature of the human body in a non-contact close range. In special circumstances, in order to avoid direct contact with the human body and prevent cross-infection, the intelligent infrared forehead thermometer is needed in many places. The smart infrared forehead thermometer provided by the 6108 program is fast and accurate, and the measurement range is wider.
table of Contents
1. Introduction of smart infrared forehead temperature gun chip solution
2. Intelligent infrared forehead temperature gun chip design scheme
Three, the detailed parameters of the smart infrared forehead thermometer chip
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1. Introduction of smart infrared forehead temperature gun chip solution
The core chip of the intelligent infrared forehead thermometer is mainly composed of ADC chip and control chip design, which can realize functions such as button control, LCD display, and power detection.
The working process of the intelligent infrared forehead temperature gun: The intelligent infrared forehead temperature gun is composed of optical system, photodetector, signal amplifier, signal processing, display output and other parts. The optical system collects the infrared radiation energy of the target in its field of view, and the size of the field of view is determined by the optical parts and position of the thermometer. The infrared radiated by the object to be measured first enters the optical system of the thermometer, and the optical system condenses the incoming infrared to make the energy more concentrated; the collected infrared is input to the photodetector, the key component of the detector is the infrared sensor, Its task is to convert the optical signal into an electrical signal; the electrical signal output from the photodetector is converted into the temperature value of the measured target after being corrected by the amplifier and signal processing circuit according to the internal algorithm of the instrument and the target emissivity.
Smart infrared forehead temperature gun chip/PCBA solution development
2. Intelligent infrared forehead temperature gun chip design scheme
In order to expand the temperature measurement range, this circuit uses 9V battery power supply. First, a high-voltage LDO RS3002 converts the battery voltage to 3V for the entire system, including powering devices such as single-chip microcomputers, backlights, and operational amplifiers, and then uses a low-power The consumption of LDO RS3236 is reduced from 3V to 1.5V. The purpose of this is to provide a reference voltage for the thermopile so that the entire measurement temperature range can be expanded. In order to be able to calculate correctly under different ambient temperatures, the single-chip microcomputer must also read the current ambient temperature. The implementation method is to read the voltage point of the NTC resistance inside the thermopile and the fixed 100kΩ resistor divider.
Since the output resistance of the thermopile is relatively high, a non-inverting amplifier should be used in the topology of the op amp. The amplification factor should be more than 100 times. It is necessary to reserve a low-pass filter to reduce the output noise. In order to maximize the temperature resolution, the op amp is required The 1/f noise is less than 5uVpp, and the DC offset voltage is less than 10uV. In this circuit, the operational amplifier RS8551 used has an ultra-low offset voltage, which is suitable for DC or low frequency signal amplification.
Smart infrared forehead temperature gun chip/PCBA solution development
Three, the detailed parameters of the smart infrared forehead thermometer chip
1. The main features of RS8551 are:
Wide working voltage range: 2.5V~5.5V.
Ultra-low offset voltage: 1uV typical, 5uV maximum.
Ultra-low temperature drift: typical value 5nV/°C, maximum value 50nV/°C.
Ultra-low input bias current: 50pA.
Unity gain bandwidth: 4.5MHz.
Quiescent current: 640uA per channel.
0.01Hz~10Hz noise: 0.75uVpp
High voltage LDO and low voltage LDO: RS3002 series and RS3236 series.
2, the main features of RS3002 are:
Wide input voltage range: 2.5V~36V, suitable for common 9V battery input.
Continuous output current: 150mA.
Ultra-low quiescent current: 2.5uA.
Low pressure drop: 10mV/mA.
Ultra-high PSRR: 54dB@1KHz.
The output voltage accuracy is optional: 1% or 2.5%.
A variety of fixed output voltages are available, available in SOT-23, SOT-89-3, and SOT-23-5 packages.
3, the main features of RS3236 are:
Wide input voltage range: 1.7V~7.5V, support 4 dry battery input.
Internal maximum output current limit point: >500mA.
Ultra-low quiescent current: 20uA.
Ultra low dropout voltage: 1mV/mA.
High PSRR: 70dB@1KHz.
The output voltage accuracy is optional: 1% or 2.5%.
A variety of fixed output voltages are available, with SOT-23, SOT-89-3, SOT-23-5, UTDFN-1*1-4L packages available.