Technical Principle Of Infrared Forehead Temperature Gun

1. Appearance drawing

A complete forehead temperature gun product is composed of shell, internal circuit board and battery. The shell belongs to the category of structural engineer design, which needs to be lightweight and durable. The following focuses on the internal structure of forehead temperature gun.

From the structure of the forehead temperature gun below, we can see that the circuit components are: LED display, infrared temperature sensor, battery, button, buzzer, etc.

2. Hardware structure diagram

According to the above composition, we can draw the general hardware structure diagram of the forehead temperature gun.

Infrared temperature sensor: it is used to collect the temperature of human body / object. The infrared forehead temperature gun is usually 1 ~ 3cm away from the forehead. The collected data is amplified by the signal amplification circuit. The signal amplification circuit is optional.

MCU microprocessor: it receives the data of infrared temperature sensor for processing. For analog sensor, it needs to add a / D conversion circuit to convert analog signal to digital signal, and then to MCU for processing; for digital temperature sensor, it can be directly processed by MCU.

Key module: used for mode switching, measuring objects, measuring forehead, measuring neck and other mode switching. The key can be customized, and can be used as power on key, system reset key, etc.

LCD display screen: MCU control, used to display temperature data.

Buzzer: alarm module, MCU set the normal temperature range, such as 35 ~ 37.3 ℃, over the upper limit or lower than the lower limit, the buzzer will give an alarm, if the temperature is too low or too high, it will not be normal.

Crystal oscillator circuit: used for MCU micro processing clock, providing oscillation source.

Battery: the battery is the main power supply of the whole system. Because of the portability of the forehead temperature gun, it must be battery powered. The most important thing for battery powered products is low power consumption. When not working, the system needs to enter sleep mode to achieve lower power consumption and prolong battery life.

Power management: the power supply voltage of modules such as infrared temperature sensor, display screen and buzzer is not necessarily the same. The battery needs to be converted to the appropriate voltage value to supply power to each module. Of course, rechargeable batteries can be used to add charging circuit.

3. Infrared temperature sensor

Forehead temperature gun is actually a single-chip microcomputer processing system, the most important is the infrared temperature sensor module, the sensor also determines the accuracy of measurement, the following is a commonly used infrared temperature sensor mlx90615, mlx90615 is a digital sensor, the development does not need to add a / D conversion circuit, high precision can reach 0.2 ℃, because of its small size and convenient development, it is now used There are more.

Small size, reduce the occupation of internal circuit space, can make the product more portable.

The working voltage is 3V. The lower the voltage, the lower the power consumption. The current in power-down mode is only 1.1ua, which means that the battery power consumption is very small when the thermometer is not working. This parameter is very important for battery powered products.