Laser projector having high heat dissipation efficiency and control method therefor

Abstract

The present application relates to the field of laser projection technologies, and specifically discloses a laser projector having high heat dissipation efficiency and a control method therefor. The laser projector comprises a housing, a projection assembly mounted in the housing, and an upper cover fixed in the housing. The upper cover divides the internal space of the housing into two chambers. An outer heat dissipation system and an inner heat dissipation system are respectively mounted in the chambers at two sides of the upper cover in the housing. The inner heat dissipation system and the projection assembly are located in the same chamber, the inner heat dissipation system is used for dissipating heat for the projection assembly, and the outer heat dissipation system is used for dissipating heat for a heat dissipation end of the inner heat dissipation system. According to the present application, the outer heat dissipation system and the inner heat dissipation system are arranged, the outer heat dissipation system and the inner heat dissipation system are separated by means of the upper cover, and the outer heat dissipation system is used for dissipating heat for the inner heat dissipation system, so that the projection assembly can be sealed, and high waterproof and dustproof performance is achieved.

Description

Laser projector with high heat dissipation efficiency and control method thereof

[0001] This application claims the benefit of Chinese patent application No. 2023112323489, filed on September 22, 2023. This application incorporates the entirety of the aforementioned Chinese patent application. Technical Field

[0002] The present application relates to the field of laser projection technology, and in particular to a laser projector with high heat dissipation efficiency and a control method thereof. Background Art

[0003] A projector, also known as a projector, is a device that projects images or videos onto a screen. It can connect to computers, VCDs, DVDs, BDs, game consoles, DVs, and other devices through various interfaces to play the corresponding video signals. Projectors are widely used in homes, offices, schools, and entertainment venues. They come in various types, including CRT, LCD, and DLP, depending on their operating mode.

[0004] During normal use, a projector generates a significant amount of heat, which requires heat dissipation. Chinese Patent No. CN200780040754.8 discloses a "projector" comprising a cooling device comprising a compressor, a radiator, a pressure reducing device, and an evaporator disposed on the main body, forming a refrigerant circuit. The cooling device supplies air, which has undergone heat exchange with the evaporator, to the optical element for cooling.

[0005] In actual use, it was found that when using a projector in hot weather, due to the high air temperature of the external environment, when the hot air passes through the evaporator to cool down, the water vapor in the hot air will be pre-cooled and condensed into small water droplets adsorbed on the evaporator, making the inside of the projector in a relatively humid environment, which is easy to cause corrosion to the internal electrical components of the projector; in addition, the internal environment of the projector is connected to the outside, and dust is easily introduced, affecting its service life.

[0006] Summary of the Invention

[0007] In the first aspect, the present application provides a laser projector with high heat dissipation efficiency, comprising a shell, a projection assembly installed in the shell, and an upper cover fixed in the shell, wherein the upper cover divides the internal space of the shell into two chambers; an external heat dissipation system and an internal heat dissipation system are respectively installed in the chambers on both sides of the upper cover in the shell, the internal heat dissipation system and the projection assembly are located in the same chamber, the internal heat dissipation system is used to dissipate heat from the projection assembly, and the external heat dissipation system is used to dissipate heat from the heat dissipation end of the internal heat dissipation system.

[0008] By adopting the above technical solution, an upper cover is provided in the shell, and the internal space of the shell is divided into two chambers by the upper cover. An external heat dissipation system and an internal heat dissipation system are provided in the two chambers respectively. The internal heat dissipation system dissipates heat to the projection component, and the external heat dissipation system dissipates heat to the heat dissipation end of the internal heat dissipation system, so that the projection component can be sealed, the overall sealing performance is improved, thereby better preventing dust and moisture, and the overall service life is increased.

[0009] Optionally, the internal heat dissipation system includes a heat exchange plate, a cooling pipe, a radiator and a cooling pump. A water channel is provided in the heat exchange plate. The cooling pipe connects the water channel and the radiator. The cooling pump is installed in series on the cooling pipe. The cooling pump circulates cooling water between the heat exchange plate and the radiator.

[0010] By adopting the above technical solution, the internal heat dissipation system is configured as a water-cooling system, and the projector's internal heat source components are tightly attached to the heat exchange plate. The cooling water within the heat exchange plate removes the heat generated by the projection component. A cooling pump then pumps the cooling water from the heat exchange plate to the heat exchanger for heat dissipation. Using a water-cooling system to dissipate heat from the projection component, the heat exchange plate is located within a sealed working chamber, and its temperature is kept constant. This prevents condensation on the heat exchange plate due to large temperature differences during the heat dissipation process, thereby extending the overall service life.

[0011] Optionally, a plurality of heat exchange plates are provided corresponding to various components of the projection assembly, and a multi-connector is provided at one end of the cooling pipe close to the heat exchange plate, and the cooling pipe is connected to the plurality of heat exchange plates through the multi-connector.

[0012] By adopting the above technical solution, a one-way multi-connector is set up, and the cooling pipe is connected to multiple heat exchange plates at the same time through the one-way multi-connector. Multiple heat exchange plates can dissipate heat for various components of the projection assembly at the same time, which can effectively improve the overall heat dissipation efficiency.

[0013] Optionally, the external heat dissipation system includes a compressor, a condenser, an expansion valve and an evaporator for cooling the radiator. The condenser, the evaporator and the compressor are interconnected by a pressure pipe, and the expansion valve is connected to one end of the pressure pipe close to the evaporator; the compressor pressurizes the refrigerant in the pressure pipe and sends it into the condenser for heat dissipation, and then inputs the refrigerant into the evaporator after passing through the expansion valve; a fan is installed at the condenser, and the air outlet direction of the fan is toward the outside of the shell.

[0014] By adopting the above technical solution, the external heat dissipation system is set as a refrigerant cooling system. The refrigerant cooling system has high cooling efficiency, can dissipate heat to the radiator of the internal heat dissipation system faster, and has higher heat exchange efficiency; a fan is installed at the condenser, and the fan can quickly dissipate heat to the condenser; the air outlet direction of the fan is directed toward the outside of the shell, which can increase the air flow speed in the shell during the heat dissipation process, and can dissipate heat to other components inside the shell.

[0015] Optionally, the evaporator and the radiator are integrated into a heat exchanger, and a low-temperature channel for the circulation of refrigerant and a high-temperature channel for the circulation of cooling water are provided in the heat exchanger. The pressure pipe is connected to the low-temperature channel, and the cooling pipe is connected to the high-temperature channel.

[0016] By adopting the above technical solution, setting up a heat exchanger and integrating the evaporator and radiator into one, the heat dissipation end of the internal heat dissipation system can be quickly cooled down, and the heat exchange efficiency is higher.

[0017] Optionally, a temperature sensor is provided in the shell on the side of the upper cover close to the projection assembly, and a controller is provided on the side of the upper cover close to the external heat dissipation system. The temperature sensor is electrically connected to the controller, and the cooling pump and the compressor are both electrically connected to the controller.

[0018] By adopting the above technical solution, a temperature sensor and a controller are set in the shell, and the temperature sensor is used to provide real-time feedback on the temperature of the projection assembly. The controller determines the heat dissipation condition of the projection assembly based on the data fed back by the temperature sensor, and then adjusts the working efficiency of the external heat dissipation assembly and the internal heat dissipation assembly to maintain the temperature of the projection assembly within an appropriate range.

[0019] Optionally, the shell includes a casing and a dust cover that are interlocked, the upper cover is fixed to the side of the casing close to the dust cover, the internal heat dissipation system is installed in the casing, and the external heat dissipation system is installed on the side of the upper cover close to the dust cover.

[0020] By adopting the above technical solution, the shell is configured as two parts, the casing and the dust cover, and the external heat dissipation system is installed on one side of the dust cover, which can effectively improve the heat dissipation efficiency of the external heat dissipation system.

[0021] Optionally, an adjustment seat is further included, and the adjustment seat is fixed to the shell through an adjustment bolt.

[0022] By adopting the above technical solution, when in use, the projection angle can be adjusted by loosening the adjustment bolt and rotating the housing as needed, so that the image projected by the projection assembly is in an ideal state.

[0023] In a second aspect, the present application provides a control method for the above-mentioned laser projector, comprising the following steps:

[0024] Normal temperature control: When the cavity temperature is between 0-20°C, the controller controls the external and internal cooling systems to reduce power and operate slowly based on feedback from the temperature sensor, so that the projection components are at normal operating temperature.

[0025] High temperature control: when the cavity temperature is between 20-45°C, the controller controls the external and internal cooling systems to run quickly based on the feedback from the temperature sensor, quickly cooling the projection component to keep it at normal operating temperature.

[0026] Low temperature control: when the cavity temperature is below 0°C, the controller controls the external cooling system to heat the heat exchanger, and the internal cooling system transports the heated cooling water to the heat exchange plate to heat the projection component, so that the projection component quickly reaches the ideal operating temperature. Then the controller switches to cooling operation mode according to the signal feedback from the temperature sensor.

[0027] By adopting the above technical solution, the cavity temperature is controlled so that the projection assembly can quickly reach a suitable operating temperature and always operate at an ideal operating temperature, which can effectively increase the service life of the projection assembly.

[0028] Optionally, it also includes self-test control. When the external cooling system and the internal cooling system cannot work normally, the temperature sensor detects that the temperature is high. The controller determines that the external cooling system and the internal cooling system are working abnormally based on the temperature sensor feedback signal and time. The controller projects a message on the screen through the projection component to remind that the temperature is too high.

[0029] By adopting the above technical solution, the controller determines whether the external heat dissipation system and the internal heat dissipation system are working normally according to the temperature feedback from the temperature sensor, and promptly projects words through the projection component to warn the user, which is convenient for use.

[0030] In summary, this application includes at least one of the following beneficial technical effects:

[0031] 1. By setting an upper cover inside the housing, the upper cover divides the internal space of the housing into two chambers, and an external heat dissipation system and an internal heat dissipation system are set in the two chambers respectively. The internal heat dissipation system dissipates heat from the projection component, and the external heat dissipation system dissipates heat from the heat dissipation end of the internal heat dissipation system, thereby sealing the projection component and improving the overall sealing performance, thereby better preventing dust and moisture, and extending the overall service life;

[0032] 2. By using a water-cooled internal cooling system, the projector's internal heat source components fit tightly against the heat exchanger plate. The cooling water within the heat exchanger plate removes the heat generated by the projection component, and a cooling pump then pumps the cooling water from the heat exchanger plate to the heat exchanger for heat dissipation. Using a water-cooled system to dissipate heat from the projection component, the heat exchanger plate is located within a sealed working chamber, and its temperature remains constant. This prevents condensation from forming on the heat exchanger plate due to large temperature differences during the heat dissipation process, thereby extending the overall service life.

[0033] 3. By setting the external heat dissipation system as a refrigerant cooling system, the refrigerant cooling system has high cooling efficiency, which can dissipate heat to the radiator of the internal heat dissipation system more quickly, and the heat exchange efficiency is higher; installing a fan at the condenser can quickly dissipate heat to the condenser, and the fan's air outlet direction is directed toward the outside of the shell. During the heat dissipation process, the air flow speed in the shell can be increased, and the heat can be dissipated to other components inside the shell;

[0034] 4. By setting a temperature sensor and a controller in the shell, the temperature sensor collects and feeds back the temperature of the projection assembly in real time. The controller determines the heat dissipation condition of the projection assembly based on the data fed back by the temperature sensor, and then adjusts the working efficiency of the external heat dissipation assembly and the internal heat dissipation assembly to maintain the temperature of the projection assembly within an appropriate range. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a schematic diagram of the overall structure of an embodiment of the present application;

[0036] FIG2 is a schematic diagram of the structure of the embodiment of the present application after the dust cover is opened;

[0037] FIG3 is a structural diagram highlighting the internal heat dissipation system;

[0038] FIG4 is a schematic diagram of heat exchange between the external heat dissipation system and the internal heat dissipation system.

[0039] Figure numerals: 1. Shell; 11. Casing; 12. Dust cover; 13. Adjustment seat; 14. Adjustment bolt; 2. Upper cover; 3. Projection assembly; 4. External cooling system; 41. Compressor; 42. Condenser; 43. Expansion valve; 44. Heat exchanger; 45. Fan; 46. Pressure pipe; 5. Internal cooling system; 51. Heat exchange plate; 511. Water channel; 52. Cooling pipe; 53. Cooling pump; 54. Multi-connector; 55. Quick connector; 6. Controller; 7. Temperature sensor. DETAILED DESCRIPTION

[0040] First, the embodiments of the present application disclose a laser projector with high heat dissipation efficiency and a control method thereof. Referring to Figures 1-3, the projector comprises a housing 1, an upper cover 2, and a projection assembly 3. The housing 1 comprises a casing 11 and a dust cover 12 that are interlocked and mounted. The upper cover 2 is fixed to the side of the casing 11 near the dust cover 12 and isolates the casing 11 and the dust cover 12 from each other. The projection assembly 3 is mounted within the casing 11. An external heat dissipation system 4 is mounted on the upper cover 2 within the dust cover 12. An internal heat dissipation system 5 for dissipating heat from the projection assembly 3 is mounted within the casing 11. The external heat dissipation system 4 is used to dissipate heat from the heat dissipation end of the internal heat dissipation system 5. A U-shaped adjustment seat 13 is mounted on the lower side of the casing 11. The two side walls of the adjustment seat 13 are fixed to the two sides of the casing 11 by adjustment bolts 14. When in use, the projection angle can be adjusted by loosening the adjustment bolts 14 and rotating the casing 11, which is convenient for use.

[0041] Referring to Figures 2 and 3, the internal heat dissipation system 5 includes a heat exchange plate 51, a cooling pipe 52, a radiator, and a cooling pump 53. The heat exchange plate 51 is a rectangular plate with a water channel 511 formed therein. The heat exchange plate 51 is connected to the radiator via the cooling pipe 52. The cooling pump 53 is connected in series to the cooling pipe 52 and circulates cooling water between the heat exchange plate 51 and the radiator. The heat exchange plate 51 can be provided with multiple components corresponding to the various components of the projection assembly 3. A multi-connector 54 is installed at one end of the cooling pipe 52 near the heat exchange plate 51. The multi-connector 54 can divide the cooling pipe 52 into multiple branches connected to the heat exchange plates 51, allowing cooling water to circulate simultaneously within multiple heat exchange plates 51.

[0042] 2 and 4 , the structure of the external heat dissipation system 4 is similar to that of a household air conditioner. The external heat dissipation system 4 includes a compressor 41, a condenser 42, an expansion valve 43, and an evaporator for cooling the radiator. The condenser 42, evaporator, and compressor 41 are interconnected via a pressure pipe 46. The expansion valve 43 is connected to one end of the pressure pipe 46 near the evaporator. The cooling medium is a refrigerant. The compressor 41 pressurizes the refrigerant and sends it to the condenser 42 for cooling. The cooled refrigerant is then sent to the evaporator through the expansion valve 43 for heat exchange. A fan 45 is installed at the condenser 42 within the dust cover 12 to dissipate heat from the condenser 42. The wind from the fan 45 blows toward the outside of the dust cover 12, removing heat from the condenser 42 and the housing 1.

[0043] Referring to Figures 2-4, in order to save costs and improve heat exchange efficiency, the evaporator and the radiator are made into one body to form a heat exchanger 44. The heat exchanger 44 is a cubic structure, and a low-temperature channel for the circulation of refrigerant and a high-temperature channel for the circulation of cooling water are provided inside the heat exchanger 44. During normal use, the refrigerant and the cooling water can directly exchange heat, thereby improving the cooling efficiency of the external heat dissipation system 4 to the internal heat dissipation system 5. The heat exchanger 44 is installed on the side of the upper cover 2 away from the casing 11. A plurality of quick connectors 55 are fixed on the upper cover 2. The heat exchanger 44 is connected to the quick connector 55 through the cooling pipe 52; the cooling pipe 52 on one side of the heat exchange plate 51 is connected to the connector. During installation or maintenance, the heat exchange plate 51 can be quickly installed and disassembled with the heat exchanger 44 through the quick connector 55.

[0044] The external heat dissipation system 4 and the internal heat dissipation system 5 can be set as multiple groups according to usage requirements. In this application, they are set as two groups, which are located on both sides of the upper cover 2 respectively.

[0045] Referring to Figures 2 and 3 , a controller 6 is also mounted on the upper cover 2, and a temperature sensor 7 is mounted on the underside of the upper cover 2. The temperature sensor 7 is electrically connected to the controller 6, which is in turn electrically connected to the cooling pump 53, the compressor 41, and the expansion valve 43. During operation, the temperature sensor 7 monitors the temperature on one side of the projection assembly 3. The controller 6 controls the efficiency of the external cooling system 4 and the internal cooling system 5 based on the signal fed back by the temperature sensor 7, thereby maintaining the projection assembly 3 at a suitable operating temperature.

[0046] The embodiment of the present application discloses a laser projector with high heat dissipation efficiency, and the implementation principle is as follows: by setting an upper cover 2 in the shell 1 to separate the external heat dissipation system 4 and the internal heat dissipation system 5, the sealing and waterproof performance of one side of the projection component 3 can be effectively improved, and the protection level can be achieved to IP65, thereby improving the overall service life; and the internal heat dissipation system 5 is set as a water cooling system, the cooling temperature of the water cooling system will not be too low, and no condensed water will be generated when cooling the projection component 3, so that the projection component 3 can work normally.

[0047] On the other hand, the present application provides a control method for the above-mentioned laser projector, comprising the following steps:

[0048] Normal temperature control: when the temperature sensor 7 detects that the cavity temperature is 0-20°C, at the beginning of operation, the controller 6 controls the projection assembly 3 to determine that the temperature is not high at this time based on the data fed back by the temperature sensor 7, and controls the external heat dissipation system 4 and the internal heat dissipation system 5 not to work; after the projection assembly 3 has been working for a period of time, the temperature sensor 7 detects that the temperature of the projection assembly 3 has risen, and the controller 6 determines that it needs to be cooled down. The controller 6 controls the external heat dissipation system 4 and the internal heat dissipation system 5 to operate slowly to keep the projection assembly 3 at a normal operating temperature.

[0049] High temperature control: when the temperature sensor 7 detects that the cavity temperature is between 20°C and 45°C, the controller 6 controls the external heat dissipation system 4 and the internal heat dissipation system 5 to operate rapidly according to the feedback of the temperature sensor 7, so as to quickly cool down the projection assembly 3 and keep the projection assembly 3 at a normal operating temperature;

[0050] Low temperature control: when the cavity temperature is lower than 0°C, the controller 6 controls the external heat dissipation system 4 to heat the heat exchanger 44 according to the signal fed back by the temperature sensor 7, and the internal heat dissipation system 5 to circulate the heated cooling water to heat the projection assembly 3, so that the projection assembly 3 quickly reaches the ideal working temperature; after the projection assembly 3 works normally, the controller 6 controls the external heat dissipation system 4 and the internal heat dissipation system 5 to switch to the cooling mode according to the signal fed back by the temperature sensor 7 to cool the projection assembly 3, so that the projection assembly 3 maintains the appropriate working temperature.

[0051] Self-check control: When the external heat dissipation system 4 and the internal heat dissipation system 5 cannot work normally, the temperature sensor 7 detects that the temperature of the projection component 3 is high, and the temperature cannot be reduced after the controller 6 controls the external heat dissipation system 4 and the internal heat dissipation system 5 to run quickly. The controller 6 determines that the external heat dissipation system 4 or the internal heat dissipation system 5 is working abnormally based on the feedback signal of the temperature sensor 7 and the running time. The controller 6 projects a message similar to "Alarm: System temperature is too high, working abnormally!" on the screen of the projection component 3 to remind the user to carry out timely maintenance.

[0052] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A laser projector with high heat dissipation efficiency, characterized by: The invention comprises a shell (1), a projection assembly (3) installed in the shell (1), and an upper cover (2) fixed in the shell (1), wherein the upper cover (2) divides the internal space of the shell (1) into two chambers; an external heat dissipation system (4) and an internal heat dissipation system (5) are respectively installed in the chambers on both sides of the upper cover (2) in the shell (1), wherein the internal heat dissipation system (5) and the projection assembly (3) are located in the same chamber, the internal heat dissipation system (5) is used to dissipate heat from the projection assembly (3), and the external heat dissipation system (4) is used to dissipate heat from the heat dissipation end of the internal heat dissipation system (5).

2. A laser projector with high heat dissipation efficiency according to claim 1, characterized in that: The internal heat dissipation system (5) comprises a heat exchange plate (51), a cooling pipe (52), a radiator and a cooling pump (53); a water channel (511) is provided inside the heat exchange plate (51); the cooling pipe (52) connects the water channel (511) and the radiator; the cooling pump (53) is installed in series on the cooling pipe (52); the cooling pump (53) circulates cooling water between the heat exchange plate (51) and the radiator.

3. The laser projector with high heat dissipation efficiency according to claim 2, characterized in that: A plurality of the heat exchange plates (51) are provided corresponding to the various components of the projection assembly (3); a multi-connector (54) is provided at one end of the cooling pipe (52) close to the heat exchange plate (51); and the cooling pipe (52) is connected to the plurality of heat exchange plates (51) via the multi-connector (54).

4. The laser projector with high heat dissipation efficiency according to claim 2, characterized in that: The external heat dissipation system (4) comprises a compressor (41), a condenser (42), an expansion valve (43) and an evaporator for cooling the radiator. The condenser (42), the evaporator and the compressor (41) are interconnected via a pressure pipe (46), and the expansion valve (43) is connected to one end of the pressure pipe (46) close to the evaporator. The compressor (41) pressurizes the refrigerant in the pressure pipe (46) and sends it to the condenser (42) for heat dissipation, and then sends the refrigerant to the evaporator through the expansion valve (43). A fan (45) is installed at the condenser (42), and the air outlet direction of the fan (45) is toward the outside of the shell (1).

5. The laser projector with high heat dissipation efficiency according to claim 4, characterized in that: The evaporator and the radiator are integrated into a heat exchanger (44), and a low-temperature channel for circulating refrigerant and a high-temperature channel for circulating cooling water are provided in the heat exchanger (44). The pressure pipe (46) is connected to the low-temperature channel, and the cooling pipe (52) is connected to the high-temperature channel.

6. The laser projector with high heat dissipation efficiency according to claim 4, characterized in that: A temperature sensor (7) is arranged in the housing (1) on a side of the upper cover (2) close to the projection assembly (3); a controller (6) is arranged on a side of the upper cover (2) close to the external heat dissipation system (4); the temperature sensor (7) is electrically connected to the controller (6); and the cooling pump (53) and the compressor (41) are both electrically connected to the controller (6).

7. The laser projector with high heat dissipation efficiency according to claim 1, characterized in that: The housing (1) comprises a casing (11) and a dust cover (12) which are interlocked, the upper cover (2) is fixed to a side of the casing (11) close to the dust cover (12), the internal heat dissipation system (5) is installed in the casing (11), and the external heat dissipation system (4) is installed on a side of the upper cover (2) close to the dust cover (12).

8. The laser projector with high heat dissipation efficiency according to claim 1, characterized in that: It also comprises an adjustment seat (13), wherein the adjustment seat (13) is fixed on the housing (1) via an adjustment bolt (14).

9. A control method for a laser projector according to any one of claims 1 to 8, characterized in that: The following steps are included: Normal temperature control: when the cavity temperature is between 0 and 20°C, the controller (6) controls the external heat dissipation system (4) and the internal heat dissipation system (5) to reduce power and operate slowly according to the feedback from the temperature sensor (7), so that the projection component (3) is at a normal operating temperature; High temperature control: when the cavity temperature is between 20°C and 45°C, the controller (6) controls the external heat dissipation system (4) and the internal heat dissipation system (5) to run quickly according to the feedback from the temperature sensor (7), so as to quickly cool down the projection component (3) and keep the projection component (3) at a normal working temperature; Low temperature control, when the cavity temperature is lower than 0°C, the controller (6) controls the external heat dissipation system (4) to heat the heat exchanger (44), and the internal heat dissipation system (5) transports the heated cooling water to the heat exchange plate (51) to heat the projection component (3), so that the projection component (3) quickly reaches the ideal working temperature, and then the controller (6) switches to the cooling operation mode according to the signal fed back by the temperature sensor (7).

10. The control method according to claim 9, characterized in that: The device also includes a self-check control. When the external heat dissipation system (4) and the internal heat dissipation system (5) cannot work normally, the temperature sensor (7) detects that the temperature is high, and the controller (6) determines that the external heat dissipation system (4) or the internal heat dissipation system (5) is working abnormally according to the feedback signal and time of the temperature sensor (7). The controller (6) projects a message on the screen through the projection component (3) to remind that the temperature is too high.

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