Patent Application
20070267568
With reference to
The carbon dioxide detector includes a casing, a microprocessor (10), a variable current source (20), a first switch (31), a second switch (32), a first infrared light source (41), a second infrared light source (42), a reflector, a light detector (50) and a voltage detecting circuit 60.
A measuring channel is formed inside the casing. The air can flow from one end of the measuring channel to enter casing and then flowing out of the casing from the other end of the measuring channel. The microprocessor (10) is configured inside the casing, which is a processing center of the carbon dioxide sensor. The variable current source (20) is coupled to a power source and the microprocessor (10). The microprocessor (10) can control an output electric current capacity the variable current source (20).
The first and second witches (31, 32) are configured inside the casing connected to the microprocessor (10) and the variable current source (20).
The first and second infrared light sources (41, 42) are configured inside the casing and respectively connected to the first and second witches (31, 32). Therefore, the infrared light sources (41, 42) are respectively connected to the variable current source (20) through the first and second switches (31, 32). The microprocessor (10) can control ON and OFF statuses of the first and second witches (31, 32), so as to light up or to turn off the first and second infrared light sources (41, 42).
The reflector is configured inside the casing facing the first and second infrared light sources (41, 42), so as to reflect the infrared light of the first and second infrared light sources (41, 42).
The light detector (50) is configured inside the casing coupled to the microprocessor (10) for receiving the reflected infrared light of the reflector, and then to send corresponding strength of the received infrared light to the microprocessor (10). The voltage detecting circuit (60) is cross-connected to two terminals of each infrared light source (41, 42) and also connected to the microprocessor (10). The voltage detecting circuit (60) is used for measuring two voltages respectively dropped on the first and second infrared light sources (41, 42), and then to send the voltages to the microprocessor (10). Since the microprocessor (10) controls the variable current source (20), the microprocessor (10) can calculate power of each of the infrared light sources (41, 42) by the formula: power=voltage*current (P=V×I).
Further, a method of the present invention is to build-in a control process in the microprocessor (10). With reference to
The intermittent measure of lighting up the light can alternatively control the ON status or OFF status of the first and second switches (31, 32). Hence when the first infrared light source (41) is lighted up (ON status), the second infrared light source (42) is turned off (OFF status) as shown in a step (101) in the diagram. On the other hand, when the second infrared light source (42) is lighted up (ON status), the first infrared light source (41) is turned off (OFF status) as shown in a step (102). In this way, the first and second infrared light sources (41, 42) can work in turn to share usage loading, so as to achieve the objective of extending the usage life span of the first and second infrared light sources (41, 42).
The electric current control measure is to detect two voltages dropped on the first and second infrared light sources (41, 42), and then to control an electric current capacity of a variable current source (20) flowing to the first and second infrared light sources (41, 42) in accordance with the detecting results. The electric current control measure includes the following three functions.
First of all, the electric current control measure controls the electric current capacity of the variable current source (20) gradually increasing current flowing to the infrared light source to be lighted up as shown in a step (201). In this way, the first and second infrared light sources (41, 42) can avoid a thermal shock due to sudden bright when the light source emits infrared rays.
Secondly, the electric current control measure further controls the variable current source (20) to have scant electric current flowed through the unlighted infrared light source as shown in a step (202). The electric current capacity that the flows though the unlighted infrared light source is approximately 10% to 15% of the required electric current capacity of the lightened infrared light source. Thereby the unlighted infrared light source has dim brightness. In this way, when the unlighted infrared light source takes turn to emit the infrared rays, not only lighting time can be decreased, but also the infrared light source can avoid the thermal shock for the infrared light source is in a preheated status.
Thirdly, according to the detecting results of the voltage detecting circuit (60) of the infrared light sources, the electric current capacity supplied to the infrared light sources by the variable current source (20) is controlled as shown in a step (203). In this way, the radiant power of the infrared light sources is fixed; so as to avoid changing a resistance value to cause a variation of the radiant power after the infrared light sources is used for a long time. The stable radiant power not only can decrease a damage possibility of the infrared light sources, but also can make the infrared light sources continue to emit the infrared rays of constant brightness. Hence an error of calculating a concentration of a specific gas in the air can be avoided.
It can be clearly understood from the above description that the present invention controls the two infrared light sources to operate in turn to share the usage loading of the infrared light sources, so as to achieve the objective of extending the usage life span of the infrared light sources. In addition, the damage possibility of the infrared light sources is decreased by controlling the electric current capacity flowing to the infrared light sources to fix the radiant power of the infrared light sources. Moreover, the electric current control measure that controls the electric current capacity of the variable current source increasingly flowing to the infrared light source to be lighted up can avoid a thermal shock due to sudden bright when the light source emits infrared rays. The electric current control measure also controls the variable current source to have scant electric current flow through the unlighted infrared light source to avoid the thermal shock. The electric current capacity that the flows though the unlighted infrared light source is approximately 10% to 15% of the required electric current capacity of the lightened infrared light source.
Therefore, the method for extending the usage life span of the infrared light sources for non-dispersive infrared (NDIR) gas sensing technology of the present invention indeed includes features of good utility and unobviousness to meet the requirements of a patent.
While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.
