WO2006098533A1

WO2006098533A1 - Analog-to-digital conversion measuring apparatus

Info

Publication number: WO2006098533A1
Application number: PCT/KR2005/001850
Authority: WO
Inventors: Mijin Park
Original assignee: Sdsystem Co., Ltd
Priority date: 2005-03-17
Filing date: 2005-06-16
Publication date: 2006-09-21
Also published as: KR20060100627A; KR100730896B1

Abstract

An analog-to-digital conversion (ADC) measuring apparatus capable of measuring a stable ADC input value even with fluctuation of a supply voltage is provided, which includes a power source, a detector, a voltage supply, a reference voltage generator which generates a reference voltage value with respect to a voltage supplied to the detector, an ADC input portion which receives an ADC input value representing a voltage depending upon change of resistivity of an inherent resistor of the detector, and an ADC calculator which calculates a ratio of the reference voltage value with respect to the ADC input value and thus produces an ADC resultant value.

Description

ANALOG-TO-DIGITAL CONVERSION MEASURING

APPARATUS

Technical Field

[1] The present invention relates to an analog-to-digital (ADC) measuring apparatus, and more particularly to, an analog-to-digital (ADC) measuring apparatus capable of measuring a stable ADC input value even with fluctuation of a supply voltage to be supplied to a detector whose resistance value varies according to external factors. Background Art

[2] In general, an analog-to-digital (ADC) measuring apparatus is an apparatus which outputs an ADC input value composed of voltages varying between a theoretically unlimited number of values, for example, an analog voltage waveform output from a detector whose inherent resistance value varies at the time of detecting brightness of light, temperature, humidity, sound and so on, as an ADC output value which is a digital signal composed of predetermined dimensions or states. Also, when an ADC output value corresponding to an ADC input value from the detector is transmitted to a home network system connected with the ADC measuring apparatus wirelessly or by wire, a home network system can recognize a peripheral situation such as brightness of light, temperature, humidity, and sound in a space where the ADC measuring apparatus has been installed.

[3] Hereinbelow, a conventional ADC measuring apparatus will be described with reference to the accompanying drawings, FIGs. 1 and 2.

[4] FIG. 1 is a circuit diagram schematically showing an example of a conventional analog-to-digital (ADC) measuring apparatus having an illuminance sensor, and FIG. 2 is a circuit diagram schematically showing an example of a conventional analog- to-digital (ADC) measuring apparatus using a reference voltage.

[5] As shown in FIG. 1, a conventional ADC measuring apparatus includes an illuminance sensor 20 which receives an operating voltage from a battery 10 being a low-power supply and measures brightness of light, a plurality of resistors Rl and R2, a circuit stabilizing capacitor C, and a microcomputer 30 which receives an ADC input value of the illuminance sensor 20 via an ADC input end ADCin and converts the received ADC input value into an ADC output value, to thereby measure brightness of light.

[6] However, the ADC measuring apparatus using the battery 10 being a low-power supply has a problem that an ADC input value input to the microcomputer 30 has an error although an identical amount of light is detected by the detector since a supply voltage supplied to the illuminance sensor 20 varies according to consumption of the power supplied from the battery 10.

[7] An ADC measuring apparatus using a reference voltage to solve the above- described problem is shown in FIG. 2. As shown in FIG. 2, a constant voltage integrated circuit (IC) or a constant voltage circuit 40 using a constant voltage diode, and a resistor R3 are additionally connected between the battery 10 and the microcomputer 30 of the conventional ADC measuring apparatus of FIG. 1, in order to supply a stable voltage to a reference voltage (Vref) end of the microcomputer 30 and the illuminance sensor 20. Accordingly, the ADC measuring apparatus of FIG. 2 measures an ADC input value of the illuminance sensor 20 corresponding to a variation of a supply voltage supplied to the illuminance sensor 20 based on a reference voltage supplied to the microcomputer 30 via the reference voltage end Vref when an operating voltage supplied from the battery 10 to the illuminance sensor 20 varies.

[8] However, the ADC measuring apparatus which receives a reference voltage from the constant voltage circuit 40 requires more expenses since an additional constant voltage circuit is connected between the microcomputer 30 and the battery 10. Also, since the constant voltage circuit 40 also consumes the voltage of the battery 10, the lifetime of the battery 10 is shortened. Disclosure of Invention Technical Problem

[9] To solve the above problems, it is an object of the present invention to provide an analog-to-digital (ADC) measuring apparatus capable of measuring a stable ADC input value even with fluctuation of a supply voltage without having an additional constant voltage circuit.

[10] It is another object of the present invention to provide an analog-to-digital (ADC) measuring apparatus which minimizes consumption of power supplied from a battery being a low-power supply, to thereby use the battery more lengthily. Technical Solution

[11] To accomplish the above object of the present invention, according to the present invention, there is provided an analog-to-digital (ADC) measuring apparatus capable of measuring a stable ADC input value even with fluctuation of a supply voltage, the ADC measuring apparatus comprising: a power source; a detector whose inherent resistance varies according to external factors; a voltage supply which receives a voltage from the power source via a supply voltage input end (Vin), and supplies a voltage to the detector connected in series with resistors (Rl, R2), via a supply voltage output end (Vout); a reference voltage generator which receives the voltage from the supply voltage output end (Vout) via a reference voltage input end (Vref) from a node (Nl) between the resistors (Rl, R2) and generates a reference voltage value with respect to the voltage supplied to the detector; an ADC input portion which receives an ADC input value representing a voltage depending upon change of resistivity of an inherent resistor (R3) of the detector which is measured using the voltage output from the supply voltage output end (Vout), via an ADC input end (ADCin) from a resistor (R4) connected to a node (N2) between the resistor (R2) and the inherent resistor (R3); and an ADC calculator which calculates a ratio of the reference voltage value with respect to the ADC input value and thus produces an ADC resultant value.

[12] Here, it is preferable that the reference voltage value is a value meeting an equation

Vref={ (R2+R3)/(R1+R2+R3) } *Vcc.

[13] Here, it is preferable that the ADC input value is a value meeting an equation

ADC={R3)/(Rl+R2+R3)}*Vcc.

[14] Here, it is preferable that the ADC output value is a value meeting an equation

X=ADC/Vref according to an algorithm for reducing a measurement error of the detector depending upon a variation of voltage of the voltage supply. Brief Description of the Drawings

[15] FIG. 1 is a circuit diagram schematically showing an example of a conventional analog-to-digital (ADC) measuring apparatus having an illuminance sensor;

[16] FIG. 2 is a circuit diagram schematically showing an example of a conventional analog-to-digital (ADC) measuring apparatus using a reference voltage;

[17] FIG. 3 is a circuit diagram schematically showing an example of an analog- to-digital (ADC) measuring apparatus capable of measuring a stable ADC input value even with fluctuation of a supply voltage according to a preferred embodiment of the present invention; and

[18] FIG. 4 is a block diagram schematically showing a microcomputer in the ADC measuring apparatus of FIG. 3. Best Mode for Carrying Out the Invention

[19] Hereinbelow, an analog-to-digital (ADC) measuring apparatus according to the present invention will be described with reference to the accompanying drawings. The like or same elements are assigned the like or same reference numerals all over the drawings, for convenience of explanation. Also, in the case that the detailed description of the relevant known functions or components may make the gist of the present invention unclear unnecessarily, the detailed description thereof will be omitted.

[20] FIG. 3 is a circuit diagram schematically showing an example of an analog- to-digital (ADC) measuring apparatus capable of measuring a stable ADC input value even with fluctuation of a supply voltage according to a preferred embodiment of the present invention, and FIG. 4 is a block diagram schematically showing a microcomputer in the ADC measuring apparatus of FIG. 3.

[21] As shown in FIG. 3, an ADC measuring apparatus according to a preferred embodiment of the present invention includes a battery 100, a detector 200 which is a device whose resistivity of an inherent resistor R3 varies according to external factors, and a microcomputer 300 which produces a reference voltage in correspondence to a supply voltage from the battery 100, supplies the supply voltage to the detector 200, and calculates a measurement value of the detector 200 based on the reference voltage, to thereby reduce an error of the measurement value due to variation of the supply voltage supplied from the battery 100.

[22] It is preferable that the battery 100 is a low-power supply such as a general dry cell which supplies a direct-current (DC) of 3 V.

[23] The detector 200 is one of various types of general sensors such as an illuminance sensor, a temperature sensor, a humidity sensor, and an infrared sensor all of which the inherent resistance values vary at the time of detecting brightness of light, temperature, humidity and sound, respectively, and thus produces an ADC input value.

[24] As shown in FIGs. 3 and 4, the microcomputer 300 includes a voltage supply 310 which receives an operating voltage from the battery 100 via a supply voltage input end (Vin), and supplies a voltage to the detector 200 connected in series with resistors (Rl, R2), via a supply voltage output end (Vout), a reference voltage generator 320 which receives the voltage from the supply voltage output end (Vout) via a reference voltage input end (Vref) from a node (Nl) between the resistors (Rl, R2) and generates a reference voltage value with respect to the voltage supplied to the detector 200, an ADC input portion 330 which receives an ADC input value representing a voltage depending upon change of resistivity of an inherent resistor (R3) of the detector 200 which is measured using the voltage output from the supply voltage output end (Vout), via an ADC input end (ADCin) from a resistor (R4) connected to a node (N2) between the resistor (R2) and the inherent resistor (R3), an ADC calculator 340 which calculates a ratio of the reference voltage value with respect to the ADC input value and thus produces an ADC output value, so that a measurement error of the detector 200 due to variation of the voltage from the battery 100 is reduced, and an ADC output portion 350 which outputs the ADC output value to an external home network system via an ADC output end (ADCout) wirelessly or by wire. Here, it is preferable that the reference voltage generator 320 and the ADC input portion 330 further include circuit stabilizing capacitors Cl and C2, respectively, in order to protect the circuit.

[25] Also, preferably, the microcomputer 300 includes an algorithm for calculating a ratio of the reference voltage value with respect to the ADC input value, and an algorithm for allowing a voltage of the battery 100 to be supplied to the detector 200 only if a control signal for controlling the detector 200 is received from the external home network system, in order to minimize consumption of the power supplied from the battery 100, to thereby reduce a measurement error of the detector 200 due to variation of the voltage from the battery 100.

[26] Here, according to a circuit designed as shown in FIG. 3, the reference voltage value produced by the reference voltage generator 320 is a value meeting an equation Vref={ (R2+R3)/(R1+R2+R3) } *Vcc.

[27] Here, according to a circuit designed as shown in FIG. 3, the ADC input value input to the ADC input portion 330 is a value meeting an equation ADC={R3)/(Rl+R2+R3)}*Vcc.

[28] Here, the ADC output value produced by the ADC calculator 340 is a value meeting an equation X=ADC/Vref according to an algorithm for reducing a measurement error of the detector 200 depending upon a variation of voltage of the battery 100.

[29] Here, a theoretical ADC output value calculated by the above equation, and an experimental output value measured by the algorithm, with respect to the ADC input value of the detector measured by the ADC measuring apparatus according to a preferred embodiment of the present invention will follow.

[30]

[31] Here, resistance values of the resistors Rl, R2, and R3 are assumed as 200Ω,

5.1kΩ, and 1.7kΩ, respectively. Also, supply voltages Vcc supplied from the battery 100 are 3.0V and 2.2V, respectively.

[32] First, the ADC output value by the equation of the ADC measuring apparatus according to the present invention is represented as follows.

[33] Assuming that a voltage output from the supply voltage output end Vout is Vcc-a when a supply voltage Vcc which is supplied from the battery 100 and input to the supply voltage input end Vin of the microcomputer 300 is 3.0V, the reference voltage value Vref-a is 2.914V as follows. Vref-a={(R2+R3)/(Rl+R2+R3)}*Vcc-a=2.914V. Under the same condition as the above, the ADC input value ADC-a is 0.729V as follows. ADC-a={R3)/(Rl+R2+R3)}*Vcc-a=0.729V. Under the same condition as the above, the ADC output value X-a is 0.2501 as follows. X-a=ADC-a/Vref-a=0.2501.

[34] Also, assuming that a voltage output from the supply voltage output end Vout is

Vcc-b when a supply voltage Vcc which is supplied from the battery 100 and input to the supply voltage input end Vin of the microcomputer 300 via the supply voltage input end Vin is 2.2V, the reference voltage value Vref-b is 2.137V as follows. Vref- b={(R2+R3)/(Rl+R2+R3)}*Vcc-b=2.137V. Under the same condition as the above, the ADC input value ADC-b is 0.534V as follows. ADC- b={R3)/(Rl+R2+R3)}*Vcc-b=0.534V. Under the same condition as the above, the ADC output value X-b is 0.2498 as follows. X-b=ADC-b/Vref-b=0.2498.

[35] Thus, although the supply voltage Vcc supplied from the battery 100 varies from

3.0V to 2.2V, that is, the supply voltage Vcc varies by about 30%, and then the varied supply voltage Vcc is supplied to the detector 200, the ADC output value corresponding to the ADC input value measured by the detector 200, that is, a deviation between X- a and X-b, has an error of 1% or less.

[36] Meanwhile, the ADC output value according to the algorithm of the ADC measuring apparatus according to the present invention is represented as follows.

[37]

[38] Thus, although the supply voltage Vcc supplied from the battery 100 varies from

3.0V to 2.2V, that is, the supply voltage Vcc varies by about 30%, and then the varied supply voltage Vcc is supplied to the detector 200, the ADC output value representing a ratio of the reference voltage value with respect to the ADC input value has a variation of 5% or less, to thereby obtain a reliable ADC output value.

[39] Thus, the ADC measuring apparatus according to the present invention can output a reliable ADC output value by calculating a ratio of an ADC input value of the detector with respect to the reference voltage value corresponding to the supply voltage even with variation of the supply voltage supplied from the battery to the detector.

[40] Also, the ADC measuring apparatus according to the present invention does not employ a conventional constant voltage circuit but allows a supply voltage from the battery to be supplied only if the ADC input value of the detector is needed, to thereby enable a more economic circuit design and minimizes an unnecessary power consumption of the battery, to thereby lengthen the lifetime of the battery.

[41] As described above, the present invention has been described with respect to particularly preferred embodiment. However, the present invention is not limited to the above embodiment, and it is possible for one who has an ordinary skill in the art to make various modifications and variations, without departing off the spirit of the present invention. Industrial Applicability

[42] As described above, the present invention provides an ADC measuring apparatus which does not employs an additional constant voltage circuit to thereby enable a more economic circuit design, and minimizes an unnecessary power consumption of the battery to thereby lengthen the lifetime of the battery. [43] Also, the present invention provides an ADC measuring apparatus which can output a reliable ADC output value by calculating a ratio of an ADC input value of the detector with respect to the reference voltage value corresponding to the supply voltage supplied from the battery to the detector even with variation of the supply voltage of the battery.

Claims

[1] An analog-to-digital (ADC) measuring apparatus capable of measuring a stable

ADC input value even with fluctuation of a supply voltage, the ADC measuring apparatus comprising: a power source; a detector whose inherent resistance varies according to external factors; a voltage supply which receives a voltage from the power source via a supply voltage input end (Vin), and supplies a voltage to the detector connected in series with resistors (Rl, R2), via a supply voltage output end (Vout); a reference voltage generator which receives the voltage from the supply voltage output end (Vout) via a reference voltage input end (Vref) from a node (Nl) between the resistors (Rl, R2) and generates a reference voltage value with respect to the voltage supplied to the detector; an ADC input portion which receives an ADC input value representing a voltage depending upon change of resistivity of an inherent resistor (R3) of the detector which is measured using the voltage output from the supply voltage output end (Vout), via an ADC input end (ADCin) from a resistor (R4) connected to a node (N2) between the resistor (R2) and the inherent resistor (R3); and an ADC calculator which calculates a ratio of the reference voltage value with respect to the ADC input value and thus produces an ADC resultant value.

[2] The ADC measuring apparatus of claim 1, wherein the reference voltage value is a value meeting an equation Vref={(R2+R3)/(Rl+R2+R3)}*Vcc.

[3] The ADC measuring apparatus of claim 2, wherein the ADC input value is a value meeting an equation ADC={R3)/(Rl+R2+R3)}*Vcc.

[4] The ADC measuring apparatus of claim 3, wherein the ADC output value is a value meeting an equation X=ADC/Vref according to an algorithm for reducing a measurement error of the detector depending upon a variation of voltage of the voltage supply.