Analog sensor status detection single wire bus multiplex system
First Claim
1. A monitoring circuit for a line bus having at least one analog sensor connected thereto, comprising:
- a microcontroller, said microcontroller polling the analog sensor with a voltage over said bus, said at least one analog sensor producing a current on said bus representative of its status in response to said polling voltage; and
a measuring circuit, said measuring circuit being responsive to said current of said bus producing by said at least one analog sensor and determining the status of said at least one analog sensor producing said current on the basis of said current the measuring circuit including;
a current mirror circuit which monitors and generates a current replica of said current produced on said bus; and
a conversion resistor for receiving said current replica.
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Accused Products
Abstract
A circuit monitors both digital and analog sensor readings by polling them from a single wire bus multiplex system. The circuit operates to sequentially address a plurality of smart sensor interfaces, each having an associated sensor, connected to the single wire bus. A voltage signal is supplied on the line that produces a current corresponding to the presence of a sensor at the polled interface and a current corresponding to a sensed digital or analog value where the sensor is of the digital or analog type, respectively. The currents on the bus are copied in a current mirror whose current output is applied to a resistor to produce a voltage, which in turn is converted into a digital number to be analyzed to determine the presence of a sensor at the addressed interface and its status. The current in the circuit is also measured to produce a voltage corresponding to circuit component variations and one corresponding to the contributions of the currents from the power supplies of the interfaces. These voltages correct the calculation of the voltage corresponding to the sensor analog value.
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Citations
17 Claims
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1. A monitoring circuit for a line bus having at least one analog sensor connected thereto, comprising:
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a microcontroller, said microcontroller polling the analog sensor with a voltage over said bus, said at least one analog sensor producing a current on said bus representative of its status in response to said polling voltage; and a measuring circuit, said measuring circuit being responsive to said current of said bus producing by said at least one analog sensor and determining the status of said at least one analog sensor producing said current on the basis of said current the measuring circuit including; a current mirror circuit which monitors and generates a current replica of said current produced on said bus; and a conversion resistor for receiving said current replica. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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14. A monitoring circuit as in claim 12 wherein each said sensor interface includes a resistor of value Rcal with said voltage Vcal being produced across said resistor Rcal of the addressed sensor interface.
- 15. A monitoring circuit as in claim 14 wherein a sensor at an addressed sensor interface receives a voltage of a first level "x" to produce the current on said bus corresponding to sensor status and said voltage polling the entire monitoring circuit to produce said current representative of the current flowing through the entire monitoring circuit is of a second level "y" greater than "x", and said computer calculates Rsense according to the equation
- space="preserve" listing-type="equation">Rsense=Rcal*(x/y*Vcal/(Vsense-Vbase)).
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16. A monitoring circuit for a bus having an analog sensor connected thereto, comprising:
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a microcontroller, said microcontroller polling the analog sensor over said bus with a voltage, said analog sensor producing a current on said bus representative of its status in response to the received polling voltage; a current mirror circuit which monitors and produces a current replica of said current on said bus; a conversion resistor which is arranged to receive said current replica and produces a voltage when said current replica passes therethrough; and a computer, said computer converts said voltage produced by said conversion resistor into a value corresponding to the status of said analog sensor. - View Dependent Claims (17)
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Specification