29-06-2012, 01:06 PM
A MICROCONTROLLER BASED CAPACITIVE PROJECT
A MICROCONTROLLER BASED CAPACITIVE.pptx (Size: 1.29 MB / Downloads: 49)
OBJECTIVES OF THIS STUDY
The objectives of this study are as follows:
• To design and construct a differential capacitive sensor.
• To interface the sensor to microcontroller with out any signal conditioning circuit.
RATIONALE FOR THE STUDY
To reduce the cost, complexity, area, and power
consumption of sensor electronic interfaces.
Direct interface circuits do not require either an intermediate signal conditioner based on amplifiers or oscillators or an ADC, but the sensor is directly connected to a general-purpose microcontroller.
DETAILED METHODOLOGY TO BE USED FOR CARRYING OUT THE STUDY
The direct interface circuit for differential capacitive sensors , relies on measuring the discharging time of several RC circuits using a timer embedded into the μC.
THE EXPECTED CONTRIBUTION FROM THE STUDY
A differential capacitive sensor can be interfaced to a general purpose μC without any intermediate
signal conditioning circuit.
Set-up cost is less as compared to it’s effective utilization to measure a very low value capacitance.
STATEMENT OF THE PROBLEM
Differential capacitive sensors usually have three parallel plates (the central plate being movable and the outer plates being fixed) and can be represented by two sensing capacitances (C1 and C2 ) with a common electrode as shown in the following fig 1 .
CONCLUSION
The differential capacitive sensors can be directly connected to a general-purpose 8-bit microcontroller without using intermediate electronics between them.
The circuit is able to measure (considering it’s simplicity and low cost ) small variation of capacitance satisfactorily.
However stray effect causing some error.