Sense Small Inductance Changes Over A Wide Range
#inductance
#Colpitts oscillator
#ATtiny12-8
#serial port
#measurement
#microprocessor
#sensor
#oscillator
#precision
#electronics
Description: Small inductance changes on the order of 0.01% can easily be sensed over a wide range with a simple circuit connected to a serial port. Using a classic Colpitts oscillator interfaced to an eight-pin Atmel ATtiny12-8 microprocessor, the period of multiple oscillator cycles, which is proportional to the inductance, can be sensed. Applications include metallic proximity sensing and seismic detection. The Colpitts oscillator output is level-shifted using resistors R4 and R5 to a zero of about 1.2 V, which is the microprocessor's analog comparator reference voltage. The oscillation frequency of a Colpitts oscillator is determined by its circuit components. The RISC-based microprocessor, operating at an instruction rate of 8 MIPS, counts the number of LC oscillator cycles between a fixed number of crystal-oscillator clocks. With the circuit shown, values of capacitors C1 and C2 should be chosen so that the maximum LC oscillator frequency is about 500 kHz. Frequency measurements are made for 32.5 ms. At the end of each measurement, four hexadecimal ASCII characters representing the number of cycles of the LC oscillator are serially transmitted. The online version of this article includes the ATtiny12 source code and HEX file.
The described circuit utilizes a classic Colpitts oscillator configuration, which is well-regarded for its stability and reliability in generating oscillations. The oscillator's frequency is primarily determined by two capacitors (C1 and C2) and an inductor (L), allowing for precise tuning to achieve the desired frequency range. The choice of C1 and C2 is critical, as they directly influence the maximum frequency output, which should be set to approximately 500 kHz for optimal performance in the intended applications.
The Atmel ATtiny12-8 microprocessor serves as the central processing unit, executing the counting of oscillator cycles. With a processing speed of 8 MIPS, the microprocessor efficiently counts the number of cycles over a defined period of 32.5 ms, leveraging its high-speed operation to ensure accurate frequency measurements. The output from the Colpitts oscillator is conditioned through resistors R4 and R5, which level-shift the signal to align with the microprocessor's analog comparator reference voltage of approximately 1.2 V. This level shifting is essential for reliable detection of the oscillator's output by the microprocessor.
The application of this circuit extends to various fields, including metallic proximity sensing, where small changes in inductance can indicate the presence of metallic objects, and seismic detection, where variations in inductance may correlate with ground movements. The serial transmission of the measured cycles as hexadecimal ASCII characters allows for easy integration with other systems or data logging applications.
In summary, this circuit design showcases the integration of a Colpitts oscillator with an ATtiny12 microprocessor to create a sensitive and responsive inductance measurement system, suitable for a range of practical applications. The inclusion of source code and HEX files in the online version enhances the accessibility and usability of the design for engineers and developers.Small inductance changes on the order of 0. 01% can easily be sensed over a wide range with a simple circuit connected to a serial port ( see the figure ). Using a classic Colpitts oscillator interfaced to an eight-pin Atmel ATtiny12-8 microprocessor, the period of multiple oscillator cycles ”which is proportional to the inductance ”can be sensed
. Applications include metallic proximity sensing and seismic detection. The Colpitts oscillator output is level-shifted using R4 and R5 to a zero of about 1. 2 V, which is the microprocessor`s analog comparator reference voltage. The oscillation frequency of a Colpitts oscillator is: The RISC-based microprocessor (operating at an instruction rate of 8 MIPS) counts the number of LC oscillator cycles between a fixed number of crystal-oscillator clocks. With the circuit shown, values of C1 and C2 should be chosen so that the maximum LC oscillator frequency is about 500 kHz.
Frequency measurements are made for 32. 5 ms. At the end of each measurement, four hex ASCII characters representing the number of cycles of the LC oscillator are serially transmitted. The online version of this article at includes the ATtiny12 source code and HEX file.
The described circuit utilizes a classic Colpitts oscillator configuration, which is well-regarded for its stability and reliability in generating oscillations. The oscillator's frequency is primarily determined by two capacitors (C1 and C2) and an inductor (L), allowing for precise tuning to achieve the desired frequency range. The choice of C1 and C2 is critical, as they directly influence the maximum frequency output, which should be set to approximately 500 kHz for optimal performance in the intended applications.
The Atmel ATtiny12-8 microprocessor serves as the central processing unit, executing the counting of oscillator cycles. With a processing speed of 8 MIPS, the microprocessor efficiently counts the number of cycles over a defined period of 32.5 ms, leveraging its high-speed operation to ensure accurate frequency measurements. The output from the Colpitts oscillator is conditioned through resistors R4 and R5, which level-shift the signal to align with the microprocessor's analog comparator reference voltage of approximately 1.2 V. This level shifting is essential for reliable detection of the oscillator's output by the microprocessor.
The application of this circuit extends to various fields, including metallic proximity sensing, where small changes in inductance can indicate the presence of metallic objects, and seismic detection, where variations in inductance may correlate with ground movements. The serial transmission of the measured cycles as hexadecimal ASCII characters allows for easy integration with other systems or data logging applications.
In summary, this circuit design showcases the integration of a Colpitts oscillator with an ATtiny12 microprocessor to create a sensitive and responsive inductance measurement system, suitable for a range of practical applications. The inclusion of source code and HEX files in the online version enhances the accessibility and usability of the design for engineers and developers.Small inductance changes on the order of 0. 01% can easily be sensed over a wide range with a simple circuit connected to a serial port ( see the figure ). Using a classic Colpitts oscillator interfaced to an eight-pin Atmel ATtiny12-8 microprocessor, the period of multiple oscillator cycles ”which is proportional to the inductance ”can be sensed
. Applications include metallic proximity sensing and seismic detection. The Colpitts oscillator output is level-shifted using R4 and R5 to a zero of about 1. 2 V, which is the microprocessor`s analog comparator reference voltage. The oscillation frequency of a Colpitts oscillator is: The RISC-based microprocessor (operating at an instruction rate of 8 MIPS) counts the number of LC oscillator cycles between a fixed number of crystal-oscillator clocks. With the circuit shown, values of C1 and C2 should be chosen so that the maximum LC oscillator frequency is about 500 kHz.
Frequency measurements are made for 32. 5 ms. At the end of each measurement, four hex ASCII characters representing the number of cycles of the LC oscillator are serially transmitted. The online version of this article at includes the ATtiny12 source code and HEX file.
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