Sensor Circuit Research Articles

The design and implementation of an instrument for converting angular velocity to linear velocity based on arduino atmega 2560

The experiment tool of converting angular velocity into linear velocity has been built to support the physics education in the Physics Department of Tadulako University. In this project, the experimental tool has been designed, manufactured, and tested to convert the angular velocity value to linear velocity based on Arduino ATMega 2560. The stages of this research begin with the design and manufacture: mechanical system, optical sensor circuit, stepper motor circuit, the circuit of LCD and keypad controlled by Arduino ATMega 2560. The next step is the building controlling program as the brain of this instrument. This experimental tool has been tested and working properly. It operates for a rotation speed range of 1 rpm - 112 rpm. The value of converted linear velocity both theoretically and measured value is relatively the same.

A 450-$\mu$ A 128-dB Dynamic Range A/D CMOS Interface for MOX Gas Sensors

This paper presents a fast high-linearity low-power versatile interface circuit for MOX gas sensor. The device is based on a resistance-to-frequency converter with digital output, featuring 128dB-Dynamic Range with 8-bit accuracy. This is achieved with a constant measurement time of 250ms (i.e. with 4Hz output data-rate). The ASIC covers the $100\Omega $ -1M $\Omega $ resistive range, with large programmability for the sensor resistance values. Large linearity (no glitches) is achieved with a single-scale measurement arrangement. The design effort reduces the power consumption to fit portable devices applications. The interface is realized in a standard CMOS 130nm technology with an area of $125000~\mu \text{m}^{2}$ and $450~\mu \text{A}$ -Total Current from a single 1.5V supply. Electrical and chemical measurements with a SnO2 sensor validate the results, showing high minimum CO detection capability in ambient air of 5ppm.

The Implementation of a Low Power Environmental Monitoring and Soil Moisture Measurement System Based on UHF RFID.

A smart sensor label based on the integration of ultra high frequency (UHF) radio frequency identification (RFID) technology and sensors is presented. The label is composed of a semi-active system that measures temperature, light, relative humidity and gravimetric water content (GWC) in the soil. The deployed system provides a simple, cost effective solution to monitor and control the growing of plants in modern agriculture and is intended be a part of a smart wireless sensor network (WSN) for agricultural monitoring. This paper is focused on analysis and development of a moisture sensor to measure GWC. It is based on a capacitance measurement solution, the accuracy of which is enhanced using several sensor driving frequencies. Thanks to the cancellation of supply voltage variations, the modeling of the GWC sensor and readout circuit was correct. The results we measured were close to modeled values. The maximum measurement resolution of the capacitive moisture sensor was 0.07 pF. To get the GWC from measured capacitance, a scale was used to weigh the mass of water in the soil. The comparison between capacitance measurement and calculated soil GWC is presented. The RFID measurement system has energy harvesting capabilities and an ultra-low power microcontroller, which uses embedded software to control the measurement properties. The microcontroller has to choose the appropriate model depending on the measured amplitude and chosen frequency to calculate the actual voltage on the sensing capacitor.

A2Event: A Micro-Watt Programmable Frequency-Time Detector for Always-On Energy-Neutral Sensing

Internet of Things (IoT) sensors are becoming more and more intelligence and unobtrusive, surrounding us in everyday life. A key requirement for those devices is to be “always-on” performing “smart” detection to catch only the events of interest when they occur. A recent and trend is to design low power circuit to extract features close to the sensors without an analog-digital conversion. The goal is to achieve place-and-forget deployment with perpetual operation: this poses the challenge of achieving micro-watt power consumption of the always-on analog event detector and of harvesting energy from environmental sources, to supply the smart sensor. This paper presents A2Event (Analog to Event), a microwatt programmable pattern recognition circuit for analog sensors, with up to 128 simultaneous time-frequency features exploiting mixed-signal low power design, which is able to generate an event when a targeted pattern is recognized. Moreover, the paper proposes a self-sustaining always-on smart audio detector that combines A2Event with energy harvesting to detect events of interests perpetually. Experimental results show that A2Event consumes only 26.89 μW in always-on mode, during the time-frequency feature-extraction, while the whole system consumes only 63 μW during pattern recognition including the power for a commercial MEMS microphone and the energy harvesting subsystem. We demonstrate that the whole smart sensor operates perpetually when powered with a small form factor flexible photovoltaic panel in indoor lighting conditions, achieving a detection accuracy of 100% in the detection of two different audio streams.

First- and Second-Order Piezoresistive Coefficients of CMOS FETs From Strong Into Weak Inversion

For many years, researchers have noted that the stress response of MOS transistors exhibits strong deviations from a pure mobility behavior as the devices exit strong inversion, but there has been no easily accessible stress model that sensor designers can use in the design of their devices. In this work, generalized piezoresistance coefficients are presented that provide continuous modeling of the stress dependencies of CMOS FETs from weak into strong inversion. The models presented here incorporate both standard mobility variations plus the additional impact of threshold voltage changes on the stress responses in all regions of operation. The theory predicts both first- and second-order longitudinal and traverse piezoresistive coefficients for PMOS and NMOS devices that are verified with experimental results. The threshold voltage variations represent common-mode terms, so orthogonal differential pairs of MOSFETs can still be utilized to directly measure the important mobility components of the overall stress response, and the impact of the threshold voltage terms on sensor circuits may be reduced with differential design.

High-accurate Resistance Measurement Method for Sensor Circuit

An accurate resistance measuring circuit which is used complementary measurement and input compensation to make radiometric method as ideal as possible and reduce the influence that OAs’ stray terms results based on radiometric method and dual-slope ADC circuit is proposed to solve the problem that we can’t balance the precision and detection range of resistance measurement. The accuracy of method is almost related to the reference resistor. It can be calculated that the resistances near the reference resistance measurement error is less than 0.02% after using the complementary measurement under the high-precision OAs, and the measurement error is an order of magnitude smaller after using the input compensation. It is shows that the measurement error could be less than 1% with non-precision OAs. This circuit can be widely applied to sensor circuit.

Development and Performance Analysis of a Cost-Effective Integrated Light Controller

An integrated sensor based daylight responsive light controller has been designed and developed. The developed cost-effective light controller performs on logical decision derived from output of integrated sensor circuit comprising of daylight sensor and occupancy sensor. The performance analysis has also been carried out to understand the actual operating condition of the system using different sensors to control lamp circuits in small indoor lighting applications. The sensitivity levels of the photo sensor (i.e. a Light Dependent Resistor or LDR) and the occupancy sensor (i.e. a Passive Infrared Sensor or PIR) circuits can be adjusted through in-built tuning facility in developed circuit after experimental measurement of the response characteristics of the both sensors. By monitoring the indoor lighting system with the developed controller, it is possible to reduce the usage of electrical energy during the absence of occupant in any room. It is also possible to vary lamp output according to the seasonal variation in daylight level by selecting different reference voltage level and to use minimum electrical energy by utilizing the available daylight. It is a low cost solution due to the advantage of components and the sensors in the market at low cost.

Dynamic and tunable metabolite control for robust minimal-equipment assessment of serum zinc

Bacterial biosensors can enable programmable, selective chemical production, but difficulties incorporating metabolic pathways into complex sensor circuits have limited their development and applications. Here we overcome these challenges and present the development of fast-responding, tunable sensor cells that produce different pigmented metabolites based on extracellular concentrations of zinc (a critical micronutrient). We create a library of dual-input synthetic promoters that decouple cell growth from zinc-specific metabolite production, enabling visible cell coloration within 4 h. Using additional transcriptional and metabolic control methods, we shift the response thresholds by an order of magnitude to measure clinically relevant zinc concentrations. The resulting sensor cells report zinc concentrations in individual donor serum samples; we demonstrate that they can provide results in a minimal-equipment fashion, serving as the basis for a field-deployable assay for zinc deficiency. The presented advances are likely generalizable to the creation of other types of sensors and diagnostics.

Wideband Hybrid Envelope Tracking Modulator With Hysteretic-Controlled Three-Level Switching Converter and Slew-Rate Enhanced Linear Amplifier

A wideband hybrid Envelope tracking (ET) modulator utilizing a hysteretic-controlled three-level switching converter (3L-SWC) and a slew-rate enhanced linear amplifier (LA) are presented. In addition to smaller ripple and lower losses of 3L-SWCs, employing the proposed hysteresis control loop results in a higher speed loop and wider bandwidth converter, enabling over 80 MHz of switching frequency. A concurrent sensor circuit monitors and regulates the flying capacitor voltage $V_{\mathrm{ CF}}$ and eliminates the conventionally required calibration loop to control it. The hysteretic-controlled 3L-SWC provides a high percentage of power amplifier (PA) supply load current with lower ripple, reducing the LA high-frequency current and ripple cancellation current, improving the overall system efficiency. A slew-rate enhancement (SRE) circuit is employed in the LA, resulting in slew rate of over 307 V/ $\mu \text{s}$ and bandwidth of over 275 MHz for the LA. The SRE circuit provides a parallel auxiliary current path directly to the gate of the class-AB output stage transistors, speeding-up the charging or discharging of output without modifying the operating point of the remaining LA, while maintaining the quiescent current of the class-AB stage. The supply modulator is fabricated in a 65-nm CMOS process. The measurement results show the tracking of long-term evolution (LTE)-40-MHz envelope with 93% peak efficiency at 1-W output power, while the SRE is disabled. Enabling the SRE, it can track LTE-80-MHz envelope with peak efficiency of 91%.

Photochemical Reduction of Silver Precursor and Elastomer Composite for Flexible and Conductive Patterning.

The development of ink-based printing techniques has enabled the fabrication of electric circuits on flexible substrates. Previous studies have shown that the process method which uses a silver (Ag) precursor (AgCF3COO) and electrospun poly(styrene-block-butadiene-block-styrene) (SBS) can yield patterns with high conductivity and stretchability. However, the only method to reduce the Ag precursor absorbed in SBS is chemical reduction using a toxic solution. Here, we developed a process to fabricate a high-conductivity pattern via laser reduction by photo-chemical reaction without toxic solutions. The Ag precursor was absorbed in electrospun SBS to form a composite layer (composite SBS) with modified properties, that could more effectively absorb the photon energy than SBS without the Ag precursor. We analyzed the properties of this material, such as its light absorption coefficient, heat conductivity, and the density of both SBS and composite SBS to allow comparison of the two materials by numerical simulation. In addition, we fabricated patterns on highly heat-sensitive substrates such as burning paper and a polyethylene terephthalate (PET) thin film, as the pattern can be implemented using very low laser energy. We expect the proposed approach to become a key technology for implementing user-designed circuits for wearable sensors and devices on various flexible substrates.

Design of a Remote Real-Time Monitoring System for Multiple Physiological Parameters Based on Smartphone.

Background Utilization of the widely used wearable sensor and smartphone technology for remote monitoring represents a healthcare breakthrough. This study aims to design a remote real-time monitoring system for multiple physiological parameters (electrocardiogram, heart rate, respiratory rate, blood oxygen saturation, and temperature) based on smartphones, considering high performance, autoalarm generation, warning transmission, and security through more than one method. Methods Data on monitoring parameters were acquired by the integrated circuits of wearable sensors and collected by an Arduino Mega 250 R3. The collected data were transmitted via a Wi-Fi interface to a smartphone. A patient application was developed to analyze, process, and display the data in numerical and graphical forms. The abnormality threshold values of parameters were identified and analyzed to generate an autoalarm in the system and transmitted with data to a doctor application via a third-generation (3G) mobile network and Wi-Fi. The performance of the proposed system was verified and evaluated. The proposed system was designed to meet main (sensing, processing, displaying, real-time transmission, autoalarm generation, and threshold value identification) and auxiliary requirements (compatibility, comfort, low power consumption and cost, small size, and suitability for ambulatory applications). Results System performance is reliable, with a sufficient average accuracy measurement (99.26%). The system demonstrates an average time delay of 14 s in transmitting data to a doctor application via Wi-Fi compared with an average time of 68 s via a 3G mobile network. The proposed system achieves low power consumption against time (4 h 21 m 30 s) and the main and auxiliary requirements for remotely monitoring multiple parameters simultaneously with secure data. Conclusions The proposed system can offer economic benefits for remotely monitoring patients living alone or in rural areas, thereby improving medical services, if manufactured in large quantities.

Analyzing the effect of the Front-end circuit for the FBAR sensor

The FBAR sensor can be affected severely by its front-end circuit, especially the phase noise; however, it has rarely been discussed up to now. Herein, we analyze the influence of phase noise in the front-end circuit on an FBAR humidity sensor. A frequency shift detecting system was designed combined with the theoretical calculation and Advanced Design System (ADS) simulation. The available range of frequency shift is seriously influenced by phase noise particularly for its lower limit, improved from 380 kHz to 200 kHz during the reduction of phase noise from − 107.92 dBc/Hz@1 MHz to − 135.97 dBc/Hz@1 MHz. Simultaneously, the display range for the FBAR humidity sensor system increases by 23% thanks to the reduction of it by − 28 dBc/Hz@1 MHz. Summarily, the phase noise optimization in the front-end circuit can effectively improve the display range of sensor systems, which is not limited to the application of FBAR humidity sensors.

Prototype single-ended and pseudo-differential charge processing circuit for micro-strip silicon and gaseous sensors read-out

Detector read-out electronics for Physics Experiments as for example Compressed Baryonic Matter experiment at FAIR, Darmstadt, Germany, should meet tight requirements concerning noise (ENC < 1000 e− rms to guarantee event reconstruction), power consumption (< 10 mW/channel) and average input hit frequency of 250 kHit/s/channel. The ICs design should take into account not only the charge processing parameters but also the impact of the environmental and system-level conditions like radiation, noisy power supply, and temperature to ensure reliable and stable operation during an experiment in a system built with tens of thousands of devices. The operation with gaseous detectors requires particularly effective protection of the inputs against electrostatic discharge. The ESD protection circuit (in particular based on MOS transistors), together with the sensor itself, or AC-coupling capacitors (after irradiation) can be however a source of additional leakage current flowing into the first stage of charge processing chain and affecting the performance. The read-out electronics (in particular first stage—charge sensitive amplifier, CSA) and detector-related noise can be mitigated using proper filtration and signal shaping. However, noise introduced by external sources, like power supply interference, can not be limited only via proper shaping and filtration. When LC filtering is not possible (due to high magnetic fields), it may be beneficial to use differential or pseudo-differential signal processing. The purpose of this work was to test several ideas to improve noise performance and to make the architecture of charge processing chain configurable to better adapt to different target radiation imaging applications. The ASIC comprises four single-ended and four pseudo-differential signal processing channels. In both types of channels configurable slow shaper configuration is used—it is switchable CR-RC2 type shaper and complex conjugate poles 3rd order shaper. CSA feedback in single-ended architecture can be selected between MOS transistor working in a linear region and double-polarity Krummenacher circuit for leakage current compensation capability. The chip was designed and fabricated in Q4 2018 using 180 nm process. Front-end single-ended and differential channels occupy the area from 950 × 60 μm2 up to 1150 × 125 μm2 and consume 5 mW up to 12 mW of power respectively. The work presents design and measurements results.

The characterization of giant magnetoresistance sensor for prototype of bridge deflection measurement

The Shift is the displacement of the object’s position from its initial state to its final state. Shifting phenomena can be found in landslides, cracks in building construction, or bridges. One of the sensors used to detect deflection is the GMR sensor. The GMR sensor is a sensor that can detect changes in magnetic fields. The configuration of permanent magnets and GMR sensors can be used to detect micro-order shifts. This research was conducted in several stages, namely making a bridge model, making a sensor circuit, signal conditioning circuit and testing characteristics. The research method is to place a permanent magnet on the static and GMR sensors on the part that is easily shifted on the bridge. The test results show that the GMR sensor can detect shifts in the 10micro order and the sensitivity of the GMR sensor can be obtained at 0.0131 Volt / mm. The voltage response of the GMR sensor to shift distance is exponential. The maximum shift test is obtained at half the bridge span. This research can be used for monitoring bridge shifts.

Enhanced of Speed Monitoring Brushless DC (BLDC) Equipment and Controller Based on Arduino

Because the BLDC motor (Brushless Motor Direct current) does not have a brush, it sounds noisy, and maintenance is more comfortable and has a higher efficiency than induction motors. The design of monitoring and motor speed controller starts with a 5 volt DC voltage from the power supply used to supply the Arduino Pro mini. In the Arduino Pro mini potentiometer as the input circuit to accelerate or slow down the motor rotation, then Arduino will control the BLDC motor through the driver circuit. When the BLDC motor runs the speed sensor circuit will read the speed of the BLDC motor is then by Arduino will be displayed to the LCD. From the test performed can be seen form PWM (Pulse Width Modulation) it and can set the form of PWM by changing the voltage using a potentiometer in the circuit.

Investigation of a Magnetic Tunnel Junction Based Sensor for the Detection of Defects in Reinforced Concrete at High Lift-Off.

Magnetic flux leakage (MFL) testing is a method of non-destructive testing (NDT), whereby the material is magnetized, and when a defect is present, the magnetic flux lines break out of the material. The magnitude of the leaked magnetic flux decreases as the lift-off (distance from the material) increases. Therefore, for detection at high lift-off, a sensitive magnetic sensor is required. To increase the output sensitivity, this paper proposes the application of magnetic tunnel junction (MTJ) sensors in a bridge circuit for the NDT of reinforced concrete at high lift-off. MTJ sensors were connected to a full-bridge circuit, where one side of the arm has two MTJ sensors connected in series, and the other contains a resistor and a variable resistor. Their responses towards a bias magnetic field were measured, and, based on the results, the sensor circuit sensitivity was 0.135 mV/mT. Finally, a reinforced concrete specimen with a 1 cm gap in the center was detected. The sensor module (with an amplifier and low pass filter circuits) could determine the gap even at 50 cm, suggesting that MTJ sensors have the potential to detect defects at high lift-off values and have a promising future in the field of NDT.

Modeling and experimental verification of a fractional damping quad-stable energy harvesting system for use in wireless sensor networks

This paper presents the theoretical modeling and experimental verification of a quad-stable non-linear electromagnetic-induction energy harvesting (QEH) system. The suspended magnet of the QEH system consists of two aluminum caps that are circumferentially filled with copper beads for smooth axial movement. A QEH system model having fractional damping is established. Experimental investigations reveal non-linear phenomena of magnet movement such as chaos and bifurcations. The quad-stable mechanism is analyzed by virtue of Poincaré sections, bifurcation diagrams, and stroboscopic sampling in relation to the suspended magnet length and QEH system configurations. The results indicate that the length of the suspended magnet is a key parameter, and its change can give rise to the subcritical and super pitchfork bifurcations as well as the saddle-node bifurcations. Compared with the linear oscillator and mono-stable nonlinear system, the QEH system by magnetic levitation oscillations can stimulate more singular points (i.e. equilibrium points) of the magnetic force potential, and thus possesses the capability of energy harvesting across a wider frequency range as well as deliver more output current to the electric load through snap-through movements of suspended magnets. Therefore it is capable of directly driving sensor circuits for use in the wireless sensor network.

Sub-pixel response of double-SOI pixel sensors for X-ray astronomy

We have been developing the X-ray silicon-on-insulator (SOI) pixel sensor called XRPIX for future astrophysical satellites. XRPIX is a monolithic active pixel sensor consisting of a high-resistivity Si sensor, thin SiO2 insulator, and CMOS pixel circuits that utilize SOI technology. Since XRPIX is capable of event-driven readouts, it can achieve high timing resolution greater than ∼10 μs, which enables low background observation by adopting the anti-coincidence technique. One of the major issues in the development of XRPIX is the electrical interference between the sensor layer and circuit layer, which causes nonuniform detection efficiency at the pixel boundaries. In order to reduce the interference, we introduce a Double-SOI (D-SOI) structure, in which a thin Si layer (middle Si) is added to the insulator layer of the SOI structure. In this structure, the middle Si layer works as an electrical shield to decouple the sensor layer and circuit layer. We measured the detector response of the XRPIX with D-SOI structure at KEK. We irradiated the X-ray beam collimated with 4 μmϕ pinhole, and scanned the device with 6 μm pitch, which is 1/6 of the pixel size. In this paper, we present the improvement in the uniformity of the detection efficiency in D-SOI sensors, and discuss the detailed X-ray response and its physical origins.

LTPS Active Pixel Circuit With Threshold Voltage Compensation for X-Ray Imaging Applications

In this article, we proposed a low-temperature poly-silicon (LTPS) active pixel sensor (APS) circuit with threshold voltage ( ${V}_{\text {th}}$ ) compensation. LTPS thin-film transistors (TFTs) are known to degrade under long-term irradiation and this is quantified. Simulation results and experimental data confirm that the proposed APS circuit compensates the instability of LTPS TFTs and is a promising, high-performance alternative to current amorphous silicon (a-Si) pixel-based X-ray detectors.

Design of Autonomous Vibration Monitoring System

The design of the vibration monitoring system is based on the hardware of vibration sensor and signal conditioning circuit, virtual instrument as a diagnosis and alarm platform, auxiliary data acquisition card and alarm equipment. When the outside intrudes into the detection range, the vibration signal is generated and collected. The alarm is realized through the linkage of security monitoring system, so the video surveillance and video recording of the detection area are completed. In addition, the system opens the illumination equipment in the detection range to compensate for the environment of the video and deter the illegal intruders. The system includes acquisition of weak vibration signal by vibration sensor,amplification and adjustment of vibration signal by CCTV. This system has high feasibility and wide coverage. It is worth popularizing in security system in the future.