Anucha Kaewpoonsuk

An Amplitude Detector for Variable Frequency Sinusoidal Signals

In this paper, a JK-flip-flop-based logic circuit is described. Using two output signals of this designed logic circuit to control a buffered peak detector followed by a simple sample-and-hold circuit in sequential operation, a sinusoidal amplitude detector is proposed. The proposed detector allows the frequency of input signals to be varied over a wide range. Experimental results verifying the performances of the proposed circuit are in close agreement with the expected values

A novel resolver-to-DC converter based on OTA-based inverse-sine function circuit

A new technique for realizing the resolver-to-DC converter using the OTA-based inverse-sine function circuit is presented. The proposed converter comprises the demodulator, absolute detector, minimum detector, plusmn unity-gain amplifier, controlled signal logic circuit, and OTA-based inverse-sine function circuit. The output voltage is linearly proportional to the resolver angle with maximum absolute error of about 0.195%, which is less than the error from the conventional resolver-to-DC converter based on the similar OTA-based inverse-sine function circuit. PSPICE simulation and experimental results verifying the performances of the proposed circuit are in close agreement with the expected values.

A simple amplitude detector-based demodulator for resolver converters

This paper presents a simple method based on sinusoidal-amplitude detector for realizing the resolver-signal demodulator. The proposed demodulator consists of two full-wave rectifiers, two ±unity-gain amplifiers, and two sinusoidal-amplitude detectors with control switches. Two output voltages are proportional to sine and cosine envelopes of resolver-shaft angle without low-pass filter. Experimental results demonstrating characteristic of the proposed circuit are included.

An accurate CCII-based voltage controlled current source

In this paper, a voltage controlled current source (VCCS) providing low distortion in output signal and wide output current range is introduced. In order to obtain the high accuracy, the proposed technique employs the designed scheme to connect in feedback loop of the basic VCCS based on second generation current conveyor (CCII). This scheme consists of instrumentation and differential amplifiers and one resistor. The performances of the proposed circuit were studied through the use of PSPICE simulation program. Simulation results are agreed with the expected values.

Real-time fault notification for billboard lighting system

This paper presents a technique to implement the alert system for the faults of billboard lighting system. The proposed system consists of the current sensor module SCT-013-005 used to measure the overall current consumption of the billboard lighting system, ARDUINO UNO R3 used as the controller to determine the faults, and GSM module used to remotely transmit faulty data to the data server as well as to the user mobile via short message service. The alert data composes the current consumption of lighting system, number of the bulbs with abnormal condition, and identification number of base station. In addition, the conditions for sending notifications can be set. The billboard lighting system using seven bulbs connected in parallel is employed to test the performance of the proposed notification system. Test results verify that the proposed system can function correctly.

ZigBee based wireless temperature monitoring system for shrimp farm

This paper proposes a design and implementation of wireless temperature monitoring system for shrimp farm based on ZigBee technology. The proposed system consists of three wire resistance temperature device (RTD) type PT-100, Current source circuit, XBee Pro module, 2.4 GHz antenna with gain 5dBi, Arduino Uno R3 microcontroller board and LabVIEW program for monitoring and control system. Experimental results with standard temperature bath show that the proposed system can monitor temperature with satisfied data. The maximum error of temperature is about 0.25 percents. The maximum range of system is about 500 meters.

Ultrasonic measuring circuit using sample and hold method

This paper presents the simple ultrasonic measuring circuit using sample and hold method. The proposed method is to measure the transit time of ultrasonic wave in fluid. The system consists of the pulse generator circuit, amplifier circuits, band pass filter, detector circuit, comparator circuit, timing circuit, saw-tooth generator circuit, and sample and hold circuit. The voltage output signal of the proposed technique is proportional to the transit time. The sugar solution with differential concentrations was measured in our experiment as an illustrative case study. Experimental results show that the proposed method can measure the transition time of the ultrasonic signal with satisfied sensitivity and good linearity.

An amplitude-to-digital converter

An alternative approach to realize the amplitude detector for variable frequency sinusoidal signals is described in this paper. Based on the counter method of the A/D converter controlled by the designed logic circuit, the proposed converter can produce digital output signals proportional to the peak amplitude of analog input signals without low-pass filter. The conversion time is two cycle periods of the input signal. In addition, the output signal with small ripple can be achieved. Experimental results verifying the performances of the proposed circuit are in close agreement with the expected values.

A simple CMOS-based algorithmic ADC

This paper presents a one-bit cell of reverse Gray-code algorithmic analog-to-digital converter. The proposed converter comprises of full-wave rectifier, current mirrors, and current comparator. The realization method is simple, small in size, and suitable for integrated circuit form. The design strategy is based on the MOS biased at the edge of conduction to provide a low accumulated error and a low distortion in the transfer characteristic. An N-bit resolution can be achieved by cascading of the N proposed one-bit cells. PSPICE simulation results supporting the characteristics of proposed circuit are agreed with the expected values.