Thepjit Cheypoca

Front-end interfacing circuit for capacitive sensor

This paper presents an interfacing circuit for capacitive sensor using charge amplifier formed a capacitance-to-voltage converter. The proposed circuit is suitable for the front-end analog-to-digital converter (ADC) and wide variable range of sensing capacitance. The achieved output voltage provides a linear transfer characteristic and fast response. The circuit configuration is implemented using only commercially available devices. The performances of proposed circuit are confirmed by experimental results.

High efficiency postprocessor for generic NC machine

Postprocessor for generic numerical control (NC) machines is introduced in this article. The proposed postprocessor can convert the cutter location data from general CAD/CAM system or the path data from halftone bitmap picture to NC machine control command in the form of standard G-code. The purpose of this work is proposed a high efficiency postprocessor that can be generated linear and helical interpolation in G-code machine command without requiring CAD/CAM system facility. The input data of the postprocessor can also be directly acquired from x-y coordinates of workpiece. The proposed postprocessor is developed using visual C# programming language under window XP environment. G-code generated from the proposed postprocessor using the cutter location data of sample bitmap picture is used for experimental demonstration with generic NC machine. As the result, the proposed postprocessor exhibits a benefit for simple NC machine tool.

Bitmap picture to toolpaths converter for NC machine

A simple method to create the toolpaths from bitmap picture of the workpiece for NC machine is described in this article. Halftone process is used to reproduce a continuous tone picture to binary tone picture for making a prototype picture. The obtained two dimensions picture with halftone process is employed to create the toolpaths of the sample workpiece. The workpiece dimension can be scaled to limitation of work table of NC machine by user with independent of picture resolution. The toolpaths are created as cutter location data (CL) that can be imported to postprocessor for NC machine. The proposed method is developed using visual C# programming language under window environment. Experimental implementation exhibits that the proposed bitmap picture to toolpath converter is efficient for the postprocessor to generate machine command for sculpture the workpiece from bitmap picture.

4–20mA current transceiver

A method for realization of current transceiver is proposed in this paper. The proposed current transceiver can simultaneously transmit and receive the industrial standard current signal 4-20 mA. Only one transmission loop or one pair of wire is required for current signal transmission and receive between two stations. The input and output signals are in the voltage form that is suitable and convenient for industrial applications. Realization of the proposed transceiver is based on the use of voltage-to-current converter to transmit and receive a current signal. Simulation results demonstrating the performance of the proposed scheme are agreed with the expected values. The leakage signal between input and output of transceiver in term of crosstalk is about -66.8 dB.

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.