Development of a Low-cost Automated Microcontroller Based Wireless Gamma Column Scanner Prototype

Abstract

The aim of this project was to develop and test a microcontroller-based column scanner prototype, where data is transmitted wirelessly, stored and displayed on to a handheld controller module to show a scan profile of the column in real-time. A laboratory-scale scanner prototype was constructed using a wood frame; 1 m length and 0.5 m width and a circular acrylic material (diameter 25 cm and radial width 10 cm) that houses a low activity source, 114 mCi 241Am radiation source (NER-492, S/N: A-377) and Velleman K2645 GM detector. The scanner is operated by two 12 VDC geared motors and two-timing belts to drive the source-detector assembly, in both vertical and horizontal plane, along the column frame for preset increment heights of 5-10 cm movements for auto counting at the preselected preset time between 1-10s. Current scanning systems are limited to only vertical scan movement and cabled. Ultrasonic proximity sensor and 3-axis accelerometer were used to determine and limit both vertical and horizontal plane orientations of source-detector, respectively. The GM detector was connected to a microcontroller-based circuit which also controls the movement motors. Four 2.4 GHz nRFfl2401 radio modules facilitated wireless communication between the scanner and the handheld module within a radius of 100 m. A handheld controller module consisting an LCD display screen (3.5” x 2.5”) was used to display the scan configurations and results. The software used to run the microcontrollers for both scanners and the handheld module was developed using the Arduino IDE, which is an open-source software using C++. The scanner offers the option to operate in both gamma scanning mode and for use in radio tracer measurements. In gamma scanning, two modes of operation are possible; automatic and manual counting. In radiotracer measurement mode, the detector is maintained in a fixed position for counting to assume a typical field radiotracer measurement. Reliability and safety features used included: CRC, Limit switch, 3-axis accelerometer and Internal watchdog. The model column is an 8” diameter PVC pipe fitted with two 5 cm wide, 6 mm mild steel rings at 22 cm intervals to represent distillation column and separation trays in a typical industrial process setup was tested for faults using the prototype. From the scan profile generated in gamma column scanning test, it was possible to locate the two separation trays and the simulated malfunction. The obtained results were validated through a comparison with the actual physical measurements. For radiotracer experiment, the instantaneous introduction and withdrawal of the radioactive source at different time vi intervals was detected from the profile drawn in real-time display on the LCD screen with peaks corresponding to the various time intervals of radioactive source introduction and withdrawal. This project has demonstrated the possibility for the adoption of wireless control of gamma-based column scanners and wireless data transmissions to increase efficiency, minimize personnel exposure through increased operation ranges by eliminating cabling, reduced costs of operation, and has the potential to use in the harsh industrial environment. However, this prototype is suited only for laboratory demonstrations on practical applications of gamma column use in the diagnosis of industrial processes.