Design and fabrication of a microcontroller based electronic weighing machine in high mass regime
Electronic weighing technology presents management with rapid, timely and accurate information that provides quick turnaround times for customers. Its popularity can be attested by its use in all the sectors of the industry. In fact, its spectrum of use spans from the traditional retail industry, to manufacturing and warehousing, to postal, health and transport industry. Ordinary microprocessor based weighing systems that utilize single point load cells, have a huge circuitry and hence render them complex to design and implement. They further have low speed and resolution. One other class of microprocessor based weighing balances utilizes faster microprocessors and has relatively high resolution. These devices often have a prohibitive price tag, as they comprise many external devices/chips. Another type of electronic weighing system utilizes a microcontroller and an 8-bit analogue-to-digital converter. It has in-built memory units to store program, data and variables. In both cases, there is compromise between range and resolution. This research work describes the design and implementation of a low-cost, high-resolution and portable digital electronic weighing system ideal for domestic, laboratory and commercial use. The system has highly reduced circuitry as it utilizes a standalone microcontroller chip. It essentially comprises of an 8bit 8051 microcontroller with a local memory module for storing data from the ADC. High resolution, without compromising range, is achieved by designing a program for interfacing a serial 10-bit ADC to the 8-bit microcontroller. This is due to the in-built Serial Programming Interface (SPI) of the microcontroller used. The developed electronic weighing balance senses, measures and displays the mass, placed on a single point load cell, on an LCD display. The system fabricated measures weights ranging from 0-19kg.