System Board 6266 MAXREFDES82 : Smart Force Sensor Overview Maxims MAXREFDES82 features a next generation industrial, smart force sensor. Mounted on a quadrant of load cells channeled into a multi-channel, 24-bit analog-to-digital converter (ADC), MAXREFDES82 senses weight and center of mass for objects placed on the platform. The scale provides full-scale responses up to 780g. The user interface provides an active display of center of mass on the platform, as well as total measured weight. In addition to serving as a smart force sensor, the design works very well as a ruggedized touch inter- face with force sensing. The system consumes less than 50mA during normal operation and features a USB interface for quick evaluation and integration. The board is designed in a compact form factor for rapid evaluation or installation. Applications 3D Human Interface Input Device Battery-Powered Instrumentation Industrial Control and Measurement Features 3D Human Interface Input High Precision Weigh Scale Low Power ADC Compact Competitive Advantages Rugged, Cost Effective, Flexible 3D Human-Interface Input Device High Precision, High Resolution Measurements Fast, Low-Power Data Acquisition Introduction Technology marches forward, constantly and irrepressibly altering the world of human to devices interfaces. From mobile device touch screens to weigh scales with electrodes for body composition, machines continue to add more capability, and different ways to gather their measurements. Every so often, a truly elegant concept emerges, merging technology, design and simplicity. MAXREFDES82 is one such elegant concept. This reference design is an industrial, smart force sensor. The design measures mass, as well as the center of mass of the object on it. This combination of features and speed means that MAXREFDES82 operates as both a weigh scale and a touch interface with force sensing. Built with a plastic plate, the system ideally meets the needs of industrial human machine inter- faces (HMI). The reference design features the MAX11254 24-bit, 6-channel, 64ksps delta-sigma ADC with SPI interface. Four load cells are mounted on a quadrant plane to detect touch forces applied on the flat plastic plate. Based on the forces applied on each individual load cell, the system displays the total force magnitude, and the coordinates of the force center. The force magnitude and coordinates are scanned approximately each 10 milliseconds. The system includes a thin-film-transistor (TFT) liquid crystal display (LCD) module, digitally showing the forces on each indi - vidual load cell, and the total force applied on the top plate. The LCD module also graphically displays the force magnitude and the coordinates of the force center. Page <1> 04/05/16 V1.0The MAXREFDES82 reference design consumes minimal energy and is powered by a USB port. A PC-side graphical user interface (GUI) program is also included to facilitate the human interface input demonstration and development. The MAXREFDES82 reference design block diagram (Figure 1) demonstrates how a touch force and its movement are cap- tured and used in a 3-dimensional (3D) human-interface input device. The design includes source files for the microcontroller to enable developers to quickly evaluate and customize the design for their specific applications with minimal firmware or hard - ware changes. The board is designed in a compact form factor for rapid evaluation or installation. Figure 1. MAXREFDES82 reference design block diagram. Detailed Description of Hardware Figure 1 shows the MAXREFDES82 reference design system block diagram. Figure 2 shows the assembly view of the design. Also refer to the schematic for circuit details. Figure 2. MAXREFDES82 reference design assembly views. Page <2> 04/05/16 V1.0