Graphical Pressure Mapping of a 2288 Sensing-Point Matrix Pressure Sensor Using Raspberry Pi

Abstract

A pressure sensor reading method has been developed continuously along with the different types of requirements, including in medical fields. A method to read piezoresistive matrix pressure sensors with 2288 sensing points is described in detail. The presentation of the output is in 2-D color graphics representing the pressure with a specific color. The matrix sensor is intended for mapping the body surface pressure of bedridden patients. The pressure sensor points are arranged into a 44 x52 matrix rows and columns. Selecting the row and column will result in choosing the correct sensing points. The selection of rows and columns utilizes multiplexers and demultiplexers to reduce the input-output pins of the microcontroller. This system requires only one channel analog-to-digital converter (ADC) because the pressure sensor points are selected using a raster scan of row and column matrix. The pitch between sensors (0.5 cm pitch) provides very detailed information about the position and the value of the pressure. Many applications require such precision, such as the profile of foot pressure, the palm of hand pressure, and the back of a bedridden patient. The speed of reading the entire matrix is about 1 second, which is fast enough for this application. An Atmega2560 microcontroller performs the raster scanning process and converts the voltage into digital values. Atmega2560 sends the data serially via USB port to a Raspberry Pi computer. This computer shows the data into a four-color gradation heatmap that maps the pressure to the sensor.