The downside is if the temperature changes, the colormap will not reflect this, obscuring the real-time visualization. Lastly, if the ‘set_clim’ function is removed and the user is able to set the clim before the loop, this can speed up the process as well. Another thing to note is that the colorbar likely will not update unless ‘plt.pause(0.01)’ is called, and unfortunately this slows down the frame rate. I don’t really recommend going over REFRESH_16_HZ due to the unstable nature of the images. One thing to note is that the refresh rate of the MLX90640 must also be changed to fit the different frame rates in order to keep up with the plotting. We were able to achieve roughly a 2.2 frames per second output rate with the blitting, however, if the image is shrunk by figsize=(9,5), it runs at roughly 3.4fps, and shrinking down to figsize=(5,3) results in about 5.4fps. The code above uses the 10x interpolation of the ‘zoom’ function to output a 240x320 thermal image. colorbar(therm1) # setup colorbar for temps cbar. zeros(mlx_shape),vmin = 0 ,vmax = 60 ) #start plot with zeros cbar = fig. subplots(figsize = ( 12, 7 )) therm1 = ax. ion() # enables interactive plotting fig,ax = plt. REFRESH_8_HZ # set refresh rate mlx_shape = ( 24, 32 ) # setup the figure for plotting plt. SDA, frequency = 400000 ) # setup I2C mlx = adafruit_mlx90640.
# MLX90640 Thermal Camera w Raspberry Pi # - 2Hz Sampling with Simple Routine # import time, board, busio import numpy as np import adafruit_mlx90640 import matplotlib.pyplot as plt i2c = busio. Using Python, we will be able to push the RPI to its limits by interpolating the MLX90640 to create a 3 frame-per-second (fps) thermal camera at 240x320 pixel resolution. Along with a Raspberry Pi computer, the MLX90640 will be used to map and record fairly high-resolution temeperature maps. It uses an array of infrared detectors (and likely filters) to detect the radiation given off by objects. The sensor used here is the MLX90640, which is a 768 pixel (24x32) thermal camera. In recent decades, as integrated circuits shrink in size, infrared detectors have become commonplace in applications of non-destructive testing, medical device technology, and motion detection of heated bodies. Shortly after the discovery of the relationship between radiation and the heat given off by black bodies, infrared detectors were patented as a way to predict temperature via non-contact instrumentation. The most significant distinction is that thermal cameras detect and filter light such that only the infrared region of the electromagnetic spectrum is recorded, not the visible region. Thermal cameras are similar to standard cameras in that they use light to record images.
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