What is it?

This is a small (0.7 " x 0.4 ") breakout board for Panasonic's latest high-gain, high-performance AMG8833 Grid-Eye IR imaging array with 8 x 8 pixels that reads out temperature at 0.25 degree C resolution at either 1 or 10 Hz. The sensor has a field of view in either direction of 60 degrees and uses just 4.5 mA in the normal mode, 800 uA in standby where data is updated every 10 or 60 seconds, and 200 uA in sleep mode. The temperature range of the AMG8833 (-55 C to 125 C) is smaller than, say, the Melexis MLX90621 (-20 C to 300 C) but the temperature resolution is better, the pixel temperatures are read directly out of the sensor registers via I2C burst read (no complicated calibration coefficients or complex math) and the sensor is powered by 3.3 V so no additional diode or LDO is required for the IR array as is the case for the MLX90621. Add the fact that the AMG833 is about half the cost of the MLX90621 and the attraction become irresistible!

I chose the high-gain, high-performance version (AMG8833) of the IR array because the datasheet claims the sensor is able to detect humans (700 x 250 mm size object more than 4 C above background) at up to 7 meters away! This means just one of these devices in a room corner is enough to detect occupancy, detect and classify motion, estimate the number of people in a room, etc. This sensor can provide a lot of information about the doings in a space while protecting the privacy of the occupants to a large degree. In other words, the thermal and spatial resolution is sufficient to tell when people are in a space, about how many, and generally what they are doing (standing around, sitting down, moving, etc) but not sufficient to recognize facial features or identify specific people.

Of course, this IR array can also detect animals too either indoors or outside for tracking movement of wildlife passing by a stationary point, detecting animal trespass, and even counting daily flows of animals. The uses of this sensor are limited to your imagination, and its low cost allows you to experiment!

Why did you make it?

I like interesting new sensors and Panasonic's Grid-Eye provides thermal imaging in a large enough array and with such ease of use and low cost to be very interesting! The MEMS sensor is packaged in a rugged but small steel can that mounts onto a 10 mm x 18 mm pcb with everything needed to start streaming thermal images to your microcontroller (I use this one) for display on the serial monitor or color display.

Running in the normal mode with 10 Hz update rate provides a video image of the temperature field in a 60-degree field of view. The 8 x 8 pixel array can detect limbs and fingers up close and distinguish individuals further away.

What makes it special?

There is no end of applications for this IR imaging sensor. You can even use two or more at the same time to extend the number of pixels available on a single I2C bus by taking advantage of the two I2C addresses available with this sensor. Simply toggle the one you want to read from to 0x69 while the others default to 0x68 and then toggle the next one, read the data, and repeat. Even at 10 Hz there is plenty of time to read all of the data from multiple sensors in between data updates. With this approach, you can build an IR camera as large as your budget allows and still maintain a small, compact form factor.

But the really cool thing about the way Panasonic designed this sensor is the interrupt scheme. You can set a low and high interrupt detection threshold and then read which particular pixel or pixels exceeded the threshold and tripped the interrupt. This means you can follow in time a moving object within the 8 x 8 pixel array by a judicious setting of the threshold and by keeping track of which pixel exceeds the threshold you program and the time of the interrupt. Given that the maximum human detection distance is 7 meters and the field of view is 60 degrees this means you can track the motion of a person (or large animal) over a maximum 8 meter x 8 meter planar area (~1 m^2 per pixel). If you know the distance to the planar area, you can convert the pixel number vs time information into x-y distance versus time. This is all done by setting thresholds in an I2C register and reading pixel position after interrupt receipt so it is 1) easy to configure, 2) fast, and 3) accurate, enabling IR motion tracking over a given area or even 3-space.

I have written a basic sketch to configure the sensor, read the data, print the properly scaled 64-pixel temperatures to the serial monitor and to a color ST7735 display using an appropriate RGB color pallete scaled from minimum to maximum pixel temperature. This should be enough for you to customize the sketch for your own display, microcontroller, and usage. This sensor is really very easy to use; no complex mathematical operations or applications of arrays of coefficients, just read the 64 int16_t register values with I2C read commands, scale the result by 0.25 degree C per LSB and display the result. Easy peasy!

Order pcbs from OSH Park and assemble some of your own or buy the fully assembled and tested AMG8833 IR array breakout board and see how easy it is to add IR thermal imaging to your project!