Hackaday Prize Entry: Raspberry Pi Thermal Imaging

High up on the list of desirable technologies that are edging into the realm of the affordable for the experimenter is the thermal camera. Once the exclusive preserve of those with huge budgets, over the last few years we’ve seen the emergence of cameras that are more affordable, and most recently a selection of thermal camera modules that are definitely within the experimenter’s range. They may not yet have high resolution, but they are a huge improvement on nothing, and they are starting to appear in projects featured on sites like this one.

One such device is the Melexis MLX90621, a 16×4 pixel thermal sensor array in a TO39 can with an I2C interface. It’s hardly an impulse purchase in single quantities and nor is it necessarily the cheapest module available, but its price is low enough for [Alpha Charlie] to experiment with interfacing it to a Raspberry Pi for adding a thermal camera overlay to the pictures from its visible light camera.

The wiring for the module is simplicity itself, and he’s created a couple of pieces of software for it that are available on his GitHub repository. mlxd is a driver daemon for the module, and mixview.py is a Python graphical overlay script that places the thermal array output over the camera output. A run-through of the device and its results can be seen in the video below the break.

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Build Your Own Thermal Camera

We have featured thermal camera projects by [Max Ritter] before, but [Max] has just taken the next step: he is offering the latest version as a build-it-yourself kit. The DIY Thermocam improves on his previous designs by capturing 60 by 80 pixel thermal images, which can be combined with visible light images from an accompanying  640 by 480 pixel camera to produce the final image. It is built around the FLIR Lepton module that has been used in many of the recent commercial thermal cameras that we have seen. Max has also added a battery and display, making the whole thing a standalone camera.

The firmware that runs all this is open-source and written in C++ for easy modification, so users can build their own thermal camera.”The approach is to offer people the self-assembly kit so that they can use it as a development platform to do whatever they want to achieve with thermal imaging”[Max] told us. The kit runs €429 (about $468), with free shipping worldwide.

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Long Exposure Thermal Photography

For apparently inexplicable reasons, the price of thermal imaging cameras has been dropping precipitously over the last few years, but there are still cool things you can do with infrared temperature sensors.

A few years ago – and while he was still writing for us – [Jeremy] came across an absurdly clever thermal imaging camera. Instead of expensive silicon, this thermal camera uses a flashlight with an RGB LED, a cheap IR temperature sensor, and a camera set up to take long exposures. By shining this flashlight/IR sensor around a dark room, a camera with a wide-open shutter can record color-coded thermal images of just about anything.

Since then, an interesting product appeared on the market. It’s the Black & Decker TLD100 Thermal Leak Detector, and it’s basically an infrared thermometer and LED flashlight stuffed into one neat package. In other words, it’s the exact same thing we saw two years ago. We’d like to thank at least one Black & Decker engineer for their readership.

[Jeremy] took this cheap, off-the-shelf leak detector and did what anyone would do after realizing where the idea behind it came from. He set up his camera, turned off the lights, and opened the shutter of his camera. The results, like the original post, don’t offer the same thermal resolution as a real thermal camera. That doesn’t mean it’s still not a great idea, though.

Simple Thermal Imager With A Lepton Module

[Andrew] designed a simple thermal imager using the FLIR Lepton module, an STM32F4 Nucleo development board, and a Gameduino 2 LCD. The whole design is connected using jumper wires, making it easy to duplicate if you happen to have all the parts lying around (who doesn’t have a bunch of thermal imaging modules lying around!?).

The STM32F4 communicates with the Lepton module using a driver that [Andrew] wrote over a 21MHz SPI bus. The driver parses SPI packets and assembles frames as they are received. Images can be mapped to pseudocolor using a couple different color maps that [Andrew] created. His code also supports min/max scaling to map the pseudocolor over the dynamic range present in the image.

Unfortunately the Lepton module that [Andrew]’s design is based is only sold in large quantities. [Andrew] suggests ripping one out of a FLIR ONE iPhone case which are more readily available. We look forward to seeing what others do with these modules once they are a bit easier to buy.

THP Hacker Bio: AKA

Thermal imaging cameras are the new hotness when it comes building DIY tools that are much less expensive than their commercial counterparts. [Mike Harrison] built a very high-resolution version from Flir’s Lepton module, but an IR temperature sensor and a servo can also create a decent image. [AKA] played around with some of these thermal imaging modules, but found them a little hard to interface. Panasonic’s Grid-EYE module, however is reasonably cheap as far as thermal imaging devices go, and can be read over an I2C bus.

[AKA]’s entry for the Hackaday Prize, the GRID-EYE Thermal Camera is one of two Prize entries that survived the great culling and made it into the quarterfinalist round. [AKA] was kind enough to sit down and do a short little interview/bio with us, available below.

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A Breakout Board For A Flir Lepton

Thermal imaging cameras are all the rage now, and one of the best IR cameras out there is Flir’s Lepton module. It’s the sensor in the FLIR ONE, a thermal imaging camera add-on for an iPhone. Somewhat surprisingly, Flir is allowing anyone to purchase this module, and that means a whole bunch of robotics and other various electronics projects. Here’s a breakout board for Flir’s Lepton.

Electron artisan [Mike] recently got his hands on a FLIR ONE, and doing what he does best, ripped the thing apart and built the world’s smallest thermal imaging camera. Compared to professional models, the resolution isn’t that great, but this module only costs about $250. Just try to find a higher resolution thermal imager that’s cheaper.

With this breakout board, you’ll obviously need a Lepton module. There’s a group buy going on right now, with each module costing just under $260.

The Lepton module is controlled over I2C, but the process of actually grabbing images happens over SPI. The images are a bit too large to be processed with all but the beefiest Arduinos, but if you’re thinking of making Predator vision with a Raspi, BeagleBone, or a larger ARM board, this is just the ticket.

You can check out some video made with the Lepton module below.

This is also project number 3000 on hackaday.io. That’s pretty cool and worthy of mention.

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