Budget Tools Review: Handheld MLX90640 Thermal Camera

September 22, 2023




Thermal cameras, once rather exotic pieces of test equipment, are now commonly available for a few hundred dollars each for low-end models, and well into the thousands for more capable units. Being able to see thermal patterns with this type of instrument is a useful tool for equipment diagnosis and optimization, and having one available could certainly generate new use ideas.

While these devices typically tend to be beyond impulse-buy territory, for this budget test equipment review I was able to get my hands on an MLX90640 IR camera, which costs a mere $98 on Amazon as of this writing. The resolution, however, may not be as good as you would like. It’s certainly not good enough to hunt commandoes in South America if that’s where your idea of thermal imaging comes from.*

These thermal units have all the basics, with none of the frills of more developed instruments. The device’s housing and electronics substrate is a quartet of printed circuit boards, with a power switch and two buttons as the only user inputs. One button saves images, while the other puts it into USB mode to transfer files to a computer. While the basic design seems like an acceptable tradeoff to keep the unit’s price down, its low resolution may not be.

Thermal Resolution: 24x32, LCD Resolution: 240x320

Raspberry Pi Pico, broken in a manner that produces a large amount of heat near the USB connector. (Image Credit: Jeremy Cook)

Looking at the unit’s stats, LCD resolving power is advertised as 240x320, while the MLX90640 IR sensor is much lower at 24x32 pixels. To put things in perspective, consider that the original Game Boy’s resolution was 160x144 pixels, and that for another hundred dollars or so other budget units are available with several times the thermal resolution, plus a housing.

My experience with the device is that it does a good job in general heat mapping applications, such as showing if your 3D printer’s heated bead is broadly uniform, if lights are indeed hot, and where (generally) heat on a PCB is coming from. Home applications, such as visualizing where heat is lost to the environment via windows or leaks, would be another way such a unit could be useful.

At the same time, the resolution is low enough that it can be difficult to tell what you’re looking at without careful consideration. If you need to know exactly which component on a PCB is fried and needs to be replaced, this will only get you in the ballpark. 

Bottom Line: Buy or Don’t Buy?

(Image Credit: Jeremy Cook)

For a sub-$100 item, this thermal camera is an entertaining device, with some useful functionality. Its basic PCB design would also make it a ripe hacking/modification target, though if that’s your goal you might consider something like Adafruit’s MLX90640 breakout. That being said, what’s reviewed here does give you a full visualization, battery, and storage setup. Strangely enough, it seems to timestamp the images to the Unix epoch, with my computer showing thermal images taken in late December 1969

The bottom line is that the device's low resolution limits it to rather basic applications, but it’s still good enough to give you a broad heat profile of the surroundings. It’s enjoyable to use, but for my purposes I’d likely look to spend a bit more money and get a higher-resolution device. That being said, we are giving away the unit reviewed here, so if you find it interesting be sure to enter the contest below:

*It’s even less useful if they cover themselves in mud to conceal heat signatures. They may then spring Ewok-style traps, constructed while gratuitously flexing, in order to overcome your advanced alien technology.

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