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DIY-Thermocam: A low-cost thermal imager based on the FLIR Lepton sensor

diy-thermocam.net

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Re: DIY-Thermocam: A low-cost thermal imager based on the FLIR Lepton sensor

#11

Post by ZiiS »

OJFord wrote: post #7

Can you make a slightly crappier version with a much cheaper visible spectrum sensor? I don't know much (obviously) about how they work, but intuitively it would seem a bit weird to me if they just happened to be restricted to exactly the same part of the spectrum as our eyes as a hardware limitation. Can you ignore data about visible red and higher in firmware, and get a thermal image that's obviously not as good as…

Yes standard sensors have a IR filter that can usually be removed. Raspberry PI sell thier camera without the filter as removal is tricky. However this is only very near IR nothing close to the capabilities of this.

Re: DIY-Thermocam: A low-cost thermal imager based on the FLIR Lepton sensor

#12

Post by kragen »

OJFord wrote: post #7

Can you make a slightly crappier version with a much cheaper visible spectrum sensor? I don't know much (obviously) about how they work, but intuitively it would seem a bit weird to me if they just happened to be restricted to exactly the same part of the spectrum as our eyes as a hardware limitation. Can you ignore data about visible red and higher in firmware, and get a thermal image that's obviously not as good as…

prolly not for room temperature; planck's law tells us there's a rapid exponential dropoff of spectral radiance with f/T, and room temperature is about a third of the draper-point temperature, so you'd expect undetectably low radiance below about 2000 nm, three times the 700-nm limit of visible light

silicon's bandgap of 1.1 electron volts corresponds to about a 1100-nm wavelength; is that the minimum photon energy a cmos sensor can detect?

if i did this calculation right, the spectral radiance at 1100nm should be a couple million times dimmer than the 700nm radiance at the draper point

        You have: h c / boltzmann 700 nm 300 K
        You want:
                Definition: 68.513185
        You have: h c / boltzmann 2000 nm 300 K
        You want:
                Definition: 23.979615
        You have: h c / boltzmann 700 nm tempC(525)
        You want:
                Definition: 25.751996
        You have: h c / boltzmann 1100 nm 300 K
        You want:
                Definition: 43.599299
        You have: exp(43.6-25.8)
        You want:
                Definition: 53757836
11³/7³ is about 4 and 54/4 is 'a couple' to me

so it's not literally impossible to detect but it seems like you would probably need special conditions like a light-tight darkroom or a thermal emitter switching on and off at a particular known frequency for millions of cycles

Re: DIY-Thermocam: A low-cost thermal imager based on the FLIR Lepton sensor

#13

Post by detaro »

OJFord wrote: post #7

Can you make a slightly crappier version with a much cheaper visible spectrum sensor? I don't know much (obviously) about how they work, but intuitively it would seem a bit weird to me if they just happened to be restricted to exactly the same part of the spectrum as our eyes as a hardware limitation. Can you ignore data about visible red and higher in firmware, and get a thermal image that's obviously not as good as…

> but intuitively it would seem a bit weird to me if they just happened to be restricted to exactly the same part of the spectrum as our eyes as a hardware limitation

being restricted to ~visible spectrum is a design goal for a camera, since we expect it to produce images that look like what we see. Your usual camera sensor will see a bit further into infrared than humans do (hence why cameras usually contain a filter filtering that out), but not so far that it is in any way useful for things that aren't burning hot. E.g. with cheap digital cameras with bad filters you might see the coals of campfire being slightly tinted wrong, because those get hot enough to be visible, but everything else is not affected, and you'd think a camera was bad if it were

Re: DIY-Thermocam: A low-cost thermal imager based on the FLIR Lepton sensor

#15

Post by doctorwho42 »

splitbrain wrote: post #3

Awesome project. But $300 is still quite steep for a thing I might maybe use once a year. I really wish these thermal sensors came down in price...

I don't know if it's been awhile since you looked, but prices have dropped if you don't look at the name brand:

Bought one of these for work (HIKmicro, 160x120/19200pixel) for ~$300. It works, it's quite good compared to any thermal camera I played with 5+ years ago (even the fancy ones).

https://www.amazon.com/HIKMICRO-Resolution-Portable-4%C2%B0F...

It's important to note that camera sensor tech has been advancing quite rapidly these past two decades.

Re: DIY-Thermocam: A low-cost thermal imager based on the FLIR Lepton sensor

#16

Post by baldeagle »

I’ve played around with the FLIR lepton a good bit and it can be pretty cool. I think the best current hackable platform is the Tcam. It is about an ESP32 combined with a Lepton. Great if you can use the iPhone app or setup a server to interact with it.

https://store.groupgets.com/products/tcam-mini-rev4-wireless...

Re: DIY-Thermocam: A low-cost thermal imager based on the FLIR Lepton sensor

#17

Post by DoingIsLearning »

Entinel wrote: post #10

For the people saying "this isn't affordable," decent thermal cameras range in the thousands of dollars.

It still isn't affordable. You can get a phone add-on from FLIR for $180/$200.

This is a great exercise in building stuff for yourself but not affordable at all.

The thousand of dollars cameras you refer to have very high resolutions which are really not the use case for the curious maker that would be interested in such a project.

Re: DIY-Thermocam: A low-cost thermal imager based on the FLIR Lepton sensor

#18

Post by rittermax »

baldeagle wrote: post #16

I’ve played around with the FLIR lepton a good bit and it can be pretty cool. I think the best current hackable platform is the Tcam. It is about an ESP32 combined with a Lepton. Great if you can use the iPhone app or setup a server to interact with it. https://store.groupgets.com/products/tcam-mini-rev4-wireless...

The tCam-Mini is also an awesome project, thanks for mentioning!

Re: DIY-Thermocam: A low-cost thermal imager based on the FLIR Lepton sensor

#20

Post by rittermax »

rtomanek wrote: post #6

$523 total? That's not my definition of affordable.

You are right, there are cheaper solutions like smartphone addons, but as a standalone thermal imager including display, storage, etc., there are not many options that are less expensive and provide the same flexibility in terms of open-source software and hardware. This is a comparable all-in-one device from FLIR itself: https://www.amazon.de/FLIR-89401-0202-C5-Kompakt-W%C3%A4rmeb...
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