thermal imaging by mechanical slow scan of a PIR sensor will it work. - Page 1
Forum section: electronics / general

author: jonovid
author_rank: Super Contributor
timestamp: December 05, 2016, 07:35:57 am
content: thermal imaging by mechanical slow scan of a PIR sensor will it work.thermal imaging is not cheap. is their a way to make a cheap PIR sensor in to a working thermal imaging unit?interested to know if PIR sensors have a similar thermal imaging hz as $2000 Thermographic cameras?if yes? then can thermal imaging by mechanical slow scan of a PIR sensor work?with SSTV PC software program or arduino plus DIY software to map the PIR sensors output.the PIR sensor moves over a map or X, Y, grid, or moving pin hole on a wheel.can have added PIR sensor cooling too, if its needed?.before I waste time on this idea.your opinions of this.I Challenge Anyone to make a $200 thermal imaging unit.that works just like the $2000 hand hold units, but a slow scan & a lot larger, But 80 to 90% cheaper.size of a 3D printer or similar. your opinions?image of a mechanical slow scan disc off the web

author: daqq
author_rank: Super Contributor
timestamp: December 05, 2016, 08:03:56 am
content: See:http://hackaday.com/2015/01/21/diy-single-pixel-digital-camera/

author: wraper
author_rank: Unknown
timestamp: December 05, 2016, 08:42:00 am
content: Even if you manage make one, it will pretty much suck for $200. Scan disc won't work for IR camera, it will emit huge amount of IR by itself, or, if shiny, reflect IR from everything around. And it's not like you can get a decent resolution with it at all. With recent price drops for entry IR cameras, for $250 you can get a seek thermal or flir one which are real thermal cameras. For $ 500 you can get i3 TE – Q1 which has 384 x 288 resolution and works really well.

author: jonovid
author_rank: Super Contributor
timestamp: December 05, 2016, 08:51:40 am
content: Quoteyes getting decent resolution seems to be a problem. price drops for entry IR cameras will end any saving. still maybe a fun project . just to see how stuff works. if i have the time.- thank you

author: Akra
author_rank: Contributor
timestamp: December 05, 2016, 09:03:50 am
content: Yes, you can build it:http://www.rapp-instruments.de/foto/Raster/thermography/termo.htm(sorry, the site is in german, but there are also pictures and schematics).And the thermal pictures doesn't look so bad, you can identify the objects and get an idea of there temperature.

author: Kaptein QK
author_rank: Regular Contributor
timestamp: December 05, 2016, 04:50:49 pm
content: Like this one?https://www.eevblog.com/forum/projects/diy-scanning-thermal-camera/msg185085/#msg185085

author: coppice
author_rank: Super Contributor
timestamp: December 05, 2016, 05:01:35 pm
content: Its not so many years since the vast majority of thermal imaging was by mechanically scanning a single pixel.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 05, 2016, 05:35:13 pm
content: Unless you have a really well supplied scrap box there is no way you can put something useable together for under $200. Yes, a single element detector is cheaper than a bolometer array, but you need to add scanners (you might be able to repurpose a bar code scanning system, though there are serious optical problems involved), position readouts, optics and a bunch of other stuff. And unless you are talking about a really slow scan you will have serious sensitivity issues. One of the tremendous advantages of the arrays is that they effective collect and integrate the scene energy over a large fraction of the frame time (even longer for the bolometers in many cases). If you spend 1/30 of a second or so on each pixel your scan times get very long and you start having issues with even relatively static scenes changing significantly during the frame. If you scan faster you solve these problems but lose sensitivity.

author: LaserSteve
author_rank: Super Contributor
timestamp: December 05, 2016, 05:45:59 pm
content: One, if Seek Thermal does their Christmas sale again this year, there is no point.So if I go home and set up post objective scanning with a pair of galvanometer scanner driven mirrors and a single point detector, will you give me 200$ for recreating 1970s technology? Hint, I might have already done this in other wavelengths....I have a pair of Cambridge Galvos with large metalized mirrors, this is a non-issue to set up.The big issue is the Pyroelectric sensor used in motion sensors needs an AC optical signal in order to respond, so you need a optical chopper in front of your four Dollar sensor to obtain any sort of linearity. Most of them have two sensor chips wired in parallel with opposing polarity , so you have a great motion sensor when there is an optical grating in front of the sensor. However this makes a for lousy imaging sensor unless you mask 1/2 of the detector using an aperture. I can order a discrete sensor, but by the time I pay that much, I might as well buy the Melexis array development kit and scan across that. The issue then becomes the very slow I2C readout for that sensor.By the time I get you an image update with a pair of mirrors moving at 60 Hz and 1 Khz or so, there will be a serious change in even a static scene. This is why early thermal viewers used an expensive spinning, mirrored, polygon, or an expensive resonant scanner that scanned at 1/4th or 1/2th the video line frequency.For the resonant scanner, this means you need a way to sense and linearize the sinusoidal variations in pixel clock. To get the update up, you need scan bidirectionally as well.I see the resonant scanner / linearizer board combo on Ebay about twice a year. They are still used in a few Confocal microscopes.Which is why the mechanical IR video cameras were rare, and expensive.You could try a Nipkow disk, if you cooled the disk and had a very hot scene, like a propane torch or soldering iron in the near field. Single element lenses with suitable coatings are sold on ebay for replacement focusing lenses for CO2 based Laser Cutters. This is all a long shot because any scanning process really, really, reduces the chance of such a cheap detector working well.To get good video, I would then need Liquid Nitrogen from work, for the Mercury Cadmium Telleuride detector I have on my desk.The moral of the story is the modern Bolometer pixel is so much much more sensitive then the ancient TGS Pyroelectric detector, its not even funny.Besides, My friend Phil Hobbs was working on a better way with his Footprints project....Scroll down to "A 10$ Thermal Infrared Imager", on his page:http://electrooptical.net/http://electrooptical.net/www/footprints/fpspie11.pdfPhil would be the first to tell you that he had the resources of IBM Research at his disposal.Steve

author: PointyOintment
author_rank: Frequent Contributor
timestamp: December 06, 2016, 11:08:19 am
content: More links:https://publiclab.org/wiki/thermal-camerahttps://publiclab.org/sites/default/files/ThermalFlashlightHowTo%20(1).pdf

author: Zero999
author_rank: Super Contributor
timestamp: December 06, 2016, 01:21:40 pm
content: Quote from: PointyOintment on December 06, 2016, 11:08:19 amGood idea but it could be more clearly drawn. Is it only me who finds dumbed down graphics and a picture of the breadboard layout harder to understand and more confusing than a proper schematic?

author: Cubdriver
author_rank: Unknown
timestamp: December 06, 2016, 03:29:35 pm
content: Quote from: Hero999 on December 06, 2016, 01:21:40 pmNo, it's not only you. It's ridiculous not to include the schematic as well. They went to the trouble of generating and labeling all those images, how much more effort would it take to put a copy of the schematic in the PDF? Granted it's a pretty simple circuit and not terribly difficult to reverse engineer and derive the schematic, you shouldn't need to do that.-Pat

author: Galenbo
author_rank: Super Contributor
timestamp: December 06, 2016, 04:42:29 pm
content: Quote from: jonovid on December 05, 2016, 07:35:57 amAll you need is a 8dollar IRgun, a smartphone and some glue or duct tape.The android camera reads the number on the IRgun display, the inside gyro/compass/Accel gives the inclination and rotation so fills a 2D picture with the data. Your hand decides where the image gets filled.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: December 06, 2016, 06:24:26 pm
content: Quote from: Galenbo on December 06, 2016, 04:42:29 pmI like the general idea. Cleaned up with a 2-axis scanner done with model airplane servos and some well thought out masking to control the IR gun FOV you might actually get something worthwhile for under $200. Still would be slow (maybe a couple of pixels/second) so would only work for really static scenes.

author: Galenbo
author_rank: Super Contributor
timestamp: December 12, 2016, 05:04:15 pm
content: Quote from: CatalinaWOW on December 06, 2016, 06:24:26 pmWhile everyone has a working old obsolete smartphone these days, you can express the price as 8dollar/pixel/0,5 second, within some linearisation limits :-)