Extech IR250 infrared thermometer disassembly and plans for thermal imaging--- make money online

One of my ongoing projects is to develop a low-cost thermal imaging camera.  In this video, I take apart an Extech IR250 infrared thermometer with the intention of grabbing an analog or digital signal so that I can record temperature measurements while using a scanning or image processing device to select portions of the scene being examined. 

Unfortunately, it looks like the analog circuitry is completely sealed inside a custom IC that is hidden under a blob of potting material.  I'll remove the IR sensor from the board and build my own analog amplification and digitization hardware.

hey everyone a local Sears store was

going out of business and had one of

these infrared thermometers marked down

to 30 bucks so I've kind of been wanting

to take one of these apart for a while

just to see exactly what kind of sensor

they use so let's hack into this thing

I've actually already kind of taken it

apart

it's an egg's tech model ir 250 and it's

actually built pretty well a pretty

solid case it's all snapped together the

case itself didn't use any fasteners it

was just plastic clips but it all held

together pretty well this model has a

laser pointer on the top and it's still

should be working yes there's a reading

there and pretty responsive so let's

take out the circuit board this all had

these head screws holding this together

which I didn't bother putting back and

there's the actual sensor so let's zoom

in on that and get a closer look okay so

here's a look at one side of the board

you got the trigger switch here this is

an atmel a EEPROM voltage regulator here

some discrete transistors I believe

these turn on and off the laser and the

backlight and the actual sensor itself

this is a full analog part some of these

sensors actually have digital

conditioning circuitry in them and they

can be queried for data over a digital

serial line but this one is actually

full analog the only number on it is 31

61 which I you know spent a long time

searching for on the internet and

eventually found out it is a PerkinElmer

part and the actual part number is th614

something I don't know but it basically

is the same part and it has a little

window here to prevent visible light

from getting in there so the window is

silicon or germanium or something so

that only long-wave infrared can get

inside there now the cut the type of

signal that the

part produces is a really really low

voltage level it has four pins one pin

is ground one pin is a thermo a

thermistor the inside there there's also

a plain old thermistor and the other two

pins are the output from the thermo-pile

which is measured in micro volts I think

the full scale range on that is like one

or two millivolts

so after realizing that this thing only

outputs a signal of 1 millivolt I

started looking around on this board for

an op-amp because you need something to

amplify that signal so let me turn it

over and I'll unscrew the display here

so that we can see what's on the other

side of the board ok so the LCD lifts

off and there's one of these I think I

called zebra stripe or some kind of a

conductive it's basically like a polymer

with a bunch of conductive bands to

connect the LCD up surprisingly there is

no discrete of op-amp on here there's a

chip hiding under this blob of potting

material which I assume has to be a

micro controller which is which is

interfacing with the eee prom over here

but yeah what's the deal with no op-amp

so I'm guessing that they have a

specialized chip in here that has analog

front-end circuitry on it in addition to

microcontroller or it could be two

actual dies on here but that I don't

think so there's probably just one under

here you'll also notice they very nicely

labeled this little header connector

here and also labeled this top think ow

I've played with some of these pins and

they're actually not that exciting the

pins in here you know it's got ground

and voltage and a reset probably for the

microcontroller and these other pins

just monitor the like whether the

trigger switches down or up or whether

the buttons over here are down er up I

didn't really see very much exciting

going on in there so my ultimate goal

here taking us apart was to see if I

could use this sensor and hopefully the

analog conditioning circuitry in here to

make my own temperature measurements or

to get an analogue a usable analog

signal out my ultimate goal is to

build a infrared imaging device maybe

just by scanning the the scene one pixel

at a time using this this one pixel

sensor unfortunately it seems that

there's no point on this board where I

have access to a decent analog signal

since all the signal processing is

happening inside here I know I probed

around on the board and didn't really

find anything analog or digital that I

could actually kind of harvest I suppose

I could you know read the LCD pins but

that that's not I mean I'm not going to

do that so the plan now is to desolder

this from the board and hook it up to an

analog devices amplifier I found an app

note on the web and using a very very

low DC offset chopper type op-amp yeah

you can amplify that millivolt signal

from the sensor here and turn it into

something you know like a couple volts

so that you can actually digitize it and

then store it inside here there is a

polyethylene lens it's a friend L lens

and this is what determines how small

the spot size is that this thermometer

measures so this thermometer is a

so-called six to one meaning that the

the target size is six times smaller

than the distance from the thermometer

the more expensive thermometers like

this one this is a twenty to one and

what makes it a twenty to one is a

silicon or germanium lens that you can

see in there and the silicon or

germanium produces a much higher quality

lens that has a longer focal length but

it also costs more which is the

trade-off here's a much larger germanium

lens from my previous thermal imaging

experiments so I guess I'll talk a

little bit about how some people have

approached the problem of doing low cost

thermal imaging one person built a

physical scanner and mounted this one

pixel thermal sensor like on it on an XY

servo platform and then scanned the

image physically you know pixel by

pixal and that's cool I think the scan

time was like a couple minutes or

something like that so I'm hoping to

improve on that a little bit one way to

do it would be to not scan the whole

device but just to put a a pair of

mirrors on galvanometers and then spin

those around so that the whole device

doesn't have to move just just the light

path or infrared path another idea I had

was to use a digital mirror device from

a DLP projector and use that to scan

across instead of actually physically

moving something I thought that it might

be faster to to use a DMD and the other

benefit is that we could change the scan

pattern in the pixel size by turning off

more than one DMD at a time so it looks

something like this if if the one pixel

sensor is here this is that little IR

window the sensor here and our DMD

device would look like this and the lens

would be here so incoming radiation goes

through the lens gets focused down on to

the DMD and then depending which pixel

is selected on the DMD that would select

which part of the image was being

scanned so I thought that would be a

pretty cool use of technology since you

know we get to control a DMD and capture

the pixels and all that stuff one

problem is that the mirror size is about

I think 1.0 16 microns I think for a lot

of DMD s and the wavelength of light

that we're changing here is about one

micron so we're going to there's some

problems there because the size of the

optic is getting close to the wavelength

at which were you know reflecting and

that becomes a problem so I don't know

about this but we'll keep the options

open here by the way this is patented of

course just like every other idea in the

world there were a couple other ideas

out there one company called redshift

has made a a different kind of thermal

imager that uses a tunable filter so

this is a really thin film that

changes its optical properties when it's

temperature changes and the thin film

can be extremely thin like you know many

nanometers or less than one micron for

sure and it can be suspended on little

that the film can be cut up into pixels

and each pixel can be thermally isolated

from each other so that's that sounds

pretty good I contacted this company and

you know they're not doing anything

they're not selling kits they're not

selling you know actual completed parts

or anything I have a feeling they were

just getting off the ground when 2009

hit and they basically just been dead in

the water ever since as far as I know

they're the only company that that

claims this technology would work I

don't know if it actually works or not

like I say I haven't seen actually a

demo kit the other another option was my

idea of using a thermochromic paint or a

liquid crystal paint on a really thin

substrate like ten micron you know

stretched plastic or something like that

and that's I don't think that's ever

going to work I think the problem is

that there needs to be pixels for each

for the for the image to really look

good if it's a continuous film all the

way across there's just too much thermal

conduction between areas on the image

alright see you later byeTop Search Keyword : online earning, , make money online, earn money online, online earning, online earning sites, make money online free, online money income, earn money online free, money online, best way to earn money online, online income site, money earning websites, best online earning sites, easiest way to earn money online, earn money payment bkash, online money income site