Jake Anderson wrote:
> I have always wondered about using the sensor out of one of those
> automatic light type things, they seem to respond to a change in temperature
> pretty quickly
>
> Mike Harrison wrote:
>   
>> On Sat, 19 May 2007 01:10:44 -0400, you wrote:
>>
>>     
>>> Hi all,
>>>
>>> The IR emitted by IR LEDs in remote controls, etc., is just slightly
>>> longer than visible light (shorter than 1 micron wavelength). The IR
>>> emitted by hot objects in the 100 deg C range is going to peak around
>>> several microns in wavelength, way too long for a regular CCD to see.
>>> The problem is not that the emission is weak but that it is the wrong
>>> wavelength.
>>>
>>> Vitaliy, I don't know what your friend was able to see on the PCB with
>>> a regular camera in "night mode" (which is usually just removing the
>>> IR filter and illuminating with IR LEDs).
>>>
>>> IR thermal imaging cameras use exotic focal plane array detectors
>>> (made not from Silicon or GaAs, etc. but from InCdTe, InSb, PbS, or
>>> similar materials, or microbolometers which are arrays of sensitive
>>> temperature sensors which absorb the incident IR and measure the
>>> resulting tiny temperature increase). I don't think you are going to
>>> find them for anything less than several thousand dollars new. You
>>> might possibly find something used on eBay for much less. A quick eBay
>>> search turned up a few hits in the low thousands of USD. The
>>> technology is the same as used in newer generation heat seeking
>>> missiles.
>>>
>>> Sean
>>>       
>> The only 'really cheap' thermal detector is an IR thermometer.
>> A while ago I hooked up one of the detectors used in these to an oscillator +speaker to give fast
>> feedback when scanning the detector over a PCB- never had time to develop this further, but with the
>> right optics (very few materials suitable for this - IR thermos tend to use moulded polythene
>> fresnel optics) this may be a viable solution as the audio makes it  very quick to home in to
>> hotspots.
>>
>> If you want a 'real' thermal imager, the cheapest solution I know of is a people counter made by
>> www.irisys.com. This has a 16x16 array, and can produce images on a PC, however you would need to
>> tweak the optics to work at the required distance. Cost is around GBP700 (~USD1400).
>> Note that as this doesn't have a chopper, it only reacts to changes in temperature.  
>>
>>     
>
>   
I'm having trouble following this thread. Are you trying to locate hot 
chips or hot connections (shorts)?

--Bob
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