# Detecting Infrared Question



## RBMKAlpha (Jan 10, 2006)

*Ok, this isn't exactly camera-related, but I've been told there are a lot of IR afficianados here. If it gets moved, I understand completely and apologize for any inconvenience. *

I'm working with my college professor to build some engineering kids for school students. The 10th grade kit involves building a "burglar alarm" using infrared. The prototype works really well - break the beam, and the buzzer sounds. 

The thing my professor is interested in is finding a way to "show" that the infrared light is there. I was wondeirng if there is any material that can react and show that there is IR light present. They sold these beads and paints that would react to UV light and change color in the sun, I'm curious if anything like that exists. 

The only other thing I can think of is building a little "black box" with a thermometer and having that show a temperature increase when the IR light from the transmission LED. 

I did a google search but didn't find anything really good. Any advice would be greatly appreciated by my team.


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## terri (Jan 10, 2006)

Interesting challenge.  I haven't an answer for you. 

There are a lot of infrared _film_ geeks here, but not infrared alone, per se. I'll let this thread sit here for a while if you'd like, to see if you get any answers that are useful. If not, holler and and I'll move this to General Q&A or anywhere you'd like.


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## Digital Matt (Jan 10, 2006)

Like Terri said, the only answers you'll get here are photography related.  That being said, most digital slrs are sensitive to IR, and with the use of an IR filter, you can filter out the visible spectrum to reveal the infrared.


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## Hertz van Rental (Jan 10, 2006)

There are some new digital video cameras (Sony does one - my brother-in-law has one) that use IR to video in low light. The camera has an IR emitter. A camera like that should show up the IR beam in real time on the monitor.
As for heating things - depends upon the IR wavelength and energy level. IR is lower down the spectrum than UV and Visible so has a lower energy level.


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## Garbz (Jan 11, 2006)

I recently built an IrDA interface for my computer. While debugging it to attempt to establish if it was capable of sending an infra red signal at all I simply photographed the LED with my digicam, and volah. Digitalcameras can easially show if there's infra red light in a dark room. Simply take a shot of your remote control to see what i mean.


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## RBMKAlpha (Jan 11, 2006)

Actually I did take a shot with my C340 in low-light with a long exposure, and something did show up. I was pleasantly surprised, it was like this purplish dot. I'll try that again later with more power going through the IR LED.


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## usndoc (Jan 11, 2006)

If you want to go cheap and simple:

http://www.radioshack.com/product/index.jsp?productId=2049727&cp=&kw=infrared&parentPage=search

http://www.radioshack.com/product/i...kwCatId=2032058&kw=infrared&parentPage=search

They also used to have a credit card sized detector with a piece of material glued to it that glowed in the presence of IR.  I have one in my kit but cannot find it in the online catalog.  It is the size of one of the half size credit cards that goes on your keychain.


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## Hertz van Rental (Jan 11, 2006)

If you get some smoke in front of the emitter you should be able to see a beam if it is focussed - like a car headlight in fog. Should show up better on a camera with infra-red capability.


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## Unimaxium (Jan 11, 2006)

How about using a visible light beam instead of an IR one? Like maybe a red laser or something? That way it would be possible to see the beam with the naked eye. I think it would be good at least for demonstration purposes.


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## RBMKAlpha (Jan 11, 2006)

We are using the Radio Shack IR pair, but might be looking for the same thing cheaper on Digikey.


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## df3photo (Jan 11, 2006)

you could try what I have done in the past, its a 5min project... take a cheapo webcam and take out the filter and replace it with 2 pieces of exposed developed film negitive... and put it back together, it makes a IR camera... check my website for detales and pictures...  Not sure if this will work for you but check it out... might get you some ideas or something...
http://www.df3photo.com/modules.php...ame=gallery&file=index&include=view_album.php


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