Detecting Laser Light

Discussion in 'The Projects Forum' started by Sparky, Mar 14, 2009.

  1. Sparky

    Thread Starter AAC Fanatic!

    Aug 1, 2005
    75
    0
    Greetings,

    I would like some guidance, suggestions, tips, and so on regarding detecting laser light.

    This is a hobby project – really intended to play with an AVR – the laser I thought would be peripheral to the project.

    I have picked a laser module from Digi-Key and would like to turn it on / off with my AVR and then detect it also with the AVR as either present or not (on / off).

    I have Googled all types of phrases regarding detecting laser light and find lots of hits – unfortunately many have to do with detecting police laser.

    I have found some stuff from Edmund Optics but I think it was too expensive.

    I found a device from Burr-Brown that had a photo-diode and some amplification all in one part for around $60.00.

    A co-worker said I could build something much cheaper than that for what I need.

    Also when it comes to using a lens – from a hobby level – how do you mount a lens, how do you know it’s at the correct distance and so on?

    Can you share tips and suggestions?

    Thanks
    Sparky_
     
  2. leftyretro

    Active Member

    Nov 25, 2008
    394
    2
    Hi Sparky;

    Well first you should explain your requirements a little better. About powering and controlling the laser from you AVR chip one needs to know the operating voltage and current consumtion of the laser module, can you supply that? On detecting the laser light, do you just want a laser on or laser off indication or do you wish to measure the intensity of the laser light falling on the detector? Also might be useful to know which AVR micro you are using.

    Lefty
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    I'd modulate the laser with a frequency, then detect the frequency with what ever photodetector your using. This will distinguish it from other sources of light.
     
  4. DickCappels

    Moderator

    Aug 21, 2008
    2,650
    632
    Assuming that your laser is red or infrared (red is soooooooo much easier to work with, if you have a choice), you can detect the light with most silicon photodetectors.

    I use photo transistors for this. You could even get an small signal in a metal can, cut the top off, and use that, though it might not be exactly opmised for your application. You can use the photo transistor from a ball mouse (the detectors in optical mice are integrated wtih a lot of other circuitry, so aren't useful). The use of discrete photo transistors can give you digital or analog outputs. If you just want a digital output, consider something like the Fairchild QSE156 (availalable from Digikey, datasheet at http://www.fairchildsemi.com/ds/QS/QSE156.pdf ).

    Hope that gets you started.
     
  5. Sparky

    Thread Starter AAC Fanatic!

    Aug 1, 2005
    75
    0
    Thank you for the input –

    Leftyretro – the laser mod I’ve settled on is from U.S. Lasers, their tech support tells me I the module is designed to turn on and off by switching a 3v level input. My intention is to use a line on an AVR to control a FET and the FET switch the 3v to the module.

    I have not picked out a specific AVR (yet)

    I do want to detect the light only – present or not – not the intensity.

    Bill_Marsden, can you provide a little more information or an example. I must admit, I don’t know right off how involved your procedure would be.

    Would I write the code to modulate the signal that drives the control to the laser?

    DickCappels – thank you for the part recommendation.


    The way I hopped this project would evolve is get this working on the table top – “turn the laser on through software, shine the laser on the detector and have the software indicate the signal was received.”

    Then – go for distance and other optics related stuff – bounce the signal and receive it over several yards, then increase the distance again.

    Thoughts suggestions?

    Thanks for the comments
    -Sparky
     
  6. marshallf3

    Well-Known Member

    Jul 26, 2010
    2,358
    201
    A laser module usually incorporates an internal collimator so it should already go for quite a distance before the spot size starts getting so large that the beam is difficult to detect.

    If you can get line of isght you can enclose your receiver in a long tube painted black inside and that should deter most any outside light interference.

    But I see this is a project so modulate away. :)
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Have you looked how old this post is? 1½ years is a bit long.
     
Loading...