laser activated switch

Discussion in 'Electronic Basics' started by news.verizon.net, Jul 10, 2003.

  1. I'm looking for a circuit for a switch that can be activated by a standard laser pointer and nothing else. I know I could probably buy some very expensive filters to only let laser light pass through, but I'd prefer something that uses a phototransistor or photodiode that can adjust sensitivity and tune to the proper frequency and or wavelength. Anyone have any ideas? Thanks.
     
    news.verizon.net, Jul 10, 2003
    #1
    1. Advertising

  2. Well, the wavelength thing sort of makes this tough. But, having faced
    similar challenges before, I can tell you that using a number of gel type
    filters from the Rosco sample book is a good place to start. Keep in mind that
    it will be nowhere near as good as a nice narrow band optical filter, it can
    still get a lot of the ambient light out of the way.
    Start by looking in the sample book at the spectral response curves and pick
    about three filters that pass your longer wave red well while blocking most
    everything else.
    The #19 (Fire) filter is a good, sharp cutoff type to start playing with.
    Overlap that on a #93 (Blue-green) and it will cut out a huge portion of the
    visible spectrum while letting roughly 50% of the laser pointer light through.
    Overlapped once again, this time with a #84 (Zephyr blue) and it will cut nearly
    everything out but allow red laser light to get through pretty well.
    Of course, this is no substitute for a real laser filter, which can
    sometimes be found for a buck or so at good surplus outlets, but if you spend a
    little time experimenting with the gel filter books and their passbands, you can
    get a pretty fair filter together.
    You know, modulating a laser pointer is really very simple and would greatly
    enhance the sensitivity of your circuit. Check my web page and you can find a
    section about laser pointers there which might be helpful.
    Finally, if you go just for light and no modulation, almost any cheap
    phototransistor can be used as your sensor and then any low current relay (or
    even a solid state relay) driven from it. But I would really rather use a
    modulated pointer and a "tone decoder" or PLL to do that.

    Cheers!

    Chip Shults
    My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
     
    Sir Charles W. Shults III, Jul 10, 2003
    #2
    1. Advertising

  3. news.verizon.net

    Joe Guest

    "Sir Charles W. Shults III" <> wrote in message
    news:4slPa.67318$...


    > You know, modulating a laser pointer is really very simple and would

    greatly
    > enhance the sensitivity of your circuit. Check my web page and you can

    find a
    > section about laser pointers there which might be helpful.


    Sir Charles,
    I checked your webpage (address below?), and could not find a reference to
    laser pointers. I am interested in learning more about this. Would you mind
    posting a link to the page you are referring to?

    > Finally, if you go just for light and no modulation, almost any cheap
    > phototransistor can be used as your sensor and then any low current relay

    (or
    > even a solid state relay) driven from it. But I would really rather use a
    > modulated pointer and a "tone decoder" or PLL to do that.
    >
    > Cheers!
    >
    > Chip Shults
    > My robotics, space and CGI web page - http://home.cfl.rr.com/aichip
    >
    >
    >


    Thank you,
    Joe
     
    Joe, Jul 11, 2003
    #3
  4. Sir Charles W. Shults III, Jul 11, 2003
    #4
  5. news.verizon.net

    Bob Masta Guest

    On Thu, 10 Jul 2003 20:27:28 GMT, "news.verizon.net"
    <> wrote:

    >I'm looking for a circuit for a switch that can be activated by a =
    >standard laser pointer and nothing else. I know I could probably buy =
    >some very expensive filters to only let laser light pass through, but =
    >I'd prefer something that uses a phototransistor or photodiode that can =
    >adjust sensitivity and tune to the proper frequency and or wavelength. =
    >Anyone have any ideas? Thanks.


    In addition to Chip's comments about filters, I wonder if maybe
    you can do something with the output of your phototransistor
    to detect laser pointer dynamics. I'm assuming here that the
    pointer is hand-held, so that the spot will not be steady on the
    sensor. (In fact, you may have a hard time hitting it at all!)
    So you might hi-pass or differentiate the output to discriminate
    against headlights, flashlights, daylight, etc.

    Just a thought...



    Bob Masta
    tech(AT)daqarta(DOT)com

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Shareware from Interstellar Research
    www.daqarta.com
     
    Bob Masta, Jul 11, 2003
    #5
  6. news.verizon.net

    C.M. Hobbs Guest

    news.verizon.net wrote:

    > I'm looking for a circuit for a switch that can be activated by a standard
    > laser pointer and nothing else. I know I could probably buy some very
    > expensive filters to only let laser light pass through, but I'd prefer
    > something that uses a phototransistor or photodiode that can adjust
    > sensitivity and tune to the proper frequency and or wavelength. Anyone
    > have any ideas? Thanks.


    i seem to remember a couple of kits that were a game of "laser darts".
    basically, a laser sensetive bullseye (using a normal laser pointer, you
    could play a game like darts). it seems to me that this would be easily
    modified for your purpose, if you can find one.

    i'll do some more research, i believe that they were fairly inexpensive.

    regards,
    chris

    --
    C.M. Hobbs [KD5RYO]
    http://www.destroyallmachines.net
     
    C.M. Hobbs, Jul 11, 2003
    #6
  7. news.verizon.net wrote:

    > I'm looking for a circuit for a switch that can be activated by a
    > standard laser pointer and nothing else. I know I could probably buy
    > some very expensive filters to only let laser light pass through, but
    > I'd prefer something that uses a phototransistor or photodiode that can
    > adjust sensitivity and tune to the proper frequency and or wavelength.


    The easiest way would be to amplitude modulate the laser light (change
    its intensity a couple of 1000 times a second). The modulation could
    then be detected in the receiver with a bandpass filter.
     
    Dr Engelbert Buxbaum, Jul 18, 2003
    #7
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Dennis Gaida

    Touch activated switch instead of Push to Make (PTM)

    Dennis Gaida, Aug 31, 2003, in forum: Electronic Basics
    Replies:
    4
    Views:
    475
    Robert Monsen
    Sep 7, 2003
  2. Replies:
    4
    Views:
    635
  3. fazil abdulla
    Replies:
    6
    Views:
    978
    Resqueline
    Apr 17, 2011
  4. fazil abdulla

    circuit for laser activated device

    fazil abdulla, Feb 16, 2011, in forum: Circuit Help
    Replies:
    1
    Views:
    525
    (*steve*)
    Feb 16, 2011
  5. mynamehere93

    Light Activated "Off" Switch, Or dark activated "On" switch

    mynamehere93, Aug 24, 2011, in forum: Electronic Projects
    Replies:
    2
    Views:
    592
    mynamehere93
    Aug 24, 2011
Loading...

Share This Page