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Laser Count

vangbevangbe Posts: 21
edited 2016-09-22 02:20 in BASIC Stamp
I'm designing something like this..


The problem is I don't have a IR Phototransistor. Where do I look for one?

This is the only one I have
http://osepp.com/products/sensors-arduino-compatible/ir-receiver/

Does it work the same way? If not, why and what's the difference?
I just finished shining a laser through it nothing's picking up.

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2016-09-22 02:22
    If you're using a visible-light laser a sensor optimized for IR will not be able to detect it. But more importantly, the detector you cite requires that the IR be modulated at 38kHz to be detected. So just shining a constant laser beam of any wavelength will not be detected.

    What is the wavelength of your laser? Can you modulate its output?

    -Phil
  • vangbevangbe Posts: 21
    edited 2016-09-22 02:47
    Phil Pilgrim (PhiPi) wrote: »
    If you're using a visible-light laser a sensor optimized for IR will not be able to detect it. But more importantly, the detector you cite requires that the IR be modulated at 38kHz to be detected. So just shining a constant laser beam of any wavelength will not be detected.

    What is the wavelength of your laser? Can you modulate its output?

    -Phil

    I'm using this one from Dollar Tree..lol

    https://www.dollartree.com/household/electronics/2-in-1-Laser-Pointer-Key-Chains/500c548c548p338654/index.pro?method=search

    It's about 650nm

    How do I measure how strong a certain light or laser is?
    It's max output is.. <5mW

    ..and if this isn't the right IR I need, then which one am I suppose to get in order for it to work with my laser?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    You could try any phototransistor that's sensitive to 650 nm (red), or you could try a light-to-voltage or light-to-frequency converter, like this one:

    https://www.parallax.com/product/604-00084

    A deep red filter in front of it will help to reduce the effects of ambient light.

    -Phil

  • vangbevangbe Posts: 21
    edited 2016-09-23 04:43
    Phil Pilgrim (PhiPi) wrote: »
    You could try any phototransistor that's sensitive to 650 nm (red), or you could try a light-to-voltage or light-to-frequency converter, like this one:

    https://www.parallax.com/product/604-00084

    A deep red filter in front of it will help to reduce the effects of ambient light.

    -Phil

    J/w, how do you measure it's sensitive if for example, you just happen to find one laying around in your toolbox?
  • vangbevangbe Posts: 21
    ..and just curious, is it possible to enhance the wavelength coming from a mobile light?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    To answer your first question, if the part number is stamped on it, you go online and get the datasheet, which will give you its spectral sensitivity range. Otherwise, just wire it up and try it.

    As to the second, what do you mean by "enhance the wavelength"?

    -Phil
  • ercoerco Posts: 20,257
    I've been trying find to uses for my old-school dime-a-dozen CdS photocells. I know they are most sensitive to yellow green, but I see them used with red LEDs and red lasers all the time.

    OK, maybe not a dime a dozen, but still dirt cheap a dime each: http://www.ebay.com/itm/10PCS-GL5506-Photoresistor-LDR-5mm-Light-Dependent-Resistor-Sensor-for-Arduino-/381479722923

    http://www.instructables.com/id/Another-Arduino-Laser-Tripwire/ (Granted, that guy is using an Arduino, so his logic is questionable, but apparently it works.) The photocell resistance will be lower when it is illuminated by the laser or any other light, and vice-versa. With some good old-fashioned experimenting, you could make a passable sensor with just a photocell and a fixed resistor forming a voltage divider. Tweak the resistor value so that the beam broken/not broken voltage output are higher and lower than the BS2's TTL threshold of ~1.4V and you can read the pin as high or low. Easy peezy, low tech has its place!
  • vangbevangbe Posts: 21
    edited 2016-09-25 21:12
    By wiring it up and try it, are you talking about trying it out by "trial and error" or are you talking about using some sort of device to measure the sensitivity? If so, how would that work and is it possible to use a device to measure it's sensitivity?

    By "enhance", I'm thinking..........
    If a phototransmitter isn't strong enough to pick up a light for example on the back of a phone, then........
    Will it be possible to somehow make the light on the mobile phone strong enough to be picked up by the phototransistor?

    I'm talking similar to a normal light bulb and making it stronger.
    Is it even possible to enhance the light on a lightbulb?
    Phil Pilgrim (PhiPi) wrote: »
    To answer your first question, if the part number is stamped on it, you go online and get the datasheet, which will give you its spectral sensitivity range. Otherwise, just wire it up and try it.

    As to the second, what do you mean by "enhance the wavelength"?

    -Phil

  • vangbevangbe Posts: 21
    edited 2016-09-25 21:14
    erco wrote: »
    I've been trying find to uses for my old-school dime-a-dozen CdS photocells. I know they are most sensitive to yellow green, but I see them used with red LEDs and red lasers all the time.

    OK, maybe not a dime a dozen, but still dirt cheap a dime each: http://www.ebay.com/itm/10PCS-GL5506-Photoresistor-LDR-5mm-Light-Dependent-Resistor-Sensor-for-Arduino-/381479722923

    http://www.instructables.com/id/Another-Arduino-Laser-Tripwire/ (Granted, that guy is using an Arduino, so his logic is questionable, but apparently it works.) The photocell resistance will be lower when it is illuminated by the laser or any other light, and vice-versa. With some good old-fashioned experimenting, you could make a passable sensor with just a photocell and a fixed resistor forming a voltage divider. Tweak the resistor value so that the beam broken/not broken voltage output are higher and lower than the BS2's TTL threshold of ~1.4V and you can read the pin as high or low. Easy peezy, low tech has its place!

    If a photocell is similar to a phototransistor, but better, then in the future, I should have no problem using it for something else? I would think...maybe

    A photocell must probably come with many usages? Correct me if I'm wrong.
    If that's the case, I might prefer a photocell over a phototransister, but what are the cons when it comes to a photocell?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    Photocells and phototransistors operate in completely different ways. Typically a photocell will have a slower response time to a sudden change. I prefer phototransistors for anything designed to interrupt light. I only use photocells in light detection.
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