Break beam IR emitter and detector

  • Thread starter Asok
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  • #1
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I need a list(data numbers) of short range IR emitter and detector(not very expensive) which can be used as a break beam sensor.. I also like to know what is the specific IC number which is used to tune the IR emitter's frequency which matches with the detectors receiving frequency. I have heard that the frequency is something like 38KHz.. If you guys can also give me a link to the circuit diagrams which I have to use for this, it will be a great help... :-)
 

Answers and Replies

  • #2
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So you need a detector that detects if a beam of light is blocked? Why on earth would you need to run it at some frequency. You take a stupid IR diode that cannot be tuned and anything like a photo diode, photo transistor or photo resistor and that is it.
There is hundreds of these things and no one will make you a list.
 
  • #3
vk6kro
Science Advisor
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So you need a detector that detects if a beam of light is blocked? Why on earth would you need to run it at some frequency. You take a stupid IR diode that cannot be tuned and anything like a photo diode, photo transistor or photo resistor and that is it.
There is hundreds of these things and no one will make you a list.
The problem is ambient light. If there is other light present, the simple LED to phototransistor setup will not work very well.

Pulsing the light from the LED allows you to filter out the steady light level and detect only the pulsing component of it. You can then use a lot of amplification of only this component.

38 KHz is commonly used as a pulsing frequency and there are receiver chips available for doing this.
They have a small lens on one surface and there is a filtering and amplifying circuit in the chip. Most TV receivers would have one of these for receiving the remote control.

They are available at large electronics stores.

You have to arrange the 38 KHz transmit frequency yourself but a 555 with an amplifier can be used for this.
 
  • #5
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hey guys... thank U so much... I was thinking of designing a device for measuring speed and distance of a foot cycle... Now I have nice begining... if you have any suggestions please post....
 
  • #6
vk6kro
Science Advisor
4,081
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It would probably be better to use a Hall probe sensor switch with a rotating magnet on one of the bicycle wheels. This is easier than arranging light sources on a bicycle.

I have seen cheap "bike computers" intended for doing this. They sell in cycle shops for about $10 and feature a nice LCD display with various functions like speed and distance, lap times etc.
 
  • #7
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maybe you are right about hall probe sensors... I just had that idea of break beam sensors, because we had a robot competition recently in our university... and we used some break beam sensors plus some other sensors for the robot...our group got the second place... anyway i searched hall probe sensors in the local market(Sri lanka), but in here I couldn't find it.... then I searched for its mechanical structure, but that was little too advance to construct... but your idea was brilliant on hall probe sensors, and I should work on it more and more, thank you and i'm waiting for your suggestions.....
 

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