IR sensors vs Phototransistors

  • Thread starter M.Usman
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  • #1
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Hi

I'm taking part in a robotics contest and that requires my robot to reach the desired destination using line tracking. The line to be tracked is made of white tape.

Now I'm in a sort of dilemma here. I was in favour of using IR sensors to track my line and through experimentation I found their response time to be quite fast and the sensors were also quite effective may I add.
But I have been advised against using them and instead was told to use phototransistors because that's what everyone else is using! Is this argument a good enough excuse? Also, do Phototransistors really have an advantage over IR sensors?

I would appreciate any help :)
 

Answers and Replies

  • #2
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What kind of IR sensors? The kind that are used for receiving remote control signals. If that's what you're using they're high gain sensors with gains in the range of 70 - 80 dB. What are you being graded on? If the grade depends only on performance and as long as they can distinguish the tape from ambient noise, I'd say you're better off with the sensors.

However if you're also being graded for designing the circuit to detect the tape, you may be better off doing the sensor amplifier yourself.
 
  • #3
vk6kro
Science Advisor
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Infra red sensors as used on TV sets require the incoming light to be switching on and off at a rate of 38 KHz, too.
So, you would need to arrange that.

They would probably be too sensitive for this application, though. Just the reflection off a shiny floor would be enough to register as a bright object instead of having to find the white tape.
 
  • #4
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Infra red sensors as used on TV sets require the incoming light to be switching on and off at a rate of 38 KHz, too.
So, you would need to arrange that.

They would probably be too sensitive for this application, though. Just the reflection off a shiny floor would be enough to register as a bright object instead of having to find the white tape.
Agreed. I have played around with them. They have automatic noise suppressor, gain adjuster etc etc, so they are only perfect for communication, not for analogue job like this one.

I had experienced that they are so sensitive at (the brightness level of) evening that they detect remote control ('s IR emissions) like wireless (by detecting it even through multiple reflections from walls and objects in the room). Just trying to give you the sense of its sensitivity.
 
  • #5
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I found their response time to be quite fast and the sensors were also quite effective may I add.
But I have been advised against using them and instead was told to use phototransistors because that's what everyone else is using! Is this argument a good enough excuse? Also, do Phototransistors really have an advantage over IR sensors?
Given that you apparently have used the IR sensors quite successfully, was the ONLY reason you were advised to use phototransistors because that's what everyone else is using?

Those IR sensors were used for many years in Chamberlain's photoeyes for garage door openers and were finally replaced with photodiodes, not because they didn't work well, but for cost reasons. Even at such close range they didn't pick up reflections from the garage floor or door.
 

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