Electronics > Electronics
Modulating
Admin:
Infrared light will work for line detection, Ive done it on several robots already. Its really common, actually. But I dont like to use it because its harder to debug than visible light. I found a green led with photoresistor is much easier, cause I can see what the robot sees.
As for modulating IR to eliminate noisee . . . I dont see how that will help. Modulation allows you to send a data signal without degradation from ambient sources, but the intensity (the thing you will be measureing, no?) will degrade no matter what. For color detection, you must measure reflection intensity . . . someone correct me if Im wrong . . .
I think the best way to go about it is to have a very high signal to noise ratio (a very bright LED with not so bright background).
Cognaut:
I could totally be wrong about this, but the way I interpreted the concept was that the "off time" would be used to sample the ambient light in order to create a base line for the "on time." That should allow the isolation of the reflection of the modulated source from the rest - I think - like a continuous autocalibration.
Admin:
--- Quote ---the "off time" would be used to sample the ambient light in order to create a base line
--- End quote ---
hmmm ok ok that will work, my mistake :P
andreahmed:
thanks for reply , but i dont want to use something like TSOP , its very sensative to IR , i just wanna use a simple emitter ,detector infrared circuit, would the phototransistor respond if i modulated the emitter at a certain frequency ?
dunk:
yea, that's the advantage of using modulated signals.
you can look for the rising edge rather than a specific level. (think of looking for a change in the signal rather than for a set value.)
therefor far less susceptible to background interference.
this is true for radio signals as well as light, sound, etc.
i'm not convinced it will be a good thing for line detection though as with a modulated signal you see the difference between "on" and "off".
this difference will be similar wether the sensor is pointing at a light colour or a dark colour.
if i was designing this application i would have several sensors in a line. make sure the line of sensors is longer than the width of the line so there is always at least one sensor over a dark patch and one sensor over the lighter line. (providing your bot is not really lost...)
the sensors that are over the line would return a different value to the ones that weren't.
this way you could again look for a difference in values rather than a set "light" or "dark" value.
dunk.
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