Problem using infra red sensors

[quris_terris]

Sir we r having a problem in fixing the IR sensors into our line following robot.As we donot know that how to fix it in the circuit.You can see the circuit diagram on the wbsite " http://www.leang.com/robotics/info/articles/linesen/".
Similar to those sensors we r using.Please tell us the logic of implementing those sensors.
What will be the analog port voltage with respect to the ground with and without emitter.

 

[seadolphine2000]

Please be more specific, what's your problem exactly.?

 

[gerryseq]

Hey,

well..according to the circuit ,the volage can swing from 0v(no emittter) to around 5V(when emitter is in full view)

I tried making a line following robot :
**broken link removed**

 

[VVV]

With a 47k pullups, it seems reasonable that the voltage would swing from 0 to 5V, but it depends on the emitters, too. They are supposed to be high-efficiency LED's. Maybe that is your problem, insufficient light. Or insufficient surface reflectivity.

Another problem could be the input impedance of the A/D, which could be too low.

Try placing a piece of white paper in front of the two coupled devices, at about the correct distance and, without anything connected to the receiver, measure its output voltage and see if it swings from 0 to 5V as you place a dark piece of paper in front of the sensors.
If not, see if increasing the current of the LED helps.
Or increasing a little the pullup, to say, 68k.
If that does not solve it, then at least see if the difference is large enough to be reliably detected by the microcontroller. For instance, if between black and white you get 1V difference, that should be OK for you to tell if the robot is on track or not.

If the voltage is always low, then the sensors are too sensitive. That is easily fixed by decreasing the pullup.
If the voltage is always close to 5V, then most likely the sensors are defective.

If everything seems to work OK in this arrangement, then check the A/D, its input impedance and, of course, your code.

 

[mario82]

If you want a greater reaches of the IR's emision you can use this circuit. The transistor must works in saturation in order to transmit and works in the region of cut to not transmit.