Pololu Robotics & Electronics
Menu
My account Comments or questions? About Pololu Contact Ordering information Distributors

Which line sensor do you suggest for better results?


#1

Hello there,

Which line sensor do you suggest for better performance in a line following competition :question: The competition stage will be exposed to some amount, if not a lot, of ambient light. I am yet to experiment with a QTR sensor which i probably will order soon. But for better results, which sensor should i go with :question: Analog or digital :question: Of course, the digital gives a 0 or 1 and the analog 0 to 1023, and its obvious that the analog one has better range. But considering a little interference from external lighting conditions, should i go with the bigger range :question: or the straightforward logical 0 or 1 :question: Yes, its the same old follow-the-white-line on a black surface or the other way around. :smiley:

Also, the white line in our competition will be 2 cm wide and i am planning to make use of PID. Is that an issue for the QTR-8A/RC sensor as they have 1cm separation between LED pairs :question: Or can I use two of the middle LED pairs simultaneously for the zero-error process :question:Hope you understand, and please forgive me if my thinking is wrong. I could use just a single center sensor and other side-sensors from the many-to-choose 8 LED pairs too, my thinking. :smiley:

Finally, how would you rate the performance of using a QTR-3A/RC in the middle supported by a QTR-1A/RC on each side :question: ( Making a 3-pi robot-like symmetrical sensor arrangement ). Will this result in a certain decrease in performance due to the use of 3 individual sensors, or will it still go at a good speed if the PID tunings are good :question: Sorry for all this ignorance, but thanks for listening out!!! :smiley: I have got lots of Qs in here, hope you got a similar quantity of As :smiley:


#2

Hello.

We generally recommend the digital versions of our QTR reflectance sensor arrays. They perform better than the analog versions under poor conditions (such as low ambient light) and have slightly farther sensing distances. Also, the digital version of the sensor is analog with respect to time. Specifically, it requires a digital I/O line to charge an output capacitor, then measures the time it takes to discharge the capacitor through the phototransistor (so you get a lot more information about the reflectance than just 0 or 1).

Some people like to have one sensor directly in the middle of the line; however, since the line in your competition is 2cm wide, it will not get lost between two sensors on the array, so it should not matter. The QTR sensor array will be able to detect and give a reading showing the line is between the two sensors.

Using the QTR-3RC in the middle with an individual sensor on each side is a viable option. As long as you are using the same type of sensor, you can use our QTR reflectance sensor AVR library to read your 3 separate sensor boards as a 5 sensor array. Each sensor is still read individually with the 8 sensor arrays, so you will not really be losing performance by using the 3 different sensor boards.

-Brandon


QTR-8RC vs QTR-8A
Fast Line Follower Build
QTR-3RC to detect Red, Green & Blue line
#3

Thankyou so much Brandon for the clear-cut information. Thanks a lot!!! :smiley:


#4

tanks Enigmerald for share this usefull post.tanks