Line Follower

We have a problem with the height of the line follower. The book says that it can be 1 inch to about 1/4 inch. But when mounting the line follower anything greater than 1/4 inch it does not work. Any help would be appreciated.

There is an error on the Inventor’s Guide insert for the Line Follower Kit. It calls out an optimal range of 0.02 - 1.0 inches. The optimal range is 3 millimeters. See the Technical Info our web page: for more details.

Just bought the kit. Ran through the manual, Able to run the programs. Got to the Linefollower acessory. Seems like there is some information that is missing. Is there a sample program that I can get so I can see what I am supposed to be doing. Dont need the sensor test, that does not help with programming. There is a step by step program for the bumper but nothing for the line follower.

There is no step by step code for the line follower. The Senor test gives an example of how to interface with one sensor. The User must write code to determine what the robot should do based on data from 3 sensors.

I just purchased the line follower kit. It appears that each module has an IR transmitter and reciever pair. Is this sensor affected by ambient infrared in the room? Or is the transmitted IR modulated and a matching demodulator used in the IR detector. TV/VCR remotes, for example, use AM on a 32 KHz or 44 KHz carrier - do the line follower sensors use a carrier or is it just “on” (zero Hz)?

The IR device does not use a carrier and therefore is not modulated / demodulated. The emitter is always “on”. It can be affected by strong ambient infrared, but works from total darkness to outside full sun. An Inventor’s Guide update is located at: Ideal spacing from the device to the line is typically 3 mm (about 1/8”).

I’m having trouble with the line followers. I install Online code, install the 3-set line follower onto Squarebot, and check the analog reading. What I see is clearly not what I expect. That happens on all 3 line followers. In case the line is bad, I used the mat that came with the line follower kit. The Terminal Window says it’s working. What’s the light-dark threshold? For example, what value must it be to change from light to dark, or vise versa? Or is it Schimitt-triggered?

There is no set threshold that will work for all environments. As the Sensor moves across a surface that is reflective, the infrared light will bounce back and give a low reading – ideally around 0. As the Sensor moves across a surface that is absorptive, the infrared light will not bounce back and give a high reading – ideally around 255. You will need to experiment with the values you are receiving to find the proper threshold. The readings you get will vary as your environment varies but in most cases you will see a noticeable difference. Also verify you have the Sensor mounted at the correct height. Try using our “Vex Sensor Test” (a quick go/no go test) located on our Downloads web page to verify if the sensor is working correctly. Review the Inventor’s for more details.