Experiences With The Lynxmotion Line Tracker Kit

Having just finished my hexapod robot and before progressing to a more advanced model with jointed legs, I decided I would like to try my hand at a wheeled robot.

I made up a robot platform to experiment with and to try different sensors on, etc. I had the ultimate view of making a complete wheeled Robot, maybe even Fire Fighter. As the platform used a single wheel drive, I decided to fit a line following device as my first accessery so I could see how it would steer.

I bought a Lynxmotion line-following kit from OZ Robotics. The kit is very simple, and consists of a PCB, three IR emitter/detectors, six resistors, a 74HC14 Schmidt inverter chip, along with a 5 volt regulator. Even as a newbie, I thought there would be no problems setting it up! After assembly I made a frame to fit in front of the wheel to carry the unit. When everything was mounted and the sensors set 0.25 inches (6mm) above the ground as recommended, I started to check out the operation and found the IRD outputs were 5volts when they should have been zero. After checking the outputs a couple of times with no joy, I dismantled the PCB and rebuilt the unit. I did this three times and every time the IRDs would not switch off! Frustrated with the thing I left it for the weekend.

On Monday morning I cranked it up again, and low-and-behold the darn thing worked perfectly! I had another job to do, so when I returned I turned on the workshop lights and switched the unit on. I couldn’t believe it - the 5 volts were back! I then realized what the problem was - the IRDs were picking up the workshop lights.

I had no further trouble, except that I had broken one of the leads on one of the IR detectors. I e-mailed OZ Robotics for a replacement, but they didn’t have one. OZ Robotics contacted Lynxmotion for a replacement, but they wanted to keep the stock they had for future kits - not so good I thought.
After reading through some catalogues I located an IR detector that appeared to be the same size, since I couldn’t find out any specs from OZ Robotics for the original one. I purchased three and replaced the one with the broken lead. It worked much better than the original, as it detected the line further from the floor and didn’t appear to be affected as much by the workshop lights.

So another newbie has learnt a lesson the hard way!

After programming the stamp with the supplied demo program, I placed the robot on a white board with a line of black insulating tape. I switched it on and away it went, following the line without any trouble. If it varied a bit to either side of the line it would find it OK. If the robot wandered too far off, it would spin in all directions looking for the line. Sometimes it would cross the line without sucessfully finding it. The program needs to have quite a bit added to it, to make the robot find the line more efficiently. I thought the cost was reasonable for somebody to get started, even though I wasn't able to buy replacement parts.

The replacement IR detector I used was made by Kondenshi (think that how you spell it) model no SG-2BC.

Editors note: US residents can purchase this kit directly from Lynxmotion for $20USD. New Zealand or Australian residents would be better off getting it from Oz Robotics.