{"id":155,"date":"2011-12-16T06:41:12","date_gmt":"2011-12-16T06:41:12","guid":{"rendered":"https:\/\/peterklemperer.com\/blog\/?p=155"},"modified":"2011-12-16T06:41:13","modified_gmt":"2011-12-16T06:41:13","slug":"lego-line-follower","status":"publish","type":"post","link":"https:\/\/peterklemperer.com\/blog\/2011\/12\/16\/lego-line-follower\/","title":{"rendered":"Lego Line Follower"},"content":{"rendered":"

Playing with Legos again tonight! I made a little simple Lego Mindstorm line follower using the light sensor and two motors providing differential drive.<\/p>\n

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Simple project tonight because I haven’t posted in forever and this was fun. More code and video after the break.<\/p>\n

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My Lego Mindstorms are super fun and are great for prototyping out new robot projects. For the line follower, I made a simple robot platform using the instructions from legoengineering.com for the design 9797 Simple Car<\/a>. The little swivel castor shown below is a nice improvement and I mounted the light sensor at the front of the robot instead of behind to prevent it from interfering with the castor.<\/p>\n

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This version shown here tonight uses the default line following code bundled with the fantastic RobotC programming environment from robotc.org. I have reproduced pseudo-code below to illustrate their approach:<\/p>\n

\r\ntask main() {\r\n  while (true) {\r\n    \/\/ if you don't see the line turn left\r\n    \/\/ otherwise turn right\r\n    if (sensorValue(lightSensor) < 55 ) {\r\n      motor(A) = 20;\r\n      motor(B) =  5;\r\n    } else {\r\n      motor(A) =  5;\r\n      motor(B) = 20;\r\n    }\r\n  } \/\/ end while\r\n} \/\/ end main\r\n<\/pre>\n
One thing I realized while testing out this code is that the difference between motor A and motor B determines the minimum line radius that can be followed. \u00a0This 4x difference works well for my small test pattern in my apartment. I could probably reduce this for a larger course.<\/p>\n