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About a year ago I was inspired by discussions about how to get an RCX robot to make perfect 90 degree turns and also by an interest in traversing mazes and collision avoidance. I had an idea to navigate and turn using an approach similar to a (...) (22 years ago, 12-Jan-02, to lugnet.robotics)
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| | Re: Precise turns of any angle!
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(...) The trouble is that the rotation sensor drops counts when you run it at low speeds - especially if it's reversing direction frequently. You can read about my experiments that prove that fact here: (URL) told that you get much better results (...) (22 years ago, 12-Jan-02, to lugnet.robotics)
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| | RE: Precise turns of any angle! -- Rotation Sensor Information
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Steve Baker has done some wonderful experiments on the accuracy of the rotation sensor which can be read at the URL at the end of this message. I have a alternative explanation for the inaccuracy in the rotation sensor when used with the standard (...) (22 years ago, 12-Jan-02, to lugnet.robotics)
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| | Re: Precise turns of any angle! -- Rotation Sensor Information
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(...) I ran my rotation sensor in an experiment at nominal motor speeds of 300 rpm and didn't lose a single count in over 10 minutes of testing. I believe the 1250 RPM figure...although you may be right about it being worse with the RIS 2.0 (...) (22 years ago, 12-Jan-02, to lugnet.robotics)
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| | Re: Precise turns of any angle!
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(...) drops counts. However, that only impacts the wall following application only to the extent that it would require periodically going through the initialization function which calculates the distance the robot currently is from the wall. The (...) (22 years ago, 12-Jan-02, to lugnet.robotics)
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| | Re: Precise turns of any angle! -- Rotation Sensor Information
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Hi, I did the rotation sensor fix for leJOS. In the course of that I did a lot of tests and analysed the ROM code, so I know a bit about this. (...) You must have been very lucky. (...) Yes, that's right for the LEGO firmware. For legOS/leJOS it's (...) (22 years ago, 13-Jan-02, to lugnet.robotics)
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| | Re: Precise turns of any angle! -- Rotation Sensor Information
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(...) Excellent! Someone who *knows*! (...) I guess so. You kinda have to hope that Lego designed the sensor to work when directly connected to a motor though - they surely imagine that this will be the most common use for 'naive' users. (...) OK - (...) (22 years ago, 13-Jan-02, to lugnet.robotics)
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| | Re: Precise turns of any angle! -- Rotation Sensor Information
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(...) Yes. Actually it's two step, the A/D interrupt sets a flag and a routine in the firmware checks the flag periodically and does the processing, most of it being calling the ROM routine. (...) No. You can read height in the diagram as voltage, (...) (22 years ago, 13-Jan-02, to lugnet.robotics)
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| | Rotation Sensor Information
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I agree this is the heart of the problem... I made a small experiment and saw strange things on my scope. Has anyone already open a Lego rotation sensor ? I'd like to have a look to internal photographs and/or see a circuit diagram. I tried to open (...) (22 years ago, 13-Jan-02, to lugnet.robotics)
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| | Re: Precise turns of any angle! -- Rotation Sensor Information
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(...) In 'The LEGO Lugger', previously posted at (URL) the extended drive shafts for both sides of a tracked vehicle, moving in opposite directions, are summed in a differential with the difference (hopefully zero)fed to the rotation sensor. Because (...) (22 years ago, 13-Jan-02, to lugnet.robotics)
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| | Re: Precise turns of any angle! -- Rotation Sensor Information
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(...) I believe that in this case, you should use a light sensor looking at a wheel that's white with a black line marked on it. The software for reading this is identical to what you would use for line following (a very well researched topic!) - (...) (22 years ago, 14-Jan-02, to lugnet.robotics)
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