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I just got my 1st rotational sensor and have a quick question for you all. I have the following gearing on my robot. Point A gears 8 <--> 40 8 <--> 40 Point B so this is: (5:1) x (5:1) = (25:1) Right? Now if I put my rotational sensor at Point A, do (...) (23 years ago, 23-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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(...) this seams to be correct :) there might be one problem. If you are to fast, the RCX might loose some ticks. The maximum speed depends on the used firmeware. Carsten (23 years ago, 23-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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How fast is too fast? I'm using the firmware from version 1.0 (...) (23 years ago, 23-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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Rotation sensors will lose counts randomly in spite of the firmware. -- Bob Fay California, USA rfay@we.mediaone.net (URL) (23 years ago, 23-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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"Bob Fay" <rfay@we.mediaone.net> wrote in message news:G7MKLo.2tB@lugnet.com... (...) I'll back that! It's totally hit-and-miss. I've done several tests on different gearings (some running the thing off a micromotor...) and no matter what, they (...) (23 years ago, 23-Jan-01, to lugnet.robotics)
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In my experience, rotational sensors are accurate to within +/-5%. 100% accurate sensors would be great, but 95% accurate sensors are still very useful. You can compensate for the inaccuracy in various ways, e.g. in the software. IMHO, this is no (...) (23 years ago, 24-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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(...) How do you compensate in software? Dean -- Coin-Op's For Sale!: (URL) Lego Workshop: (URL) Lego Club: (URL) (23 years ago, 24-Jan-01, to lugnet.robotics)
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"Dean Husby" <nntp@akasa.bc.ca> wrote in message news:3A6E7170.F38BA6...a.bc.ca... (...) accurate sensors would (...) compensate for the inaccuracy (...) disappointed or not to use them. (...) Exactly... you can't. Unless you use another sensor, (...) (23 years ago, 24-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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(...) OK - time for the rigerous scientific approach here (well - OK - the half-assed semi-scientific Steve Baker method :-)... I'm typing this email as I run the tests...so right now, I don't know the answers... Test 1: Connect two rotation sensors (...) (23 years ago, 24-Jan-01, to lugnet.robotics)
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(...) I think the PIC series of microcontrollers have some sample code for reading quadrature-type rotational sensors (a la mousewheels). Perhaps one could design a PIC-based intermediate module that was dedicated to reading rotational sensors (...) (23 years ago, 24-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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I guess I didn't word that very well. I didn't mean that you can make an inaccurate sensor look like an accurate sensor via software. What I meant is that you write your software to know that the sensor is not accurate, i.e. the software doesn't act (...) (23 years ago, 24-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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What kinds of sprocket(s) does Lego currently use with tracks? A long time ago (in decades), I remember a set that used Caterpillar-link-style tracks, and they used a long-toothed sprocket to drive the tracks. It might work to put one of those (...) (23 years ago, 25-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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Thanks for all the inputs! After testing out the rotational sensor with teh 25:1 gearing I have discovered that it will count 402 clicks for 1 rotation. So the sesnor is reading only 2 extra clicks easy to fix in the software to get my robot to (...) (23 years ago, 25-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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(...) But I don't think you did what we reported IS the problem... Did you run the motor FORWARD, then REVERSE so we can see the missing positions? That's where the errors come in. Dean -- Coin-Op's For Sale!: (URL) Lego Workshop: (URL) Lego Club: (...) (23 years ago, 25-Jan-01, to lugnet.robotics)
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(...) Just don't go past it's Max or Min areas or you'll have a problem. This is probably a good place for the white slip gear... Dean -- Coin-Op's For Sale!: (URL) Lego Workshop: (URL) Lego Club: (URL) (23 years ago, 25-Jan-01, to lugnet.robotics)
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Thanks to all for the good information that has been related here. Most of my applications were low rpm which seems to be a definite fault area. I like to use them for absolute programming of positions. I now see the problem in using them in these (...) (23 years ago, 25-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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(...) I just read the very interesting posting regarding testing the rotation sensor to evaluate the "missing counts" phenomenon. The above snippit would indicate that the rotation sensor is handled differently from other sensors. It isn't! It is (...) (23 years ago, 25-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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"Steve Baker" <lego-robotics@crynwr.com> wrote in message news:3A6EFF8A.416F3D...ail.net... (...) Nice post, but you only ran the sensors counting up for x number of seconds. Try *reversing*. Then watch what happens... (IE, bring a sensor back home. (...) (23 years ago, 26-Jan-01, to lugnet.robotics)
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| | Re: Rotational Sensor & Gearing Down
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(...) I find it really frustrating that this has to be "discovered" over and over. I believe my fix for LegOS (a year ago?) fixes this problem. The sensor itself is very good. It only ever returns the discrete voltages (which vary by cable length (...) (23 years ago, 26-Jan-01, to lugnet.robotics)
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