 | | What is RPM of Gear Motor???
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I just made an optical shaft encoder with the light sensor and a spinning paper disc, and measured somewhere near 1300 RPM using datalogging on the RCX. Does anyone know if this is close to the technical specs of the gear motor that I was using to (...) (25 years ago, 6-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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I found only this post in a search of LUGNET Robotics for "RPM" (...) -- Did you check the web site first?: (URL) (25 years ago, 6-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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oops. forgot to divide by 2. make that between 600 and 720 RPM. I called pitsco lego dacta and they report 350 RPM... i wonder if i'm doing something else wrong in my analysis... but i can't find it! anyone else? (...) (25 years ago, 6-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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thanks. i found out that my time axis on my graph had numbers about half of what they should have been, so I got around 350 RPM too. yay. -Ben (...) (25 years ago, 6-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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Keep checking the math. I clocked the motor at 330 - 350 rpm. I used the rotation sensor driven directly by the motor. From analysis of the RCX firmware, the rotation sensor should be accurate to 1250 rpm, so I'm pretty confident of it being in the (...) (25 years ago, 6-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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(...) Dave- Where are you getting that 1250 rpm upper limit from? While I haven't counted exactly yet, I'm dropping only 20 counts out of every thousand at ~15,000 rpm. I had assumed this was mainly gear slop, since it only appears to occur while (...) (25 years ago, 7-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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Using a Futaba 9ZAP radio with a built in optical tachometer and the two bladed LEGO prop I got 380 rpm for the gearhead motor and 4320 rpm for the older nongeared motor. Of course this was done with a battery box and brand new batteries so I am (...) (25 years ago, 7-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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My memory is a bit fuzzy here since it was a while back, but according to my notes... * sensors are sampled every 3ms * rotation sensor is a quadrature encoder with a 4:1 gearing in front of it (one rotation of the axle yields 16 "ticks"). * sensor (...) (25 years ago, 7-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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(...) Oh! Math mistake on my part... 16 instead of 4. Hmm... the ~15K was an off the top of the head estimate, which would go down to ~4K if divided by four again like it should be :) I'll have exact numbers some time today. Like I said, it is (...) (25 years ago, 7-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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(...) You could get close using the differential as an adder. The ratio of speeds above is about 11:1 (its 11.3:1, but lets keep things as integers). That is a prime number, and we know there aren't any lego gear options that give you an 11:1, so (...) (25 years ago, 7-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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(...) Assuming those numbers are correct (I've been too slack to actually look up the tooth counts), I'll give further clarification on my earlier post. I'm using a combination of three 40:8 combos, giving me an effective ratio of 125:1. The gearing (...) (25 years ago, 7-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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Well, this took me a while, but it appears that the rotation sensor is reliably counting at nearly 2500 rpm. Here are the numbers: ~650 ticks per second. This count is not quite constant, but the error is within 5 percent. The way it is geared, this (...) (25 years ago, 13-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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In article (...) 650 ticks per second works out to about 1.5 ms per tick. I didn't think the RCX sampled inputs that fast - I thought it was 3.0 ms per sample. If so, this would mean that the RCX is capable of adding 2 to the rotation value during a (...) (25 years ago, 13-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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(...) Nope-it's not. I use LegOS, and that only adds 1- I know that particular section of code inside and out. Therefore, it must be the sampling time. Or a really egregious error on my part. (...) <snips much code> (...) Yes, but at this speed, you (...) (25 years ago, 13-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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In article (...) I don't know anything about legOS - perhaps it has its own sensor sampling code. I was looking through the standard Lego firmware to determine the 1250 rpm number, and I verified it with a few experiments, but again using standard (...) (25 years ago, 14-Jul-99, to lugnet.robotics)
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| | Re: What is RPM of Gear Motor???
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(...) Ah! I thought the 3 ms you were referring to was a function of the hardware, not the software- I thought it might have something to do with the A-to-D in the chip. FYI, in legOS, the rotation sensor can technically be sampled as often as the (...) (25 years ago, 14-Jul-99, to lugnet.robotics)
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