Robotics : 24930


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Subject:	Re: new Mindstorms servos?
Newsgroups:	lugnet.robotics
Date:	Sat, 7 Jan 2006 22:52:09 GMT
Viewed:	2111 times

In lugnet.robotics, Yann Vernier wrote:

In lugnet.robotics, Matthew Ruschmann wrote:

brick (which is claimed to be about the size of the RCX). Who knows about torque and all. I am guessing the characteristics are about the same as

I’d say quite a bit of torque. It’s possible they sacrificed some speed compared to the recent minimotors. Check out the tail of the “Sting” model, in the video clip at http://www.botmag.com/articles/lego_mindstorms_robot_news_1.shtml. The rendered image of that model at http://assets.lego.com/upload/contentTemplating/LEGOAboutUs-ImageLibrary/images/2057/pic3BF7BE94-24DA-4ADC-AC18-95224F5AAAE9.jpg shows quite clearly that the tail it’s hitting with is directly connected to one motor.

The speed of the motor attached to another robot in the video shows that its speed is significantly slower than the 71427 motors supplied with the RCX 1.0 to 2.0. I suggest more like 60-100rpm rather than 300. This gives more torque for the same amount of electric current.

Seeing as the new system uses 6-wire phone cable, I looked up the spec for it in a catalogue and it showed that for 0.2 square mm wire cores the max current is 250mA, about the same as for a fully loaded 71427 motor. Therefore I suggest that the motor electrical power is the same but that the built in reduction gearing in the new motors makes better use of that power because the internal gears have less friction than LEGO plastic gears. Therefore the new motor has slightly more torque than a 71427 motor geared down by 3:1 or 5:1.

This also tells me that daisy-chaining motors on one port would be unfeasible even if it were possible, since the current limit would be exceeded. This makes the system ripe for a motor power interface that would use separate (rechargeable?) batteries to allow the RCX NXT to control RC Car motors for a really powerful wheeled or tracked robot. It would also allow the RCX NXT to send minimal current to the interface, preserving its own batteries.

Mark

Message has 1 Reply:

		Re: new Mindstorms servos?
Hi, (...) in the video I counted about eight revolutions in 5 seconds, that would put it at about 96 rpm. JÃ¼rgen (18 years ago, 8-Jan-06, to lugnet.robotics)

Message is in Reply To:

		Re: new Mindstorms servos?
(...) I'd say quite a bit of torque. It's possible they sacrificed some speed compared to the recent minimotors. Check out the tail of the "Sting" model, in the video clip at (URL). The rendered image of that model at (URL) shows quite clearly that (...) (18 years ago, 7-Jan-06, to lugnet.robotics, FTX)

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