Mini Motors with NXT

[TasV]

I need a small 9V motor for an NXT Mindstorms robot my Son and I are working on (no rush... we have 12 months to get it right), and I need a small 9V motor that doesn't take up much room or have much weight. I have an M PF motor (58120c01) which is quite small and we can use this without any trouble because I know I can get it to work with NXT using a converter cable but I was looking at the smaller 9V 4 x 4 x 3 1/3 motor (47154c01) and the 9V Mini-Motor (43362c01)... and even the tiny 2986... and wondering if these could also be powered and controlled by the NXT brick? They have a different attachment to the newer PF motors but I don't know if this will make a difference? Any ideas? It needs to be possible back-drive them too. (interesting link: http://www.philohome.com/motors/motorcomp.htm seems to suggest NXT can power them but am still not sure)

Edited March 19, 2013 by TasV

[OleBM]

If I am correct, you should be able to connect 9V elements to your NXT with this cable: https://www.bricklink.com/catalogItemPic.asp?P=x1676

I'm not into NXT myself though, so I'm hoping that someone with the experience will confirm what I'm saying here

[TasV]

Thanks OleBM, I was also thinking it should be possible. My understanding of the power ports in the NXT brick is that they just supply a variable power supply to run the motors at different speeds and directions (though they also convey sensed data in the form of rotations (RPM and degrees)), and therefore should be able to run these other 9V motors with the appropriate converter cable. I thought I'd try and get some learned feedback before going out and buying any.

Edited March 19, 2013 by TasV

[DLuders]

@ TasV: Yes, that cable that OleBM found will power any of the old-style Lego 9V motors that have the electrified 2x2 black plate (including all of the ones you listed in your post above).

[TasV]

Thanks Dluders!

Do you think the 2986 would have enough power to open and close this grabber, grab a 16g soda can and hold it (the grips on the jaws should do that just by friction) while it was being lifted by a LA?

I am liking the look of this little motor because, whilst it is really slow, it is has very little size and weight.

Edited March 19, 2013 by TasV

[DLuders]

@ TasV: There are mixed opinions about that -- read this previous Eurobricks topic about the Lego 2986 9V Micromotor. I personally don't think it could do it.

The 5119 Micromotor (2986 on Peeron, and 70823 in TLG) is used in the 8480 Space Shuttle set. From Brickfactory.info , here is a picture of it being used in the alternate (submarine) model. There is an old-style 2x2 electric plate attached to the 5306b "Electric, Wire with Brick 2 x 2 x 2/3 Pair" cable that clips onto the backside of the 9V Micromotor:

[OleBM]

I have the micro-motor, and the torque on this one is not powerful at all. I must say I don't like the idea of incorporating the motor into large mechanics, since I consider this motor to be light function capable only (turning details, turning fake steering wheels etc.)

In this video, you can see how the micromotor performs under stress (it pleas for mercy!) :

http://www.youtube.com/watch?v=6iXkTfnEtk4

But I'm recommending you to buy one, so you can see for yourself what little marvel that motor really is

[Alasdair Ryan]

I use the micro motor on my grab I make for the 8043,it is slow but because I used a worm gear it is fine.

A micro motor is perfect for what you want to do.

[TasV]

The worm gear does substantially reduce the effort required to open and close these grabbers... and it looks like it can be driven backwards and forwards. The link Dluders provided mentions these micro-motors tend to jam up. Have people found this to be an issue? I could rig up some technic connectors to prevent the pulley from coming off too. Some accounts I've read also mention stacking these micro-motors. I guess that would be to distribute the load between them so they aren't working so hard???

Edited March 19, 2013 by TasV

[Alasdair Ryan]

The grab I made above does not jam,when the grab opens and closes fully it will rotate 360 continuous.

Since you have a worm gear in your design I don't think your need two micro motors to power the grab.

Edited March 19, 2013 by Alasdair Ryan

[TasV]

Thanks for the advice! The grabber shown above was just our LDD of it. When we made it we left the bevelled gears out, so that linkage will not be included. It will be directly driven straight to the worm gear from the motor as we don't need to change the direction of the rotation anymore. Does the light grey pulley ever slip when under load?

Edited March 19, 2013 by TasV

[TasV]

Ok... just bought one of these little micro-motors to trial... also found a really neat looking gear box (45360) as well that I just know will come in handy. Why is it that whenever I go into BrickLink I always end up spending way more than I had planned

[Alasdair Ryan]

Sometimes they can slip,but the trick is to have them power a set of gears to the function and not drive the function directly.

Edited March 19, 2013 by Alasdair Ryan

[pluto7443]

Why not attach an extension cable to the converter wire, and then use a PF M Motor?

[TasV]

Why not attach an extension cable to the converter wire, and then use a PF M Motor?

This is what I had intended to do and still might. The PF M motor is slim and fairly light but I went looking for even smaller motors last night to see if I could go even smaller. It doesn't need to work for very long or very often as the robot has to make its way through a course first and then locate a soda can at the end of the course, lift it approx. 10cm off the ground, and then locate a red block and place the can onto the red block after travelling a max. of 60cm to the block. The speed of the 2986 is going to be the problem (its max. speed is only something like 35-36 rpm and running that worm gear the grabber will go even slower) so I might end up going with the M motor or trying to find one of those 9V 4x4x3 1/3 mini-motors. On the plus side the 2986 will make the movement smooth and deliberate though I'll be relying heavily on the light touch and grip created by the rubber tires in the jaws. The slipping pulley is a concern as I can't gear it down any more but I don't think the worm gear will create much fiction or load. The thing I like about the 2986, and the other older motors, is that the cable is thinner and more pliable compared with the M motor's cable which is wider, thicker, and less pliable and so it is less likely to affect the motion of the linear actuator or even the lift mechanism. When attaching some of the sensors with the standard NXT cables it has been a major pain at times because the cables are so rigid that they will literally push the sensors at connection points causing them to tilt. This occurs when I try to put too sharp a bend in the cable by forcing it into too tight a spot causing the cable to flex in the opposite direction and tilting the sensor despite being connected with up to three pins on various configurations of liftarms. I use the thinner cables with LED lights on the robot (to make our own light source to overcome the variation we encounter in ambient light in competition venues) and these have proven very nice to work with and easy to stash out of the way without affecting any other part of the robot.

I also got this reply from Phillipe Hurbain:

I can't tell for sure if 2986 will be able to exercise your gripper.

This small motor is not powerful but with the wormscrew you used that

should be OK (it will be VERY slow ;)

Note also that this motor is said to jam if it is run at normal power

but is mechanically blocked.

Cheers,

Philo

I think I will overcome this through the program by setting the duration of the motor's activity so it doesn't ever become mechanically block.