Lego dynamo?

[Aethersprite]

A few months ago my friends and I tried to build one with the NXT 2.0 set for a Physics project in school. I don't have pictures of it, but it involved spinning a magnet in a coil of wires, with the entire structure (including gear system) built with Technic pieces. We abandoned the idea of using Lego a while later because we were getting like, a few milliamps or something.

So I'm just curious. Is a Lego dynamo actually possible, and has anyone built one before? Thanks.

Edited November 7, 2010 by Lockon Stratos

[allanp]

A few months ago my friends and I tried to build one with the NXT 2.0 set for a Physics project in school. I don't have pictures of it, but it involved spinning a magnet in a coil of wires, with the entire structure (including gear system) built with Technic pieces. We abandoned the idea of using Lego a while later because we were getting like, a few milliamps or something.

So I'm just curious. Is a Lego dynamo actually possible, and has anyone built one before? Thanks.

Well the obvious answer is to just use a standard lego motor in reverse. Any lego motor will act as a dynamo.

However if you actually want to build a dynamo then make sure your magnet is spinning in a way that changes the magnetic feild in the coil as it spins, ie don't spin it on the north-south pole axis as the magnetic feild is symetrical about that plane, so the feild won't change as it is rotated. Spin it on an axis that is at 90 degrees to it. Also bear in mind that the magnetic feild quickly gets weaker the further you move away from it, so wrap you coil as tightly about the spinning magnet as possible without it touching. Hope this helps.

Edited November 7, 2010 by allanp

[mahjqa]

A motor does the trick. You know how you put electricity in it, it starts running? Turns out it works both ways. Turn a motor, and it's connecting wires start supplying electricity.

You can check this yourself. Connect two motors together, and turn one. The other will go as well.

[Tropy]

So I'm just curious. Is a Lego dynamo actually possible, and has anyone built one before? Thanks.

I guess the old 9V motor has a higher efficiency as a dynamo compared to the new PF motors...and actually i'm not sure at all if the new PF motors will do the job since there is some electronics into them...somebody might be of better help here around...

[allanp]

I guess the old 9V motor has a higher efficiency as a dynamo compared to the new PF motors...and actually i'm not sure at all if the new PF motors will do the job since there is some electronics into them...somebody might be of better help here around...

The PF motors do work quite well as a dynamo. There is a new PF motor in the renewable energy educational set that is designed specifically to be used as a motor and dynamo.

[backbone]

I guess the old 9V motor has a higher efficiency as a dynamo compared to the new PF motors...and actually i'm not sure at all if the new PF motors will do the job since there is some electronics into them...somebody might be of better help here around...

Connect two medium motors, insert axles into both, and rotate one. It works.

[DLuders]

@ Lockon Stratos: "Philo" (Phillippe Hurbain) calculated the efficiency of all of the various Lego motors on the webpage http://philohome.com/motors/motorcomp.htm .

I e-mailed him a while back about the new Lego "e-Motor", but he has not tested that yet because they are still quite rare. The Lego Education Store website http://www.legoeducation.us/store/detail.aspx?pt=22&searchtype=0&sport=3&c=0&t=1&l=0&ID=2028&bhcp=1 lists the e-Motor as being "Temporarily Out of Stock", but it has been that way for months. I read somewhere that they will become available again at the end of 2010.

It says that "The E-Motor is a 9V motor with an internal gearbox. Its 9.5:1 gearing ratio provides a maximum torque of 4.5 Ncm and approximately 800 rotations per minute without load. It also functions as a very efficient generator."