Mindboards

Hello Philo and everyone,

I wonder how can this guy make the Magic Wand rotate 360 degree clockwise forever without twisting the cable between the NXT brick and the Wand?
http://www.youtube.com/watch?v=eWxwGUYFM5M

Also, I wonder if there is a way record the LED pattern onto the wand's circuit, then attach a small external power so that it doesn't have to connect to the brick all the time? ....

Thank you

You make a frame to which you attach the rotating part of the motor. Attach the white part of the motor to the NXT. The frame stays put, while the NXT rotates around. Balancing the whole thing will be tricky. The Magic Wand connects to the NXT and nothing ever gets twisted up.

- Xander

Must have spent a fair bit of time getting that balanced but it is a great version of the wand!

I think I would make a circular plate with concentric conducting rings and use carbon brushes to transfer the signals from the NXT to the 8574 & LEDS.

I think Xander's solution is the best one, using brushes you will experience bad contacts from time to time and i2c will not perform good enough I'm afraid...

Pity, I have been wondering for a while how to make something similar for my son's band (9 letters in the name).

Not a Lego-based solution, but I suppose I could etch the name onto a disc and have the wipers travel across it transferring power to LEDS on the rotating arm. Not as flexible as this version but less likely to get nicked at a show!

Xander is right, that is (just about) how I did it. I to have considered slip-rings, but am afraid of erratic signals (as Philo mentioned). It would certainly be better as far as getting things to work physically.

Hi Matt,

Many, many Moons ago I worked on Emergency Service Vehicle light & siren repairs. There was a couple of sets of Sirens that where Rotating Polarised Pezio units.

To allow the current to get from the battery to the rotating speaker they used two bronze disks that had an insulator through the centre of the disk, creating two halves.

The first disk had had each 1/2 circle connect to the power source to supply the power which was passed to the rotating second disk placed on top.

The top disk was connected to a Bridge Rectifier's A.C. input and the bridges output when too the electronics.

I have came across the same principle in children's toys a couple of times as well.

If you used a multi-ringed disk, you could get the I2C across as well.....

I trust this may be of assistance to you?

Well, there are these little things called "phone cord untanglers", which are 4 contact slip-rings. It sounds like the device you described is similar, but for higher power. I am just afraid of noise in the signals, that's why I haven't gotten any yet.