Movie clips of my optical orbo motor

[joegatt]

Hi all.

You can see a movie clip of my optical orbo starting up at

http://www.youtube.com/watch?v=z7FB8bfNuAw

and running at 500RPM at

http://www.youtube.com/watch?v=NcNn4aRz8mg


The lessons learned so far are:

- A VCR rotating head has suitable bearings, just as Wings suggested. All you have to do is remove the motor (when possible).

- A hard disk motor has too much drag, even on open circuit.

- Beginners should start off with small ferrite rings (13mm outer diameter). Larger cores would need a larger PSU to saturate. I am currently using an old car battery.

- A small magnet behind the toroid appears to help, as was indicated by Tinselkoala.

- A large 9000uF electrolytic capacitor close to the circuit increases the torque, but distorts the flat waveform of the toroid pulse. This improvement is probably due to the poor loading response of my power source.

- Optical switching is the best way to investigate O.U.  Hall sensor leads are sometimes slightly ferromagnetic in themselves and may cause slight cogging or drag. Hall sensor positioning should therefore be carefully planned.


Regards
Joseph

[haithar]

seen that back-emf in the scope shots?

[joegatt]

Only the coil's back EMF at the start and end of the pulse. Actually, Haithar, your comment has given me the urge to try and see what happens when I use my hand as a brake. Unfortunately I can't do that just now as I've accidentally fried my toroidal coil. In fact my Orbo motor will probably be down for several days while I wind me a new coil.  I really need to install some kind of thermal cutout for my next toroidal.

I also wanted to point out that I had been running the Orbo motor without core saturation all along. I find this strange. The "magnetic shielding" is beginning to look a lot more like magnetic displacement, rather than some sharp cutoff effect.

Regards
Joseph