Sunday, 22 September 2013

Magnet Madness

This morning...  Reinstalled the sensors and cable tied everything back into place.   The spacer supports are not very good, I'll probably replace these with new lengths of aluminum tube and make a better job sometime.

This is rather puzzling.....

First paragraph of the assembly preparation talks about installing magnets into the reduction gear slots, with the exception of the hand gear, which needs no magnet...

... and fair enough, no magnet was installed there on my Armdroid.

The magnets are required for operating reed switches - a magnetic field causes the contacts inside to close, or open if they are normally closed.  When the magnetic field ceases, the reed switch returns to original position, making or breaking the electrical circuit.

But wait.....  What's this reed switch for ?

It's positioned directly in front of the hand reduction gearing in the middle - the very one which has no magnet inside!

That supporting bracket is described as "hand switch bracket" (part no. 16) in the parts listing.

What possible sense is there for having a reed switch without a magnetic field to activate it ?

The controlling computer will never get sensible feedback because it's state will always remain the same.

Perhaps I'll temporarily add a small magnet and experiment later what happens to figure out this discrepancy....   Have I discovered another mistake in the manual/blueprints, or maybe the designer's changed their mind implementing  feedback here?

Any ideas, anybody ?