Hi MIKE.

19-Mar-04 10:18:04, MIKE ROSS wrote to George White


 MR> However, a positive feedback entails returning energy to a system
 MR> during part of an oscillation cycle. In the case of a relay, it
 MR> really exhibits an electromechanical hysterisis.
                                          ^^^^^^^^^^^
_That's_ what I really meant when I said positive feedback.
My sloppy wording; sorry.


 MR> Many things
 MR> exhibit hysterisis without ever requiring a positive feedback. If
 MR> it was really positive feedback then wouldn't a relay oscillate?
 MR> (bounce or chatter is something else)

no more than a schmitt inverter does.

to get oscilation you need feedback with a phase shift and/or delay.

 MR> In my own understanding one description is that it exhibits a
 MR> positive reluctance (i.e. increase in magnetic conductance) but
 MR> not a feedback. Say, if one were to add capacitance to this system
 MR> could it oscillate?

If you involve the switch also then yes, some automotive blinker units
are based around a relay and a capacitor.

The rotory selectors used in electro-mechanical phone exchanges also had a
capacitor that could be used with contacts on the drive solenoid and one of
the selector arms advance the arm back to the home position.

 -=> Bye <=-

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