[Jukebox-list] External start switch and Megger

[Di Di Mao]

Reminds me of the days when the early series Simpson
260 meters reigned supreme.  They used a 22.5 volt
battery in the ohmmeter.  Using one to test the then
available Germanium transistors was disasterous!

When I tried to imagine how you would make an external
switch it occurred to me you need the motor speed as
an input factor.  Without it, you're just
approximating the actual function of the centrifugal
switch.  In other words, I dismissed the idea as
potentially unreliable, at least in some situations.

When the link to the device was posted, I could see
that they are overlooking all that!

So what's inside? Just a timing circuit and a triac,
most likely.  A one shot of some sort, maybe a 555
timer (or a relay).  You would set the time to be long
enough for the motor to start under worst case
conditions.  A little extra on time for the start
windings probably wouldn't be very bad, but too much
will overheat the motor in short order.  Of course,
you need to have access to the start winding.



      ____________________________________________________________________________________
Be a better friend, newshound, and 
know-it-all with Yahoo! Mobile.  Try it now.  http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ