Hi Chris, I understand.  I think I see this arrangement in a cut-away of =
a Geophone. One magnet, and two coils, one top and one bottom, perhaps =
wound as you describe.
Thanks, Ted
  ----- Original Message -----=20
  From: ChrisAtUpw@..........
  To: psn-l@.................
  Sent: Monday, May 28, 2007 9:11 AM
  Subject: Re: Geophone questions


  In a message dated 2007/05/28, tchannel@.............. writes:


    Hi Geoffrey,   This is a follow up question.
    Which would create the most useful current, under these conditions:
    The coil, being a donut, 1" hole, 3/4" thick.
    The magnet inserted into the 1" hole, is a ring, 1/4" thick, 3/4" =
OD, with a=20
    1/4" hole in the center.

    1  The N pole enters and exit the top 1/4" of the coil, in and out.  =
This=20
    results in only the N pole entering the coil.
    or
    2  The magnet, at rest, is now midway inserted into the coil.  This =
results=20
    in both the N and S poles actively engaging the coil. My thinking is =
that=20
    you would be getting a push/pull affect, as it moves in either =
direction.


  Hi Geoff, Ted,

         1 gives the max output=20
        =20
         In 2 you DO get a push pull effect, but since the movement =
direction and the winding direction are all constant, the induced =
voltages tend to CANCEL !

         If you want to use a single magnet like this, you need to wind =
two coils on the same former, end to end but connected serially in the =
opposite sense. The overall coil length might be 3x the magnet length, =
or a bit more. =20

         Regards,








Hi Chris, I understand.  I think I =
see this=20
arrangement in a cut-away of a Geophone. One magnet, and two coils, one =
top and=20
one bottom, perhaps wound as you describe.
Thanks, Ted

  
----- Original Message ----- 
  From:=20
  ChrisAtUpw@....... 
  
To: psn-l@.............. 
  
Sent: Monday, May 28, 2007 9:11 =
AM
  
Subject: Re: Geophone =
questions
  

In a=20
  message dated 2007/05/28, tchannel@..............=20
  writes:


  Hi Geoffrey,   This is a follow up =
question.
Which=20
    would create the most useful current, under these conditions:
The =
coil,=20
    being a donut, 1" hole, 3/4" thick.
The magnet inserted into the =
1" hole,=20
    is a ring, 1/4" thick, 3/4" OD, with a 
1/4" hole in the=20
    center.

1  The N pole enters and exit the top 1/4" of =
the coil,=20
    in and out.  This 
results in only the N pole entering the=20
    coil.
or
2  The magnet, at rest, is now midway inserted =
into the=20
    coil.  This results 
in both the N and S poles actively =
engaging the=20
    coil. My thinking is that 
you would be getting a push/pull =
affect, as it=20
    moves in either direction.

Hi Geoff,=20
  Ted,

       1 gives the max =
output=20
  
      =20
  
       In 2 you DO get a push pull =
effect,=20
  but since the movement direction and the winding direction are all =
constant,=20
  the induced voltages tend to CANCEL=20
  !

       If you want to use a =
single=20
  magnet like this, you need to wind two coils on the same former, end =
to end=20
  but connected serially in the opposite sense. The overall coil length =
might be=20
  3x the magnet length, or a bit more. =20
  

      =20
  Regards,

       Chris =
Chapman=20