## PSN-L Email List Message

Subject: Re: Scientific American 1884 Part 2
From: tchannel1@............
Date: Mon, 17 Mar 2008 17:43:53 -0600

```Hi Chris,  Is this the type of Hall Effect Magnetic field detector chip  =
http://www.allegromicro.com/en/Products/Design/an/an27701.pdf

I see one chip can determined direction. X and Y?      If this is so, is =
there a way to apply that directional information to trip a relay or =
otherwise light a series of LED's
They look inexpensive, \$2, so if not one, we could use several, (8) to =
form a compass.

Thanks, Ted
----- Original Message -----=20
From: ChrisAtUpw@..........
To: psn-l@.................
Sent: Monday, March 17, 2008 4:37 PM
Subject: Re: Scientific American 1884 Part 2

In a message dated 2008/03/17, tchannel1@............ writes:

But how would one record the pendulum direction of movement?=20

Hi Ted,

If you want tthe system to work for small quakes, use either a =
vertical magnet and two pairs of Hall Effect Magnetic field detector =
chips or use a disk on the end of the penduum, a lamp and four =
photocells.  Either of these could give you the X and Y sensitivities.
Or make it to the design and accept that it is not a very =
sensitive device. Maybe put a flat on the top of the pendulum and set a =
ball bearing on the flat? This might give appreciable sensitivity?

Regards,
=20

Hi Chris,  Is this the type of =
Hall Effect=20
Magnetic field detector chip  ht=
tp://www.allegromicro.com/en/Products/Design/an/an27701.pdf

I see one chip can determined =
direction. X and=20
Y?      If this is so, is there a way to apply =
that=20
directional information to trip a relay or otherwise light a series of=20
LED's
They look inexpensive, \$2, so if not =
one, we could=20
use several, (8) to form a compass.

Thanks, Ted

----- Original Message -----
From:=20
ChrisAtUpw@.......
To: psn-l@..............
Sent: Monday, March 17, 2008 =
4:37=20
PM
Subject: Re: Scientific =
American 1884=20
Part 2
In a=20
message dated 2008/03/17, tchannel1@............=20
writes:
But how would one record the pendulum direction of =
movement?=20
Hi=20
Ted,       If you want tthe =
system to=20
work for small quakes, use either a vertical magnet and two pairs of =
Hall=20
Effect Magnetic field detector chips or use a disk on the end of the =
penduum,=20
a lamp and four photocells.  Either of these could give you the X =
and Y=20
sensitivities.       Or make it to =
the=20
design and accept that it is not a very sensitive device. Maybe put a =
flat on=20
the top of the pendulum and set a ball bearing on the flat? This might =
give=20
appreciable sensitivity?      =20
Regards,      =20
Chris Chapman=20

```