Subject: Re: STM-8 Questions From: Mike Speed mike8s2@......... Date: Thu, 1 Jan 2004 07:33:06 -0800 (PST) Dear Sir, On the "Block Diagram of Hardware Store Broadband Seismometer...", what is the value of the feedback resistor on A2 (I see the value of the Integral Feedback resistor is 107K)? I assume that resistor is supposed to be connected to the output of A2, but from the drawing there are just two dots there. Greg --------------------------------- Do you Yahoo!? Find out what made the Top Yahoo! Searches of 2003
Dear Sir,

On the "Block Diagram of Hardware Store Broadband Seismometer...", what is the value of the feedback resistor on A2 (I see the value of the Integral Feedback resistor is 107K)?  I assume that resistor is supposed to be connected to the output of A2, but from the drawing there are just two dots there.

Greg

Do you Yahoo!?
Find out what made the Top Yahoo! Searches of 2003 Subject: Re: STM-8 Questions From: "kpayea" kpayea@........... Date: Thu, 1 Jan 2004 11:16:16 -0800 I used zero ohms - a wire. A2 is configured as a buffer, since there is = no resistor from the negative input to ground. Keith ----- Original Message -----=20 From: Mike Speed=20 To: psn-l@................. Sent: Thursday, January 01, 2004 7:33 AM Subject: Re: STM-8 Questions Dear Sir, On the "Block Diagram of Hardware Store Broadband = Seismometer...", what is the value of the feedback resistor on A2 (I see = the value of the Integral Feedback resistor is 107K)? I assume that = resistor is supposed to be connected to the output of A2, but from the = drawing there are just two dots there. Greg -------------------------------------------------------------------------= ----- Do you Yahoo!? Find out what made the Top Yahoo! Searches of 2003
I used zero ohms - a wire.  A2 is = configured=20 as a buffer, since there is no resistor from the negative input to=20 ground.

Keith
----- Original Message -----
From:=20 Mike = Speed=20
Sent: Thursday, January 01, = 2004 7:33=20 AM
Subject: Re: STM-8 = Questions

Dear Sir,

On the "Block Diagram of Hardware Store Broadband=20 Seismometer...", what is the value of the feedback resistor on = A2 (I=20 see the value of the Integral Feedback resistor is = 107K)?  I=20 assume that resistor is supposed to be connected to the output = of A2,=20 but from the drawing there are just two dots there.

Greg

Do you Yahoo!?
Hi all,
Included herein is a reply from Chris Chapman in relation to this subject.  The reason for
this approach is that Chris uses the AOL email system which can neither send to, or be

----- Original Message -----
From: Meredith Lamb
To: psn-l
Sent: 12/6/2003 9:53:24 PM
Subject: A "new" seismo base plate adjustment screw/s approach

Hi all,

Have tried researching this on the PSN web site search function, but I see no reference.
It maybe nothing new...(?)...but it sure works great!  Best of all, there is little to no adjustment
screw wobble, with quite solid firm movement.....and no base plate bolt threading (tapping)
to be done.  The normal "fitting" of the nuts to the bolts, alone by themselves is quite loose
and non-exact....but not in this application.

Basically this approach uses a standard bolt and three nuts, but, the seismo base has
only some predetermined chamfer widening of the bolt hole/s that is larger than the bolt
(adjustment screw) diameter, but only wide enough to make contact with the chamfer on
the nuts.

The nuts themselves have 6 planes (hexagonal outer shape), and some chamfering on
the outside top/bottom outside edges.  Non-chamfered nuts are useless.

One nut is above the other two; this is a locking nut only....which may or maynot be
absolutely necessary depending on how much tension the other two nuts are adjusted too.

A crude guide to trying/using this; could be the "base material" I used.  It was actually
a hardened tool steel machinist "parallel", that had two holes through the item.  The actual
hole/s were .5" in diameter but the chamfer was wider and made full contact with the nuts
chamfer (.575").  The actual bolt thread diameter was .311".  Here, the hole drilling and
chamfer was done with a likely professional grade machine somewhere of course, but it
was likely done straight into the item without a lateral tilt offset.  If your hole and chamfer is
done by hand, the bolt may not be exactly standing upright 180 degrees to the "base plate"
material when installed.   Visually for this "model", I couldn't see any bolt tilt.

One nut is threaded on the bolt, then passed through the base material, and the other
nut is threaded on lightly finger tightened to where....the bolt can be turned (adjusted) but the
nuts don't.   With the two nuts on the bolt thread, increased turning of "a" nut, narrows
the space for the inside bolt thread, and lessens the "normal" bolt freedom to wobble.
Increased finger tightening of "a" nut makes this "bolt wobble" almost nil, and of course
makes it harder to turn the bolt (adjustment screw), but the firmness of the approach
seems to enhance the mechanical stability quite noteably.  One might call this a
holding/tension/friction adjustment nut.  A wrench isn't needed of course for this or
the locking nut.

One may have a tough time trying to use non-chamfered holes for this approach;
most of my attempts failed with various material.  Various large drills (movement
limited) could be used for creating a chamfer; but their is other tools for this also.

One "could" epoxy the nut/s.  Epoxy one or both after adjusting the nut/s to  your
satisfaction.  Its possible the top nut "could" remain free of any cement, to adjust
the fitting tension on the nut to their satisfaction, whenever they wish

For smooth bolt thread movement action,  I'd suggest that the bolt/s be re-die-ed to
eliminate burrs, or clogging matterial that might be in the threads.  I'd look for a

One might also consider that in the base plate hole and between the nuts is a air
space that might serve as a "lubricant reservoir", for any of a variety of such lubricants
or types for various material.   A thicker variety of non-liquifying grease might be a good
bet (auto grease) for the iron/steel bolts/nuts functioning over time, as well as anti-rust
prevention.

One might try this out on scrap material first before plunging into using it on the planned
for base plate installation.  One doesn't need expensive adjustment bolts/nuts with this
route.

Merry Christmas and happy new year everyone!

Take care, Meredith Lamb

12/19/03

Hi Meredith,

Ordinary grease is made from oil and soap. The soap decays with time, but some soaps are better than others. The high temperature Molybdenum disulphide grease used on cars is fairly good and the moving surfaces get coated with the solid MoS2 lubricant. Vaseline also lasts a very long time. Don't use graphite grease; it is inclined to promote corrosion.

The critical point is that the expansion coefficients of the adjustment bolt and the nut or threaded baseplate need to be identical. This greatly reduces any tendency for the adjustment to creep as the temperature changes.

You can buy large multi flute countersink cutters quite cheaply, but I am not sure that this angle is quite correct for the nuts. Countersinks may have angles of 60, 82, or 90 degrees, 90 being the most common. You can get drills with a cone of 118 degrees, but 135 degrees is more common. The ordinary drills with two flutes do not centre very well over a smaller hole and are inclined to chatter. You can get smoother cutting by using a drill press and opening up the hole first with a standard countersink. The bevel angle cut on nuts may not be very well defined. It seems to vary from 100 to 110 degrees in the ones that I have measured and the depth of the cut may be asymmetrical - check both ends of the nut.
Drilling an accurate clearance hole in the baseplate with a drill press and then sticking a nut onto the flat surface is another option and this gives a high strength glue joint.

You can buy special nuts which have a large 45 deg chamfer on one end. These should be excellent when used with holes shaped with a 90 deg multi fluted countersink cutter.

You can also buy special nuts designed for insertion into sheet metal. They are longer than ordinary nuts and are turned down to a small tube at on e end. When used in sheet metal, the turned down end is inserted through a hole in the sheet and the end is splayed with a press or a ball hammer. However, they can also be pushed into a plain hole drilled in say Al plate and secured with epoxy or Loctite. You can use one at both ends of a hole drilled through thick plate. This can provide a very precisely aligned rigid mounting.

Another method of providing a thread in soft Al plate is to drill out a central clearance hole for the bolt and then use a 'special' counterbore cutter to drill a flat bottomed hole slightly smaller than the outer diameter of the nut, to the length of the nut. You then press in a nut into the hole, maybe adding epoxy or Loctite, using a vice or a press. The six corners of the nut bed into the softer Al quite easily.

To get epoxy to perform well, the surfaces need to conform closely and there needs to be an appreciable gl ue area. It does not hole a sharp edge very well.

One thing that I have been doing is to drill the end of the vertical adjusting screws with a centre drill. I then stick a Stainless Steel ball bearing into the V cup, with epoxy. The diameter of the bearing is slightly less than the tap drill size for the thread used eg use a 5 mm ball for a 6 mm OD thread. This seems to give a contact which does not change with time. The wide angle points which are sometimes used seem to 'bed into' the mounting plates and may wander a bit. The seismometer is mounted on 2" squares of 1/4" thick stainless steel bonded to a concrete floor.

I drill and tap the hole in the steel seismometer baseplate. I put a nut and a wavy washer on the bolt, screw it into position and tension the nut. You can get wavy washers in phosphor bronze and stainless steel. They look like a very thin ordinary washer but are bent to have three S shaped curves which act as a spring. A dab of rubber contact adhesive will keep the nut from rotating as the suspension is levelled and the wavy washer keeps the screw thread under tension.

Regards,

Chris Chapman

Hi all,  Forgive this mistake; but I left out portions of the latest draft on the subject by Chris
Chapman.  The subject is quite relivant to amateur seismology.  Below is the complete draft......

Hi Meredith,

Ordinary grease is made from oil and soap.  The soap decays with time, but some soaps
are better than others.  The high temperature Molydenum disulphide grease used on cars
is fairly good and the moving surfaces get coated with the solid MoS2 lubricant.  Vaseline
also lasts a very long time.  Don't use graphite grease; it is inclined to promote corrosion.

The critical point is that the expansion coefficients of the adjustment bolt and the nut or
threaded baseplate need to be identical.  This greatly reduces any tendenccy for the
adjustment to creep as the temperature changes.

You can buy large mulit flute countersink cutters quite cheaply, but I am not sure that
this angle is quite correct for the nuts.  Countersinks may have angles of 60, 82, or 90
degrees, with 90 being the most common.  You can get drills with a cone of 118 degrees,
but 135 degrees is more common.  The ordinary drills with two flutes do not centre very
well over a smaller hole and are inclined to chatter.  You can get smoother cutting by
using a drill press and opening up the hole first with a standard countersink.  The bevel
angle cut on nuts may not be very well defined.  It seems to vary from 100 to 110 degrees
in the ones that I have measured and the depth of the cut may be asymmetrical - check
both ends of the nut.  The 5/16" UNF bolts seem to have asymmetrical chamfers, but
these are closer to 90 degree.  The outside tips have a ridge on them, so the outside
diameter of the countersunk hole should be the same as that measured across the flats
- 0.500" in this case.

Drilling an accurate clearance hole in the baseplate with a drill press and then sticking
a nut onto the flat surface is another option and this does give a high strength glue joint.

You can buy special nuts which have a large 45 degree chamfer on one end.  These
should be excellent when used with holes shaped with a 90 degree multi fluted
countersink cutter.

You can also buy special nuts designed for insertion into sheet metal.  They are longer
than ordinary nuts and are turned down to a small tube at one end.  When used in sheet
metal, the turned down end is inserted through a hole in the sheet and the end is splayed
with a press or a ball hammer.  However, they can also be pushed into a plain hole
drilled in say aluminum plate and secured with epoxy or loctite.  You can use one at
both ends of a hole drilled through thick plate.  This can provide a very precisely
aligned rigid mounting.

Another method of providing a thread in solft aluminum plate is to drill out a central
clearance hole for the bolt and then use a "special" counterbore cutter to drill a flat
bottomed hole slightly smaller than the outer diameter of the nut, to the length of the
nut.  You then press in a nut into the hole, maybe adding epoxy or Loctite, using a vice
or a press.  The six corners of the nut bed into the softer aluminum quite easily.

For epoxy to give a high strength joint, the surfaces need to conform closely and there
needs to ba an appreciable glue area.  Epoxy will not stick a sharp edge to a conical
hole very well.

One thing that I have been doing is to drill the end of the vertical adjusting screws with
a centre drill.  I then stick a stainless steel ball bearing into the V cup, with epoxy.  The
diameter of the bearing is slightly less than the tap drill size for the thread used, i.e., use
a 5 mm ball for a 6 mm OD thread.  This seems to give a contact which does not change
with time.  The wide angle points which are sometimes used seem to "bed into" the
mounting plates and may wander a bit.  The seismometer is mounted on 2" squares of
1/4" thick stainless steel bonded to a concrete floor.

I drill and tap the hole in the steel seismometer baseplate.  I put a nut and a wavy
washer on the bolt, screw it into position and tension the nut.  You can get wavy /
crinkle washers in phosphor bonze and stainless steel.  They look like a very thin
ordinary washer but are bent to have three S shaped curves which act as a spring.  A
dab of rubber contact adhesive will keep the nut from rotating as the suspension is
leveled and the wavy washer keeps the screw thread under tension.

Regards, Chris Chapman

(This is a forwarded email reply from Chris Chapman)

I am starting to collect materials for a vertical seismo based on the STM-8 design.  I have a rather small (7") speaker that I am considering for using  for the magnet and feedback coil, but I'm wondering if the magnet is strong  enough. Can anybody give me some insight into how big a magnet is needed or  whether I would have to make adjustments elsewhere in the design to compensate for a smaller magnet?

Larry Conklin
Liverpool, NY
lconklin@............

Hi Larry,

This 'bit of string' sounds quite a bit too short! But it depends on how much mass you are planning to use. Check on the values given in Sean's description? The usual speaker systems use external Alnico cylinder magnets with a pole piece of 1.0" to 1.5" dia., maybe 4" outside diameter. The original speakers were 12" to 15" dia or even larger. You can measure the push well enough with one of the small 100 gm electronic scales, or by lifting a coin vertically. The cheaper speakers use Ferrite magnets, which were much more bulky, have lower fields, high stray fields and are much more temperature dependant.
One of the problems with speaker magnet systems is that the space for the coil only allows a few thou radial clearance. Ideally, you would find construction / setup much easier if you could turn out the pole gap a bit on a lathe to give maybe 15 thou clearance, inside and outside. The olde r speakers were bolted together, which made them easy to disassemble. Turned pole faces need a coat of rust resistant priming paint / electro-plating. The central column and the backplate of a speaker are usually one item. 16 ohm speakers are preferable, if you can get them.
Another alternative is to use four rectangular NdFeB magnets, maybe 5/16" to 1/2" thick, mounted on two vertical mild steel backing plates held apart with soft iron spacers. You then wind yourself a rectangular flat coil to fit in the central pole gap. The movement is parallel to the pole gap. www.Wondermagnet.com sometimes have magnet pairs already mounted onto a mild steel backing plate, Ref 0031. They also sell magnet wire. It is easy to visually check the magnet to pole face clearance in flat systems.
It is also quite possible to use 1"~1.5" dia NdFeB disk magnets as the centre column and add a circular end polepiece, a circular backing plate and a mild s teel outer tube. It very much depends on what you can make / have made. I have used magnet columns about 1" long - two 1/2" thick magnets. I make the former out of 3.5 thou Al foil with a layer of tissue paper insulation, stuck onto an 1/8" Al end disk with air holes in it. I first machine a wood former, then dip it in candle wax, turn it down to size and mount up the end plate and the foil tube with epoxy. You then wind and varnish the coil. You warm the wax with a hair dryer and slide off the finished coil.

Regards,

Chris Chapman

Subject: Re: Another STM-8 question From: "Larry Conklin" lconklin@............ Date: Thu, 5 Feb 2004 17:18:06 -0500 Chris, Thanks for the info. Kieth Payea suggested a simple test that I can run = to evaluate the adequacy of the speaker magnet that I have. If it does = prove to be too wimpy, I appreciate your suggestions for alternatives. Larry ----- Original Message -----=20 From: Meredith Lamb=20 To: psn-l=20 Sent: Thursday, February 05, 2004 12:08 AM Subject: Re: Another STM-8 question (This is a forwarded email reply from Chris Chapman) I am starting to collect materials for a vertical seismo based on the = STM-8 design. I have a rather small (7") speaker that I am considering = for using for the magnet and feedback coil, but I'm wondering if the = magnet is strong enough. Can anybody give me some insight into how big = a magnet is needed or whether I would have to make adjustments = elsewhere in the design to compensate for a smaller magnet? Larry Conklin Liverpool, NY lconklin@............ Hi Larry, This 'bit of string' sounds quite a bit too short! But it = depends on how much mass you are planning to use. Check on the values = given in Sean's description? The usual speaker systems use external = Alnico cylinder magnets with a pole piece of 1.0" to 1.5" dia., maybe 4" = outside diameter. The original speakers were 12" to 15" dia or even = larger. You can measure the push well enough with one of the small 100 = gm electronic scales, or by lifting a coin vertically. The cheaper = speakers use Ferrite magnets, which were much more bulky, have lower = fields, high stray fields and are much more temperature dependant.=20 One of the problems with speaker magnet systems is that the = space for the coil only allows a few thou radial clearance. Ideally, you = would find construction / setup much easier if you could turn out the = pole gap a bit on a lathe to give maybe 15 thou clear! ance, inside and = outside. The older speakers were bolted together, which made them easy = to disassemble. Turned pole faces need a coat of rust resistant priming = paint / electro-plating. The central column and the backplate of a = speaker are usually one item. 16 ohm speakers are preferable, if you can = get them. Another alternative is to use four rectangular NdFeB magnets, = maybe 5/16" to 1/2" thick, mounted on two vertical mild steel backing = plates held apart with soft iron spacers. You then wind yourself a = rectangular flat coil to fit in the central pole gap. The movement is = parallel to the pole gap. www.Wondermagnet.com sometimes have magnet = pairs already mounted onto a mild steel backing plate, Ref 0031. They = also sell magnet wire. It is easy to visually check the magnet to pole = face clearance in flat systems. It is also quite possible to use 1"~1.5" dia NdFeB disk magnets = as the centre column an! d add a circular end polepiece, a circular = backing plate and a mild st eel outer tube. It very much depends on what = you can make / have made. I have used magnet columns about 1" long - two = 1/2" thick magnets. I make the former out of 3.5 thou Al foil with a = layer of tissue paper insulation, stuck onto an 1/8" Al end disk with = air holes in it. I first machine a wood former, then dip it in candle = wax, turn it down to size and mount up the end plate and the foil tube = with epoxy. You then wind and varnish the coil. You warm the wax with a = hair dryer and slide off the finished coil. Regards, Chris Chapman=20
Chris,

Thanks for the info.  Kieth Payea suggested = a simple=20 test that I can run to evaluate the adequacy of the speaker magnet that = I=20 have.  If it does prove to be too wimpy, I appreciate your = suggestions for=20 alternatives.

Larry
----- Original Message -----
From:=20 Meredith Lamb
To: psn-l
Sent: Thursday, February 05, = 2004 12:08=20 AM
Subject: Re: Another STM-8 = question

(This is a forwarded email reply from Chris Chapman)

I am starting to collect materials for a vertical seismo based on = the=20 STM-8 design.  I have a rather small (7") speaker that I am = considering=20 for using  for the magnet and feedback coil, but I'm wondering if = the=20 magnet is strong  enough. Can anybody give me some insight into = how big a=20 magnet is needed or  whether I would have to make adjustments = elsewhere=20 in the design to compensate for a smaller magnet?

Larry=20 Conklin
Liverpool, NY
lconklin@............

Hi = Larry,

=20 This 'bit of string' sounds quite a bit too short! But it depends on = how much=20 mass you are planning to use. Check on the values given in Sean's = description?=20 The usual speaker systems use external Alnico cylinder magnets with a = pole=20 piece of 1.0" to 1.5" dia., maybe 4" outside diameter. The = original=20 speakers were 12" to 15" dia or even larger. You can measure the push = well=20 enough with one of the small 100 gm electronic scales, or by lifting a = coin=20 vertically. The cheaper speakers use Ferrite magnets, which were much = more=20 bulky, have lower fields, high stray fields and are much more = temperature=20 dependant.
One of the = problems with=20 speaker magnet systems is that the space for the coil only allows a = few thou=20 radial clearance. Ideally, you would find construction / setup much = easier if=20 you could turn out the pole gap a bit on a lathe to give maybe 15 thou = clear!=20 ance, inside and outside. The older speakers were bolted together, = which made=20 them easy to disassemble. Turned pole faces need a coat of rust = resistant=20 priming paint / electro-plating. The central column and the backplate = of a=20 speaker are usually one item. 16 ohm speakers are preferable, if you = can get=20 them.
Another alternative is = to use=20 four rectangular NdFeB magnets, maybe 5/16" to 1/2" thick, mounted on = two=20 vertical mild steel backing plates held apart with soft iron spacers. = You then=20 wind yourself a rectangular flat coil to fit in the central pole gap. = The=20 movement is parallel to the pole gap. www.Wondermagnet.com sometimes = have=20 magnet pairs already mounted onto a mild steel backing plate, Ref = 0031. They=20 also sell magnet wire. It is easy to visually check the magnet to pole = face=20 clearance in flat systems.
It = is also=20 quite possible to use 1"~1.5" dia NdFeB disk magnets as the centre = column an!=20 d add a circular end polepiece, a circular backing plate and a mild st = eel=20 outer tube. It very much depends on what you can make / have made. I = have used=20 magnet columns about 1" long - two 1/2" thick magnets. I make the = former out=20 of 3.5 thou Al foil with a layer of tissue paper insulation, stuck = onto an=20 1/8" Al end disk with air holes in it. I first machine a wood former, = then dip=20 it in candle wax, turn it down to size and mount up the end plate and = the foil=20 tube with epoxy. You then wind and varnish the coil. You warm the wax = with a=20 hair dryer and slide off the finished=20 coil.

=20 Regards,

Chris Chapman=20

Subject: Re: Another STM-8 question From: "Barry" gbl@....... Date: Thu, 5 Feb 2004 18:40:15 -0800 Hi Larry I've made about 6-7 magnet/coil assemblies for the verticals I have and = I also had problems with speaker magnets(12" radio shack woofers) and = their clearances. I used Sean Thomas' coil construction description with = magnets purchased from Mcmaster. They work well with the coil = construction description STM describes. I used a homemade balance beam = with razor blade fulcrum to determine the coil factor (G). Regards Barry ----- Original Message -----=20 From: Larry Conklin=20 To: psn-l@................. Sent: Thursday, February 05, 2004 2:18 PM Subject: Re: Another STM-8 question Chris, Thanks for the info. Kieth Payea suggested a simple test that I can = run to evaluate the adequacy of the speaker magnet that I have. If it = does prove to be too wimpy, I appreciate your suggestions for = alternatives. Larry ----- Original Message -----=20 From: Meredith Lamb=20 To: psn-l=20 Sent: Thursday, February 05, 2004 12:08 AM Subject: Re: Another STM-8 question (This is a forwarded email reply from Chris Chapman) I am starting to collect materials for a vertical seismo based on = the STM-8 design. I have a rather small (7") speaker that I am = considering for using for the magnet and feedback coil, but I'm = wondering if the magnet is strong enough. Can anybody give me some = insight into how big a magnet is needed or whether I would have to make = adjustments elsewhere in the design to compensate for a smaller magnet? Larry Conklin Liverpool, NY lconklin@............ Hi Larry, This 'bit of string' sounds quite a bit too short! But it = depends on how much mass you are planning to use. Check on the values = given in Sean's description? The usual speaker systems use external = Alnico cylinder magnets with a pole piece of 1.0" to 1.5" dia., maybe 4" = outside diameter. The original speakers were 12" to 15" dia or even = larger. You can measure the push well enough with one of the small 100 = gm electronic scales, or by lifting a coin vertically. The cheaper = speakers use Ferrite magnets, which were much more bulky, have lower = fields, high stray fields and are much more temperature dependant.=20 One of the problems with speaker magnet systems is that the = space for the coil only allows a few thou radial clearance. Ideally, you = would find construction / setup much easier if you could turn out the = pole gap a bit on a lathe to give maybe 15 thou clear! ance, inside and = outside. The older speakers were bolted together, which made them easy = to disassemble. Turned pole faces need a coat of rust resistant priming = paint / electro-plating. The central column and the backplate of a = speaker are usually one item. 16 ohm speakers are preferable, if you can = get them. Another alternative is to use four rectangular NdFeB magnets, = maybe 5/16" to 1/2" thick, mounted on two vertical mild steel backing = plates held apart with soft iron spacers. You then wind yourself a = rectangular flat coil to fit in the central pole gap. The movement is = parallel to the pole gap. www.Wondermagnet.com sometimes have magnet = pairs already mounted onto a mild steel backing plate, Ref 0031. They = also sell magnet wire. It is easy to visually check the magnet to pole = face clearance in flat systems. It is also quite possible to use 1"~1.5" dia NdFeB disk = magnets as the centre column an! d add a circular end polepiece, a = circular backing plate and a mild st eel outer tube. It very much = depends on what you can make / have made. I have used magnet columns = about 1" long - two 1/2" thick magnets. I make the former out of 3.5 = thou Al foil with a layer of tissue paper insulation, stuck onto an 1/8" = Al end disk with air holes in it. I first machine a wood former, then = dip it in candle wax, turn it down to size and mount up the end plate = and the foil tube with epoxy. You then wind and varnish the coil. You = warm the wax with a hair dryer and slide off the finished coil. Regards, Chris Chapman=20
Hi Larry
I've made about 6-7 magnet/coil assemblies for = the=20 verticals I have and I also had problems with speaker magnets(12" = radio=20 shack woofers) and their clearances. I used Sean Thomas' coil = construction=20 description with magnets purchased from Mcmaster. They work well with = the coil=20 construction description STM describes. I used a homemade balance = beam with=20 razor blade fulcrum to determine the coil factor (G).
Regards
Barry
----- Original Message -----
From:=20 Larry=20 Conklin
Sent: Thursday, February 05, = 2004 2:18=20 PM
Subject: Re: Another STM-8 = question

Chris,

Thanks for the info.  Kieth Payea = suggested a=20 simple test that I can run to evaluate the adequacy of the speaker = magnet that=20 I have.  If it does prove to be too wimpy, I appreciate your = suggestions=20 for alternatives.

Larry
----- Original Message -----
From:=20 Meredith Lamb
To: psn-l
Sent: Thursday, February 05, = 2004 12:08=20 AM
Subject: Re: Another STM-8=20 question

(This is a forwarded email reply from Chris Chapman)

I am starting to collect materials for a vertical seismo based = on the=20 STM-8 design.  I have a rather small (7") speaker that I am = considering=20 for using  for the magnet and feedback coil, but I'm wondering = if the=20 magnet is strong  enough. Can anybody give me some insight into = how big=20 a magnet is needed or  whether I would have to make adjustments = elsewhere in the design to compensate for a smaller = magnet?

Larry=20 Conklin
Liverpool, NY
lconklin@............

Hi = Larry,

=20 This 'bit of string' sounds quite a bit too short! But it depends on = how=20 much mass you are planning to use. Check on the values given in = Sean's=20 description? The usual speaker systems use external Alnico cylinder = magnets=20 with a pole piece of 1.0" to 1.5" dia., maybe 4" outside = diameter. The=20 original speakers were 12" to 15" dia or even larger. You can = measure the=20 push well enough with one of the small 100 gm electronic scales, or = by=20 lifting a coin vertically. The cheaper speakers use Ferrite magnets, = which=20 were much more bulky, have lower fields, high stray fields and are = much more=20 temperature dependant.
One = of the=20 problems with speaker magnet systems is that the space for the coil = only=20 allows a few thou radial clearance. Ideally, you would find = construction /=20 setup much easier if you could turn out the pole gap a bit on a = lathe to=20 give maybe 15 thou clear! ance, inside and outside. The older = speakers were=20 bolted together, which made them easy to disassemble. Turned pole = faces need=20 a coat of rust resistant priming paint / electro-plating. The = central column=20 and the backplate of a speaker are usually one item. 16 ohm speakers = are=20 preferable, if you can get = them.
=20 Another alternative is to use four rectangular NdFeB magnets, maybe = 5/16" to=20 1/2" thick, mounted on two vertical mild steel backing plates held = apart=20 with soft iron spacers. You then wind yourself a rectangular flat = coil to=20 fit in the central pole gap. The movement is parallel to the pole = gap.=20 www.Wondermagnet.com sometimes have magnet pairs already mounted = onto a mild=20 steel backing plate, Ref 0031. They also sell magnet wire. It is = easy to=20 visually check the magnet to pole face clearance in flat=20 systems.
It is also quite = possible=20 to use 1"~1.5" dia NdFeB disk magnets as the centre column an! d add = a=20 circular end polepiece, a circular backing plate and a mild st eel = outer=20 tube. It very much depends on what you can make / have made. I have = used=20 magnet columns about 1" long - two 1/2" thick magnets. I make the = former out=20 of 3.5 thou Al foil with a layer of tissue paper insulation, stuck = onto an=20 1/8" Al end disk with air holes in it. I first machine a wood = former, then=20 dip it in candle wax, turn it down to size and mount up the end = plate and=20 the foil tube with epoxy. You then wind and varnish the coil. You = warm the=20 wax with a hair dryer and slide off the finished=20 coil.

=20 Regards,

Chris Chapman=20

some interest to amateurs as well.  Note that the URL for Sitek given on his
web site should be:

http://www.sitek.se/

Cheers,
John

Date: Thu, 4 Mar 2004 09:21:41 +0100
To: boltuc@...................... perkins@......... lahr@....................
benz@......... bellini@......... stucchi@...........
pierre-yves.bard@.................... j.bommer@.........
bruestle@..................... hilmar.bungum@..........
nico@................... faeh@................... mgarcia@............
ggrue@............... dmrosa2@........... mcguire@............
rmwm@.......... stefan@................... paolo@..................
From: Dario Slejko <dslejko@..............>
Subject: new Wood-Anderson in Trieste
Cc: fgentile@..............
X-Spam-Score: -9.1 () PWZIP2_PS,SEISMOLOGY_PS,SPAM_PHRASE_00_01
X-Scanned-By: MIMEDefang 2.30 (www . roaringpenguin . com / mimedefang)
X-MIMETrack: Itemize by SMTP Server on gscodenh01/SERVER/USGS/DOI(Release 5.0.12HF345 | August
14, 2003) at 03/04/2004 01:22:01 AM,
Serialize by POP3 Server on gscodenm05/SERVER/USGS/DOI(Release 5.0.12HF345
| August 14, 2003) at 03/04/2004 01:27:11 AM,
Serialize complete at 03/04/2004 01:27:11 AM

Dear all,
a digital acquisition system for the Wood-Anderson seismometer has been
designed in Trieste by by collegue Francesco Gentile
(fgentile@................ The system is now operating and you can read
http://doga.ogs.trieste.it/doga/risk/woodanderson/index.html
Best regards,
Dario Slejko

--------------------------------------------------------------
Dario Slejko
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale
Borgo Grotta Gigante 42c, 34010 Sgonico (Trieste), Italy
tel. +39 040 2140248; fax +39 040 327307
e-mail dslejko@..............
--------------------------------------------------------------

##################################/ John C. Lahr
#################################/ Emeritus Seismologist
################################/ U.S. Geological Survey
===========================/ Geologic Hazards Team, MS966
##############################/ PO Box 25046
#############################//##############################
############################//###############################
Phone: (303) 273-8596 /=============================
Fax: (303) 273-8600 /##################################
lahr@........ /###################################
/####################################
http://jclahr.com/science/
Subject: Re: new Wood-Anderson in Trieste From: John or Jan Lahr johnjan@........ Date: Fri, 05 Mar 2004 21:02:55 -0700
I checked on the price of the 1L20.  It's \$335
from On-Trak Photonics, Inc, Lake Forest, CA.

This is not an inexpensive solution, at least at this time!

John

To: psn-l@..............
From: John or Jan Lahr <johnjan@........>
Subject: Fwd: new Wood-Anderson in Trieste

The clever, position-sensing system described by Dario Slejko (see below) may be of
some interest to amateurs as well.  Note that the URL for Sitek given on his
web site should be:

http://www.sitek.se/

Cheers,
John

From: Dario Slejko <dslejko@..............>

Dear all,
a digital acquisition system for the Wood-Anderson seismometer has been
designed in Trieste by by collegue Francesco Gentile
(fgentile@................ The system is now operating and you can read
http://doga.ogs.trieste.it/doga/risk/woodanderson/index.html
Best regards,
Dario Slejko

--------------------------------------------------------------
Dario Slejko
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale
Borgo Grotta Gigante 42c, 34010 Sgonico (Trieste), Italy
tel. +39 040 2140248; fax +39 040 327307
e-mail dslejko@..............
--------------------------------------------------------------
Subject: Re: new Wood-Anderson in Trieste From: "Meredith Lamb" meredithlamb@............. Date: Mon, 8 Mar 2004 16:16:13 -0700 Hi all, If anyone has the technical expertise to reply....I'am wondering what is the advantage (or disadvantage/s) of this item over that of acouple of single photogenerative cells? It looks (more or less) like a half bridge circuit to me. Take care, Meredith ----- Original Message ----- From: John or Jan Lahr To: psn-l@.............. Sent: 3/5/2004 9:03:08 PM Subject: Re: new Wood-Anderson in Trieste I checked on the price of the 1L20. It's \$335 from On-Trak Photonics, Inc, Lake Forest, CA. This is not an inexpensive solution, at least at this time! John To: psn-l@.............. From: John or Jan Lahr Subject: Fwd: new Wood-Anderson in Trieste The clever, position-sensing system described by Dario Slejko (see below) may be of some interest to amateurs as well. Note that the URL for Sitek given on his web site should be: http://www.sitek.se/ Cheers, John
Hi all,

If anyone has the technical expertise to reply....I'am wondering what is the
advantage (or disadvantage/s) of this item over that of acouple of single
photogenerative cells?

It looks (more or less) like a half bridge circuit to me.

Take care, Meredith

----- Original Message -----
Sent: 3/5/2004 9:03:08 PM
Subject: Re: new Wood-Anderson in Trieste

I checked on the price of the 1L20.  It's \$335
from On-Trak Photonics, Inc, Lake Forest, CA.

This is not an inexpensive solution, at least at this time!

John

To: psn-l@..............
From: John or Jan Lahr <johnjan@........>
Subject: Fwd: new Wood-Anderson in Trieste

The clever, position-sensing system described by Dario Slejko (see below) may be of
some interest to amateurs as well.  Note that the URL for Sitek given on his
web site should be:

http://www.sitek.se/

Cheers,
John

Subject: Re: new Wood-Anderson in Trieste From: "Meredith Lamb" meredithlamb@............. Date: Tue, 9 Mar 2004 22:15:16 -0700 This is a forwarded email reply from Chris Chapman. ----- Original Message ----- From: Meredith Lamb To: psn-l@.............. Sent: 3/8/2004 11:46:06 AM Subject: Re: new Wood-Anderson in Trieste Hi all, If anyone has the technical expertise to reply.... I'am wondering what is the advantage (or disadvantage/s) of this item over that of acouple of single photogenerative cells? It looks (more or less) like a half bridge circuit to me. Take care, Meredith ----- Original Message ----- From: John or Jan Lahr To: psn-l@.............. Sent: 3/5/2004 9:03:08 PM Subject: Re: new Wood-Anderson in Trieste I checked on the price of the 1L20. It's \$335 from On-Trak Photonics, Inc, Lake Forest, CA. This is not an inexpensive solution, at least at this time! John To: psn-l@.............. From: John or Jan Lahr Subject: Fwd: new Wood-Anderson in Trieste The clever, position-sensing system described by Dario Slejko (see below) may be of some interest to amateurs as well. Note that the URL for Sitek given on his web site should be: http://www.sitek.se/ Cheers, John Hi Meredith, Looking at the 1L20 data sheet, the resolution is quoted as being about 100 nm. I am uncertain whether this refers to the use of the cell with a laser or not, but I suspect not. The semiconductor lasers may have 10x the noise of a tungsten filament bulb. You can get relatively quiet LEDs, but their construction does not often allow you to use them as point light sources and the change in light output over 0 to 100 deg C range may be a factor of x5. You do have quite a serious thermal stability problem, but it can be solved. It is relatively easy using large area Si photodiodes and a tungsten filament bulb to get a resolution of 15 nm at 10 Hz bandwidth. You can buy twin / quad photocells on a common substrate. Regards, Chris Chapman
This is a forwarded email reply from Chris Chapman.

----- Original Message -----
From: Meredith Lamb
To: psn-l@..............
Sent: 3/8/2004 11:46:06 AM
Subject: Re: new Wood-Anderson in Trieste

Hi all,
If anyone has the technical expertise to reply.... I'am wondering what is the
advantage (or disadvantage/s) of this item over that of acouple of single
photogenerative cells?
It looks (more or less) like a half bridge circuit to me.
Take care, Meredith

----- Original Message -----
From: John or Jan Lahr
To: psn-l@..............
Sent: 3/5/2004 9:03:08 PM
Subject: Re: new Wood-Anderson in Trieste
I checked on the price of the 1L20.  It's \$335
from On-Trak Photonics, Inc, Lake Forest, CA.
This is not an inexpensive solution, at least at this time!
John

To: psn-l@..............
From: John or Jan Lahr <johnjan@........>
Subject: Fwd: new Wood-Anderson in Trieste
The clever, position-sensing system described by Dario Slejko (see below) may be of some interest to amateurs as well.  Note that the URL for Sitek given on his
web site should be:
http://www.sitek.se/
Cheers,
John
Hi Meredith,

Looking at the 1L20 data sheet, the resolution is quoted as being about 100 nm. I am uncertain whether this refers to the use of the cell with a laser or not, but I suspect not. The semiconductor lasers may have 10x the noise of a tungsten filament bulb. You can get relatively quiet L EDs, but their construction does not often allow you to use them as point light sources and the change in light output over 0 to 100 deg C range may be a factor of x5. You do have quite a serious thermal stability problem, but it can be solved.
It is relatively easy using large area Si photodiodes and a tungsten filament bulb to get a resolution of 15 nm at 10 Hz bandwidth. You can buy twin / quad photocells on a common substrate.

Regards,

Chris Chapman
Subject: ebay auction From: BOB BARNS royb1@........... Date: Fri, 12 Mar 2004 10:35:42 -0500 MARK PRODUCTS SEISMOGRAPH SENSORS w/ CABLES Item number: 3803503727 ends 3/18 appears to be 3 geophones Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: ebay auction From: "Doug Crice" dcrice@............ Date: Fri, 12 Mar 2004 08:26:53 -0800 These are interesting, but it isn't clear what the natural frequency is. For earthquake purposes, you would do better to buy one of those = 3-component 4.5 sensors from Larry. Doug Crice Geostuff http://www.georadar.com/geostuff.htm 12996 Somerset Drive phone 1-530-274-4445 Grass Valley, CA 95945 USA fax 1-530-274-4446 =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of BOB BARNS Sent: Friday, March 12, 2004 7:36 AM To: psn mail Subject: ebay auction MARK PRODUCTS SEISMOGRAPH SENSORS w/ CABLES Item number: 3803503727 ends 3/18 appears to be 3 geophones Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: more paper needed... From: "Kareem Lanier" kareem@............. Date: Sun, 14 Mar 2004 19:28:13 -0800 Does anyone know where I can get more seismographic paper for my ps2 system. Kinemetrics has this paper but it's extremely pricey. The dimensions are 24" x 13.5". Kareem ---------------------------------------------------------------------------- ------------------- Kareem's HeyJooJoo.Com - Discover, Explore, Learn & Play All of my outgoing and incoming emails are scanned for viruses and worms by my antivirus software.
Does anyone know where I can get more = seismographic=20 paper for my ps2 system. Kinemetrics has this paper but it's extremely = pricey.=20 The dimensions are 24" x 13.5".

Kareem

----------------------------------------------------------------= -------------------------------
Kareem's = HeyJooJoo.Com - Discover, Explore, = Learn &=20 Play
All of my = outgoing and=20 incoming emails are scanned for viruses and worms by my antivirus=20 software.

Subject: Re: more paper needed... From: Raul Alvarez ralvarez@........ Date: Mon, 15 Mar 2004 06:38:17 -0700 Hi Kareem, Does the paper have any specific coating? If it's regular paper, you coud check with an office supply store that carries plotter paper. This comes in sizes up to about 36". Standard "size" is by letter i.e. size A, B, C etc. I think "C" paper would fit your need. You will have to cut it to size. Raul Kareem Lanier wrote: > Does anyone know where I can get more seismographic paper for my ps2 > system. Kinemetrics has this paper but it's extremely pricey. The > dimensions are 24" x 13.5". > > Kareem > > ----------------------------------------------------------------------------------------------- > Kareem's HeyJooJoo.Com > - Discover, Explore, Learn & Play > All of my outgoing and incoming emails are scanned for viruses and > worms by my antivirus software. > Hi Kareem,

Does the paper have any specific coating?  If it's regular paper, you coud check with an office supply store that carries plotter paper. This comes in sizes up to about 36".  Standard "size" is by letter i.e. size A, B, C etc.  I think "C" paper would fit your need.  You will have to cut it to size.

Raul

Kareem Lanier wrote:
Does anyone know where I can get more seismographic paper for my ps2 system. Kinemetrics has this paper but it's extremely pricey. The dimensions are 24" x 13.5".

Kareem

-----------------------------------------------------------------------------------------------
Kareem's HeyJooJoo.Com - Discover, Explore, Learn & Play
All of my outgoing and incoming emails are scanned for viruses and worms by my antivirus software.

Subject: RE: more paper needed... From: "Kareem Lanier" kareem@............. Date: Mon, 15 Mar 2004 06:17:08 -0800 There's no special coating that I'm aware of. I've been using regular paper that was simply cut. This was messy and time consuming to have this done. Although when I was able to get a hold of the actual seismograph paper, it was glossy. Kareem _____ From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Raul Alvarez Sent: Monday, March 15, 2004 5:38 AM To: psn-l@.............. Subject: Re: more paper needed... Hi Kareem, Does the paper have any specific coating? If it's regular paper, you coud check with an office supply store that carries plotter paper. This comes in sizes up to about 36". Standard "size" is by letter i.e. size A, B, C etc. I think "C" paper would fit your need. You will have to cut it to size. Raul Kareem Lanier wrote: Does anyone know where I can get more seismographic paper for my ps2 system. Kinemetrics has this paper but it's extremely pricey. The dimensions are 24" x 13.5". Kareem ---------------------------------------------------------------------------- ------------------- Kareem's HeyJooJoo.Com - Discover, Explore, Learn & Play All of my outgoing and incoming emails are scanned for viruses and worms by my antivirus software.
There's no special = coating that=20 I'm aware of. I've been using regular paper that was simply cut. This = was messy=20 and time consuming to have this done. Although when I was able to get a = hold of=20 the actual seismograph paper, it was glossy.
Kareem

From: psn-l-request@................. [mailto:psn-l-request@............... On Behalf Of Raul=20 Alvarez
Sent: Monday, March 15, 2004 5:38 AM
To:=20 psn-l@..............
Subject: Re: more paper=20 needed...

Hi Kareem,

Does the paper have any specific = coating?  If=20 it's regular paper, you coud check with an office supply store that = carries=20 plotter paper. This comes in sizes up to about 36".  Standard = "size" is by=20 letter i.e. size A, B, C etc.  I think "C" paper would fit your = need. =20 You will have to cut it to size.

Raul

Kareem Lanier = wrote:
Does anyone know where I can get more = seismographic=20 paper for my ps2 system. Kinemetrics has this paper but it's extremely = pricey.=20 The dimensions are 24" x 13.5".

Kareem

----------------------------------------------------------------= -------------------------------
Kareem's = HeyJooJoo.Com - Discover, Explore, = Learn &=20 Play
All of my = outgoing and=20 incoming emails are scanned for viruses and worms by my antivirus = software.