PSN-L Email List Message

Subject: Re: Real time traces
From: Barry Lotz barry_lotz@.............
Date: Sat, 5 Dec 2009 11:29:50 -0800 (PST)


Hi Dave
I sent a note to Brett but maybe you are the one to ask. Now that my sensor=
s are behaving I would like to experiment with a sensor similar to yours. W=
here did you buy your spring stock? I checked the internet and only found l=
arger quantities. Is there a way to calculate the sensor geometric control =
points? ie spring attachments, center of mass & center of hinge?


Regards
=0ABarry
=0Ahttp://www.seismicvault.com


--- On Sat, 8/15/09, Dave Nelson  wrote:

From: Dave Nelson 
Subject: Re: Real time traces
To: psn-l@..............
Date: Saturday, August 15, 2009, 6:43 PM

=0A=0A =0A =0A=0AHi Meredith.=0A=A0=0AThe spring is cut to width on my pers=
onal shear and =0Aheat treated in the home oven in the automatic cleaning m=
ode.=A0 The heat =0Atreat significantly increases the yield strength. The t=
emperature is just right =0Aas measured with a thermocouple. The width for =
the instrument pictured is 16 mm =0Aand thickness is 12 mils.=A0 (Sorry for=
 the mixed units -- our European =0Afriends will think we can't=A0 make up =
our minds )=A0=0A=A0=0A=A0I have a large quantity of the raw material =0Afo=
r the springs -- enough for any conceivable quantity of instruments. I am =
=0Aworking on the =A0repeatability in the shearing process. Right now I can=
 do =0A+- ~.15mm.=0A=A0=0AAs you suggest the period is=A0 a function of =0A=
the spring length and adjusted at the clamp. It sometimes takes a few tries=
 but =0Athe process is quite easy.=A0 The period and rough centering are do=
ne with =0Athe=A0 center capacitor plate PC board =A0removed to allow for a=
 motion =0Aover large angle for convenience. The final mass centering is do=
ne by adjusting =0Athe moveable mass =A0either by eye or using the LED's on=
 the electronics =0Aboard with the loop open. The integrator is designed to=
 hold center over a wide =0Atemperature range so reentering is probably not=
 necessary under all but the most =0Asevere climatic temperature changes. W=
e estimate +- 30C=A0 but that is not =0Afully confirmed.=0A=A0=0A=A0=0AActu=
ator is homebrew based in a Neodymium magnet =0Apurchased on Ebay. The coil=
 is wound on a modified PAC plumbing part=A0 (1 =0A1/4 Schedule 40 plug fro=
m Lowes).=A0=A0It takes a few minutes of lathe =0Awork to make it=A0. The c=
oil is 770 turns=A0of # 32 for about 50 ohms and =0A15 N/A. I fabricate the=
 magnet assembly also but it does take some minor=A0 =0AMIG tack welds. The=
 materials are available=A0=A0from Online Metals. =0A=0A=A0=0AThere is anot=
her small mass at he coil attach point =0Aof=A0~ 10 grams.=A0 =0A=A0=0AThe =
overall size of the basic mechanism exclusive =0Aof the case is 4.5 x 9.5 i=
nches. I have a new (untried) design which will be 4.5 =0Ax  5 inches in a =
somewhat different configuration which may=A0allow for=A0 =0Abuoyancy compe=
nsation. =A0The new design is also easier to build or at least =0Athat is t=
he goal. =0A=A0=0A=A0=0ARegards, Dave =0A=A0=0A=A0=0A=A0=0A=A0=0A----- Orig=
inal Message ----- =0A=0A  From: =0A  meredith lamb =0A  To: psn-l@webtroni=
cs.com =0A  Sent: Sunday, August 16, 2009 00:18=0A  Subject: Re: Real time =
traces=0A =20
=0A  Hi Dave,=0A  =A0=0A  Thanks for the info.=A0 Was wondering about the m=
ain spring =0A  width...its hard to judge from the photo; and where you got=
 such=0A  and the ~ cost?=A0 The photo spring looks to be a original coil s=
trip =0A  or a good home shear.=A0 I understand (via the web) its=0A  magne=
tic; but apparently it works fine regardless of the boom end =0A  coil/magn=
et actuator feedback influence.=A0=0A  =A0=0A  Midway atop your vertical me=
chanism there appears to be a screw =0A  adjustable mass balance or centeri=
ng=A0counterweight.=0A  =A0=0A  I presume....that the main spring period is=
 adjusted via the back clamp =0A  alone.=A0 =0A  =A0=0A  The very small siz=
e=A0of the vertical is rather=A0startling for the =0A  ~ giant ~ mechanisms=
 we're used too seeing on PSN.=0A  I can't really tell if their is more add=
ed mass to the boom via =0A  the=A0photo's besides the ~ frame, coil,=A0cap=
acitance plate.=0A  =A0=0A  What did you use for the coil?=A0 Homebrew woun=
d or otherwise a =0A  commerical coil?=0A  =A0=0A  What is the magnet, ring=
 ceramic or neodymium?=0A  =A0=0A  Take care, Meredith Lamb=0A  =A0=0A  =A0=
=0A  On Fri, Aug 14, 2009 at 12:12 PM, Dave Nelson  wr=
ote:
=0A  =0A    =0A    Hi Meredith,=0A    =A0=0A    The spring is 17-7=A0 stain=
less condition C =0A    heat treated to condition CH900. Thickness is 12 mi=
ls. =A0The pivots are =0A    2 mil stainless single axis=A0.=A0 Pivot lengt=
h is only about 12 mils. =0A    They are held=A0 tension by the=A0C spring.=
 A two axis pivot is not =0A    necessary.=0A    =A0=0A    =A0=0A    Dave =
Hi Dave
I sent a note to Brett but maybe y= ou are the one to ask. Now that my sensors are behaving I would like to exp= eriment with a sensor similar to yours. Where did you buy your spring stock= ? I checked the internet and only found larger quantities. Is there a way t= o calculate the sensor geometric control points? ie spring attachments, cen= ter of mass & center of hinge?


Regards
=0ABarry
=0Ahtt= p://www.seismicvault.com


--- On Sat, 8/15/09, Dave Nelson = <davefnelson@.......> wrote:

= From: Dave Nelson <davefnelson@.......>
Subject: Re: Real time tra= ces
To: psn-l@..............
Date: Saturday, August 15, 2009, 6:43 PM=

=0A=0A =0A =0A=0A
Hi Meredith.
=0A
 
=0A
The spring is cut to width on my personal shear and =0Aheat treated in the= home oven in the automatic cleaning mode.  The heat =0Atreat signific= antly increases the yield strength. The temperature is just right =0Aas mea= sured with a thermocouple. The width for the instrument pictured is 16 mm = =0Aand thickness is 12 mils.  (Sorry for the mixed units -- our Europe= an =0Afriends will think we can't  make up our minds ) =0A
 
=0A
 I have a large quantity of the raw materia= l =0Afor the springs -- enough for any conceivable quantity of instruments.= I am =0Aworking on the  repeatability in the shearing process. Right = now I can do =0A+- ~.15mm.
=0A
 
=0A
As you sugge= st the period is  a function of =0Athe spring length and adjusted at t= he clamp. It sometimes takes a few tries but =0Athe process is quite easy.&= nbsp; The period and rough centering are done with =0Athe  center capa= citor plate PC board  removed to allow for a motion =0Aover large angl= e for convenience. The final mass centering is done by adjusting =0Athe mov= eable mass  either by eye or using the LED's on the electronics =0Aboa= rd with the loop open. The integrator is designed to hold center over a wid= e =0Atemperature range so reentering is probably not necessary under all bu= t the most =0Asevere climatic temperature changes. We estimate +- 30C = but that is not =0Afully confirmed.
=0A
 
=0A
 
=0A
Actuator is homebr= ew based in a Neodymium magnet =0Apurchased on Ebay. The coil is wound on a= modified PAC plumbing part  (1 =0A1/4 Schedule 40 plug from Lowes).&n= bsp; It takes a few minutes of lathe =0Awork to make it . The coi= l is 770 turns of # 32 for about 50 ohms and =0A15 N/A. I fabricate th= e magnet assembly also but it does take some minor  =0AMIG tack welds.= The materials are available  from Online Metals. =0A=0A
 
=0A
There is another small mass at he coil attach poin= t =0Aof ~ 10 grams. 
=0A
 
=0A
The o= verall size of the basic mechanism exclusive =0Aof the case is 4.5 x 9.5 in= ches. I have a new (untried) design which will be 4.5 =0Ax 5 inches in a s= omewhat different configuration which may allow for  =0Abuoyancy = compensation.  The new design is also easier to build or at least =0At= hat is the goal.
=0A
 
=0A
 
= =0A
Regards, Dave
=0A
=  
=0A
 
=0A
=  
=0A
 =0A
----- Original Message -----
=0A
=0A
From: =0A <= a rel=3D"nofollow" title=3D"paleoartifact@........." ymailto=3D"mailto:pale= oartifact@........." target=3D"_blank" href=3D"/mc/compose?to=3Dpaleoartifa= ct@.........">meredith lamb
=0A =0A =
Sent: Sunday, = August 16, 2009 00:18
=0A
Subject: Re: Real time traces
=0A

= =0A
Hi Dave,
=0A
 
=0A
Thanks for the info= ..  Was wondering about the main spring =0A width...its hard to judge = from the photo; and where you got such
=0A
and the ~ cost? = The photo spring looks to be a original coil strip =0A or a good home she= ar.  I understand (via the web) its
=0A
magnetic; but appar= ently it works fine regardless of the boom end =0A coil/magnet actuator fe= edback influence. 
=0A
 
=0A
Midway atop yo= ur vertical mechanism there appears to be a screw =0A adjustable mass bala= nce or centering counterweight.
=0A
 
=0A
I= presume....that the main spring period is adjusted via the back clamp =0A = alone. 
=0A
 
=0A
The very small size&nbs= p;of the vertical is rather startling for the =0A ~ giant ~ mechanism= s we're used too seeing on PSN.
=0A
I can't really tell if their= is more added mass to the boom via =0A the photo's besides the ~ fra= me, coil, capacitance plate.
=0A
 
=0A
What= did you use for the coil?  Homebrew wound or otherwise a =0A commeri= cal coil?
=0A
 
=0A
What is the magnet, ring cer= amic or neodymium?
=0A
 
=0A
Take care, Meredith= Lamb
=0A
 
=0A
 
=0A

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