Electromechanical shutter system for planetary photography using semiconductor electronics and automatic time recordin

Mozer, C. F.

English

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A . ., . -  7 a I 
, 
8 J NEW MEXICO STATE UNIVERSITY 
I 
OBSERVATORY 
BOX Y 
UNIVERSITY PARK 
NEW MEXICO 88070 
U S A  
TCU-ONC: 
LAS CRUCES, N. M. 
JAGUSON 6-6611 
TN-70 1-66 -1 1 
WITH AUTOMATIC TIME RECORDING CAPABILITY 
> 
(NASA CR O R  TMX O R  AD NUMBER) 
C.  F. Mozer 
GPO PRICE d 
CFSTI PRICEtS) s 
ff 653 July 65 
December 1965 
Supported by 
NASA Grant NsG-142-61 
https://ntrs.nasa.gov/search.jsp?R=19660006321 2020-03-16T21:39:29+00:00Z
.. 
TN- 701-66- 11 
ELECTRONIC SHU'ITER CONTROL FOR PLANETARY PHOTOGRAPHY 
WITH AUTOMATIC TIME RECORDING CAPABILITY 
C. 
N e w  Mexico S t a t e  
h i v e  rs i t y 
An e lectromechanicaZ 
semiconductor e tectronics 
F. Mozer 
University Observatory 
Park, New Mexico 
/5-m 
shutter system incorporating 
and featuring mechanical sim- 
pZiCit8 i s  described, 
sinpte and accurate means of triggering accessoq devices 
a t  the t h e  of shutter opening, This capabilitu i s  used 
to autonrzticalty record the times a t  which eqosures are 
nrzde--a convenience of great inportawe i n  p l a n e i x q  
photographi! Q 
The system also incorporates a 
INTRODUC TI ON 
This  paper describes an e l ec t ron ic  camera s h u t t e r  control  system 
now i n  use i n  New Mexico S t a t e  University Observatory@s p lane tary  
camera. 
graphy, but i t s  s impl ic i ty ,  r e l i a b i l i t y ,  and accuracy should make it 
attractive f o r  other  appl icat ions.  
The system was intended pr imari ly  f o r  use in plane tary  photo- 
Elec t ronic  s h u t t e r  cont ro l  offers severa l  advantages over t h e  
mechanical cont ro l  commonly used i n  camera shu t t e r s .  
s h u t t e r  by press ing  a switch a t  t h e  end of a long, f l e x i b l e  cable  
t ransmi ts  only a neg l ig ib l e  mechanical "shake" t o  the te lescope.  The 
switch can be a snap-action type, permit t ing ha i r - t r i gge r  s e n s i t i v i t y  
with concolgitant minimization of r e f l e x  time. 
Triggering t h e  
Event pu lses  a t  t he  
TN- 70 1-66 - 1 1 
Page 2 
beginning and end of s h u t t e r  operation a r e  ava i lab le  f o r  t r i gge r ing  
accessory devices (e.g. the  automatic time recording system described 
i n  this  paper), Probably the  most important advantage of the  e lec-  
t r o n i c  sys t en  i s  mechanical s implici ty:  t he  complex arrangement of 
gears,  r a t che t s ,  levers ,  and springs t h a t  generate time information 
and motive force  i n  mechanical shu t t e r s  i sc  i n  the  e l ec t ron ic  system, 
replaced by a s ing le  moving part coupled with e l ec t ron ic  time-generating 
and dr iv ing  circuits, This r e s u l t s  i n  a high order of mechanical relia- 
b i l i t y  which, with t h e  inherent ly  high r e l i a b i l i t y  of t he  associated 
semiconductor e lec t ronics ,  provides a dependable ove ra l l  system, 
f i n a l  advantage i s  the  wide range of s h u t t e r  times avai lable;  i n  the 
system described below continuous adjustment i s  ava i lab le  over t he  
range .01 second t o  100 seconds. 
A 
MEC"1CA.L SYSTEM 
The s h u t t e r  i n  New Mexico S ta t e  University Observatory! s planetary 
camera i s  a common "between-the-lens" l e a f  type. 
operate i n  a similar manner; the system described below should therefore  
be adaptable t o  almost any shu t t e r  of t h i s  typeo 
Most leaf- type s h u t t e r s  
The leaves of t h e  s h u t t e r  pivot about small p ins  a t tached t o  the  
s h u t t e r  frame, 
by an ac tua t ing  r i n g  t h a t  ro t a t e s  about t h e  s h u t t e r  opening. 
i s  at tached t o  the  leaves by addi t ional  p ivot  pins.  
p ivo t s  f o r  each l e a f  a r e  c losely spaced, s o  t h a t  s l ight ,  r o t a t i o n  of t he  
ac tua t ing  r ing  moves the  leaves through t h e  la rge  angle necessary t o  
open and c lose  the  shu t t e r ,  
They are pivoted i n  unison t o  open and c lose  the  aperture  
The r i n g  
The f ixed  and moving 
The motion t h a t  must be provided t o  opemte  
TN-701-66-11 
Pagc 3 
t he  s h u t t e r  i s  thus  a reciprocation of t h e  ac tua t ing  r ing ,  
s h u t t e r  i n  use at t h i s  observatory, a small t ab  a t tached  t o  t h e  r i n g  
extends through a s l o t  i n t o  the por t ion  of  t h e  s h u t t e r  body t h a t  o r i -  
g ina l ly  housed t h e  mechanical timing and dr iv ing  system, 
motion of t h i s  t a b  opens and closes t h e  shu t t e r ;  t h e  t o t a l  t r a v e l  
required i s  approximately 118 inch, 
In  t h e  
Reciprocating 
The required motion is  imparted t o  t h e  t a b  by a simple push-pull 
solenoid arrangement (Figure 1). 
t i n g  system i s  composed of  t h e  L-shaped fork which moves t h e  tab and 
t h e  two s lugs  t h a t ,  under t h e  influence o f  solenoid f i e l d s ,  p u l l  t he  
fork back and for th .  
assembly, 
t h e  block a l s o  provides t h e  guide s t r u c t u r e  i n  which t h e  ac tua t ing  
assembly moves. 
p rope r t i e s - -pa r t i cu la r ly  its very low "s t ic t ion ."  
pended between aluminum angle supports by means of s t e e l  b o l t s  screwed 
i n t o  the  axial  hole from each end; t hese  b o l t s  a l s o  increase  the  mag- 
netic e f f i c i ency  of t h e  system and provide t r a v e l  adjustment. 
of epoxy cement on t h e  ends of  the  b o l t s  prevent metal-to-metal contact 
between s lug  and b o l t ,  
assembly e 
The s ing le  moving p a r t  of t h e  actua- 
These three  p ieces  b o l t  toge ther  t o  form a r i g i d  
1 Both solenoids a r e  wound on a monolithic block of  Teflon; 
Teflon was chosen p r i n c i p a l l y  because of i t s  bearing 
The block is sus- 
Drops 
Figure 2 is  a photograph of t h e  shut te r -so lenoid  
ELECTRONIC SYSTEM 
The general circuit concept used represents  an obvious choice, and 
has  been similarly appl ied  elsewhere (Vurek and Conlon, 1963), Time 
information is generated by a monostable mul t iv ibra tor  whose output i s  
lTrademark, E, I ,  DuPont Company, 
TN-701-66-11 
Page 4 
TEFLON BLOCK- 
-800T *34W 
EACH COIL  
STEEL SCREW 
#10-32 
STEEL SLUG 
BO-DIA 
x\ w ACTUATING TABJ 
\\aA SHUTTER APERTURE A\ ' 
/BRASS PLATE 
ATTACHED TO 
SHUTTER FRAME 
F i g u r e  1 
SHUTTER Ai'TUATOR ASSEMBLY 
TN- 70 l - 6 6 -  1 1 
Page 5 
TN170 1-66 - 11 
Page 6 
used, after i s o l a t i o n  and wave-shaping, t o  d r ive  low-impedance cur ren t  
switches t h a t  ac tua te  the  solenoids, The present system d i f f e r s  fmm 
t h a t  described by Vurek and Conlon p r i n c i p a l l y  i n  time generating and 
output switching techniques, A unique f ea tu re  of t h i s  system i s  a 
b i s t a b l e  c h a r a c t e r i s t i c  t h a t  locks t h e  s h u t t e r  e i t h e r  open or closed. 
%e ou+,pl-rt circuit i s  designed t o  provide a small, constant cur ren t  
(about 50 ma) t o  both solenoids. Under t h i s  quiescent condition t h e  
ac tua tor  assembly tends t o  be held a t  t he  end of  t h e  solenoid block 
it i s  neares t  t o ,  Large current pulses of sho r t  duration provided 
by t h e  switches move t h e  ac tua tor  back and f o r t h ;  the  small quiescent 
cu r ren t  holds it a t  t h e  des i red  end of i t s  travel,  The epoxy drops 
in t ruded  between t h e  b o l t s  and slugs prevent b o l t  and s lug  from 
appearing magnetically as a s ingle  piece; much l a rge r  cur ren t  pu lses  
would be necessary t o  produce motion i f  t h i s  were the  caseD 
The circuit i s  shown i n  Figure 3 .  The one-shot (monostable multi-  
v ibra tor )  i s  composed of a f l i p - f l o p  (Q, and Q ) and a m i j u n c t i o n  
t r a n s i s t o r  re laxa t ion  o s c i l l a t o r  ( Q , ) .  This c i r c u i t  i s  based on a 
similar c i r c u i t  given i n  t h e  Go E, Trmtsistor Manual (1962). The 
quiescent condition of t he  f l i p - f l o p  i s  Q 
pulse  applied through D1 t o  t h e  base of Q2 by c losure  of S1 t u r n s  Q2 
off; regenerative feedback turns  Q, on, 
CTs) s e l ec t ed  by RANGE switch S2 begins t o  discharge through R8 and 
I$. toward t h e  c o l l e c t o r  voltage of Q When t h e  emitter voltage of 
t h e  unijunction (Q ) reaches i ts  f i r i n g  voltage nV t he  m i j u n c t i o n  
fires, producing a negative pulse across R 
2 
OFF, Q, ON, A p o s i t i v e  1 
The timing capac i tor  (CTL or 
1" 
3 BBD 
This pulse  i s  applied 10 
TN-701-66-11 
Page 7 
REMOTE CONTROL 
0 - H A N D L E  
L, 
2N1305 
OS 
IZizEJ m w  --  
I SHUTTER SOLENOIDS I 
Figure 3 
SHUTTER TIMm AND D R I V I N G  C I R C U I T  
TNh701-66-11 
Page 8 
through D, t o  t h e  base of Q, turning it on; regenerative feedback 
then turns Q 
cent  state, 
b r ing  t h e  circuit wholly t o  i t s  quiescent state; t h i s  is done rap id ly  
off, and t h e  c i r c u i t  has  returned almost t o  the  quies- 1 
The timing capac i tor  (CTL or C ) m u s t  be recharged t o  TS 
by DRQ which i s  forward biased un t i l  C i s  recharged, T 
rer,t~~ng!!lar W i w e f O r S  Zppgring at the  colleetois of Q a d  1 
Q, are current-amplified by Darlington-connected ampl i f ie rs  Q, and Q, 
opera t ing  as emitter-followers,  The outputs of these  s t ages  are dif- 
f e ren t i a t ed ,  and the  r e s u l t a n t  p o s i t i v e  pu l ses  t r i g g e r  cont ro l led  
rect i f ier  switches SCR and SCR Since the  waveform at  t h e  c o l l e c t o r  
of Q 
ga t e  of SCR 
t i v e  pulse  appears a t  t h e  ga te  o f  SCR at  t h e  end of t h e  cycle. 
t hus  switches t o  open the  shut te r ;  SCR2 switches t o  c lose  t h e  s h u t t e r ,  
1 2 "  
i s  a posit ive-going rectangle, a p o s i t i v e  pulse  appears a t  the  1 
at t h e  beginning of t h e  time cycle, Conversely, a posi-  
SCRl 
1 
2 
The energy required t o  open and close t h e  s h u t t e r  is s to red  i n  
capac i tors  C5 and CgB which a r e  "dumped" through t h e  solenoids by t h e  
SCR's, 
l a rge  t o  limit current (with SCR's ON) t o  a value below SCR holding cur- 
r en t ;  t h i s  provides p o s i t i v e  SCR t u rno f f ,  
constant 50 ma through t h e  solenoids t o  provide t h e  b i s t a b l e  charac te r -  
i s t ic ,  
C5 and C6 are charged through R 18 and R19, which a re  s u f f i c i e n t l y  
R16 and R " t r ick le11  a 17 
Time c a l i b r a t i o n  is achieved by p lac ing  a small f u l l - c i r c l e  
p r o t r a c t o r  around t h e  bushing of t h e  timing potentiometer %, Times  
a re  measured at  five-degree i n t e r v a l s  using an oscil loscope ( f o r  sho r t  
times) and a clock ( for  times exceeding t h e  c a p a b i l i t i e s  of t h e  
- TNS701-66-11 
Page 9 
oscil loscope).  Times v so  angles are then p l o t t e d  on log  paper, and 
t h e  angles corresponding t o  desired time markings a r e  read from t h e  
graphs and drawn on t h e  f i n a l  d i a l ,  
times should be continuously adjustable over t h e  range .01 second t o  
100 seconds approximately, w i t h  some overlap of t he  two ranges, 
With t h e  component values shown, 
Switches Sg and S4 allow for t h e  incorporation of two s p e c i a l  
f ea tu re s  i n t o  t h e  system, 
an i n d e f i n i t e  period of time, S 
The s h u t t e r  i s  then opened i n  the normal mannero A t  t he  end of  t h e  
des i red  per iod  S, i s  closed; the c i r c u i t  then goes through i t s  reg- 
u l a r  timing cycle, a t  t h e  end o f  which it c loses  t h e  s h u t t e r ,  
If it i s  des i red  t o  open the  s h u t t e r  f o r  
i s  opened, breaking t h e  timing loop, 3 
S 4 
emitter of  Q 
t r i g g e r i n g  accessory devices (e,go t h e  t i m e  recorder system described 
below) 
switches t h e  negative-going rectangle appearing at the  
t o  a p in  of  connector P 5 43 where it is  ava i l ab le  f o r  
AUTOMATIC TIME RECORDING ACCESSORY 
I t  is of ten  necessary i n  planetary photography t o  have an accurate 
record of the  p rec i se  time a t  which individual exposures are made, 
is espec ia l ly  t r u e  of rap id ly  ro t a t ing  p l ane t s  such as J u p i t e r ,  where 
a timing e r r o r  of 10 seconds would produce a corresponding e r r o r  of 
O z l  i n  t he  measured longitude o f  a Jovian fea ture .  
recorded on each photographic p l a t e  and perhaps 20 p l a t e s  being taken 
on a f u l l y  scheduled n igh t ,  the problem of  manual recording of accurate 
event times would be formidable, i f  not impossible, 
recording is t he re fo re  necessary and such a system i s  described below, 
T h i s  
With 60 images being 
Automatic time 
TN2701-66-11 
Page 10 
A Simplex Productopraph' i s  used at N e w  Mexico S t a t e  University 
Observatory f o r  automatic time recording, 
command, t he  month, day, hour, minute, and second of  the  command s igna l ;  
t he  record i s  pr in ted  on paper tape,  
575 VA switch closure.  
This machine p r i n t s ,  on 
The required command s igna l  i s  a 
The c i r c u i t  used t o  t r i gge r  t h e  t i m e  recorder i s  shown i n  Figure , 
The negative-going rectangle from the  c o l l e c t o r  o f  Qs ( i n  Figure 4b, 
3) i s  d i f f e ren t i a t ed  by C1 Rl ,  and t h e  r e su l t an t  negative pulse is  
current-amplified by emitter-follower Q 
negative pulse  is  s teered  by D 
A port ion of t he  r e su l t an t  1" 
t o  t r i g g e r  t h e  one-shot composed of 1 
3 
Q2 and Q,. 
c o l l e c t o r  of Q ,  and i s  amplified by t h e  cascaded emitter-follower Q 
and Q,. 
gized when Q, i s  turned on by t h e  one-shot, 
voltage suppression t o  p ro tec t  Q 
su re  time, and R 2 
t r i g g e r  t h e  one-shot 
A negative-going rectangle 5 0  m s  long appears at t h e  
4 
The c o i l  of r e l a y  K1 is  t h e  emitter load of QsB and i s  ener- 
D provides reverse- 
allows adjustment of re lay  clo- 
selects the f rac t ion  of t h e  input pulse  necessary t o  
3 
R 5" 5 
POWER SUPPLY 
Power requirements o f  t h e  system a re  moderate, The timing and 
switch-driving c i r c u i t  requires  -24v DC a t  a constant 60 ma,  t h e  
solenoid switching c i r c u i t  requires -72v DC at 100 ma, with surges t o  
150 ma, and t h e  time recorder t r igger ing  c i r c u i t  requires  -2411 DC a t  
'Simplex Time Recorder Coo 
3The one-shot is an adaptation of a c i r c u i t  given i n  Transistor 
Gardner, Massachusetts. 
Circuit Design (1963), 
. TN-701-46-11 
Page 11 . ' J 
1 
INPUT 
I I7 
a. Accessory 
3 0 0  0 COIL 
QI.O2,03.04: 
OS: 
DI : 
D2. D3 : 
2N404 
2N13M 
IN34A 
IN2069 
T r i g g e r  
c. Circuit 
Modification 
-' TN-701-66-11 
Page 13 
REFERENCES 
General E lec tr i c  Company (1962) Transistor M a n u a Z ,  Sixth  Edition, 
Syracuse, General E lec tr i c  Coo,  p. 200, 
Texas Instruments Coo (1963), Transistor C i r c u i t  Design, N e w  York, 
M c G r a w - H i l l  Book Company, Inc., p ,  413, 
Vurek, Gerald G, and Conlon, Joseph M, (1963) "Electromechanical 
Shutter f o r  U l t  ravi o let  Time - lapse Photography," Re ue%u of 
S c i e n t i f i c  Instmunents, 5 583, 


Electronic shutter control for planetary photography with automatic time recording capability

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