TRACE Shutter Documentation The TRACE shutter uses modified MDI electronics. The modification makes possible dwell type exposures using the wide opening that can be varied from 0 (this gives a 20 ms exposure) to 262 seconds in increments of 4 ms. The shutter is not capable of automatically making exposures between 2 & 20 milliseconds. The CCD may be exposed however by using multiple narrow type exposures while the CCD is integrating. The shutter moves in 2 directions. This means the recock (as was done on MDI) is not necessary. After an exposure is complete the shutter will be ready for either type of next exposure. MOTOR (based on measurements of the prototype motor): 3 phase brushless DC motor, 6 poles Part No: RB-00704-F02 Terminal Resistance: 9.0 Ohms Torque Constant: .170 Nm/Amp Terminal Inductance: .0071 H No Load Speed (15 V): 84 rad/sec Moment of Inertia: .002 oz-in-sec**2 (calculated) Narrow Exposure: 2.0 ms, .07 ms uniformity (calculated) Minimum Wide Exposure: 20 ms, .2 ms uniformity (calculated), 22 ms preliminary prototype measurement. Dwell Type Exposure: 48ms to 262 sec, .05 ms uniformity (MDI measurement) Peak Current: 1500 mA Operating Temperature: 0 to 40 C. Survival Temperature: -40 to 60 C. Mass (allocated, motor + blade): 561g Mass (prototype; without wire shield, fittings, cover & blade): 352g TIMING (T=0 when command is sent): OPENOUT High OPENOUT Low AXIS Low ----------------------------------------------------------------- Narrow 14 ms 27 ms 63 ms * Wide (0) 14 ms 44 ms 80 ms Wide (exp) 14 ms exp + 23 ms exp + 59 ms Reset NA NA ________ ms *Successive narrow exposures may be taken on a 50 ms cadence. An exposure may be commanded up to 32 ms before the AXIS line goes low. Prototype Measurements (29-Mar-96): Dwell Time (ms) 0 40 100 --------------------------------------------------------------------------- Average CW Center Exposure 20.281 40.229 100.299 Average CCW Center Exposure 22.209 40.183 100.244 Average CW Spacial Uniformity 0.110 0.066 0.080 Average CCW Spacial Uniformity 0.111 0.075 0.071 CW Histogram Full Width 0.020 0.020 0.047 CCW Histogram Full Width 0.016 0.035 0.027 CW & CCW Histogram Full Width 0.090 0.078 0.086 40 exposures @ 14.0 Volts ELECTRICAL INTERFACE: Commands: The shutter uses Card Select 2 0 Nothing 1 Wide Exposure 2 Reset 3 Narrow Exposure 4 *Load Low Byte Exposure (1 LSB = 4 mSec) 5 *Load High Byte Exposure 6 Read RAM 7 Read Position (0 - 71) *The ones compliment of the exposure time must be loaded into the exposure counters before each exposure. The loaded exposure time gets reset (to a 262 second exposure) when a reset command is given. After an exposure has been made the last exposure setting gets "used up", and if a wide type exposure is then taken without first loading a new exposure the result will be a 20 ms exposure. OPENOUT: The shutter electronics provides a signial that is intended to be used by the CCD electronics so that the CCD will know when to integrate and when to read out. Openout goes high about 1 or 2 ms before any light reaches the first corner of the CCD and it goes low about 1 or 2 ms after light stops falling on the last corner of the CCD. Encoder: 1 LSB of the encoder = 5 degrees. Note that the motor normally stops at an encoder transition, so there are 2 possible encoder readings for each stopped position: MOVE JUST MADE POSITION ------------------------------- RESET 23 or 24 CCW WIDE EXPOSURE 23 or 24 CW NARROW EXPOSURE 23 or 24 CW WIDE EXPOSURE 51 or 52 CCW NARROW EXPOSURE 51 or 52 When the shutter is opened (during a long exposure) the encoder reads 0 or 3. Reading the RAM: The shutter electronics has 2k x 8 bits of RAM. Only the first 144 bytes are used. The RAM contains, as data, the time since the encoder was turned on (the start of an expose or reset command) that the encoder was last at the position being read out. Times are 16-bit values (1 count = 1/256 millisecond) stored in successive addresses corresponding to the various encoder positions: TIME(position)| LSB(0) | MSB(0) | LSB(1) | MSB(1) | LSB(2) | MSB(2)|.... --------------------------------------------------------------------- RAM ADDRESS | 00 | 01 | 02 | 03 | 04 | 05 |.... The exposure at different parts of the field can be found by subtracting the time the opening edge went by from when the closing edge went by that same position: Place in Shutter Field Exposure ---------------------------------------------------- BEGINNING OF CW WIDE T(07) - T(59) T(08) - T(60) T(09) - T(61) T(10) - T(62) CENTER T(11) - T(63) T(12) - T(64) T(13) - T(65) T(14) - T(66) END T(15) - T(67) BEGINNING OF CCW WIDE T(68) - T(16) CENTER T(64) - T(12) END T(60) - T(08) Connectors: Motor Function Backplane J205 (verified -------------------------------------- 96-08-05) 1 Encoder A 27 22 2 Encoder B 26 23 3 Encoder C 25 24 4 Encoder RTN 24 21 5 IRED - 28 26 6 IRED + 29 25 7 Phase A 30 27 8 Phase B 31 28 9 Phase C 32 29 13-June-1997 I took some pictures to calibrate the shutter exposures. I made a control file that takes pictures at ECW's 0, 4, 13, & 20. I ran it first with the stimulus at 12 Volts, then 2 more times with the stimulus off to get dark images. I ran it twice dark so I could extrapolate backward to get what the dark images would have been at the time of the 12 Volt images (the camera warms up). ECW 0 is a single pass of the narrow shutter opening, ECW 4 is a double pass. ECW 13 is the minimum wide exposure, and ECW 20 is a 64 ms exposure. This table shows average DN for the entire images. I assume that the 64 ms is perfect, and based on that I calculate the exposure for the others. ECW 0 ECW 4 ECW 13 ECW 20 ------------------------------------------------------------------ 12 Volt Stimulus 379.7 433.3 882.9 2055.7 first dark 341.6 351.4 346.8 356.1 second dark 346.7 356.8 352.2 361.4 dark (extrapolated back) 336.5 346.0 341.4 350.8 12 V - dark 43.2 87.3 541.5 1704.9 calculated exposure (ms) 1.62 3.28 20.33 64.00