The Augustine Theater Experience
Sharp XV-Z9000U SMART Calibration
Step 3: Test Photocells
Relevant SMART web pages:
http://home.pacbell.net/steve367/photocell.html
http://home.pacbell.net/steve367/setup.html
| Materials & Tools List | Cost | Notes |
| Avia DVD | ||
| Avia filters | Red, green, and blue filters that came with the DVD. | |
| Electrical tape | 0.47 | |
| Marker | ||
| Masking tape |
Steps
Turned out the lights and displayed Avia's "Black" window (IRE 0). Hit pause so the DVD wouldn't advance to the next pattern.
The SMART web site says that "all of the good photocells gave resistance
values at IRE 0 of several M Ohms or more, i.e. between 1.5 and 7 M Ohms." I
tested all of my photocells at IRE 0 and here are the results:
Photocell 1: 0.659 MAs I tested, I labeled each photocell with masking tape and a marker.
Photocell 2: 0.408 M
Photocell 3: 0.543 M
Photocell 4: 3.440 M
Photocell 5: 4.420 M
It looks like I have two good photocells -- 4 and 5. But there is another test I should run. I need to know if the photocell I chose is sensitive enough at its current distance to low light levels. According to the SMART "Setup" web page, I need to take readings at IRE 0 with a blue filter. "If the reading with the lens cap on is higher than that with the lens cap off, ideally a factor of two or more, your detector is sufficiently sensitive enough for use with the SMART system."
First I needed to alter my detector and attach the blue filter:
- Used electrical tape to close the opening in the pipe to fit an Avia filter.
- Used electrical tape to attach the blue filter.
Couldn't get any reading with the detector in its original location. I had to
move it to the other side of the couch. I sat the tripod on three cardboard
boxes, extended the tripod as high as possible, and re-pointed the detector to
make sure the projector's light was falling square on the photocell. The front
of the detector is now 31.5" from the edge of the projector's focus ring.
My test results with photocell 5 and the detector in its new position:
IRE 0, blue filter, lens cap off: 8.00 M
IRE 0, blue filter, lens cap on (Sharp lens cap is clear plastic): 14.60 M
The "lens cap on" reading is not quite twice as high, but the two measurements are significantly different and that's good. Photocell 5 it is.
- Bent the photocell's leads to make it stable on the end cap.
- Taped its leads to the back of the end cap.
- Permanently attached its leads to the speaker wire by crimping the wire
crimpers.
