ENGR-101
Week 02: Shutter Speed Measurement
Today’s Agenda
11:00 Role Call
Welcoming Remarks
Fun Motivation (Related YouTube Video)
11:15 Experiment 1: Extract camera flash circuit board
11:35 Experiment 2: Oscilloscope and FG setup: burst and trigger
11:55 Experiment 3: Camera flash circuit board installation
12:15 Experiment 4: Reading measurements (with cursors)
12:35 Discussion Points
13:00 Adjourn
Generation Gap: Class of 198X vs. Class of 2015+
Terabyte
World
Atari 400 (16K) – IBM XT (1 MB)
Class of 1980x
Megabyte Generation
Pentium 3 (40 MB) – Multicore (GB)
Class of 2015+
Gigabyte Generation
Worldwide Optical Content
Worldwide Printed Content
US Broadcast Media
Worldwide Film Content
Internet
Worldwide Magnetic Content
World Telephone Calls
Electronic Flow of New Info
Giga = 10^6
Tera = 10^12
103 TB
1,633 TB
14,893 TB
420,254 TB
532,897 TB
4,999,230 TB
17,200,000 TB
17, 903, 340 TB
Peta = 10^15
Source: Hans Moravec “When Will Computer Hardware Match the Human Brain”, 1997
Biological evolution and human technology both show continual acceleration.
The time between events continues to decrease; 2B years from the origin of
life to cells and 14 years between the PC and World Wide Web.
• 2014: Getting Lost
• 2019: Libraries
• 2020: Copyright
• 2030: Keys
• 2033: Coins
• 2036: IC cars
• 2050+: Ugliness, Nation States, Death
Source: “What’s Next” and the
“Future Exploration Network”
Erosion of Boundaries in the Information Age
• Between products and services: think cell phones
• Between producers and users: think social media
• Between IT, comm, media, consumer electronics: think Amazon
• Between IT and non-IT industries: think Walmart
• Between academia, industry, disciplines, theory, applied research
1895: “Heavier than air flying machines are impossible”, Lord Kelvin
48 years
1943: “I think there’s a world market for maybe 5 computers”, Thomas Watson
34 years
1977: “There is no reason why anyone should have a PC in their home”, Ken Olsen
4 years
1981: “640K ought to be enough for anyone”, Bill Gates
What can we expect in the next 10000 years?
2
Motivation for Today’s Lab
• Bring camera: A disposable camera will be disassembled
• Search and read about disposable cameras
• http://www.ehow.com/how-does_5031419_disposable-cameras-made.html
• http://www.youtube.com/watch?v=emjm-HJAsME&feature=related
• Search how camera flashes work
• http://electronics.howstuffworks.com/camera-flash1.htm
• What are coil guns and tasers?
• http://www.youtube.com/watch?v=epaMq1vee_c
• What is a film ASA rating and how does this relate to shutter speed?
• http://en.wikipedia.org/wiki/Film_speed
• Roughly calculate the shutter speed needed for a disposable camera
http://www.youtube.com/watch?v=epaMq1vee_c
Experiment 1: Extract camera flash circuit board
Goal: Dissect disposable camera to extract flash circuit
Step 1:
• Remove battery
• Pry apart front and back sides of casing
• Remove film
• Pry apart flash circuit board assembly
Photograph each
stage of disassembly
ENGR Website: http://core.coe.drexel.edu/node/283
Extra: http://www.youtube.com/watch?v=emjm-HJAsME
Lab Notebook:
1-A: Explain how the shutter mechanism works (in your own words/sketches)
- What causes the film advance after the capture button is pressed?
- What prevents a double-exposure of the film?
- How does the shutter mechanism operate?
- How does the flash circuit physically operate?
1-B: Include photos at each stage of the disassembly
Experiment 2: Oscilloscope and FG setup: burst and trigger
Goal: Calibrate instrumentation in order to measure flash
Step 1: • Generate square wave at 100 Hz, 5 VPP, 2.5 VDC offset, 5 ms pulse width
• Attach function generator to Channel 2Y on oscilloscope
• Push Wave Gen
• On oscilloscope, press “Autoscale”
Step 1
Step 2:
Step 2
• On oscilloscope, press the “1” button (directly above input connector)
• Set trigger level to 4.0 VDC
Step 3:
• Press Wave Gen
• Set frequency to pulse of 1 Hz
Step 4:
• On oscilloscope’s Trigger section: Mode – Normal.
Experiment 3: Camera flash circuit board installation
Step 1: • Scope Channel 1X: camera flash sensor
• Scope Channel 2Y: camera shutter sensor
• Scope or PC USB: camera USB connector
Step 2:
• Re-install battery
• Fit camera flash circuit board on the measurement board
Step 3:
• Push the camera flash circuit board button
• If necessary adjust Time/Div and Delay setting to get following display
Experiment 4: Reading measurements (with cursors)
Goal: Use voltage and time cursors to measure flash times
Step 1:
• Select Cursor. Set Cursor Mode to Manual
• Rotate knob to align cursors.
Step 2:
• Top wave: Flash Pulse Width (time flash remains lit)
• Adjust voltage cursors to measure max voltage difference (delta VF)
• Position V2 cursor at 0.5*delta VF
• Position time cursor T1 at start voltage step
• Position time cursor T2 at time where V2 intersects flash signal
delta VF
Start of Voltage Step: T1
0.5 delta VF
T2: Time V2 hits 0.5 delta VF
Record Delta T = T2 – T1. This is called the Flash Pulse Width
Step 3:
• Bottom wave: Shutter Pulse Width (time shutter remains open)
• Adjust voltage cursors to measure max voltage difference (delta VS)
• Position V2 cursor at 0.5*delta VS
• Position time cursor T1 on the rising part of shutter signal (V2)
• Position time cursor T2 on the falling part of shutter speed (V2)
delta VS
Rise point for V2
0.5 delta VS
T1
T2
Fall point for V2
Record Delta T = T2 – T1. This is called the Shutter Pulse Width
Step 4:
• Leading Edge Offset (time between shutter-opening and flash-on)
• Place V1 cursor at 0.5 * delta VS for bottom wave (shutter signal)
• Place V2 cursor at 0.5* delta VF for top wave (shutter signal)
• Place T1 at V1 (rising) intersection
• Place T2 at V2 (rising) intersection
V2: 0.5 delta VF
V1: 0.5 delta VS
T1
T2
Record Delta T = T2 – T1. This is called the Leading Edge Offset
Step 5:
• Trailing Edge Offset (time between flash-off and shutter-close)
• Place V1 cursor at 0.5 * delta VS for bottom wave (shutter signal)
• Place V2 cursor at 0.5* delta VF for top wave (flash signal)
• Place T1 at V1 (falling) intersection
• Place T2 at V2 (falling) intersection
V2: 0.5 delta VF
V1: 0.5 delta VS
T2
T1
Record Delta T = T2 – T1. This is called the Trailing Edge Offset
Lab Notebook: We want 2 more trials of time data. Repeat Experiment 3 and 4
In your notebook, complete the table below with your values
Trial
1
2
3
Avg.
Flash Pulse
Width (ms)
Shutter Pulse
Width (ms)
Leading Edge
Offset (ms)
Trailing Edge
Offset (ms)
Discussion Points
Take Home Points:
• Disposable camera has fixed features e.g. fixed shutter time
• Changes in shutter time will change photo’s brightness
• Future labs aim to physically modify the plastic shutter
• These modifications will change shutter times and hence photos
Source: http://www.increa.com/reverse/dc/
Film ASA (or iSO) Ratings e.g. ISO 100, ISO 800
• Low numbers: slower film = needs more light = longer exposures (slow shutter)
• High numbers: faster films = needs less light = shorter exposure (fast shutter)
• Slow film = sharper, detailed photos
• Fast film = higher contrast and grainy photos
Next Time: Week 03 – Intro to Shutter Modification
• Bring camera: A disposable camera will be disassembled
• Search and read about disposable cameras
• http://www.ehow.com/how-does_5031419_disposable-cameras-made.html
• http://www.youtube.com/watch?v=emjm-HJAsME&feature=related
• Search how camera flashes work
• http://electronics.howstuffworks.com/camera-flash1.htm
• What are coil guns and tasers?
• http://www.youtube.com/watch?v=epaMq1vee_c
• What is a film ASA rating and how does this relate to shutter speed?
• http://en.wikipedia.org/wiki/Film_speed
• Roughly calculate the shutter speed needed for a disposable camera