How to make an accurate shutter speed tester

Discussion in 'Large Format' started by john_miller|16, Nov 22, 2002.

  1. This is not a question but a protocol of how to build a very accurate and easy
    shutter speed tester in order to measure shutter speeds up to 1/2000th of a
    second on your computer (sound card). I used it for my Nikon FA but since I'm
    also into LF, it comes also quite handy with copals or compurs.

    The heart of the shutter tester is a phototransistor which closes the circuit
    upon irradiation with a laser beam from a hand-held laser pointer. These
    devices act incredibly fast - much faster than any shutter. The electronic signal
    is then being forwarded to the microphone input of the sound card in the
    computer. To visualize the signal, use the program Cool Edit 2000 which is a
    freeware. The sampling rate must set in the program to the highest possible
    value supported by your sound card in order to have highest resolution. If you
    just measure shutter speeds up to 1/250th of a second, don't worry too much
    about it if you are not equipped with a brand new sound card - I'm not either.
    Lower speeds are still way good enough for LF shutters.

    Make shure that the laser pointer hits the phototransistor vertical from the top
    without any angle. Otherwise the signal gets weak. Solder everything together
    as indicated in the scheme. Plug then the devico in the microphone input of
    the sound card and start Cool Edit 2000. Push the record button in the
    window and fire the shutter a couple of times. Then stop the recording and
    measure the elapsed time between the peaks. That's your shutter speed.

    Have fun!
    Rick
     
  2. Can I make a suggestion Rick?<br>Many soundcards have the facility for powering an electret condenser mic via the ring of the stereo jack used for the mic input. These cards provide around 3v for the purpose.<br>If you use this 'phantom' mic supply to power your circuit, you can then do away with the need for a battery too!<p>Some older soundcards have an internal jumper that needs to be set to enable the remote mic power option.<p>BTW Rick, 4300pF isn't a common preferred value of capacitor, not here in europe anyway. 4700pF is the nearest common value, or 3900pF, and either of those should work just as well as that oddball 4300pF job.
     
  3. I should add that you'll go a long way to get a 4000 ohm resistor straight off the shelf too. 3900 ohms is the nearest preferred value in the common E12 series.
     
  4. Pete,

    As you can see in the above attached scheme, you are perfectly well in the
    indicated range for the capacitor and the resistor value.
    The device is so simple that even other phototransistors than the indicated
    BPW-40 can be used too (for example BPW-42 and else).

    Rick
     
  5. Hi Rick. No criticism intended.<br>I was just trying to help anyone who knows nothing about electronic components and their preferred values.<br>Such a person could waste a lot of time trying to source a 4300pF capacitor or a 4000 ohm resistor, and I was simply pointing out that the nearest preferred values are 4700pF and 3900 ohms, respectively.<br>If you walk into a shop and ask for those preferred values, then you're more likely to get the items, and less likely to be treated like a complete idiot by the retailer.
     
  6. That is surpurb information to have.

    Thanks - I love it.
     
  7. Ok,.. I made the device but, At the Radio Shack on the island here they only had a infra red phototransister. Is this ok? It looks like the one in your drawing. It has a clear plastic dome top.
    Also, my mic has a stereo plug and so does the sound card. (sound blaster live.) I made the device with a mono plug as per drawing. Does any of this matter? My sound card also has an aux input but I don't know if this will work with the program.
    Speaking of the program... When I first used it, I held the shutter up to the mic and tripped it. (I hadn't made the device yet.) I messed around with it till The display then showed and sounded through the speakers the noise that the shutter made. Now however, after i fiddeled around some more, I did something (I don't know what.) And the display shows the sound to be very weak. Like a flat line and I can't hear it. It's like the mic is muted and I checked that. It works great. Any help as to settings in the program would be great. My son is bringing over his laser thing this weekend so I can try the device, but I'm afraid I'll hit a dead end.
    By the way, When using the mic at first, I could read the lower shutter speeds from the sound waveform. 1 sec to 1/4 sec.
    Thanks in advance for any help anyone can give.
    dee
     
  8. Got it figured out now. My mic wasn't turned on for record mode.
    Everything works great now. This is a handy device. All componets were purchased at Radio Shack for less than $10.00 with solder! I used the mono plug just plugging it in half way. (didn't have to buy a mono to stereo adapter.) Thanks for the info and schems.
    I wonder what else there is out there that can be built at home cheaply and use the computer to run it? Any body know anything about densitometers, or light meters for enlargers?
     
  9. I built one of these but for regular light (I don't know if there's a difference). They work great.
     
  10. I'm about to try this.

    Can someone who succeeded in making one out of RadioShack parts post the RadioShack part numbers for each item?

    That will help save a lot of trouble and confusion.

    thanks
     
  11. Give these guys a call. I'll bet they have what you're looking for. Durst Selpla? Tauba? Autotub? Seipla? God only knows - I wish I had kept my instructions for the 609 - if I find them I'll post them for you.
    http://www.cambridgeworld.com/durst_darkroom_accessories_for_older.htm
     
  12. Sorry, I misplaced the above. Above post should have gone to this thread:

    http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00MCIl
     
  13. Having recently built the tester using the Radio Shack Infrared Transistor and getting fair results and questionable results with Graflex/Graphic Focal Plane Shutters I decided to give the curtain tester in this http://www.kyphoto.com/classics/combinationtester.html tester a try.
    I eliminated the battery and used a 10K ohm resistor. The microphone input in my computer(s) (PC) pick up the transistor(s) without any extra power.
    The Radio Shack parts are:
    Photo Transistor: catalog number 276-145 http://www.radioshack.com/product/index.jsp?productId=2049724
    1/8 stereo plug: catalog number 274-284 http://www.radioshack.com/product/index.jsp?productId=2104061
    1/8 mono plug: catalog number 274-286 http://www.radioshack.com/product/index.jsp?productId=2062452 use this for making a single transistor tester.
    4.7k ohm 1/4 watt resistor catalog number 271-1330 http://www.radioshack.com/product/index.jsp?productId=2062346
    10k ohm 1/4 watt resistor (like I used) catalog number 271-1335 http://www.radioshack.com/product/index.jsp?productId=2062347
    24 gage speaker wire catalog 278-1509 for a single transistor tester
    http://www.radioshack.com/product/index.jsp?productId=2036278
    24 gage audio cable catalog number 278-513 http://www.radioshack.com/product/index.jsp?productId=2062643 for single wire two transistor tester.
    15 watt soldering iron catalog number 64-2051 http://www.radioshack.com/product/index.jsp?productId=2062728
    rosin core solder catalog number 64-005 http://www.radioshack.com/product/index.jsp?productId=2062711
    You can also order phototransistors from online electronic parts retailers such as http://www.mouser.com/
    In the event the schematic link goes bad the collector(s) (marked C) is connected to the resistor. The resistor is connected to the common contact of the plug, mono or stereo. The common contact is the longest lead with the wire clamp on it. The emitter(s) (marked E) are connected to the signal contact(s), these will be the two shorter contacts on the stereo plug or the shorter one on the mono plug. If you are using the audio cable connect the shield to the resistor and one of the colored wires to one transistors emitter and the other colored wire to the other. For a two transistor (diode) tester to test a 35mm shutter curtain the center of the transistors are placed exactly 18mm apart. For horizontal travel multiply the time difference between the two by 2 and on vertical travel multiply by 1.33. 18mm is half of the horizontal with of a 35mm frame and 3/4 of the vertical height.
    The major advantage of this setup is that with Audacity http://audacity.sourceforge.net/ you do not need to set the display to waveform as you do with the pdf diagram.
    A laser pointer can be used or red lighting gel can be put over the transistor and a bright flashlight or 60w clear incandescent light bulb can be used to trigger the sensor.
    I have also purchased two photodiodes from Mouser and connected them Anode to signal lead, cathode to resistor to common lead. The photodiodes have a faster switching time and produce a square wave output in audacity making reading faster shutter times easier. I have not done enough testing to tell how fast a shutter time will read accurately. My Graphic 1000 speed shutter reads 1/3 stop slow at 1/250, and a stop slow at 1/1000. I may do some film testing at the fast speeds with the shutter in the future.
    I have mounted the photo transistors and the photodiodes on pieces of 1/4 foam core that I can attach to various cameras and shutters for testing.
     
  14. The attached is a composite screen shots of a freshly serviced Graphex #2 shutter tested with a tester using the kyphoto (linked in the previous post) tester using a Radio Shack photo transistor with red Bogen lighting gel over the transistor and a mini mag set to spot held 1/2 inch above the shutter opening with the lens cells removed. The shutter aperture was wide open and there was no difference in results with the aperture at f16.
    I also have a tester using the same design with a photo diode that has a 10° angle of view and it produced the same results as the RS photo transistor on the 1/400 shutter speed.
    00aDVc-454755584.jpg
     

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