John Miller , Nov 22, 2002; 08:50 a.m.
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
Pete Andrews 
, Nov 22, 2002; 11:01 a.m.
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.
Pete Andrews , Nov 22, 2002; 11:10 a.m.
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.
John Miller , Nov 22, 2002; 11:40 a.m.
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
Pete Andrews , Nov 22, 2002; 12:01 p.m.
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.
Edward Paulson , Nov 22, 2002; 02:02 p.m.
That is surpurb information to have.
Thanks - I love it.
dee seegers , Nov 29, 2002; 11:50 a.m.
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
dee seegers , Dec 01, 2002; 11:07 a.m.
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?
Jeff Bishop , Jul 05, 2005; 09:33 p.m.
I built one of these but for regular light (I don't know if there's a difference). They work great.
Jack Lam , Aug 14, 2007; 01:17 a.m.
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
