Graflex.org

45PSS · Joined: 28 Sep 2001 Posts: 4081

Using this diagram as a guide
http://www.baytan.org/prak/shutter.html
go to Radio Shack and get a
1/8 mono phone plug catalog #274-286
Infrared Photo transistor catalog #276-145
and some hookup wire if you have none.

I no longer use a laser pointer, deep red filter material/lighting control film equivlent to a #25 red filter over the sensor and standard CFL, 2AA MiniMag or similar light source works as well.

Download and install
http://audacity.sourceforge.net/download/

Using the hookup wire (22 gauge speaker wire works well) connect the photo transistor collector C to the center contact on the mono plug. Connect the emitter E to the outside connector of the mono plug. The length of the wire can be as long as needed to comfortably connect to your computers microphone jack and reach the camera/shutter you wish to test.

Using a piece of foam core, cardboard, matt board make a small hole that the photo transistor will just fit into.

Position the photo transistor over the rear of the shutter and centered.

Plug the photo transistor into the computers microphone jack.

Start Audacity then pause-record. In the resulting record window select Waveform db from the audio track drop down options.

Set the shutter to the speed to be tested, position the laser pointer on the front center of the shutter, release pause in audacity, trip the shutter, press stop in audacity.

Using the time expansion and shift tools in audacity measure the time between the point where the base line first goes down to where it starts to go above line. The peaks will flatten out more as the time line expands.

http://www.flutotscamerarepair.com/Shutterspeed.htm

Leigh · Joined: 05 Sep 2011 Posts: 6

An incandescent lamp will work much better than a laser, not being sensitive to direction.

Any photo-transistor will work. It doesn't need to be infrared.

Just some suggestions.

- Leigh

45PSS · Joined: 28 Sep 2001 Posts: 4081

Can you provide a source for those photo transistors that the average Joe can easily get?

They use to be readily available and when I tried to get one from my regular electronic parts supply they were not available.

The adaption post is a result of inquires on other photo forms from members looking for a source and comments from members here about shutter speeds and testing.

At $2 for the Radio Shack transistor and no need for the battery, bias resistor and coupling capacitor this is a very inexpensive option.
The transistor has a response of 650-900 nano meters. A #25 red filter over the transistor with a very bright incandescent light source works also but the narrow beam from the laser pointer makes for a precise on off.

So, please enlighten us.

Leigh · Joined: 05 Sep 2011 Posts: 6

Mouser has over 300 different phototransistors. The cheapest one with leads being the Lite-On LTR-4206 at $0.14 in singles (1,550 pcs in stock). At 100mW dissipation, 100nA dark current and 10μS response it would seem well-suited to this application.

The Everlight EL-PT204-6B is the same price (7,721 pcs in stock), with 75mW dissipation and other specs similar to the LTR-4206. Sensitivity of both devices is 1mW/cm^2.

These are both infrared detectors, but remember that over 90% of the energy output from a tungsten bulb is in the infrared.

I expect Digi-Key would have a larger selection, but I didn't bother to check. Mouser has no order minimum; Digi-Key does.

I've never bought anything from RS, and never will.

Using a laser source adds an aiming constraint to equipment operation that would be eliminated by using tungsten. On/Off switching times are strictly a matter of the energy impinging on the detector, regardless of its source, and the response time of the detector.

However, rise/fall times are very dependent on load resistance (Rl), with the 10μS value being for a 1,000-ohm load. The Tr/Tf values change almost linearly with increases in Rl, so at Rl = 4,000 ohms the value is about 40μS.

You don't need a red filter in this application. They're used in environments that have lots of fluorescent light impinging on an unshielded detector, which can induce noise and possibly swamp the detector. You don't have that in this case.

If you're concerned, both the Everlight part mentioned above and the Lite-On LTR-4206E part have black epoxy cases that filter out all light above the sensitive wavelengths, at the $0.14 price.

- Leigh

Mouser: www.mouser.com
DigiKey: www.digikey.com

45PSS · Joined: 28 Sep 2001 Posts: 4081

When testing the RS infrared transistor it did not respond well to an incandescent light bulb, a 250 Watt Photoflood, or a CFL. It would respond to a 2 AA cell Mini Mag shone through a #25 red filter. The RS IR transmitter output is too weak to use.

I did put a 1.2K (1200 ohm) resistor between the transistor's collector and the center contact of the mic plug but it is not absolutely necessary.

Use rosin core solder only for electrical applications.

45PSS · Joined: 28 Sep 2001 Posts: 4081

After testing several shutters this simple tester is not accurate above 1/100 second. It does not read the focal plane shutter found in Graflex SLR's correctly.

The response time of the RS transistor is not listed. The response time of most similar transistors at one of the retailers linked above is .010ms rise, .015ms fall.

The view angle is 30° to 40° which is playing a part also.

Leigh · Joined: 05 Sep 2011 Posts: 6

45PSS wrote:

The response time of the RS transistor is not listed. The response time of most similar transistors at one of the retailers linked above is .010ms rise, .015ms fall.

Those times are pretty typical.

You'd probably get better performance using photo diodes.

That's what we used in the optical ethernet switch that I helped design.
It works at 1000 Megabits/second, which is faster than most shutters.

- Leigh

45PSS · Joined: 28 Sep 2001 Posts: 4081

After picking up another RS photo transistor and a stereo plug, mounting both transistors on a board 1 inch apart, covering with some dark red light gel sheet, lighting with a 60W clear ceiling fan lamp in a work socket, positioned so that the reflex mirror just clears the bulb, I got the same results with both and the same time delay between the start times at all apertures and tensions.

45PSS · Joined: 28 Sep 2001 Posts: 4081

I have switched to using the diagram at http://www.kyphoto.com/classics/combinationtester.html .
It was set up for 35mm shutter testing but can be used on any shutter.
I have also purchased photodiodes from Mouser.
The transistor collector(s) or diodes cathode(s) are connected through a resistor to the common lead of a mono or stereo plug. The transistor(s) emitter(s) are connected to the signal lead(s) of the plug. The battery is not needed. The output of the transistor(s) or diode(s) are much higher in this configuration and no special adjustments in the recording program are needed but you may have to lower your microphone input level.

For a leaf shutter you use 1 photo transistor or diode and a mono plug.

I posted a reply to http://photo.net/large-format-photography-forum/0044cW?start=10 detailing this with Radio Shack catalog numbers for the parts and tools needed.

Drew Bedo · Joined: 26 Mar 2012 Posts: 1

Hello everyone,

I am new to this issue and not an electronic DIY guy. I have a passing understanding of current, resistance and so on, but don't really understand circuts or how the various components interact.

With all that said: I am interested in the concept of using a light sensor to generate an audio signal and analysing it with a computer. Having read this thread and some of the links: Does it work as a practical matter?m Is there a definative set of directions for the hardware?

45PSS · Joined: 28 Sep 2001 Posts: 4081

The composite screen shots of the waveform produced and expanded in Audacity is at the end of this thread on Photo.net, http://photo.net/large-format-photography-forum/0044cW?start=10. The shutter being tested is a freshly serviced Graphex #2.
The tester was the kyphoto linked diagram with a Radio Shack transistor with Bogen red lighting gel over it and a mini mag set to spot focus and held 1/2 inch above the shutter opening with the lens cells removed.
The aperture was wide open (f4.7) and the waveform/time did not change when the shutter was stopped down to f16 at the same speed setting.
After testing at the 1/400 speed I switched to a narrow view photo diode (from mouser) tester and got the same waveform and time for that speed.

Radio Shack used for reference as they are hobbyist oriented and in many smaller towns.
-----------------------
Parts to build:
15W soldering iron
http://www.radioshack.com/product/index.jsp?productId=2062728
Rosin core solder (only type usable in electronics)
http://www.radioshack.com/product/index.jsp?productId=2062711
24 Gage speaker wire
http://www.radioshack.com/product/index.jsp?productId=2036278
10k ohm resistor
http://www.radioshack.com/product/index.jsp?productId=2062347
1/8 inch mono plug
http://www.radioshack.com/product/index.jsp?productId=2062452
Photo transistor
http://www.radioshack.com/product/index.jsp?productId=2049724

____________________________
If you have no electronics knowledge I suggest getting a beginners electronic hobby book that explains the basics and read/study it. One such book may be
http://www.dummies.com/store/product/Electronics-For-Dummies-2nd-Edition.productCd-0470286970.html

peter k · Joined: 26 Dec 2009 Posts: 207

Like the concept... going to put it together, any changes, or anything to add before I do the do?

willysmb · Joined: 28 Feb 2004 Posts: 128

Dear member

From 2 month ago I bought a Shutter speed tester for my Iphone, because my old system need a serial socket on my Pc and my new pc have not serial socket !!!

So, I'm very happy with my new tester.

http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=251344162964

peter k · Joined: 26 Dec 2009 Posts: 207

yes, a good solution fer ya, but alas, I do not have (gasp) an 'I' phone... ;-)

peter k · Joined: 26 Dec 2009 Posts: 207

Having printed everything out, and going over it and making a material list, I have a couple of clarification questions ... from...

#1)

Quote:

Graflex ~ Mon Mar 12, 2012: I have also purchased photodiodes from Mouser.

and so you made an identical circuit, but used these instead? Because ...

Quote:

PhotoNet Mar 11, 2012: The photodiodes have a faster switching time and produce a square wave output in audacity making reading faster shutter times easier.

Were talking about two separate testers, with similar circuits, except for the Radio Shack transistor being replaced (from mouser) by the photo diode, correct?

#2)
If using just one RS Transistor, is there a need for an audio cable?
If the audio cable is needed, for 'noise elimination', how is it wired?
You state:

PhotoNet Mar 11, 2012:

Quote:

"In the event the schematic link goes bad ..." "... 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. "

So please verify.. the other colored wirer to the other emitter, of the second transistor, which were not using, is not connected to anything!
The shield is the connection from the common contact of the plug, to the 4.7k resistor. Using 24 gage speaker wire to go from the 4.7k to the 10k and then on to to C, of the RS transistor, ... correct?

Thanks for the clarification.. going to be a fun project.. looking forward to using it, Thanks for your research, modification and testing of the idea ...