shutter tester development

[bergytone]

i'm beginning to research building an optical shutter speed tester. Not one that uses a phototransistor and an audio program like Audacity to interpret the signal, but a self contained, handheld battery operated box that has it's own light source and ihas self check/calibrate modes. It would use a high speed optical photodiode based sensor. Id like it to have a small LCD screen to display the results.

If all goes well, I'd like to build a bunch and offer them for sale to the APUG group. Maybe even a kit form (think heathkit) for all of you DIY peeps. Not sure what a good price point would be, but I think it can be done for a sale price of $75. If anyone has any input on something like this, I'd love to hear it.

I've got a thread going in the 'exposure' area showing my initial waveforms taken from the detector in the photo I posted above. Interpreting the waveforms is a little tricky due to the prenumbra effect of a shutter moving in the path of light.

 

[bergytone]

I moved this discussion to the groups as it would be easier for those that want to follow my progress to find and comment.

If you want to see what led up this discussion, go to the forum for exposure and look at the thread shutter speed testing and measurement. There are lots of waveforms posted.

Here's what I've done recently. There was a comment that suggested that I move the sensor back in a 'tube' to make it much more directional. I tried this using a 1/2" long section of black tubing. the inside diameter was about 1/8" in diameter. Doing this, I also put the tubing through a black cloth mask, so that no light would get around the tubing and hit the sensor.
The resulting waveform were almost identical to the ones taken without the tube. I have uploaded a picture to the gallery above so you can see the setup with the tube. Also uploaded is a shot of the 1/1000th on the the Nikon FM with this tube aperature. The tube was located in the very center of the focal plane and less than .1" away from the shutter curtain.

I next made up a narrow slit out of brass foil to tape over the detector. the slit was .020 wide. Photo attached above. A waveform taken with the Nikon at 1/1000 showed a much narrowed pulse, as could be expected. BUT... the signal level was way down. So the sacrifice to get the fast signal narrowed is loss in signal strength. I don't think this sensor could be used with a folder camera where the sensor is a few inches from the shutter... signal level would be unusable.

More to come....

 

[bergytone]

Haven't done much lately. I think I've set on a detector design... a compromise between directionality and sensitivity. Now it's onward to find the proper case and LCD display. Doing to use a Microchip PIC dsp processor, they are cheap, fast and my software friend knows them inside and out. ... stay tuned.

 

[bergytone]

Still making progress. My software guy has the sensor, and he's going to breadboard the PIC microchip processor so we can start doing some math. With a sampling rate of over 1MSPS, we can slice the readings from the sensor into small samples that we can do some mathematical integration on and truly get a time/amplitude profile of a captured waveform. This will yield a much better accuracy than just setting some threshold point arbitrarily picked. Working on the display now.

 

[bergytone]

It's been a while since I updated this group posting. I am still making progress on the shutter speed tester. I am now looking at a dual sensor design so I can measure curtain speed on 35mm cameras.When measuring leaf shutters, then only one sensor would be necessary. I've picked out a nice color LCD display and a small handheld plastic case. I have been doing a lot of testing on the bench so far, and I've got both my PCB layout guy and my software guy in the loop. I estimate to have a prototype up and running by late summer. I'm very excited about this project and will move toward a marketable product.

 

[bergytone]

Here's a few renderings of the case of my shutter tester under development:

https://flic.kr/p/tpGWTp
https://flic.kr/p/t83hUN
https://flic.kr/p/tpDavF

A lot of work needs to be done writing the software to drive the color LCD and read the dual sensors. It's coming along nicely, and I will be looking for some help with testing my prototypes.

 

[stormpetrel]

Very nice project!
Which brand of press button did you use for your shutter tester?

 

[bergytone]

The press button is e-switch TL2285OA. Has a nice feel and a variety of caps that can be put on it. It is a through hole part and I don't think it's available in surface mount.

 

[bergytone]

I'm going out for PCBs today. Should have my first prototypes in about 10 days. I'm excited about getting this product going. It will have it's own light source and dual sensors for measuring curtain speeds or use the one sensor for measuring leaf shutters. A large, 2.2 inch color LCD will be able to display the actual measured waveform for up to 10 tests for comparative purposes. I'm hoping to have it on the market for $99 USD, but keep an eye out for a kickstarter program to get funding to build 100 production units and offer them at a much reduced cost.