Large format and film camera shutter speed tester

[DonF]

Here's an Arduino-based shutter speed tester. It is all interrupt driven using low-level timer operation. It uses comparator-based input capture with an external trigger voltage reference for fast and and accurate timing.

It uses any bright light source and a photodiode detector.

It measures from 1 second to 1/3000 second with worst-case accuracy of just under 5%. It's accuracy is much better at speeds under 1/1000. The timer granularity is 16 microseconds. Extensive error-checking detects timing anomalies and discards bad results.



Thinking of doing this as a kit or at least selling the programmed chip/PIC/

Regards,

Don

 

[AgX]

We already have a member offering a ready-made tester, the Phocron. What would be the technical differences between both?

 

[DonF]

We already have a member offering a ready-made tester, the Phocron. What would be the technical differences between both?

The Phocron looks nice. It has a color display, automatic averaging, an oscilloscope and a built-in light source. I think it may use a pulsed light source, then use the sensor to count pulses to determine timing, since it has a calibration routine. The deluxe model does curtain measurements on focal plane shutters.

It was too expensive and complex for my needs. I needed a quick, inexpensive and accurate way to characterize my old shutters. My design works with any light source. It auto-resets after each test. It detects 4 possible timing errors caused by missed trigger edges, misaligned sensor, and other internal timer errors and displays an error rather than an incorrect result. I don’t mind using a pen and pad to record my timings and working out the mean and standard deviation on my own.

The trick in one of these working well with an Arduino is getting the trigger and timing fast enough and repeatable enough to give good accuracy across the measurement range required and the capabilities of the micro controller. My design seems to work well and is simple enough for a hobbiest to put together. It uses one chip, and a handful of ordinary capacitors and resistors. The display is the most common type of LCD there is and very inexpensive to source. A serial color display is nice but lots more expensive.

Guess that about covers it.

Don

 

[BrianShaw]

Competition is always good. Looks like it will be a nice product. What’s the projection on price?

 

[DonF]

Competition is always good. Looks like it will be a nice product. What’s the projection on price?

I'm working with another photographer on mechanical packaging options. A few enhancements, like min/max and running average might be nice. The display and prototype was to debug detection timing and check accuracy against an oscilloscope with different sensors and trigger algorithms.

Don

 

[mweintraub]

As a software developer, I just love getting errors while doing demos. I feel your pain!

I would love to learn PIC programming. I tried and gave up before.