Open source f/stop enlarger timer

[polyglot]

Hi all,

My enlarger didn't come with a timer, I'm sick of the metronome and doing annoying logarithmic sums in my head. So I've built this timer and decided to release it as open-source for anyone else who wants to build one. It shouldn't be difficult for anyone experienced with electronics; it's mostly just a matter of wiring the right pins together on a few devices.

There is a thread on APUG with a little more discussion but I figured there might be some interest in it here too.

Please let me know if you (try to) build this so I have some idea of how many of these are out there and what level of interest there is.

[IanMazursky]

Wow! Really amazing work.
Ive been thinking about using an Arduino for a shutter timer (connect to a cable release somehow?) and for an enlarger timer for a while.
But ive never been good at programming. What you did is so cool!

I saw from your page that you are planning to be able to store the exposure times in the Arduino for future recall.
Would you know how many you would be able to store? Im guessing with a larger keypad you might be able to name them or code them in some way.
I know this might be a lot, but could the program also be extended for time exposures in addition to the current Fstop timing?

I think i will give this a try in a few months after i clear out some other projects. Looks like a lot of fun.

[polyglot]

Currently it stores 8 exposures per program and 7 programs within the Arduino. That part is working.

Most of the EEPROM space is taken up by the text descriptions (14 bytes) for each exposure so I'm considering reducing the length of the descriptions and/or the number of steps per program; that way I can fit 10-20 programs in the 1kB available. There's no way the Arduino can be the permanent storage for all of one's prints so it really only needs to store a long session's worth ready for archiving to a PC afterwards (or loading up a bunch of settings for previously-printed images before a session). And 7 unique prints is enough for 99% of the time I think.

While you could modify the source to do linear timing, I don't plan to do that. You should feel free to download the source and change it up yourself though; it'd be a very simple change, just remove all the exponential stuff from Program::compile() where it generates linear times from the stops.

I haven't built an intervalometer yet and plan to probably next year; when I do it will include a high current output for a solenoid to push a release cable. I encourage you to go buy an Arduino (they're under $20 on eBay incl shipping) and just have a play with it. While they are programmed in C/C++ and I've written an unusually large quantity of that so I'm biased, there are plenty of libraries available and they are all-around damn easy to write code for.

[William Whitaker]

Is there an app for this? Seriously, could it be written for the iPhone?

[polyglot]

Is there an app for this? Seriously, could it be written for the iPhone?

Will: sure it could, and for bonus points the phone LCD will fog your paper. There's also no simple way of interfacing hardware (the enlarger relay) to an iPhone that doesn't cost more than this would - anything connecting to an iPhone must conform to the Apple MFI rules. You could do it with an Android (ignoring fog issues still), but the Android hardware development kit is an even larger version of this microcontroller (the mega2560), so this is still the easiest approach.

I've updated the webpage with video, or watch it here.

[William Whitaker]

Well, naturally I assumed that there was a means to write the code such that the screen could be dimmed. But I'm about as far from a programmer as one can get. I don't know about such things. Just thinking about it makes my head hurt.

[aduncanson]

Thanks for posting the video. It helps a lot. I particularly like seeing how the dodge is implemented.

[ic-racer]

polyglot, that is a great project. I had not seen the Arduino before. That would have been great back in the 80s. I remember in art school rigging up a relay board to the game port of my Atari 800 XL to run a kinetic sculpture.

[nolindan]

The Arduino is based on the AVR series of microprocessors (uP). The uP alone sells for $3 or so, and for may applications that's all you need.

It used to be that developing software for a uP involved writing a check to Intel for $50,000 for a 'development system'. With the development of uP with Flash memories and JTAG debuging interfaces all that is needed is the uP chip and a $39 interface cable.

You can find an AVR DIY community at http://www.avrfreaks.net/

[Brian C. Miller]

Cheap development systems weren't that expensive, unless you wanted the full Intel big blue box (yes, they were big and blue) systems. All you needed was a two-sided circuit board, microprocessor, support chips, and ROM burner. The AIM and KIM were $500-ish for a circuit board with a hex keypad, I think.

(I am not showing my age by writing this, I am not showing my age by writing this, I am not showing my age by writing this, ...)