Open source f/stop enlarger timer

Update: PCBs now available and the design files are posted; PM me your email address if you want one. $8 plus shipping, $15 with a rotary encoder, relay and some of the other required parts like pin headers.

Update: construction photos posted.

New software release. PCBs all sold out.

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Originally Posted by polyglot

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.

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The iPhone display can display a wide range of colors-surely one safe for photo paper could be identified? It might be a little more demanding/ expensive to go the iPhone route, but multi-functional devices are generally worth the extra effort, and everyone already owns a smart phone.

Also, your timer is very cool! Thank you for sharing!

Quote:

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Originally Posted by Jay DeFehr

The iPhone display can display a wide range of colors-surely one safe for photo paper could be identified? It might be a little more demanding/ expensive to go the iPhone route, but multi-functional devices are generally worth the extra effort, and everyone already owns a smart phone.

Also, your timer is very cool! Thank you for sharing!

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If you're interested in the smartphone approach, look at Droid in the Dark. Someone on APUG is putting together an integrated suite of stuff including fstop timer that connects to a droid via Bluetooth. In theory the hardware is just a mains switch hanging off a BT adapter and of course you do all the control on the phone.

I would love the ability to have a huge touchscreen for input, not to mention the massive storage & internet connectivity available in a smartphone, but in practise the interface hardware is an expensive superset of everything in my timer and my paper testing shows that iPhones at least will fog paper with the LCD in dark-red mode. The attenuation of blue from the backlight just isn't sufficient, however if you had true-LED (eg OLED) display instead of an LCD in front of backlights, it would be possible to achieve a paper-safe display depending on the LEDs used in the display.

Edit: I'm part way through writing a Java program that talks to the timer over USB. Given that it's Java/USB, I would expect it to be fairly easy to port it to a droid and control my timer over the USB port (with cable, sorry) using a smartphone or tablet if you really wanted to. You can run (not to mention easily specify) much more-complex exposure programs when not constrained by a tiny memory and display.

New v0.6 software release with support for baseboard spot-metering. You'll need to do your paper-calibration manually for now, but I may add the ability to load paper-curves into the timer one day.

PCBs are USD20 shipped anywhere (USD10 if you bought the previous revision) and I have plenty in stock, or you can build it from scratch using prototype board as the design is completely open source. PM me if you want to build one.

I just stick a piece of ruby lith over the phone when in the darkroom.

Update: I have added a couple of demonstration videos, which demonstrate simple exposures, test strip generation, multi-step exposure programs, scaling prints, drydown compensation and baseboard metering.

Polyglot,

What about a complete pack with all the hardware required to build the f-stop timer, as a ready-to-mount pack?

Cheers,

Renato

While that would be possible, it would be much more expensive than you just buying the parts directly. Shipping stuff to Australia and then onwards internationally is quite costly.