Free f-stop timer?

polyglot

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That's free as in libre, not gratis.

I've just about finished building my f-stop timer. Without blowing my trumpet too hard, it has most of the features of the commercially-available units and is easier (especially for beginners) to use.

It's based on an Arduino, which is a very accessible platform. If you can follow a schematic and solder, you could build this; if you can program in C++, you can improve on it. No programming skills are required though, that part is all complete.

Do people have a serious interest (not just dreaming) in building this from GPL schematics and source code? Total cost for a unit would be in the ballpark of $40-60 plus a few hours of your time for assembly (basic electronics & mechanical aptitude is required). If there is sufficient interest backed with prepayment, I could have a small run of PCBs made up to simplify construction greatly and that would raise the cost by maybe $10-20/unit.

Features are:
- 0.01 stop resolution
- drydown correction with 0.01 stop resolution
- timing to approx 1ms resolution
- max exposure 1000s, min exposure 10ms (limited by enlarger warmup)
- direct numeric entry of EV in decimal stops with 4x4 keypad
- can save/load 7 print-programs to/from flash
- up to 8 exposures per program
- each exposure has a 14-char textual description to prompt you
- exposure footswitch and focus mode
- menu-driven operation with text prompts
- audible success/fail notifications
- transfer saved programs to/from PC (future feature)
- 16x2 red-backlit LCD with layer of rubylith to make it safe
- adjustable LCD backlight brightness

Major things it lacks at the moment:
- support for more dodges than the base exposure (e.g. three separate 1-stop dodges), i.e. concurrent dodges / operator-is-an-octopus mode
- closed-loop mode and enlarger warmup correction
- split-grade automation (input a contrast change, have it calculate new times)

They're not things I need at the moment, so are lower priority.

I'm online for only another week and then off for five weeks so I'll post photos etc of the timer after I get back in October. Let me know your thoughts.
 
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Monito

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Very interesting project. Gets me thinking, so I have a question or two along these lines.

Would enlarger warmup correction be implemented by some sort of calibration that the user would have to obtain and apply? Or would it make sense to put a photocell in the enlarger housing so that it would integrate the warmup photon rate? I could imagine that a hot bulb would warm up faster than a cold one. A sensor in the lamp housing would seem to be a very desirable way to go.

As to interest in building the unit, I haven't given it much thought as I've got a very nice basic timer (00.0 to 99.9 s). Drydown correction would be good to gain. I wouldn't spend on a fancy factory made unit, but I'd enjoy the handiwork of building a unit and could probably talk myself into a $50 to $80 unit. Without seeing and pricing out costs locally here, I'd guess that it would be at the high end, just on the idea that stuff always seems to be more expensive in the end.

Does yours have battery backup or some power feature, perhaps with line voltage passthrough output socket so that it can keep a program or menu choices or parameters such as the drydown percentage?

There is something to be said for putting lots of rotary knobs on a unit so you can dial in the time since that changes the most frequently. Punch up/down buttons for time work reasonably well. Is the main time controlled by menu only?

I have yet to try split-grade printing but it sounds exciting, and smooth automation for that sounds inviting.

Personally I'm intrigued and want to encourage you but can't commit to anything right at this instant. Thanks for your work and sharing and good luck with the project.
 

yeknom02

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I am a big fan of electronics projects, so if no interaction with a computer is required, I'm definitely interested. I have recently thought about the Darkroom Automation timer, which looks great but simply unaffordable at the moment. I have been wanting to try split-grade printing, though, so that feature would be very welcome in my book.

One thing I am interested in is the power setup. The Paterson Digital timer I have now just has one outlet for the enlarger, but I wonder if it's possible to have another constantly powered outlet for, say, my safelight.
 

billdlv

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If the cost to build was around 50-60 us $ I would be interested. I have an existing timer already but I have wanted a f-stop timer for a while. I too have looked at the darkroom automation units and they look quite nice, but too expensive for me as well at the moment.
 

Barry S

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I'm definitely interested as I'd love an f-stop timer and don't mind a bit of soldering. Put me down for a PCB.
 

samcomet

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Definite interest from me too! congrats and cheers for now, sam
 

paul ron

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That isn't free! Must be new math or did I miss something here?

Do you also give free HD for life for only $100/month?

.
 

tkamiya

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Provided parts aren't SMD, I'm very interested. I can possibly assist in this project as well.

I have C programming and SBC design and construction experience. (and so as PCB)
 

yeknom02

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paul ron said:
That isn't free! Must be new math or did I miss something here?

Do you also give free HD for life for only $100/month?
Click to expand...

Just in case you weren't being sarcastic, this is straight from Wikipedia:
gratis versus libre is the distinction between two meanings of the English adjective "free"; namely, "for zero price" (gratis) and "with few or no restrictions" (libre).

The proposed project adheres to the libre definition in that its construction is "open source" in a way and is not going to be proprietary. At least that's my understanding.
 
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polyglot

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Some clarifications... no SMD parts as I don't have the equipment for that.

You would need to purchase:
- an Arduino (e.g. Duemilanove, $20)
- a red LCD & rubylith ($10)
- a keypad ($3)
- an opto-coupled solid-state mains relay (?)
- power supply parts and case ($20-$100 depending on how fancy you want to be)
- circuit board ($3 veroboard, $20? for custom)
- assorted ribbon cable, connectors, pin headers, screws, etc ($10-20)
- hopefully buy NOTHING from me (I can't be bothered posting you stuff)

You'll also need a PC or Mac, soldering iron and the usual fabrication tools. No, I won't sell you a kit or completed version; there's no value to be added there and if you're in the US, you can buy the bits cheaper than I can. There is practically nothing required in the box other than the micro and the user interface; no other logic is required.

If you wanted to be even cheaper and have the tools+skills, you could skip the Arduino and use a straight ATmega328 in a veroboard, though that would lose the USB connection for transferring programs to a computer.

Randian & free-market trolls need not apply.
 
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tkamiya

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Sounds really interesting.

So you'd supply the schematic and the software? I guess rest can be purchased from places like www.sparkfun.com if you are in US.
 

Monito

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paul ron said:
That isn't free! Must be new math or did I miss something here?
Click to expand...

Yes. You missed something. He wrote "Free. That's libre not gratis."

The root "libre" is the same root as for "liberty", a concept dear to the hearts of Americans, or so we are told. In this context that means free from copyright or trademark or patent restrictions.

"gratis" would mean "no cost". Same root as for "gratuity" = money for a tip, given freely, not part of the bill.

"paul ron", ... hmm, ... Ron Paul the libertarian? Libertarians would be expected to know the most about the distinction, one would hope.
 
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Monito

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polyglot said:
Some clarifications...
Click to expand...

Thanks.

What powers the timer? A battery? Does it have to be connected to a PC to reprogram it everytime the power gets turned off?

[on edit:] Oh, I see, power supply & case $20 to $100 "depending on how fancy you want to be." Ok, fair enough. Thanks.
 
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amedway

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also interested, eagerly awaiting further details. I'd also be in for the PCB if you go that far.
 

Nicholas Lindan

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Well, that adds up to $164, less if you have a well supplied junque box to raid for parts. Which may explain why the Darkroom Automation timer costs $259 - which has all new parts [and advertising cost, tooling charges, instruction manual printing costs, labor costs, a cut for DigitalTruth] and has a close to negative profit margin.

DIY makes sense for things are are labor intensive and don't have much tooling/purchase parts cost: painting the house, mowing the lawn, cooking dinner. It also makes sense if it is a labor of love: building your own drag-race car or wet-plate camera.

However, where most of the cost is in the parts, and tooling is extensive [and where DIY involves a lot of time with a drill and file], it is hard to justify a DIY solution.

Darkroom Automation is a labor of love ... or so I have to keep telling myself.
 
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polyglot

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Powerswitchtail is a good option, especially for people without the proper training for dealing with mains voltage. And you can certainly buy most of the bits from sparkfun, though they seem a little expensive to me for the generic bits and pieces. I bought most of my stuff from eBay.

The device is powered from the mains, since it is switching mains. No need for batteries etc as it saves all of its settings to internal EEPROM. The simplest power supply you can have for it would be an iPhone charger ($5 on eBay) which gives you 5V 500mA on a USB port; everything in the timer can be powered through the Arduino's USB port. You don't need a PC to use it as long as you don't want to save more than 7 stored programs; the PC is needed only for backing up your stored exposure programs.

While I disagree with some of Nicholas' pricing estimates (I just bought most of those parts and the prices I listed are what I paid), there is of course a sliding scale of quality and you can literally spend as much as you want when building this. For sure I am not using a custom wooden box, I'm using a black ABS prototype box or maybe a diecast one if I'm feeling fancy. And yes, I am making good use of my huge electronics "junquebox"

In terms of value proposition vs products like Nicholas', there is only value in using this if you know where to buy cheap parts, don't value your time, have the necessary skills+tools on hand and/or want to be able to hack your timer to add new functionality. If you want an off-the-shelf, supported thing that Just Works you should go buy a finished product. Nicholas' point about no profit margin with a sale price of $259 should tell you why I'm not selling these things as finished products or kits; it's a labour of love for me too and I choose to make my IP available to those who want to replicate the laborious part.

The interesting thing about the GPL is that commercial operations like Darkroom Automations can take my published source code and sell you this very product in a fancy wooden box with fancy keypads etc at whatever price-point they desire; the only hook is that they must publish the source code. If it runs mine unmodified then they can just point to mine but if there are any improvements, they must publish those improvements so that the rest of us can make use of them.
 

tkamiya

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I value my time and money. However, value of my FUN often wins.... (where did that $100 go?)
 
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polyglot

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And it is released for your edification, commentary and feedback.

Sorry no pics yet as my red LCD hasn't arrived so all the development was with a big blue one. Once I get back from holidays I'll finish the assembly and shoot some video of it in action - if you're quick with the soldering iron, it's possible you could get to use this to print before I do!
 
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