Arduino based diy f-stop timer

RSalles

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Hi,

Are you planning to distribute pre-assembled PCB's for this project? I would like to use a F-Stop timer in my lab, but have no time for or resources locally available,
PS: as your website appears to be in French and you are in Swiss, à quelle ville habitez vous maintenant?

Cheers,

Renato
 
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Elias

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Thank you Trask and Renato

To Renato, no I am not planning to distribute hardware, for the following reasons.

This is my very first attempt to build any sort of electronic device: I take full responsability for myself but, as a biologist, I know very well how to kill any human with a single electric shock ! Nevertheless, I will provide soon a list of components and low voltage side schematics.

For the code, this is also my very first attempt to code in Arduino / C language, therefore I am more than conscious that my code is far from clean and needs to be optimized and documented. It is planned for the next weeks and I will share with the community as I am very grateful to all open source contributors.

Finally, cidadão do mundo, hoje moro com minha familia em Genebra. Estarei na Bahia em breve, bem longe do RS. Estou a disposição para quaisquer esclarecimentos sobre este projeto, por email para detalhes. Obrigado pelo interesse.

Thank you all
 

RSalles

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Thanks Elias, as soon as the project is finished - alpha release I mean - just drop a line in the forum, as I'll probably try to go for the parts to assemble it.
PS: Bem vindo ao forum, morei em Biènne - cantão de Berna, não muito longe de onde vc está, por isso perguntei. Saudações soteropolitanas rsrsrs, e um abraço,

Cheers,

Renato
 

Michael Guzzi

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Damn, don't know how I missed this thread! Welcome to APUG!

It's a very, very nice first attempt! Looks very nicely assembled.

Please do post the code, as an amateur C programmer myself I always enjoy looking at how different people tackle different problems.

Cheers! (Saudações do RS!)

Michael
 

Luckless

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One suggestion to keep in mind when documenting/commenting code:
Code tells you WHAT the code does, comments tell you what it is supposed to do, and ideally why it is supposed to do that.

c = a + b; very obviously assigns the sum of a and b to c, and a comment stating as such doesn't add much.

A comment that the line is supposed to assign the normalized value of the sum of a and b to c would have been great at helping notice that c = a + b; is in fact the wrong code and is a critical bug.
 
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Elias

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Thank you all for your positive comments, really appreciated !

Luckless, I will definitely follow your advice, thank you.

Hans and Michael, I will post code and diagram later, please allow some time to debug, clean and comment code, and draw a diagram. I still have some minor issues with unwanted flickering and one or two unexpected display behaviors. Nothing too frightening but clearly to be addressed.

Cheers

Saudações aos Riograndenses !
 
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Elias

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Hi All,
as said before, please find the informations for this open-source f-stop timer.

Please remember that this timer is intended to be of simple use, give some test strips and programming sequences features, but in no case to be a print database and therefore keeps no data on EEPROM memory.

Any constructive comments, suggestions, corrections, improvements, modifications are very welcome:

the Arduino code

the Schematics

the PCB

Thank you

Elia
 

locutus

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For those that want to have PCB's, dirtypcbs.com is really damn cheap and fast.
 

Leigh B

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What's an f-stop timer?

- Leigh
 
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Elias

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Leigh B said:
What's an f-stop timer?

- Leigh
Click to expand...

Thank you Marco.

Leigh, it is a timer which uses f-stops as time units instead of seconds. F-stops follow the same rationale as your camera, adding one stop doubles the time of exposure under your enlarger, therefore, instead of having to do exponential maths to increase or decrease your exposures, you only have to add or substract stop(s), i.e. very simple addition, just as with your diaphragm. In other words, instead of counting 1,2,4,8,16,32..., you count 0,1,2,3,4,5,.... (2`0 =1,...2`5=32)

This particular timer works in f-stops, and shows the corresponding time on the lower display which is used for countdown.

F-stops are particularly practical for test strips as they follow the very same rationale as the zone system. Therefore, you may contract or extend your test strip range simply by setting the base time and the increment between zones, according to contrast. For example, using #00 contrast paper, setting an increment of 1/2 stop, your strip will extend over 5 stops: base + 4. Using #5 paper, with an increment of 1/5, your strip will extend over 3 full stops: base + 2. Great for split grade.

Hope this helps

Elia
 
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Elias

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Hi All,

this is a video showing the latest development of the f-stop timer, including now a full control of a LED variable contrast enlarger head.

The control operations are meant to be short and simple, with shortcuts to ease the splitgrade printing process. The code will be available soon.

Cheers
 

MattKing

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Looks great!
Can you indicate which enlarger light sources/heads this is set up for/compatible with?
 
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Elias

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Thanks Matt !
The system is intended to control any LED driver controlled by PWM. Two PWMs are generated, one for the green channel, one for the blue.

The PCB includes a 6 pins connector with the following pins, allowing PWM transmission to any drivers, and the use of an extra I2C 7-seg display for outboard grade display:
+5v
Gnd
PWM Green
PWM blue
SDA
SCL

Cheers
 
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