DIY Enlarger Timer Circuit?

kittyhawk88 · Nov 16, 2010

I've built a simple web page to follow the developments of this timer . Here's the link.

I've posted on it a jpg of the timer interface..

http://www.geocities.ws/fstoptimer/

olleorama · Nov 16, 2010

Good work kittyhawk. I want an outlet for a foot control to start the thing. Or for focus. Can that be incorporated?

kittyhawk88 · Nov 17, 2010

Hi Olleorama,
a foot switch is really quite simple to incorporate. As I see it. The timer switching section has only 2 modes. Either safelight on and enlarger off or enlarger on safelight off. So the switching section just needs to have 2 way relay. I think a double pole double throw.. I need to think this one out. However a dual relay would be a better bet as someone somewhere will want to focus with the safelight on.

I'll add that to the requirements.

I will build the relays and terminal blocks into the enlarger but will leave the user to onnect it up. The eletrical regulations problem.. I don't have the moeny to get this pass regulatory requirements. So it's up to the user to wire those switches in country dependant etc. I'm working on a $39.00 USD target so that it's affordable. We want people to convert to f stop timing no discourage them.

I'll add the option into the website.

kittyhawk88 · Nov 17, 2010

Updated Timer Interface

Worked out how to post pictures.

Here's the link if it does not work.
http://www.geocities.ws/fstoptimer/
I've started on the code design.
Have chosen to implement this design with PIC Microcontroller with an external quartz oscillator for accuracy to +- 0.001 seconds.
will implement a 6 volts switched relay output. you can use this to drive a relay.
C1 and C2 are toggled on and off . So you can switch the dark room lights on or off.
Focus lets you switch the enlarger on with no time limit
Reset lets you start all over again
Reset followed by > key lets you set time period
Reset followed by > key then left key lets you set test strip mode

Beep - sets beep off or on. When beep is off LEDs light to indicate time.
Beep on - needs no explanation

Start - starts the timer - Also slaved to footswitch.

Footswitch - will use a standard 3.5mm jack

9/12 volts input. Lets you use an external plug pack to power the unit instead of 4 AAs. Useful if using unit to drive external relays to power switch enlarger on or off and safelights on or off.

Comments please..

kittyhawk88 · Nov 17, 2010

Would anybody object if we added say $5.00 USD to the completed meter purchase price to donated to the running of APUG?
Comments please , thanks.

George Nova Scotia · Nov 19, 2010

Very interesting project. I have more timers than I need at present but no f-stop timer, when you come up with the final cost I'll have to take a long look.

One suggestion, interchange the start and beep switches. Keeping the start away from the reset and placing it the corner may prevent accidents in the dark.

John Koehrer · Nov 20, 2010

I'd be interested at the $40-$50 mark depending on shipping to the US.
I'd also like to find something like this that would go from 1/30 sec to ~5 sec. in a similar price range. Kit form would be nice for me just for S&G.

ic-racer · Nov 20, 2010

Steve Smith said:
I still have it somewhere. I will see if I can find it.

Steve.

I just checked to confirm it, but the box for the old timer pictured above has survived 35 years and has wound up housing the glow-driver on my R/C plane field box. In between housing a timer and the glow-driver it surprisingly housed my first home-made guitar distortion circuit, ca 1980.

kittyhawk88 · Nov 23, 2010

F STop timer revised + progress updates..

Thanks Guys..

I've taken on board the suggestion to move the buttons..

There is s suggestion to simplify it to simply beep and light at every quarter stop.
What say you to that ?

Update:

Started work on the board layout . Using Protel.
BAsic program logic desing is nearly there.
Please bear with me while I work on this.

It's nearly X'mas and my boss wants me to tidy up so we can close up in time.

I am still shooting at 39+5 APUG donation.

I'll design 2 versions.
A Diyer version with all the board layout ready for relays and connectors.
This allows the 'kit ' folks to solder in the relays to switch your enlargers. you need to find your own box for this.

The safe retail version will be 6 v output to allow you to switch the enlarger externally.. using another box and relays.. another kit to be offered at some stage.

As for other time periods. I am implementing this timing using an external oscillator..

Given it is all software driven, The timer can be programmed to be any time period.

Hey maybe a built in USB port to allow you guys to flash the firmware..

This can become the universal timer , garden timer, enlarger timer etc. by just flashing the firmware..

I plan to get this done by Jan 2011...

Any beta testers out there.. PM me please.. thanks

kittyhawk88 · Nov 23, 2010

f stop timer revised 1/4 stops key layout

Had a rethink and changed the key layout and LED layout. Simplifies the board layout a lot.

Normal mode - Will count up to selected time.
Test Strip mode - will count down.

jp498 · Nov 23, 2010

Count me in for a kit or two.

I'd bet we'd have a lot more relay choices if the relay voltage were 12 vdc. For instance, jameco does not have any 6v relays, but lots of 5,12,24v ones. I've been using about 40 omron 12v dpdt relays in my house to operate the lights for 10 years now and have only had one relay malfunction.

If there were room in the box for a relay & socket & power supply for the circuitry, that would be ideal too.

paul ron · Nov 23, 2010

Take the electronic timers out of microwave ovens, they make great darkroom timers. Hook your enlarger to the relay, simple to find the correct outputs with a VOM. By pass the safety interlocks or use em to ensure the doors are closed n lights are off if you want to get fancy. Oh and the more sophisticated ovens have special programing to cook differnt foods... this can be used for multi exposure presets.

kittyhawk88 · Nov 24, 2010

o.k. will take that into consideration...
I was going to power the board with 2 AAs and keep footprint as low as possible. due to cost constraints.
I can provide schematics on how to drive an external 12 volt relay at some stage, it's really quite easy. Then you can choose whatever relay you like. Also remoting the relays will allow you to use the timer interface close to the workspace and have a standard long RC cable to connnect to your mains relays.. that was the intention.

thanks for input

Lee L · Nov 24, 2010

For an interesting relay option google "powerswitchtail". You'll find a short US standard AC extension cord with a 5VDC relay box wired in-line and two shielded screw terminals for the input. It's designed for an Arduino or something similar.

Not that cheap, but reasonable for something convenient, flexible, and easy to re-purpose.

Lee

anikin · Nov 24, 2010

When I'm making f-stop test strips, I'm often having a feeling that as time gets below 16 seconds, I'm not very precise with opening test strips. It would be nice if the timer turned off the enlarger once it reached the next f-stop and gave me a second to open the next strip. So how's this for an idea for test-strip making:

I'd like to propose to add a test-strip mode with pauses. For example, if I'm making 1-stop test strips, it would run like follows.

enlarger on
start countdown at 64
at 32 enlarger off and pause
I open next test strip and press pedal or a button
enlarger on, countdown from 32 to 16
enlarger off, pause
I open next test strip and press pedal or button
enlarger on, countdown from 16 to 8
enlarger off, pause
I open next test strip and press pedal or button
enlarger on, countdown from 8 to 4
enlarger off pause
I open last test strip and press pedal or button
enlarger on, countdown to 0
enlarger off - teststrip is done.

Alternatively, instead of having to press pedal or button, the timer could just give a second or two of darkness before resuming count-down. Would such a mode be useful?

kittyhawk88 · Nov 25, 2010

I've been mulling over the test strip part for a while. What you are proposing is easy to implement. I'll take that on board with the coding. for F stop mode.

the powerswitchall gadget sound interesting.

I'll add all these suggestions to the website in a few days..

Thanks guys.

Lee L · Nov 25, 2010

kittyhawk88 said:
the powerswitchall gadget sound interesting

Just to avoid confusion and fruitless searches, it's powerswitchtail, 'tail' rather than 'all'. It does seem to be standard to run the words together in the product name.

I've only seen it in grounded standard US AC wall plug configuration. I guess you could replace the male and female AC plugs for your local standard plugs.

Lee

jp498 · Nov 26, 2010

That powerswitchtail looks pretty good and is pretty inexpensive!

kittyhawk88 · Jan 4, 2011

Latest version of F Stop Timer

Had some time to think things over on the timer..

Here is the latest revision.

Got everyones input in.

Counts down like a normal timer.
Counts down in strip mode.
Has a 1/4 stop option.
Foot switch

Burn Switch.

Happy New Year to All.

kittyhawk88 · Feb 12, 2011

F Stop Timer - DIY Simulator Ready - Next stage Hardware

Hi folks,
I have finished a software simulation version of the proposed enalrger. It's a 4MB file . Send me a private mail and I'll send it along for your comments.

Once I have refined the F Stop timer. I'll go to components and hardware.

Please let me know what you guys think.

Lee L · Feb 12, 2011

kittyhawk88 said:
Hi folks,
I have finished a software simulation version of the proposed enalrger [timer].

Running in what environment?

Lee

ras351 · Feb 14, 2011

kittyhawk88 said:
DIY F Stop Timer.
Always counts up from 0 to 64 seconds.

I'll second that this is potentially going to be a problem for some people. Why don't you use a PIC with a CCP module, set it to compare/interrupt at 0.1 seconds and have a 16bit unsigned short as the counter? This will give you over 6500 seconds - this is what I've done with my homebrew timer/analyser and it works well. You don't need better than 0.1 second resolution for switching even if internally your clock rate is significantly higher but I wouldn't go less.

Secondly, although you leave the output to the purchaser, I suggest you consider the solid state relays which can be driven directly from the PIC. They'll trigger from 3-32V, are well isolated, work fine with the loads provided by both my enlargers (LPL7700MX ,Durst L1000/CLS450) and are much more robust than their mechanical ancestors. The only need for a mechanical relay would be for a high powered enlarger head but they typically have low current timer inputs as part of the power supply anyway.

Regards,
Roger.

kittyhawk88 · Mar 24, 2011

F Stop Timer - Hardware Test Board Ready - Any takers ?

At long last... It is done.. I'm currently putting it through it's paces - 12 volt plug pack input. Hexadecimal display to show current time and countdown time.

Timer only counts down...

Solid state relay switches on and off 2 channels max 240Volts 8 amperes..

Software driven for easy updates.

RS232 - for direct communication with timer..

Multi-mode programmable to control my garden sprinklers as well ! needs sprinkler software instead of f stop software..

Hope you guys like it..

Cost : Don't even ask..

Target cost: Approximately $65USD

Enjoy....

anikin · Mar 26, 2011

Beauty!

ic-racer · Mar 27, 2011

That is very nice. Are you soldering on those surface mount chips yourself or have you subcontracted out for assembly?

DIY Enlarger Timer Circuit?

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