Homebrew f/stop timer

[DonF]

Well Don, I got side tracked by a million other jobs but I got there in the end. I have the timer working and boxed up. Hope you like the photos.
I designed the pcb and got it made in China (10 of them for $11 delivered). I decided to use a transformer with two 9V secondary's, that way I could provide a separate supply for the relay board and the arduino circuit keeping them totally isolated. The components on the board are just rectifiers, voltage regs and smoothing capacitors for the two supplies.

I bought a red lcd for the display but unfortunately it didn't seem to work, so just a regular one in for now until I get another.
I didn't want to chop plugs off my Durst enlarger so fitted a euro style 2 pin socket on the back of the box, that way my enlarger cables stay original.

Ralph

Ralph, that is an amazing build! I like that you used the Arduino Micro (?) for the build. Did you have any issues using the Micro, which I believe uses a ATmega32u4 rather than the Atmega AT328p that I used? The timer architectures are somewhat different.

Good call on the separate relay supplies. I has some resets when switching the inductive load represented by the enlarger power supply transformer until I added a snubbing network across the load contacts of the relay.

Best regards,

Don

 

[Just Fouterin']

Thank you Don, hope your well.
I don't think i noticed any problem with the way the countdown or stopwatch timers worked so I guess everything's ok. That particular little arduino has been kicking about my bench and been played with for dozens of different circuits. For some reason I couldn't get any sound from the speaker at first, then I tried changing the digital output pin and it worked, so I think the relay and speaker pins are swapped around in my case, don't know why it worked like this, but it did !. Also for this keypad I had to swap the configuration of rows and columns but that was all. I was gonna share the eagle cad file for the circuit board but the site says its the wrong file format for uploading ?

 

[RalphLambrecht]

I don't care about all that. Just one friend doing something for another.

life just ain't that simple anymore.

 

[DonF]

life just ain't that simple anymore.

This was a question of me not having time to construct a unit for someone else, nothing to do with "friendship", legal issues, etc. Documenting what I did so others could replicate it seems sufficiently generous to me.

Don

 

[rbultman]

Another member on the forum, polyglot, created one as well. Here is a link to his project. I bought a PCB from him and all of the components to make one. Life got in the way and I never finished it. This project makes me want to move forward with an f-stop timer!

 

[DonF]

Another member on the forum, polyglot, created one as well. Here is a link to his project. I bought a PCB from him and all of the components to make one. Life got in the way and I never finished it. This project makes me want to move forward with an f-stop timer!

That's a different design then this, of course. Although a fine project, the user interface seemed a bit overly complex to me when I went looking for plans to build up an f.stop timer. I ran across the Arduino project on the previously-mentioned Italian web site, which had a simplified feature set while still supporting basic enlarger timer focus/countdown/count-up functions as well as dodge/burn function and f/stop increments/decrements from an entered base-time, which is all I really required.

Don

 

[CarlosU]

Don, I am attempting to load the code onto uno. I keep getting "Timerino.h: no such file or directory" error. Also where do I define that I am using LCD, from what I read it is "1" in MYMODEL. I found a neat LDC that gives me RGB backlight options, keyboard is the one with the sticky back. I am at best a beginner with arduino so please like if you are talking to to a someone who knows nothing of it.

 

[John51]

I dislike the way settings are changed with electronic equipment. I appreciate the low cost and the functionality but holding my finger on a button while watching the changing numbers increase in speed annoys me.

My Rayco digital timer has 3 rotary dials. X10/Seconds/X0.1 Takes a fraction of a second to set anything from 0.1 to 99.9 seconds. A wall chart can tell me what to set it to for f-stop printing. I could also have timings for different papers on the wall. A bigger wall = more channels.

If somebody comes up with a timer that has all the bells and whistles but the settings are done with dials, then I'd be interested.

 

[koraks]

It's quite trivial to use 3 rotary encoders for this. Although it's overkill IMO. I recently built a development clock/timer that uses a single rotary encoder to set times from 1 second up to 99 minutes 59 seconds. I programmed it in such a way that the faster you turn the encoder, the faster the numbers change. This makes it easy to quickly to go from something like 1 minute to 15 minutes, and it's very intuitive to use.

Nobody's stopping you from doing something similar!

 

[CarlosU]

I may have figured it out. It gave me a done loading. Now to rebuild the bread board and test it.
Oh yeah picked up another camera yesterday N8008, 35-105 lens, SB24 flash, 18 rolls of film and 100ft of Ilford Delta 400 for $25.
Carlos

 

[Luckless]

Looks like a neat little project, and I might have to build one for myself and play around with different interface designs.

- And for a physical device, designing a solid and reliable interface is always a 'fun challenge' while trying to balance cost vs usability.

I'm curious as to what you used to filter your screen, and how well that has worked for you.

 

[StepheKoontz]

This looks like a super fun project, thanks for sharing! I might also tie this into my room light switches, which are also arduino controlled via radio signals

 

[koraks]

I might also tie this into my room light switches, which are also arduino controlled via radio signals

That is very convenient! I installed a cheap Chinese 433mhz kit for this purpose. I'm glad I did! It's fascinating how annoying walking from one side of the darkroom to the other gets while printing, just to flip the light switch.

 

[MattKing]

That is very convenient! I installed a cheap Chinese 433mhz kit for this purpose. I'm glad I did! It's fascinating how annoying walking from one side of the darkroom to the other gets while printing, just to flip the light switch.

I've actually designed that walk into darkrooms - turning on the light in a darkroom isn't something you want to do without having to think about it.
Of course, that was for shared darkrooms.
For room lights, my favourite is a pull chain from a ceiling fixture.

 

[L Gebhardt]

It's quite trivial to use 3 rotary encoders for this. Although it's overkill IMO. I recently built a development clock/timer that uses a single rotary encoder to set times from 1 second up to 99 minutes 59 seconds. I programmed it in such a way that the faster you turn the encoder, the faster the numbers change. This makes it easy to quickly to go from something like 1 minute to 15 minutes, and it's very intuitive to use.

Nobody's stopping you from doing something similar!

Polyglot's fstop timer project uses a single rotary encoder to set the time, as well as direct entry by a keypad. I use the same on my fork of his code for my variable contrast controller. It works quite well for even large settings changes. Because it's fstop based there isn't a big need for such acceleration since every click is the same sized jump in exposure. The acceleration seems like a great idea for a timer using direct time entry.

 

[DonF]

Looks like a neat little project, and I might have to build one for myself and play around with different interface designs.

- And for a physical device, designing a solid and reliable interface is always a 'fun challenge' while trying to balance cost vs usability.

I'm curious as to what you used to filter your screen, and how well that has worked for you.

I taped a strip of Rubylith over the screen with black electrical tape, directly over the opening cutout. The display is otherwise inverted blue and white.

Don

 

[DonF]

I've actually designed that walk into darkrooms - turning on the light in a darkroom isn't something you want to do without having to think about it.
Of course, that was for shared darkrooms.
For room lights, my favourite is a pull chain from a ceiling fixture.

"Alexa, turn on the darkroom safelight." works with my Wink setup!

 

[CarlosU]

Help!!! I have fallen and I can't get up.
I breadboard with a nano board, got that to work. I transferred onto a PCB........... Keypad works fine. Function switch works fine, I see things changing on the LCD.

HELP the start switch does nothing, D 11 does not change state. The only thing I see is the "L" LED goes from on to off.

In standby mode (waiting for me to do something)
Start switch in the off position shows 1.75VDC between D13 and GND, goes to "0" when I press start. D11 going to the relays does not change sitting at 4.4VDC.
D12 to GND sits at 4.4VDC and drops to "0" when I press the function button.

I have checked continuity and cross continuity on everything all checks good. I have used power from the computers USB and a plug in phone charger, I get the same.
I have already re-soldered the LCD to the PCB, no change.
Can someone point me in the right direction.

Thanks
Carlos

 

[DonF]

Help!!! I have fallen and I can't get up.
I breadboard with a nano board, got that to work. I transferred onto a PCB........... Keypad works fine. Function switch works fine, I see things changing on the LCD.

HELP the start switch does nothing, D 11 does not change state. The only thing I see is the "L" LED goes from on to off.

In standby mode (waiting for me to do something)
Start switch in the off position shows 1.75VDC between D13 and GND, goes to "0" when I press start. D11 going to the relays does not change sitting at 4.4VDC.
D12 to GND sits at 4.4VDC and drops to "0" when I press the function button.

I have checked continuity and cross continuity on everything all checks good. I have used power from the computers USB and a plug in phone charger, I get the same.
I have already re-soldered the LCD to the PCB, no change.
Can someone point me in the right direction.

Thanks
Carlos

Carlos, I think I spotted a bug in the original Italian code base that is causing your issue.

Two input buttons are defined, one for the start/stop the other for mode select. These activate their functions by a button pulling them to ground. This requires that a pull-up resistor be tied between the pin and Vcc so the pin will assume a "high" inactive state. Without the pullup resistor, the pin may assume an indeterminate high or low state when not pressed.

The buttons circuits do not have an external pullup connected. The software should have defined the input pins so the internal Arduino pullups were active on the pins.

Take a look at lines 1066 and 1067:

pinMode(mainbtn, INPUT);
pinMode(selector, INPUT);

Change these two lines to:

pinMode(mainbtn, INPUT_PULLUP);
pinMode(selector, INPUT_PULLUP);

This will activate the internal pullup resistors. No circuit modifications are required.

I think this will solve the issue. Local noise or something about your circuit layout is causing the two input pins to float to the low state. A transition from high to low is never seen.

Make the change, reload the Arduino, and I think you will be good to go.

All others should consider making the change as well. I have not experienced issues without it, but the circuit could be prone to false triggering if the change is not made.

Let me know!

Don Froula

 

[DonF]

Help!!! I have fallen and I can't get up.
I breadboard with a nano board, got that to work. I transferred onto a PCB........... Keypad works fine. Function switch works fine, I see things changing on the LCD.

HELP the start switch does nothing, D 11 does not change state. The only thing I see is the "L" LED goes from on to off.

In standby mode (waiting for me to do something)
Start switch in the off position shows 1.75VDC between D13 and GND, goes to "0" when I press start. D11 going to the relays does not change sitting at 4.4VDC.
D12 to GND sits at 4.4VDC and drops to "0" when I press the function button.

I have checked continuity and cross continuity on everything all checks good. I have used power from the computers USB and a plug in phone charger, I get the same.
I have already re-soldered the LCD to the PCB, no change.
Can someone point me in the right direction.

Thanks
Carlos

Carlos, I think you may have loaded an earlier version of the code that was posted. This earlier version has the bug I mentioned. I corrected it in a later version.

Be sure to use the code in the posting dated July 19, 2016.

Best,

Don F.

 

[CarlosU]

Don, I had the correct version with PULLUP code on line 1178, but I went ahead and downloaded the code again and I still get the same thing.
I may have to rebuild it again, not something I was looking forward to.

Carlos

 

[CarlosU]

Well I breadboard the timer again on a different Nano board and I get the exact same thing. I am going to remove the nano from the breadboard replace with the Uno board. If it works then I either have 2 bad nano boards or something we are not seeing is different between Uno and Nano. More will be revealed.
Thanks
Carlos

 

[koraks]

Try this: move the start button to another pin (not D13) and make the necessary changes in the pin definition in your software. Since D13 is connected to the onboard led on a nano, it doesn't work well for an input. The 1.72V you're seeing is likely the forward voltage of the onboard led, which is in an undefined state between logic 'high' and 'low' - but apparently it's read as 'low' consistently. Just use any other GPIO pin that's currently not used.

 

[CarlosU]

Don, that worked. I swapped out out D10 and D13. I am just starting to play with Arduino, so with using D13 for the piezo, do I need to change the pinmode to LOW, since we know that D13 is showing 1.72vdc?
Thanks
Carlos

 

[koraks]

Good to hear it works. I personally avoid using D13 for anything since its connected to the onboard led. Connecting it to a piezo may or may not work, and you may get some digital noise on the piezo during startup until you silence it in the setup routine. I've had this minor issue with an esp8266.