Arduino temperature controlled development tray

Isaac Rousso · Mar 28, 2021

Hey everyone! (New here, first post!)
For colour printing in the dark room,
I’m thinking of experimenting with Arduino (a small electrical controller board). I’m thinking to connect the controller to a temperature sensor and heating pads which I will attach to the bottom of a development tray and see if I can keep the temperature steady that way.

I wonder how come there’s no heated development tray available on the market...

Also, does anyone know of a scientific way of determining if a chemical (developer/fixer, etc) has been exhausted? I’m trying to figure out what other types of sensors I can hook up to the controller (such as a PH sensor and the like) to be able to monitor specific attributes of the chemicals so I won’t need to guess if they are still good or not?

radiant · Mar 28, 2021

Welcome to pandora's box, um, sorry, Photrio!

I'm planning to do the same. I'm going to try using 3D printer heated bed (12V) and run it with constant power. I think that is probably enough for my purposes.

Btw: There are tray warmers available commercially.

ic-racer · Mar 28, 2021

Technical bulletins of the chemistry should be able to guide you in replenishment process control. Here is some info for Fuji RA-4 replenisher.

ic-racer · Mar 28, 2021

Isaac Rousso said:
I wonder how come there’s no heated development tray available on the market...

Food warmers have been used as tray heaters. Also, Nova pioneered heated vertical trays back in the 1980s.

Isaac Rousso · Mar 28, 2021

vedostuu said:
Welcome to pandora's box, um, sorry, Photrio!

I'm planning to do the same. I'm going to try using 3D printer heated bed (12V) and run it with constant power. I think that is probably enough for my purposes.

Btw: There are tray warmers available commercially.

3D printed tray is the next logical step
But before I make that investment, I’ll start with a more modest setup

Isaac Rousso · Mar 28, 2021

ic-racer said:
Food warmers have been used as tray heaters. Also, Nova pioneered heated vertical trays back in the 1980s.
View attachment 270857

yeah, that’s definitely something to explore.

I’m thinking to also have a mobile app that lets you set the temperature and shows you the state of things.

By that I mean the read outs of the sensors, which at the moment I’m thinking to integrate temperature, PH, and (if I can find a reasonably priced) specific gravity sensors

Isaac Rousso · Mar 28, 2021

Do you know of a good, easy to understand, resource to read about the chemistry involved so i could use that to understand what would be worthwhile measuring?

AgX · Mar 28, 2021

Isaac Rousso said:
I wonder how come there’s no heated development tray available on the market...

A heated tray warmer (a heated platform to place a tray on) had been introduced by Kaiser decennia ago and is still on offer!
I got such myself.

https://www.kaiser-fototechnik.de/en/produkte/artikel.php?nr=4141

Isaac Rousso · Mar 28, 2021

Ohhh boy! That’s almost 300 euros! ‍

bdial · Mar 28, 2021

Isaac Rousso said:
Do you know of a good, easy to understand, resource to read about the chemistry involved so i could use that to understand what would be worthwhile measuring?

Look at some of the books member Laser has been posting for sale in the classifieds, or shot him a message and ask what he may have available that might fit your need.

Isaac Rousso · Mar 28, 2021

Thank you

ic-racer · Mar 28, 2021

Isaac Rousso said:
Do you know of a good, easy to understand, resource to read about the chemistry involved so i could use that to understand what would be worthwhile measuring?

How the Colenta processor does it:

Manual version for E6. May try something similar:

AgX · Apr 10, 2021

Isaac Rousso said:
Ohhh boy! That’s almost 300 euros! ‍

You can save quite a bit this way:
https://www.filmkorn.org/warming-plate-as-tempering-aid/?lang=en

Isaac Rousso · Apr 10, 2021

AgX said:
You can save quite a bit this way:
https://www.filmkorn.org/warming-plate-as-tempering-aid/?lang=en

Thank you

Nicholas Lindan · Apr 10, 2021

Rather that using an Arduino you can use a ~$20 PID controller. They all have auto-tuning now and so are much easier to use. And cheaper, once you factor in displays, buttons, wall wart ...

Some come with a waterproof temperature probe - but it looks like you have to drill a hole in the side of the tray to mount it.

Available on the usual VBCA web sites: ebay, Amazon, etc..

tom williams · Apr 10, 2021

Isaac Rousso said:
Hey everyone! (New here, first post!)
For colour printing in the dark room,
I’m thinking of experimenting with Arduino (a small electrical controller board). I’m thinking to connect the controller to a temperature sensor and heating pads which I will attach to the bottom of a development tray and see if I can keep the temperature steady that way.

Isaac, maybe you know all this already, but just in case: there are a number of Arduino temperature-sensing prototypes modeled on the web - https://www.tutorialspoint.com/arduino/arduino_temperature_sensor.htm, for instance - that I would think could be incorporated into a temperature-control apparatus. There are Arduino-based ph sensors modeled on the web also. In the example at the url I mentioned, you'd just have to drop the humidity bit and add a relay to a heating element. Such processes are also modeled on the web with more than one type of Arduino board. There may be some applications displayed on the web that could give you some insight into user interface and relay control: I'm thinking of a few Arduino- or ATMEGA328-based darkroom timers I've seen. (the ATMEGA328 is the Arduino Uno microcontroller). Once you successfully model the application with the Arduino board, you can easily construct an ATMEGA328-based board, and save your Arduino board for the next prototyping project.

radiant · Apr 14, 2021

I just tested my 3D printer heated bed + cheap chinese relay based temperature controller.

First of all the chinese product is great deal, I think it cost me 8$. It has many functionalities and all ready - altough Arduino progamming is easy for me I wouldn't consider building my own..

Secondary I connected the heated bed so that it draws 3A at 12V - I thought this is sufficient. But it is certainly not. I need to hook it up differently and I'm not sure if that is enough to keep water at 35 degrees.

Just some pointers to others if this is any help ..

AgX · Apr 14, 2021

The Kaiser 30x40cm got 300W.

Isaac Rousso · Apr 14, 2021

Hey!
Thank you all for your feedback and comments!
Thus far, I've managed to have a basic setup with a waterproof sensor plugged into the Arduino, showing me the temperature in a web browser.
The next step is to add to the setup the heating pads and control them such that they keep a tray with water at a constant temperature.
The following step would be to allow the Arduino to receive a target temperature as input and bring the tray with water to that target temprature and maintaining it.
Then the last step would be to have a mobile application (iOs/Andriod) controlling the whole setup!
I'll share my progress (in case you're interested) and also the setup/code so you can replicate it if you wish

tom williams · May 5, 2021

Isaac Rousso said:
Hey!
Thank you all for your feedback and comments!
Thus far, I've managed to have a basic setup with a waterproof sensor plugged into the Arduino, showing me the temperature in a web browser.
The next step is to add to the setup the heating pads and control them such that they keep a tray with water at a constant temperature.
The following step would be to allow the Arduino to receive a target temperature as input and bring the tray with water to that target temprature and maintaining it.
Then the last step would be to have a mobile application (iOs/Andriod) controlling the whole setup!
I'll share my progress (in case you're interested) and also the setup/code so you can replicate it if you wish

Isaac, I'll be interested to hear about your progress, and to see your implementation code if you decide to share it.
When you designed and built your water bath and temperature sensing scheme, did you consider and provide for stirring? I can get temps different by up to a couple of degrees before and after stirring

Isaac Rousso · May 5, 2021

tom williams said:
Isaac, I'll be interested to hear about your progress, and to see your implementation code if you decide to share it.
When you designed and built your water bath and temperature sensing scheme, did you consider and provide for stirring? I can get temps different by up to a couple of degrees before and after stirring

Hey!
For sure, the solution that I'm building has 3 parts
1. the code that runs on the Arduino
2. the backend API (server), implemented in Ruby on Rails, that the Arduino board sends information to
3. a mobile application (iOS/Andriod), implemented in React Native, that communicates with the backend API and shows the data that the Arduino circuit is sending

All 3 different code bases are on Github. as soon as I have a working MVP (minimal viable product) I'll post it here

I haven't gotten to stirring yet, although I was considering it.
The circuit consists of an Arduino board, waterproof temperature sensors and heating pads.
The logic is quite straightforward: read the temperature and control the heating pads such that the liquid temperature remains constant (based on the input set by the mobile app).

I'm waiting on some parts to be delivered to me, as they were back-ordered. hopefully, I'll post again shortly with a working solution.

AgX · May 6, 2021

The joy of tinkering aside, what are the benefits of your approach compared to an off-the-shelf sous-vide heater, heating the processing bath directly?

I see as possible benefits the chance to install a stronger heating element and stronger circulating pump, where you even could select on the direction of flow.

tom williams · May 6, 2021

AgX said:
The joy of tinkering aside, what are the benefits of your approach compared to an off-the-shelf sous-vide heater, heating the processing bath directly?

I see as possible benefits the chance to install a stronger heating element and stronger circulating pump, where you even could select on the direction of flow.

AgX, I don't presume to answer for the OP, but cost is often the driver motivating DIY solutions. And 'joy of tinkering' is not to be underestimated. I find certain other benefits to the DIY approach, such as
- pinpoint customization for individual circumstances. One might be able to fit a DIY solution to existing equipment more efficiently, and at lower cost, than trying to force an off-the-shelf component to fit. The OP's tray heater could be an example: he might have to buy new trays to work with a sous-vide heater that is otherwise suitable.
- familiarity with the hardware and software of your darkroom. A fix for a problem might be more easily executed, with smaller delays, if you know your setup inside out. If something goes awry with my DIY darkroom timer, it's plausible that I could fix it in short order.
- avoidance of excessive consumerism. Used parts, or new parts salvaged from discarded hardware, may fit a darkroom plan, with modification.

That said, the DIY approach can be a drain on time and energy, at least in my case. I often have to try to balance the pleasure of making the (almost) perfect accessory, and economy, with using available time efficiently.

Isaac Rousso · May 6, 2021

tom williams said:
AgX, I don't presume to answer for the OP, but cost is often the driver motivating DIY solutions. And 'joy of tinkering' is not to be underestimated. I find certain other benefits to the DIY approach, such as
- pinpoint customization for individual circumstances. One might be able to fit a DIY solution to existing equipment more efficiently, and at lower cost, than trying to force an off-the-shelf component to fit. The OP's tray heater could be an example: he might have to buy new trays to work with a sous-vide heater that is otherwise suitable.
- familiarity with the hardware and software of your darkroom. A fix for a problem might be more easily executed, with smaller delays, if you know your setup inside out. If something goes awry with my DIY darkroom timer, it's plausible that I could fix it in short order.
- avoidance of excessive consumerism. Used parts, or new parts salvaged from discarded hardware, may fit a darkroom plan, with modification.

That said, the DIY approach can be a drain on time and energy, at least in my case. I often have to try to balance the pleasure of making the (almost) perfect accessory, and economy, with using available time efficiently.

Thank you for that response

To add to what Tom said, mostly for me - I think the use-case is for colour dark-room prints development.
I don't want to buy a JOBO system, instead, I want to develop the prints using regular development trays (same flow for B&W),
but in order to control the temperature of the chemicals - I need a way to heat the liquids and maintain their temperature constant.
I don't know if it's feasible to submerge an open development tray inside a sous-vide bath - that sounds a bit messy - especially in complete darkness.

How are you currently developing colour darkroom prints?
From what I can see online - almost exclusively - everyone is using Jobo Film Processor and Lift Kit (CPE 3 and similar models) - but those cost around $2000!!!
sure, they have the advantage of not needing to develop the prints in complete darkness, but I wanted to experiment with a DYI solution...

AgX · May 6, 2021

I got an early 70's CPP. Thus one not necessarily needs to buy a 2000$ machine, but as indicated in many threads one must be willing for tinkering. It takes up to a 50x60cm print.

Alternatively one can use for prints a roller-transport machine, which allows for faster throughput, if such is actually desired, but can be bulky and again there is that tinkering issue with old machines. Or one can use vertical dip-in slit-processors as from Jobo or Nova, or self-made.
A open tray I never seriously considered, already due to its large bath-surface.

Arduino temperature controlled development tray

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