The Making of An Open Source Arduino Development Controller

Last weekend I got the itch to write some Arduino code, mostly for fun. I wanted to see how much code it might take to write a controller to help with various tasks during film development. Specifically heating water (and tracking it’s temperature), rotating a tank (and changing directions periodically), and tracking the development steps. Turns out, it’s really not that much code. By the end of the weekend I had fleshed out a software proof of concept of what that might look like. The source is available here.

So this week I tried to actually make that code do something useful in the real world by heating actual water (using a submersible heating element) and tracking the temperature using the PID method. It works! Mostly. The PID settings need to be tuned and mounting the heater is going to take some work plus I need a water pump to circulate the water (that’s in the mail). I think, however, that I can get a working solution to what really is the main thing I’m trying to solve for: heating water and keeping the temperature stable reliably without having to spend a lot of time worrying about the water bath. Instead I can focus on developing. The problem is the water from my tap fluctuates as does the “darkroom” (really just my spare bathroom) so it takes quite a while to get the bath right – longer than the actual development! If I can solve that I can both save time (or at least do something else while the bath is heating up) and might be able to get stable enough temperatures to consider doing E-6 development (as in slide film).

Where it goes from here though could be neat. I grabbed a DC motor and H-bridge and connected that up as well to see if I can spin a motor – it’s not hard. The hard part, however, is building the means to connect the motor to something that can ultimately rotate the tank (that could also sit in the water bath). One step at a time! I’m certainly not the first to try and come up with something like this and, of course, great commercial solutions exist for this. I just like the fun of seeing if I can do it all DIY style (that and I don’t process enough film to justify the cost of say a full JOBO setup). Heck for simple heating and circulating water, a Sous Vide would have worked well enough. But that’s not fun! Granted while I don’t have lots of spare time, sometimes I need a break and this might be a good thing to tinker on. I don’t have any timetable currently – as I said, one step at a time! That next step is getting the water bath solution working well enough that I can start using it reliably. Then we’ll see what the next steps might entail.

Heck maybe at some point I’ll see what it takes to cool water. I actually develop black and white much more frequently than color buyt have similar issues there too, only with needing to cool the water (at least in the summertime). Thinking a peltier cooler or a pump that runs water through copper pipes into an ice bath I can turn off and on or something.

Anyways I plan on posting progress as I work on it here. Here’s hoping soon I can share that, yes, I can reliably heat some water! The source code is officially open source so, who knows what the future could hold for the project! If all I can manage to do is heat water, that’s ok too!