FWIW there is a PID library for arduino http://playground.arduino.cc/Code/PIDLibrary
"I tried the DIY/cheap way out and it was actually more expensive to go that route with buying all the parts and the time involved. "
Absolutely. But sooo much fun. ;)
"Well, Chan, if you are serious about using a roller drum..........."
That is the route that I am taking now. I've just done some initial testing with SS reels and tanks on a Unicolor drum roller. Results are acceptable as far as even development. I have to fine-tune rotation speed mind you, and / or development time.
To head off the "get a Jobo" comments, I do have an ATL. It just isn't cut out for EFFECIENT volume processing. I have at least 10 SS tanks that I use when I do my processing marathons.
I plan to rig up a couple rollers and DC motors into a wide wallpaper trough, using my "maguyvered" ;) tempering bath controller to keep my chemistry and tank at process temperature.
I have way too much time on my hands. Heh.
A fairly cheap alternative is a fish aquarium. You can get recirculating water filter/heaters for them that can be cranked up to the proper temperature. Usually they are a bit too deep, so you have to find some sort of a filler or platform to put the bottles on.
In my case, the water pump was for either a large aquarium or a water fountain. The aquarium heaters have the issues discussed (and worked around) above. Personally, I think if you use a PID (which is accurate to .1 degree C) you're better off using a stronger heating element. But that's a personal preference. I have no idea how accurate the controller is in an aquarium heater, but I doubt it is as accurate as a PID controller. But it is probably good enough.
Good idea. I am going to get a Jobo drum and then somehow putting 2 roller rods under the water. The rods need not be driven just free rotating. Putting the drum on top of them and then a motor driven rubber roller pushing down on the drum would drive it.
I just finished my first 2 rolls of C-41 in my home made setup. The 200 watt heater seems to be undersized for my setup, it seems that there will be a 300 watt sometime in the future. For right now though, it works ok. Without anything in the container, I can get the water up to 102(F), but as soon as I put my chems in to warm up, the temp dropped 6 degrees and stayed there. So I put the chems in the bathroom sink filled with very hot water to warm them up. Once warm and put in the bath, they held just fine and the heater was able to keep the temperature stable during developing.
As soon as the negs are dry, I'll scan them and post the link for some critiques.
This is what I use:
1. Blueline 250w titanium heater element (http://www.bluelineaquatics.com/products/heaters/).
2. Blueline temperature controller (http://www.bluelineaquatics.com/products/heaters/).
3. Koralia Pico Evolution Evo-Mag 300 GPH Nano Aquarium Pump (bunch of ebay sources).
4. Coleman 28qt cooler I picked up at Bevmo for beer during get-togethers.
5. 3 1L accordion containers for FD, CD, BX or 2 1L accordion containers for CD, BX (Freestyle).
6. A couple small bricks I picked up from Home Depot to keep the containers from floating around.
I bought the heater+controller for 95$ as a combo deal on eBay, the pump for 20$, and the Coleman for 20-30$ but it's cost was of course amortized against it's intended use: beer.
The reason I specifically went for a titanium element and an external controller rather than an all in one cheapo-unit is that the former usually go beyond 100F (even if unsafe for fish) just by design. One is able to set temps of up to 110F if I remember correctly. The controller itself uses an external probe and is basically a fancy relay for the heater itself. The pump you just plug in. I fill the Coleman up with 90F+ water from the sink, turn the controller on to 37-38C, place my 1L accordion containers containing FD, CD, BX (E-6) or CD, BX (C-41) and let it stabilize for 20-30 minutes. I don't bother heating the stab for either processes. The bricks I just submerge and wedge against the containers to stop them from floating or moving around.
Heating element, pump, probe in water:
My coveted mercury-based Kodak Process Thermometer:
2-stage C-41 setup:
First roll of Astia (E-6) I developed with the setup:
Another roll of Astia (this one in Polyester fold-flaps, so there's reflection glare):
Nothing beat the moment I pulled the slides out of the tank and saw such jeweled color against the light. It was better than the first time developing black and white, honestly. Recently I picked up a Phototherm bath but haven't used it for any development other than testing that it worked properly. It's cost was around the same aggregate cost for the ghetto-route, but I can tell the temperature stabilization is more precise and the built in pump is nice. It's entirely self-contained and well-designed but I don't think it'll make a difference in the final product (just less hassle).