DIY Jobo-style (sort of) processor?

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cooltouch

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Right now I just use a Patterson tank and reels to develop my B&W film, but I'd like to get back into developing color again, especially slides because it's become so inconvenient and expensive to have them developed. Way back in the 80s I used to develop my own slides, and it was a real hassle trying to keep my bath at +/- 1/2 degree F, so it's gotten me to wonder just how difficult it would be to build a tank that would hold a bath at an exact temperature. I'm thinking it would actually be pretty easy.

In my case, I wouldn't need the rollers that some Jobo systems have or the lifts or whatever other gizmos they contain -- just room enough for the bottled chems to be put in the bath and to roll around the developing tank manually. Or maybe I could just agitate it every 30 seconds or so the way I do it with my B&W films. That would still work as well I'm thinking. I also have a couple of the tanks with the spinners for agitation. They seem to work fine for 35mm, but I've gotten streaks with my 120 when using them, so I don't use them anymore -- at least for 120.

Ever seen a heater used in reptile terrariums? It's just a large flat plastic pad with a heating element inside and with an adhesive side so it can be pasted onto the terrarium tank's bottom surface. It plugs into a wall socket and heats up to raise the air temperature far enough inside the terrarium so the reptiles are comfortable -- probably with an air temperature around 105F to 110F. This is most likely too warm for color chems I'm thinking, but one can rig a dimmer switch up to an outlet box and use this to control temperature.

So just wondering if anyone else here has had thoughts along these lines and what, if anything, you might have come up with?
 
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cooltouch

cooltouch

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Thanks for the reply. But in the true spirit of DIY, I'm hoping I can build my little outfit for a small fraction of what Nova charges for their rigs. And rather than using a $60 heater, I already have a reptile heater and if that one won't work, I can get an aquarium heater for about a third of Nova's prices. And I can use a dimmer switch hooked up to an outlet to control the temperature, which I actually already have. Besides, Nova's in the UK and I'm in the US. Shipping costs would be prohibitive.
 

michaelbsc

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An aquarium heater in a scavanged Coleman cooler (or equivalent) will maintain temperature as well as the same heater will in an aquarium.

The problem with those is that they are on/off control with a deadband so the contacts don't cycle continually. You can probably expect +/- 2 degrees. Maybe +/- 1.

If you are savvy with op amps you can build a simple proportional controller with a solid state output for less than 10 bucks if you discount labor.

If you care about being quick about it then just watch for a PhotoTherm temperature bath on evilBay.
 

Muihlinn

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And rather than using a $60 heater, I already have a reptile heater and if that one won't work, I can get an aquarium heater for about a third of Nova's prices.

The reliability and accuracy of nova's temperature controller stuff is far away and beyond you can get with that kind of heaters, indeed, for a cost.

Anyhoo you can get the idea and try a similar approach now that you have the same tanks. IMHO - and also humble experience - DIY for kinda sophisticated stuff almost always leads to spend not much less money in the making and end having second-rate stuff.

Despite as it sounds, I'm not trying to discourage you, go ahead.
 

domaz

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Just get a PID controller off Ebay for $30 a Thermocouple and a stand-alone (no thermostat) aquarium heating element and you are set. If you want to get fancy you can get a Solid State Relay and have better temperature control than a Jobo (which are just on/off).
 

michaelbsc

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Just get a PID controller off Ebay for $30 a Thermocouple and a stand-alone (no thermostat) aquarium heating element and you are set. If you want to get fancy you can get a Solid State Relay and have better temperature control than a Jobo (which are just on/off).

Like these? (I have no association with the seller. I just found these with a search for "PID Controller" in the field. In fact, this is a reasonable deal in my mind, and I'll probably buy some myself.)

Here's a BIN with *FREE SHIPPING* http://cgi.ebay.com/Digital-PID-Tem...034?pt=LH_DefaultDomain_0&hash=item3363651912

And here's an auction where the shipping pays for the controller. http://cgi.ebay.com/PID-Temperature...407?pt=LH_DefaultDomain_0&hash=item3363c1e087

Still need a heater element, but if tuned properly it will be dead on, as domaz says. You said you have a heater, so you may be home free.
 
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