RE: Water heater advice

Fish tank heaters are OK for some purposes, but because they use a
thermostatic bi-metallic mechanical contact to control their heating
cycle, they can vary from +/- 3 degrees Fahrenheit in accuracy, which
can be a problem if you are trying to keep tight tolerances on your
developing of E-6 or C-41 film. About 10 years a go I built a
proportional temperature controller circuit using a TDA1023 proportional
TRAC controller IC. Phillips still makes this IC. I used a modified
fish tank heater (controlling contacts removed) and a water bath inside
a camping cooler. According to my lab grade thermometer, the temperature
never varies more than +/- 0.5 degree Fahrenheit. That is just as good
as the expensive JOBO temperature controller and better than the one
Porter's sells. If you have experience in electronics or have a friend
who is experienced, then it is a fairly easy project to do. I would be
happy to scan the article and e-mail it to you if you'd like.

Fred Cousins

-----Original Message-----
From: Baird, Darryl [mailto:dbaird@umflint.edu]
Sent: Thursday, April 08, 2004 7:50 PM
To: Alt Photo
Subject: Water heater advice

Hello all,

I'm looking at making a cheapo heated water bath, for color negative
processing...our local labs are too careless with their machinery.

Looking at alternative to Jobo, I find a submersible water heater at
Adorama, but out of stock. I've started to look at hydroponic and fish
tank heaters as alternatives. They are cheaper and the specifications
seem in order, but I wonder if anyone else has trodden this path
before.

ideas, suggestions, ???

thanks

Darryl

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