Temp Control and Data Logging

[Kirk Keyes]

In another thread, the question of temp control and measurement came up.

I'm curious about approaches people have been using for controlling temperatures during emulsion making, and if anyone has tried to data log the temp readings so that one has a good record of the temperatures and times during the process.

I guess I should start - I've got a Corning PC-420 stirring hotplate and the temp controller probe that you can get for it. I find the temp controller to be a bit tricky to figure out what it's doing sometimes, it's not as smart as one could wish for. But then it's just a hotplate, not a computer... So I find that I have to set the temp on the controller lower than what I want, and let it heat up to below what I want, and then make smaller adjustments to get the temp where I want it, otherwise, it will overshoot the temp I'm trying to get to. Once I figured out that approach, it does a pretty good job of holding the temp where I want.

For data logging temps, I have not done anything fancy, just a pad of paper that I write what I do on it. I also record the time and temp if I think I need to or if it is changing. For time, I have a digital clock that I start at 12:00:00 when I begin the run and then all the times are easy to compare to each other and easy to record.

I know there are some pretty inexpensive digital thermometers with data loggers that are sold for use in high schools and other amatuer projects, and it seems like it would be cool to get something like that.

And for head control, is anyone using a heating mantle or heater tape to heat stuff up with?

[Photo Engineer]

Well, to be a purist Kirk, the ramp rate in degrees / minute is critical as well as other factors, so data logging is indeed useful, but these emulsions, at these scales, work just fine and are repeatable.

The ISO 40 emulsion has a bit of a problem when scaled very large, as the temperature changes involved change the ramp rate due to volume and this changes the digestion rate. I get a more polydisperse emulsion and less Iodide is churned to the top.

PE

[Kirk Keyes]

That was a quick reply - certainly, data logging is not necessarily something needed, but it seems like it would be a useful think, when one gets more advanced in this field. But I'm just wondering if...

[Lee L]

I don't know if you're looking for an off the shelf solution to temp data logging, or if you want to DIY to some degree. I just got one of these for Christmas http://www.adafruit.com/index.php?ma...products_id=68 and it would be a good starting point for rolling your own. It's very flexible and not too steep a learning curve, and it will take single wire probes, control X-10 systems, and interface with Python, Processing, and many other languages for logging data over a serial or serial-USB port. You can get a card reader interface to log to a file on an on-board flash card. I've already made a lightning trigger for an electronic cable release. Search in google for arduino for other ideas and tutorials. The board and all associated software are open source, runs on Mac, Windows, Linux/Unix. Basic unit is about $30.

Lee

[rmazzullo]

Lee,

Thanks for the link...this is more in line with what I am planning.

Kirk,

I found heater tape that is fairly inexpensive, and is available indifferent widths and lengths. I was considering using a deep pan of fine sand to hold the containers of solutions, and submerge the heating tape and thermocouples at different points in the pan to adjust and monitor temps. The only advantage there is that the tape and probes are held in place by the sand. The idea might be good for doing temperature critical film processing, etc., but not for this. I have a different setup in mind.

Bob M.

[optique]

Lee,

I about fell out of my chair when I say you write "Arduino".

I spent a lot of time on Arduino and other microcontrollers which I find a million uses for.

Data and temp logging is probably the most common application that people write, and the OP could quickly put this together.

For me, however, I finally made up my mind that I can not do both hobbies simultaneously, micro development and photography, so I chose photography.
Steve.

I don't know if you're looking for an off the shelf solution to temp data logging, or if you want to DIY to some degree. I just got one of these for Christmas http://www.adafruit.com/index.php?ma...products_id=68 and it would be a good starting point for rolling your own. It's very flexible and not too steep a learning curve, and it will take single wire probes, control X-10 systems, and interface with Python, Processing, and many other languages for logging data over a serial or serial-USB port. You can get a card reader interface to log to a file on an on-board flash card. I've already made a lightning trigger for an electronic cable release. Search in google for arduino for other ideas and tutorials. The board and all associated software are open source, runs on Mac, Windows, Linux/Unix. Basic unit is about $30.

Lee

[Lee L]

Lee,
I about fell out of my chair when I say you write "Arduino".
<snip>
For me, however, I finally made up my mind that I can not do both hobbies simultaneously, micro development and photography, so I chose photography.
Steve.

Steve,

Yeah, it's hard to fit in all my interests, so I try to tie them together when I can.

While you're out of your chair, I grew up in Baytown.

Lee

[optique]

Lee,

Cool. We lived close by.
Small world.
Steve.

[totalamateur]

Wouldn't a thermocouple and an ADC work? I'm not big into this sort of thing, but I know you can buy the little bi-metal sensors that attach to some volt meters pretty cheap, it seems like you could just plug it into an ADC and calibrate it w/ freezing or boiling water.

It's been a while since I've played with one of these but the last one I remember had a serial port hook - up with software included.

Anyhoo.

BTW im in houston too. Trippy.

[Photo Engineer]

Kirk;

If you wish to see a datalog, I have included it in the files I sent you after the Workshop. It includes flow rates, vAg and temperature datalogs for a hypothetical emulsion. It will be in the book. This run time data is critical to documentation of all Kodak emulsions.

PE