Phriendly Phil’s Velociraptor Pharm n’ Pettin’ Zoo

I have to keep reminding myself of that.

It’s not clear from the previous post how I will get one chest freezer to keep things at two different temperatures. That’s because it’s impossible to do that with just a chest freezer.

What I plan to do is to keep the chest freezer cold enough to maintain the lowest temperature I need held. Anything that needs to be warmer will be heated to the proper temperature, probably with a heating pad.

One of the features planned for this temperature controller is a “master cool” mode, where the master cooling device will not run as long as everything is already cool enough. In my case, this would be the freezer, and the idea is that if the freezer does not run constantly, energy will be saved.

I got a nice bonus at work last month, and decided to get a new toy. After toying with the idea of setting up a ventilation system so I could brew in the basement, I decided to set up a temperature controller so I can keep better control of the fermentation temperature of my beers.

Now, there are some nice controllers available on the market, but they run around $50 for analog or $80 for digital, and only control one device. This would be good for fermentation, but it would be nice to also be able to use the same cooler for serving beers, which would be too cold for ale fermentations.

I had heard a lot about the Arduino and a quick question to Professor Google brought me to an article on uC Hobby describing a project by Sean Coates that did just what I was thinking of.

I decided to run with the Arduino, and at first an LED display, but I quickly decided that I wanted a serial LCD display so as to take up fewer output lines. A brief deliberation led me to stick with the thermistors of Coates’ original design, rather than LM-35 or 1-Wire sensors (Coates has since gone to LM-35s.) I decided on a 4-channel controller, although I may change my mind on that.

I ordered the Bare Bones Board by Modern Device, and also a low-cost serial LCD driver kit and LCD display which they sell. Since the BBB does not have a USB driver as the official Arduino boards do (why have one just for programming the thing) I also bought a USB cable from them for programming.

I bought ten thermistors on eBay for around 60 cents each, shipped. For around 45 dollars, I bought six Opto22 solid state relays (these are $22 new from the manufacturer.) Total costs, including the cable, are $110 so far, and I have extra thermistors and SSRs for another project.

Next post — clipping leads and heading to Radio Shack, or: re-learning soldering.