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Electromadness continues…

As many of you know, I’ve been tinkering trying to figure out what it will take to get a computer-controlled homebrewing sculpture up and running. I’ve been amassing electronics components for the past few months (at the cost of brewing gear and ingredients, unfortunatley) and spending my evenings playing around instead of formulating new recipes and figuring out how to squeeze 200 gallons in this year. Rather than spending a gazillion dollars on a commercially available data acquisition card, I’ve gone the el-cheapo route and decided to build the electronics myself. Most likely my designs will employ the PICAXE microchip, one of the coolest little pieces of hobbyist electronics on the planet.

My recent efforts have been around getting temperature readings… and while the PICAXE chip is capable of getting 10-bit temperature readings with its native analog-to-digital command and an LM34 linear sensor, or 12-bit temperatures using a very specific (and somewhat expensive) sensor, the DS18B20, neither of these have really satisfied me. The 10 bit readings just don’t have the kind of accuracy I want, and the DS18B20 has a 750ms (almost a full second) delay while the reading is being taken. I did work up a prototype circuit that can send the data either to an LCD screen or my PC, as shown below…. but it was mostly a proof a concept.

LCD Proof-of-concept

Enter the MCP3208 12-bit SPI interface chip, and some code courtesy of Peter Anderson. Armed with these little gems, I prototyped a circuit to not only test the accuracy, but to also check my skeleton conversion routines in the VB.NET app that will eventually power my sculpture. It appears to approach the accuracy of the DS18B20, but is wicked fast in comparison.

MCP3208 and PICAXE 18X prototype with LM34 sensors

The chip on the left is the MCP3208 with a single reading coming to it on Channel 0 (bottom sensor). The right chip is the PICAXE 18x, somewhat obscured by the 4 conductor wire that communicates with the MCP3208. It is also reading a second LM34 sensor on Pin #1 using its native 10-bit read command. The data is sent via serial link back to the PC through the 3-conductor cable that disappears out the top of the picture.

My .NET application captures the data and processes it in blocks, converting the raw values to “unitized” values on-the-fly. My intent is to allow the user to change units at will, and to store the raw value as well as converted value in a database for analysis later on…

VB.NET terminal receiving of data

Another benefit of the MCP3208 is that it also take 3 outputs and 1 input and converts them into 8 12-bit inputs, since the MCP3208 has 8 different channels… so it is actually increasing the number of data devices I can implement using a single PICAXE chip. Given the flexibility of the PICAXE development environment, I honestly don’t think I will run out of available inputs or outputs.

Slowly but surely, I am building the knowledge necessary to outfit a brewing sculpture with enough electronics and technology to make Charlie Papazian shake his head in shame and disown me as a fellow homebrewer.

But damn, won’t it be cool.

I have started to chronicle some of this silliness on our site in a Tech Section, which I haven’t officially added to the sidebar of the site. I will at some point when its ready for prime-time.

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Categories: Uncategorized
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  1. June 10, 2007 at 6:39 am

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