Everyone,
It has been over six months since my last post. I owe the many of you who have been following this project an update. Plus, I have encouraging developments to report.
Life has a way of interfering with these hobby projects. I'll start with a brief run-down of "real life".
First, early last summer I moved the family from Lincoln NE, to Richmond VA. At the same time I went from being a contractor for my primary client, to a full time employee. Anyone who has made the sift from contractor to employee knows that employees have a lot less flexibility. The move and everything that went with it pretty much consumed the entire summer, and most of the fall.
The other challenge I faced was I had no workshop in VA. Since I rent here in VA, I couldn't put up a small building. So with the wife's blessing (she is a saint most days) I purchased a 23' travel trailer which I converted into a sweet little workshop in short order.
Now, back to the project. When you work on something for over a year, the warts start to really bother you. Some of these warts start to look like cancerous tumors. And cancer must be removed. So, what I'm trying to say is that I redesigned most of the system. Again.
I'm calling this the second generation solution, although it is really the forth combination of hardware. I had two goals this time around. First, eliminate the custom electronics and only use off-the-shelf parts. I had bit off more than I could chew. Second, I needed a more reliable way to connect everything together.
The previous architecture is essentially a control board, a sensor board and a relay board. There is actually a forth component, and I wish I had recognized this earlier. The interconnects between the components. In the first versions these were all wired together, using shielded communications wire. The method I used to interconnect them wasn't reliable. One of the decisions I made this summer was to replace my previous interconnects with a regular old Ethernet network. Ethernet is very good at moving data long distances, reliably. So the new architecture uses Ethernet as a data bus.
The relay board is another thing that I was building by hand before. I found a nice, affordable, Ethernet controlled relay board. It just plugs into the network and has screw terminals for attaching equipment. Easy as pie.
The control board (main CPU really) was already an industrial embedded computer running Android. It was already network equipped, so it too just plugged in. Also most of the software "just worked".
Anyone who has followed this project knows that the sensor has been a challenge. The holy grail is an affordable, off the shelf sensor. My brother and I have found two very promising sensors. One is a string-pot, the other is a linear sensor that operates a lot like a mouse. Neither of these has an Ethernet interface. However I have located an embedded micro-controller (
http://www.sparkfun.com/products/9474 - the nerds out there will appreciate this link) that will mostly replace my home-built circuits and provide the Ethernet connectivity.
Several of you have contacted me directly. I really appreciate the feedback and encouragement. I had promised myself that I wouldn't post anything until I had a working system to demonstrate. But, the interest in this project remains high and those who have been following this for over a year deserve an update.
To recap, the second generation architecture is moving right along. And I am very happy with the hardware design, this time around it feels completely "right". It eliminates nearly all custom electronics from the picture. Is very affordable, and is proving to be very easy to program the software for. One of the nice "fringe benefits" of this approach is that the the connection between the control board and the rest of the system can be wireless. No additional work necessary, just attach a wireless access point and away you go. From an engineering standpoint, remote set-works is a gimme.
Again, thanks for the continued interest in this project. I'll let everyone know when I have something working. It has been over a year, and if I've learned one thing it is not to guess how much longer a project will take. All of the off-the-shelf technology has really reduced the complexity of the build. I'm optimistic that I can get this knocked out before the coming of the zombie apocalypse. Please keep the encouragement and suggestions coming.
Shannon
