>>> Michele Baldessari <[EMAIL PROTECTED]> 5/15/2007 12:07 AM >>> * David Dudley ([EMAIL PROTECTED]) wrote: > The cards have Atheros WiFi cards installed as well as a USB Cellular > CDMA card that allow them to communicate their readings to the central > site on a timed basis. Would be nice if I could use the on board GPIO > chip for some of the small stuff, but the I/O capabilities that I need > from that chip don't come out on the connector, I think.
Hi David, could you elaborate on what USB Cellular CDMA card you used? I'll probably have to setup a few systems that need it, so I'd be interested. thanks in advance, Michele Michele, Would you believe it's taken me until now to get time to respond to this? Sorry, I've been rather snowed with other projects. I've got a few minutes to collect my thoughts, so I'll elaborate on what I'm doing here. I work for the City of Corpus Christi Utility Monitoring department. We monitor and control valves, pumps, flows, levels, pressures, and so forth on various points throughout the city (actually, our service area is around 600 square miles, but whose counting...). Most of our sites use remote PLC units that communicate through radio to our central monitoring site, but for a variety of reasons, we've begun looking into lower cost methods of monitoring some of the low usage sites. For instance, since we're on the coast, some of our sites do nothing more than monitor the tide level, and the outflow rate from some of out pipelines into the Gulf of Mexico. This involves nothing more than reading two analog levels, and perhaps supplying the status of the power system for the site. Installing a remote PLC unit for these types of locations can cost upwards of $5,000 - $7,000 just to monitor the two or three points required. I began working with the Soekris 4801 to replace those sites. To acquire the analogs, I use a ELAN P222 cardbus adapter card to supply two cardbus slots. Into the bottom slot of the adapter, I have a Measurement Computing Cardbus Analog card inserted that supplies access to the analog readings. Each unit also has a AXIOM Navigation GPS unit attached which provides their exact location, so I don't have to necessarily keep track of which system I installed at which location, just changing the hardware at the location adapts based on it's GPS location. I've had a couple of the AXIOM units struck by lightning, and haven't been able to locate a supplier for the units any more, so AXIOM Navigation may be out of business, or something. The communications for the unit is supplied by either having one or more of the Ethernet ports plugged into a local ethernet switch adjacent to the site (in one case, I'm actually monitoring the sump level of an unmanned switching center), an Atheros WiFi Mini-PCI card on the 4801, or by inserting a Sprint S720 cellular card into the top slot of the cardbus adapter. Most sites have a combination of devices where I have at least 2 separate communication paths back to our central site. The Sprint S720 card actually contains a USB hub with a USB cellular interface connected. After a patch to NetBSD to make it recognize the exact card involved, I use the standard PPP software to communicate and talk to it. To this point, it has been working successfully. Power for the system is supplied by a 12 volt 8AH Sealed Lead-Acid battery, which is kept charged either by a solar panel, or a Southwest Windpower Air-X Wind Turbine. In the NetBSD system, I have a tunnel device defined that is targeted to a device on my central site, so routing takes care of getting data from the remote site to the central site, and I don't get involved with details of how to get from there to here. The remote unit sends in an update every 15 minutes, and if it uses the cellular connection (which usually is not necessary), it connects and disconnects as needed. David Dudley
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