Concept for monitoring solution w/out PC

foosman · April 2009

I'm kicking around an idea for a monitoring solution that:
1) Does not require a PC running.
2) Is low power.
3) Is low cost (~ $100 or less)

I'm looking at using a Linksys NSLU2. This is a network attached storage device that has been hacked and capable of running a full blown Linux OS (http://www.nslu2-linux.org/). You can attach either a USB HD or a FLASH stick to use as storage. My initial idea is to connect it to a Fronius inverter thru the Fronius Interface easy card which uses RS232. This would work with any inverter that has RS232 and an open interface. The idea:
- Connect NSLU2 to my network via built in networking.
- Add a FLASH stick
- Add a USB to RS232 cable
- Run a Cat5 cable between NSLU2 and inverter. A set of $2 RJ45 to DB9 connectors will allow the connection between the cable and inverter.

The NSLU2 uses about 3W of power. It is capable of running a web-server. I would write code to periodically poll the inverter and update a web page. The cost should be under $100 for the NSLU2, USB to RS232 cable, etc.

Has anyone done anything similar?

BB. · April 2009

Re: Concept for monitoring solution w/out PC

Roderick did one for Palm (open source).

Solar Guppy has some that he did for PC (private source?).

-Bill

RandomJoe · April 2009

Re: Concept for monitoring solution w/out PC

I thought I had seen a couple of people on Otherpower talk about using a NSLU2 for datalogging as well, but I'm not finding anything with the search there right now. Then again, I seem to be pretty bad with search engines in general...! :roll:

Edit: Okay, must be the Otherpower search engine. (The website for the forum is actually 'fieldlines.com'.) I just searched with Google, restricting it to the 'fieldlines.com' domain and it found several hits mentioning 'nslu2'.

I'm cobbling together some Python scripts to collect / display / analyze the data from my Outback Mate. (I just recently got the Mate, so I'm not terribly far along - right now it logs all the data to CSV files, which serves my immediate purposes - I can go back and see how things performed on a given day. The rest will progress as I have time.) It also logs my weather station, but I'm using an existing project for that - http://www.wviewweather.com/. The website mentions it too can be embedded in an NSLU2. It generates all the web pages as well, which is where I'll probably look for pointers when I get into that part of my Mate project.

Right now I'm on an Atom-based "car PC" that uses about 25W. (Most of it in the chipset.) Programming is a hobby for me, so I'm no great expert, thus I stick with what I know best which is x86! I also use the computer for regular browsing (I'm on it now) and remote access from work, so it serves multiple purposes. I am seriously considering replacing it with an Eee PC, though. It uses all of 10W, measured with the KillAWatt, and that's with the screen going. That'd be a nice reduction over the thing I'm using right now.

Is the NSLU2 still available? I thought I had found a while ago that they were discontinued. Looks like that project does support some other brands, I might go see if one of the others is still in production. I'm not fond of purchasing used stuff off eBay... Just too cynical!

Solar Guppy · April 2009

Re: Concept for monitoring solution w/out PC

Its cheaper and easier ( more main stream ) to just use used PC's. On eBay you can find lots of good Pentium laptops that would be fine for low power monitoring in the 20-40 dollar range, bonus is you get a screen where the linksys doesn't have one.

You can also find older VIA based ITX systems similarly priced.

foosman · April 2009

Re: Concept for monitoring solution w/out PC

Good information! I was able to find a Perl script on Fieldlines that will help me as I was not sure how to handle the serial port interface in Perl. I may use Python, but I've written lots of Perl in the past, so it is a safe bet for me. Also, I will see what I can leverage from the weather monitoring station code in terms of building the HTML code. I have a co-worker who is willing to help on the HTML and says it is easy. I may also use a SQL database for archive purposes.

As for using a laptop. This is a good idea. I've got several old ones lying around and may use one for developing the code and debugging. However, I still like the NSLU2 as it uses so little power, is fanless and is more of a challenge

I've seen NEW NSLU2 for sale on Amazon, Ebay, etc. Looks like I can get one for about $60. I like the idea of playing with the NSLU2 as I'm thinking of other non-Solar applications where it is useful.

dwh · April 2009

Re: Concept for monitoring solution w/out PC

RandomJoe wrote: »

Right now I'm on an Atom-based "car PC" that uses about 25W.

I thought about buying one of these. A friend of mine has one from Acer. I tried it out and liked it a lot (and it has an Atheros based wifi card so packet injection works easily in Linux).

But then, before I got around to buying it, he started having problems. First one of the shift keys broke off, then the hard drive started developing bad sectors - and he'd had it just under a month! Yikes!

He took it back to Radio Shack and gave them 50 bucks more and they gave him the next model up from the first one, nice since the new one has the "6 hour" battery pack.

That was a few weeks ago and no problems with the new one...yet. I'm going to wait a while and see what happens before I buy.

foosman · April 2009

Re: Concept for monitoring solution w/out PC

If your an Apple fan, rumor is they have a netbook coming soon.

I was at a Freescale conference about a year ago and a VP from a company that makes netbooks said the bill of material was $100 to make one. Crazy.

n3qik · April 2009

Re: Concept for monitoring solution w/out PC

I currently using an Asus 1002HA with SB Server 2003 installed to work with my T.E.D. plus more as I get to finish other stuff.

Even with the blot from Server OS, still runs reasonably fast.

westbranch · April 2009

Re: Concept for monitoring solution w/out PC

Roderick and I worked out a way for a Palm V, or Vx, or younger apparently, to download data from a Xantrex XBM battery monitor via RS232 port. took a bit of time and electronics expertise, from a friend locally, but it was really quite simple overall... and I am not electronically savvy.

uses the Palm desktop facility to Sync data to my base computer and then Excel to view and graph.

has been most helpful in determining what is going on with my AGM battery

Dont know if that is what you want but Roderick has the new programming available... just give him a jingle.

cheers,
Eric

foosman · May 2009

Re: Concept for monitoring solution w/out PC

I thought I'd give an update in case anyone is interested. My goal is to provide nearly real-time data from a Fronius inverter, dynamically build graphs/html pages and collect data into a database. I want to do this as an embedded system which does not require a PC running.

I bought the SLUG (Linksys NSLU2), re-flashed it with Linux (SlugOS) and after some pain have everything installed I should need (webserver, PHP, sqlite, etc.). I've attached an 80GB hard drive (USB powered 2.5" drive so no power supply needed). I'm waiting on a USB to RS232 cable to arrive. So far I've been very impressed with the SLUG. I've developed several Flash-based charts using amCharts and have the SLUG serving these via lighttpd web-server. I've setup a cron job to run a script every 2 minutes that will eventually poll the inverter. Everything is coming along nicely, I just need more time to work on it.

Next step is to get RS232 communications running and write code to poll the inverter (oh yeah...PV system has not been installed yet, so I'll have to simulate the inverter). Then I need to finish the PHP code/html code and then put it online.

My goal is to be running in 1 month, based on only getting a few hours a week to work on this.

stephendv · May 2009

Re: Concept for monitoring solution w/out PC

If you want really low power you could go for an Arduino microcontroller: http://www.arduino.cc/
Can be expanded with ethernet, xbee, wifi, bluetooth and SD card, but programming is somewhat limited by the small amount of available RAM and slow processor.

foosman · May 2009

Re: Concept for monitoring solution w/out PC

Looks cool, but it's based on Atmega micro-controllers with a limited embedded OS (i.e.- probably lacks support for a file system, which will be needed to store the amount of data I'd like to collect in order to compare the power output over years) and forget about running a web server or SQL on it.

However, if you're using it just to communicate with the inverter and upload data to some other location which is storing the data and hosting a web page, then it might be a good choice. I might consider a Rev. 2 that does this...just grab the data and ship it off to a web server somewhere. All my heavy lifting (development) so far is in POSIX compliant C. This will port nicely to anything with a C compiler. I can cross compile on Windows, Linux, etc. w/out problems. Most micro-controllers have C compilers.

My goal is to have a stand alone monitor that simply connects into my home network (router)...I'd have to do some research on how to handle the TCP/IP communications w/ a low cost micro-controller as that's an unknown to me.

Anyhow...cool suggestion...you've got the gears in my brain turning.

mikeo · May 2009

Re: Concept for monitoring solution w/out PC

I thought I'd give an update in case anyone is interested. My goal is to provide nearly real-time data from a Fronius inverter, dynamically build graphs/html pages and collect data into a database. I want to do this as an embedded system which does not require a PC running.

I am interested in doing a wireless remote system for my PV installation. I have a Davis Vantage Pro weather station and am wondering if I can hack one of their remoter sensor boards to send voltage and current directly from my shunt to the weather console. Then I could download the data on some schedule, daily, weekly or monthly and calculate power and monitor system performance.

http://www.davisnet.com/product_documents/weather/manuals/VP2_Manual_Temp_Stn_Rev_A.pdf

foosman · June 2009

Re: Concept for monitoring solution w/out PC

For anyone looking for a low cost stand alone controller/computer that runs Linux:
http://www.marvell.com/featured/plugcomputing.jsp

This is cool.

stephendv · June 2009

Re: Concept for monitoring solution w/out PC

Some more options for cheap linux PCs:
http://www.pcengines.ch/alix.htm
and
http://beagleboard.org/

Concept for monitoring solution w/out PC

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