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Monitoring/controlling with Linux on the cheap

There are numerous controller solutions on the market. Some of them are really, really nice, but, they aren't cheap either. With this economy and a kid in college, it has to be cheap (or free) before I will consider it. While I don't have a pile of cash sitting around (thanks to UF), I do have a few old POS laptops that have nothing to do but reminisce of days gone by. Rather than collect dust, I'm putting one (or more) of them to work.

This article requires the following:

A working install of Linux.
A working knowledge of Linux. You don't need to be an expert, but you do need to understand mounting file systems and what not. This is not a tutorial on how to use Linux. :)
A 1-wire adapter. I'm using the serial port version (DS9097U-XXX), but there are USB versions that work with this also. I recommend buying at least two (to have one for "play").
1-wire temperature sensors and switches. I'm using DS18S20 for temperature sensors, and DS2406 for switching. You can buy them most anywhere (Jameco, Digi-Key, etc). Make sure you order the TO-92 packaging unless you have ninja soldering skills. If you don't want to make your own sensors/switches, you can order them pre-assembled from numerous sources (here, here, here). That (assembled) 8 relay board from Hobby Boards for ~$70 is one heck of a deal.
You can get a few free ones from Maxim: here. Enter the part number (DS18S20), click GO, then select the "Sample Now" button on the items you're interested in. Do the same for the DS2406 and any other 1-wire device you want a free sample of. Not all items are available for sample so poke around. Don't be greedy - accept the default quantity of 2 and be happy.

I did this on a fresh install of Fedora 14. However, these procedures should work on most any distribution. Before you install anything though, check to make sure it's not already installed by your distribution (no need to have it twice).

All source that was downloaded was extracted into /usr/src as typical.

Download and install FUSE: http://fuse.sourceforge.net/
Follow the directions in the INSTALL file. From the command line:

Code:

    # ./configure

    # make

    # make install

Download and install owfs: http://sourceforge.net/projects/owfs/files/owfs/2.8p8/
Follow the directions in the INSTALL file. From the command line:

Code:

    # ./configure --prefix=/opt/owfs

    # make install

You can run owfs in a number of different ways (google it), but I choose to run the client/server model. Since I want all this mess started and mounted on startup, I edit my /etc/rc.local file to achieve that as such:

Code:

    #

    # fire up the 1-wire stuff

    #

    /opt/owfs/bin/owserver -d /dev/ttyS0 -F -p 1961

    /opt/owfs/bin/owfs -s localhost:1961 -m /mnt/1wire -F --allow_other

Adjust the /dev/ttyS0 term to match the serial port your 1-wire adapter is plugged into (/dev/ttyS0 is serial port #1, etc). You can use any port you want - I chose 1961 because that's my birthyear.

Now you are ready to attach some 1-wire devices. As mentioned above, you can buy them, or, you can make them yourself. I can't say how "hard" it is - only you can decide that. I'd say it's about "medium" on the hard scale. I'm not that good with a soldering iron - I can manage, but I don't do a pretty job of it. It works, but it ain't pretty. :)

Use these schematics for making your own:click

The DS18S20 temperature sensors are very easy to hook up and use. Two pins to ground, the other to the 1-wire bus line. The DS2406 is a bit more involved, but doable. I used this schematic for my DS2406 switches as I already had those parts laying around here. Aside from the DS2406, these parts are CHEAP. Once you have that circuit working, attach the +/- 5 volts output to a SSR rated to handle your intended load.

Once you have the 1-wire devices connected, cd to the mount point of your 1-wire. For me it's /mnt/1wire:

Code:

[root@x24 1wire]# cd /mnt/1wire/

Get a directory listing:

Code:

    [root@x24 1wire]# ls -l

    total 0

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 10.26CC4F000800

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 10.E1B64F000800

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 12.50547D000000

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 12.6A497D000000

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 alarm

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 bus.0

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 settings

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 simultaneous

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 statistics

    drwxr-xr-x. 1 root root 30 Apr 20 00:59 structure

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 system

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 uncached

    [root@x24 1wire]#

The entries that begin with "10" and "12" are four 1 wire devices that I have hooked up at the time of this writing. Devices that begin with "10" are DS18S20 and those that begin with "12" are DS2406. Those are the "family" id values (the rest of that number is it's address).

The directory structure of a DS18S20:

Code:

    [root@x24 1wire]# cd 10.26CC4F000800/

    [root@x24 10.26CC4F000800]# ls -l

    total 0

    -r--r--r--. 1 root root  16 Apr 20 00:59 address

    -r--r--r--. 1 root root 256 Apr 20 00:59 alias

    -r--r--r--. 1 root root   2 Apr 20 00:59 crc8

    drwxrwxrwx. 1 root root   8 Apr 20 11:42 errata

    -r--r--r--. 1 root root   2 Apr 20 00:59 family

    -r--r--r--. 1 root root  12 Apr 20 00:59 id

    -r--r--r--. 1 root root  16 Apr 20 00:59 locator

    -r--r--r--. 1 root root   1 Apr 20 11:42 power

    -r--r--r--. 1 root root  16 Apr 20 00:59 r_address

    -r--r--r--. 1 root root  12 Apr 20 00:59 r_id

    -r--r--r--. 1 root root  16 Apr 20 00:59 r_locator

    -r--r--r--. 1 root root  12 Apr 20 00:59 temperature

    -rw-rw-rw-. 1 root root  12 Apr 20 11:42 temphigh

    -rw-rw-rw-. 1 root root  12 Apr 20 11:42 templow

    -r--r--r--. 1 root root  32 Apr 20 00:59 type

    [root@x24 10.26CC4F000800]#

To read the temperature, "cat temperature":

Code:

    [root@x24 10.26CC4F000800]# cat temperature

         66.9875

    [root@x24 10.26CC4F000800]#

In the above example, the temperature is 66.9875 degrees (in my fermentation fridge). Here's how you get to that value in a bash script:

Code:

     #

     # the device name of the DS18S20 temperature sensor

     #

     fermilabDev="/mnt/fermiTemp/temperature"



     #

     # read (and log) the temperature of the fridge

     #

     fermilabTemp=$(cat $fermilabDev | tr -d ' ')

     logger -t fermilab "$fermilabTemp degrees"

The DS2406 shows up a bit differently in the file system:

Code:

    [root@x24 1wire]# cd 12.6A497D000000/

    [root@x24 12.6A497D000000]# ls -l

    total 0

    -r--r--r--. 1 root root  16 Apr 20 00:59 address

    -r--r--r--. 1 root root 256 Apr 20 00:59 alias

    -r--r--r--. 1 root root  12 Apr 20 11:48 channels

    -r--r--r--. 1 root root   2 Apr 20 00:59 crc8

    -r--r--r--. 1 root root   2 Apr 20 00:59 family

    -r--r--r--. 1 root root   1 Apr 20 11:48 flipflop.A

    -r--r--r--. 1 root root   3 Apr 20 11:48 flipflop.ALL

    -r--r--r--. 1 root root   1 Apr 20 11:48 flipflop.B

    -r--r--r--. 1 root root  12 Apr 20 11:48 flipflop.BYTE

    -r--r--r--. 1 root root  12 Apr 20 00:59 id

    -rw-rw-rw-. 1 root root   1 Apr 20 11:48 latch.A

    -rw-rw-rw-. 1 root root   3 Apr 20 11:48 latch.ALL

    -rw-rw-rw-. 1 root root   1 Apr 20 11:48 latch.B

    -rw-rw-rw-. 1 root root  12 Apr 20 11:48 latch.BYTE

    -r--r--r--. 1 root root  16 Apr 20 00:59 locator

    -rw-rw-rw-. 1 root root 128 Apr 20 00:59 memory

    drwxrwxrwx. 1 root root   8 Apr 20 11:48 pages

    -rw-rw-rw-. 1 root root   1 Apr 20 11:48 PIO.A

    -rw-rw-rw-. 1 root root   3 Apr 20 11:48 PIO.ALL

    -rw-rw-rw-. 1 root root   1 Apr 20 11:48 PIO.B

    -rw-rw-rw-. 1 root root  12 Apr 20 11:48 PIO.BYTE

    -r--r--r--. 1 root root   1 Apr 20 11:48 power

    -r--r--r--. 1 root root  16 Apr 20 00:59 r_address

    -r--r--r--. 1 root root  12 Apr 20 00:59 r_id

    -r--r--r--. 1 root root  16 Apr 20 00:59 r_locator

    -r--r--r--. 1 root root   1 Apr 20 00:59 sensed.A

    -r--r--r--. 1 root root   3 Apr 20 00:59 sensed.ALL

    -r--r--r--. 1 root root   1 Apr 20 00:59 sensed.B

    -r--r--r--. 1 root root  12 Apr 20 00:59 sensed.BYTE

    -rw-rw-rw-. 1 root root  12 Apr 20 11:48 set_alarm

    drwxrwxrwx. 1 root root   8 Apr 20 11:48 T8A

    drwxrwxrwx. 1 root root   8 Apr 20 11:48 TAI8570

    -r--r--r--. 1 root root  32 Apr 20 00:59 type

    [root@x24 12.6A497D000000]#

To turn the DS2406 switch "on", you do this:

Code:

[root@x24 12.6A497D000000]# echo "1">PIO.A

and to turn it off:

Code:

[root@x24 12.6A497D000000]# echo "0">PIO.A

The TO-92 package of the DS2406 has only one switch line, so PIO.B is not usable on this device.

To make your life easier, you may want to create sym links to the 1-wire devices. Repeating the above directory structure:

Code:

    [root@x24 1wire]# ls -l

    total 0

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 10.26CC4F000800

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 10.E1B64F000800

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 12.50547D000000

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 12.6A497D000000

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 alarm

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 bus.0

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 settings

    drwxrwxrwx. 1 root root  8 Apr 20 11:39 simultaneous

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 statistics

    drwxr-xr-x. 1 root root 30 Apr 20 00:59 structure

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 system

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 uncached

    [root@x24 1wire]#

The sym links make it easier to refer to the 1-wire devices in your scripts/programs using a logical name, rather than some goofy alpha-numeric that means nothing us humans:

Code:

    [root@x24 mnt]# cd /mnt

    [root@x24 mnt]# ls -l

    total 0

    drwxr-xr-x. 1 root root  8 Apr 20 00:59 1wire

    lrwxrwxrwx. 1 root root 21 Apr 20 00:14 fermiOutsideTemp -> 1wire/10.E1B64F000800

    lrwxrwxrwx. 1 root root 21 Apr 20 00:10 fermiSwitch -> 1wire/12.6A497D000000

    lrwxrwxrwx. 1 root root 21 Apr 14 10:38 fermiTemp -> 1wire/10.26CC4F000800

    lrwxrwxrwx. 1 root root 21 Apr 20 01:05 switch1 -> 1wire/12.50547D000000

    [root@x24 mnt]#

Now, all you need to do is write some scripts (in whatever language you're comfortable with) that does something useful with the above.

Enjoy, and YMMV. :)

Nice write up!
I've been thinking of doing the same and using a ti launchpad instead of an adapter. Its $4.50 plus you get some additional IO.

Excellent! I have started using a 1-wire sensor system with windows and it would be nice to have a Linux option.

I applied for a "free" DS2406 recently and they wanted to charge me $75 for a kit?? Not sure I did it right, but will try again. I kind of made it look like I was interested for my wife's company, who does electronic R&D...

I may play with this info and see what I can do. Might be bugging you for some script help in the future!

Well, I must have done something wrong last time. I was easily able to order a sample for the switch this time. Sweet!

Homercidal,

You did nothing wrong last time - they sell a developer kit too. The link above is to a different area (as you have already found out).

The nice thing about using owfs is that it exposes 1-wire devices as a file system, which, takes almost all the work out of playing with those devices - no bit twiddling. It's frightening simple once it's all setup. Last I checked, owfs wasn't quite ready for prime-time on Windows - it might be worth a checking into though.

Scripting... with owfs, anything that can interface with the file system, can do 1-wire. Bash, python, perl, php, etc. For example, my ferm fridge (Fermilab) is controlled by a simple bash script that gets fired up once every 2 mins by cron. I'm currently working on expanding this control mechanism to a HERMS system, but I'm not done with that yet...

I have done a bit of bash scripting in college. I don't think I still have the Unix reference book, but I'll check. LOTS of information on scripting online though.

After seeing how it's done a little bit, it's starting to make some sense and really does seem very simple. I'm mostly interested in using it for controlling, since my temp monitor is already basically set up and working well. What I can see happening is using this to not just control a ferm chamber, but maybe 2 or more AND sending the temps to a file for reference.

I should get all my friends to order samples for me...

Quote:

I should get all my friends to order samples for me...

the ole "you drink my beer, order me some free parts" routine, eh? Works for me. :)

Quote:

Originally Posted by Homercidal (Post 2854941)

What I can see happening is using this to not just control a ferm chamber, but maybe 2 or more AND sending the temps to a file for reference.

http://www.mrtg.org/rrdtool/

Here is some PHP code that plays with the device names I used in the examples above. You can run it from the command line, or from a web server. If your language of choice can open, read, write and close a file, it can do 1-wire via owfs:

PHP Code:


		
			
<?php



    // display the temperature

    displayTemp();        

    

    // toggle the switch

    setSwitch("1");

    sleep(1);

    setSwitch("0");

    

    exit;

    

    



function displayTemp() {

    //

    // the device name of the temp probe

    //

    $devTemp = "/mnt/fermiTemp/temperature";

    

    //

    // open the temperature device

    //

    $fp = fopen($devTemp,"r");

    if ($fp == null) {

        echo "error opening $devName\n";

        exit;

    }

    

    //

    // read the temperature

    //

    $temp = trim(fread($fp,1024));

    

    //

    // close the file handle

    //

    fclose($fp);

    

    //

    // display the temperature

    //

    echo "The temp is: $temp\n";

}

    

    

function setSwitch($state) { 

    //

    // the device name of the DS2406 switch

    //

    $devSwitch = "/mnt/fermiSwitch/PIO.A";

    

    //

    // open the temperature device

    //

    $fp = fopen($devSwitch,"w");

    if ($fp == null) {

        echo "error opening $devSwitch\n";

        exit;

    }

    

    //

    // set the switch state

    //

    if (fwrite($fp,$state) === FALSE) {

        echo "error writing to $devSwitch\n";

        exit;    

    }

    

    //

    // close the file handle

    //

    fclose($fp);

    

    //

    // display the temperature

    //

    echo "The switch is set to: $state\n";

}



?>