It will plug directly into the Tentacle Board. You will also need the EZO™ RTD Temperature Circuit that plugs into the Tentacle, which enables you to read the specific signal coming off this probe. Each probe needs a corresponding EZO Circuit.

This probe comes with a rather short cable that necessitated us buying one of these.

It will plug directly into the Tentacle Board. You will also need the EZO™ pH Circuit that plugs into the Tentacle, which enables you to read the specific signal coming off this probe. Each probe needs a corresponding EZO Circuit.

Designed for small spaces, this small probe gives you the same quality readings found in our lab-grade Dissolved Oxygen just smaller.  Because smaller probes use fewer precious metals, we can get the price lower. Keep in mind; smaller probes hold less electrolyte. Because of this, they need to be refilled more frequently than full-size or industrial probes. Each probe needs a corresponding EZO Circuit.

• Out of the box, the probes do need calibration.
• If you put an extension cable on the probes they will need calibration.
• Over time the probes need to be re-calibrated.

Temperature.

Boil a jug of water to 100c.
Calibrate the probe to this temperature.

You can buy one-time solutions to re-calibrate the pH and DO probes.

pH.

We have re-calibrated the pH probe by using normal tap water, getting a reading using pH test solution, and seeing a pH of 7.  This gave us the mid-bound reading. We then used the test solution and got a reading from a tank that was a pH of 4. This gave us a low-bound reading.

Dissolved Oxygen.

Taking the probe out of the water, with or without an extension cable. You can interrogate the probe and when the numbers settle down to a constant, then you can generally know you are getting a reading of 8 ppm, and calibrate the probe to this setting.

Working with Linux and Cacti is a moving target.

If you are doing a new installation, please contact me if you would like some help and so I can update this documentation to reflect the process, now, at the end of 2021.

apt-get install cacti

Answer yes to install.

Choose Apache as your webserver

Choose Yes to configure cacti

Choose a password for cacti

I use 4cacti

Let’s open cacti for the first time

http://127.0.0.1/cacti

the user is admin the password is 4cacti

Let’s create a monitor for this Raspberry Pi

Create -> New Device -> Description (some name) Hostname (127.0.0.1)

Go to Graphs -> Default Tree -> Machine -> Raspberry

And you will see the default graphs of

Click on Graphs to see plots of what you are monitoring.

Back at the console, we can Create -> New Graphs and New Devices.

You have to have a Device before you can have a Graph, and the Device you need to create first is for this Raspberry Pi.

So click on Create and click on New Device.

1. You will need to fill out a Description, it can be whatever you like.
2. Hostname is 127.0.0.1, as it is this device and this is the fastest way to get this device to respond. It could be a totally different IP address if you are getting information from a different location.
3. Location can be ‘None’
4. Poller Association is ‘Main Poller’
5. Leave Device site Association as ‘Edge’
6. Device Template is Local Linux Machine as the Raspberry Pi is a ‘Local Linux Machine’.
7. Number of Collections Threads, leave as one, this will be more than enough.
8. Then enable Device.
9. Create

This duplicate now needs:

1. A Name: Dissolved Oxygen
2. Input Type:  leave it at Script/Command
3. Input String: This is the secret sauce, and we will get into this more a bit later. For now we need

   /usr/bin/python <path_cacti>/scripts/i2c_cacti.py <code>

4. For this first part, now Click Save.

Input Field: You will have to delete the existing Input Field by clicking on the red x, then click the plus to create a new one.

This is what you will want here.

Click Save

Output Fields: You will have to delete the existing Input Field by clicking on the red x, then click the plus to create a new one.

This is what you will want here.

1. Name: Dissolved Oxygen
2. Name: |host_description| – Dissolved Oxygen, this makes the map more meaningful.
3. Data Input Method:  Choose Dissolved Oxygen, that we have just previously created.
4. Data Source Profile: % Minute Collection.
5. Data Source Active: On
6. Data Source Item: Change to
7. Internal Data Source Name: PPM
8. Minimum Value: 0
9. Maximum Value: 20, we will never have a number of 10 or so unless there is an error.
10. Data Source Type: GAUGE, what the probe says is what we record.
11. Output Field: We may have to save the setup first to then see the DO Field that we have previously created.
12. Code: 97, this is something we know from what we will be looking at later.

This is a bit involved.

1. Graph Template Items
   These are the parts of the graph.
   
   

    

   1. Item 1
      1. (PPM): DO ppm
      2. AREA
      3. AVERAGE
      4. 50%
      5. 4668E4
      6. Save
   2. Now do Item 2 – 5 as seen in the main picture.
2. Graph Item Inputs.
   You will have to delete the existing Input Field by clicking on the red x, then click the plus to create a new one.
   Data Source [PPM]
   
   Legend Color
   
3. Graph Template [edit: Dissolved Oxygen]
   Make sure this reflects correctly for Dissolved Oxygen.
   
4. Graph template Options
   Generally, you can leave this long next section alone.
   

Once we have set up the Cacti side we need the python side to give us a number when we query the probes.

The following script needs to be put in this directory, /usr/share/cacti/site/scripts/i2c_cacti.py, and called i2c_cacti.py

#!/usr/bin/python

import io
import sys
import fcntl
import time
import copy
import string
from AtlasI2C import (
	 AtlasI2C
)

def print_devices(device_list, device):
    for i in device_list:
        if(i == device):
            print("--> " + i.get_device_info())
        else:
            print(" - " + i.get_device_info())
    #print("")
    
def get_devices():
    device = AtlasI2C()
    device_address_list = device.list_i2c_devices()
    device_list = []
    
    for i in device_address_list:
        device.set_i2c_address(i)
        response = device.query("I")
        moduletype = response.split(",")[1] 
        response = device.query("name,?").split(",")[1]
        device_list.append(AtlasI2C(address = i, moduletype = moduletype, name = response))
    return device_list 
       

def main():

    device_list = get_devices()
        
    device = device_list[0]

    #print_devices(device_list, device)
    # Only uncomment in testing
    
    real_raw_input = vars(__builtins__).get('raw_input', input)

    if len(sys.argv) < 2:         user_cmd = "ALL:r"         cmd_list = user_cmd.split(":")         for dev in device_list:             dev.write(cmd_list[1])         # figure out how long to wait before reading the response         timeout = device_list[0].get_command_timeout(cmd_list[1].strip())         # if we dont have a timeout, dont try to read, since it means we issued a sleep command         if(timeout):             time.sleep(timeout)             for dev in device_list:                 print(dev.read())     else:         user_cmd = sys.argv[1]+":r"         try:             cmd_list = user_cmd.split(":")             if(len(cmd_list) > 1):
                addr = cmd_list[0]
                # go through the devices to figure out if its available
                # and swith to it if it is
                switched = False
                for i in device_list:
                    if(i.address == int(addr)):
                        device = i
                        switched = True
                if(switched):
                    aReturn = device.query(cmd_list[1]).split(":")
                    #print(device.query(cmd_list[1]))
                    aReturn[1] = aReturn[1].replace(" ", "")
                    #print aReturn[1],
                    sys.stdout.write(aReturn[1])
                else:
                    print("No device found at address " + addr)
            else:
                # if no address change, just send the command to the device
                print(device.query(user_cmd))
        except IOError:
            print("Query failed \n - Address may be invalid, use list command to see available addresses")
                    
if __name__ == '__main__':
    main()

I use emacs.

sudo apt-get install emacs

emacs -nw /usr/share/cacti/site/scripts/i2c_cacti.py

When you run /usr/share/cacti/site/scripts/i2c_cacti.py you get the following:

Success DO 97 : 7.93
Success pH 99 : 3.636
Success RTD 102 TempProbe: 26.068

/usr/share/cacti/site/scripts/i2c_cacti.py 97
Gives you
7.93
With no new line

sudo apt-get install emacs/usr/share/cacti/site/scripts/i2c_cacti.py