pythonmodbuspymodbus

Python loop for modbus


i have a modbus tcp/ip calorimeter from which i get values 1 or 0..

Each time calorimeter reaches 10kw it signals "0" otherwise its 1

In python i want script to run all the time and record / calculate each 10 kilowats.

Example:

Current kw: 260000 (manually read it from calorimeter and enter it to python)

Signal "0" (reached 10kw) - time 10:23

Signal "0" (reached 10kw) - time 10:35

Signal "0" (reached 10kw) - time 10:41

current kw: 260030
times reached 10kw: 3x

Problem is that when calorimeter reaches 10 kilowats it signals multiple zeros at same time and python sums all of them instead of only 1

Example:

1
1
1
1
0 (calorimeter reaches 10kw)
0
0
0
0
1
1
1

What should i do so i could read only first zero for each signal or how else could i calculate this?

Current code:

from pymodbus.client import ModbusTcpClient
from datetime import datetime

IP = '192.168.22.95'
client = ModbusTcpClient(IP)

current_kw = 260000

while True:

    a = client.read_holding_registers(0, 1)
    b = a.registers

    if b[0]==0:
        date = datetime.now()
        current_kw += 10
        print (current_kw, "kW")

Solution

  • Good way to solve this would be by keeping the status from previous reading and adding 10 kW only if previous state was 1.

    Set the new variable

    client = ModbusTcpClient(IP)
    last_state = 1
    current_kw = 260000
    

    And check for change in status in the if

    if b[0]==0 and last_state==1:
    

    Don't forget to set the variable on the end of while loop to last read state.

    last_state=b[0]
    

    Final code would look like this.

    from pymodbus.client import ModbusTcpClient
    from datetime import datetime
    
    IP = '192.168.22.95'
    client = ModbusTcpClient(IP)
    last_state = 1
    current_kw = 260000
    
    while True:
    
        a = client.read_holding_registers(0, 1)
        b = a.registers
    
        if b[0]==0 and last_state==1:
            date = datetime.now()
            current_kw += 10
            print (current_kw, "kW")
        last_state=b[0]