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| # Reading PZEM-004t power sensor (new version v3.0) through Modbus-RTU protocol over TTL UART | |
| # Run as: | |
| # python3 pzem_004t.py | |
| # To install dependencies: | |
| # pip install modbus-tk | |
| # pip install pyserial | |
| import serial | |
| import modbus_tk.defines as cst | |
| from modbus_tk import modbus_rtu | |
| # Connect to the sensor | |
| sensor = serial.Serial( | |
| port='/dev/PZEM_sensor', | |
| baudrate=9600, | |
| bytesize=8, | |
| parity='N', | |
| stopbits=1, | |
| xonxoff=0 | |
| ) | |
| master = modbus_rtu.RtuMaster(sensor) | |
| master.set_timeout(2.0) | |
| master.set_verbose(True) | |
| data = master.execute(1, cst.READ_INPUT_REGISTERS, 0, 10) | |
| voltage = data[0] / 10.0 # [V] | |
| current = (data[1] + (data[2] << 16)) / 1000.0 # [A] | |
| power = (data[3] + (data[4] << 16)) / 10.0 # [W] | |
| energy = data[5] + (data[6] << 16) # [Wh] | |
| frequency = data[7] / 10.0 # [Hz] | |
| powerFactor = data[8] / 100.0 | |
| alarm = data[9] # 0 = no alarm | |
| print('Voltage [V]: ', voltage) | |
| print('Current [A]: ', current) | |
| print('Power [W]: ', power) # active power (V * I * power factor) | |
| print('Energy [Wh]: ', energy) | |
| print('Frequency [Hz]: ', frequency) | |
| print('Power factor []: ', powerFactor) | |
| print('Alarm : ', alarm) | |
| # Changing power alarm value to 100 W | |
| # master.execute(1, cst.WRITE_SINGLE_REGISTER, 1, output_value=100) | |
| try: | |
| master.close() | |
| if sensor.is_open: | |
| sensor.close() | |
| except: | |
| pass |
Hi,
works like a charm, thanks for sharing.
Regards.
Please, can you help? (new to RS485 )
Traceback (most recent call last):
File "test4.py", line 28, in
data = master.execute(1, cst.READ_INPUT_REGISTERS, 0, 10)
File "/usr/local/lib/python3.7/dist-packages/modbus_tk/utils.py", line 39, in new
raise excpt
File "/usr/local/lib/python3.7/dist-packages/modbus_tk/utils.py", line 37, in new
ret = fcn(*args, **kwargs)
File "/usr/local/lib/python3.7/dist-packages/modbus_tk/modbus.py", line 306, in execute
response_pdu = query.parse_response(response)
File "/usr/local/lib/python3.7/dist-packages/modbus_tk/modbus_rtu.py", line 46, in parse_response
raise ModbusInvalidResponseError("Response length is invalid {0}".format(len(response)))
modbus_tk.exceptions.ModbusInvalidResponseError: Response length is invalid 0
Check the rx tx pin & try to cross the cable in your USB to TTL dongle
This works like a charm. Thx for sharing. I'm using this in a statistics project for my outdoor spa.
Regards !
Thank you for this effort! Worked like a charm on my version 3 board under Linux. Great to test the board before moving it to Raspberry Pi monitoring system (Domoticz) to be certain it was working.
Cheers!!
hello to all, i'm trying to conect my pzem004t v3 to HA to get the readings, but i don't understand how and where to put your file?
Can you explain to me, please?
Hello, first of all, thank you for your work. I used your code and it works perfect. In this moment, I want to expand my current work I want to use three PZEM sensor. I looked into the modbus_tk library documentation but it is not clear to me a way to read data from three sensors in the same channel. I would be grateful if you could support me in this project. Thank you very much.
Hello, first of all, thank you for your work. I used your code and it works perfect. In this moment, I want to expand my current work I want to use three PZEM sensor. I looked into the modbus_tk library documentation but it is not clear to me a way to read data from three sensors in the same channel. I would be grateful if you could support me in this project. Thank you very much.
Hi, Felix. I'm glad you found this useful.
If you have 3 sensors communicating over UART (let's say using USB to UART adapters on a PC/Raspberry Pi), then you need 3 separate UART channels (3 USB to UART adapters). Then you will have three sensors defined like this:
sensor1 = serial.Serial(
port='/dev/ttyUSB0',
baudrate=9600,
bytesize=8,
parity='N',
stopbits=1,
xonxoff=0
)
sensor2 = serial.Serial(
port='/dev/ttyUSB1',
baudrate=9600,
bytesize=8,
parity='N',
stopbits=1,
xonxoff=0
)
sensor3 = serial.Serial(
port='/dev/ttyUSB2',
baudrate=9600,
bytesize=8,
parity='N',
stopbits=1,
xonxoff=0
)
The /dev/ttyUSBX definition for the assigned ports is just an example. This may vary on your system.
Then apply modbus initialization and commands on each sensorX object separately.
Cheers.
Wow, thanks connermacleod69!! That's great info to have at hand. Would you mind sharing what model(s) from the catalog you have used?
Merci @bandaangosta !
this only print the data once right and not a loop? what does the .close() method do?
this only print the data once right and not a loop?
Hi, @FujiwaraKengo . That is correct, data is printed out only once and then the scripts ends, closing the communication channel. You could put the reading part in a loop (lines 27 to 43), allowing for a reasonable waiting time between iterations, or call the full script periodically.
Can this script be modified for usage with Windows? Changing "/dev/PZEM_sensor" to the comport of the FTDI-cable results in
Traceback (most recent call last):
File "g:\PZEM-004T\pzem_004t.py", line 27, in <module>
data = master.execute(1, cst.READ_INPUT_REGISTERS, 0, 10)
File "c:\Users\Bart\AppData\Local\Programs\Python\Python310\lib\site-packages\modbus_tk\utils.py", line 39, in new
raise excpt
File "c:\Users\Bart\AppData\Local\Programs\Python\Python310\lib\site-packages\modbus_tk\utils.py", line 37, in new
ret = fcn(*args, **kwargs)
File "c:\Users\Bart\AppData\Local\Programs\Python\Python310\lib\site-packages\modbus_tk\modbus.py", line 356, in execute
response_pdu = query.parse_response(response)
File "c:\Users\Bart\AppData\Local\Programs\Python\Python310\lib\site-packages\modbus_tk\modbus_rtu.py", line 46, in parse_response
raise ModbusInvalidResponseError("Response length is invalid {0}".format(len(response)))
modbus_tk.exceptions.ModbusInvalidResponseError: Response length is invalid 0
Yes, I checked the Tx-/Rx-connections.
edit: Hmm, seems it does this when there are no readings (didn't connect AC-side), I am getting output when AC-side is connected. So I added an try/except for modbus_rtu.ModbusInvalidResponseError and an if-statement to check if data contains something.
Now to figure out how to change the address from Python.
edit: data = master.execute(1, cst.WRITE_SINGLE_REGISTER, 2, output_value=2)
seems to do that :)
Please, can you help? (new to RS485 )
Traceback (most recent call last):
File "test4.py", line 28, in
data = master.execute(1, cst.READ_INPUT_REGISTERS, 0, 10)
File "/usr/local/lib/python3.7/dist-packages/modbus_tk/utils.py", line 39, in new
raise excpt
File "/usr/local/lib/python3.7/dist-packages/modbus_tk/utils.py", line 37, in new
ret = fcn(*args, **kwargs)
File "/usr/local/lib/python3.7/dist-packages/modbus_tk/modbus.py", line 306, in execute
response_pdu = query.parse_response(response)
File "/usr/local/lib/python3.7/dist-packages/modbus_tk/modbus_rtu.py", line 46, in parse_response
raise ModbusInvalidResponseError("Response length is invalid {0}".format(len(response)))
modbus_tk.exceptions.ModbusInvalidResponseError: Response length is invalid 0