DHT11 Sensor with RPI

helloworldddd · 2 Nov 2020, 06:50

hello, i am currently working on my side hobby. im fairly new with pyqt, and im stuck in this step for quite sometime. ive created a UI showing the temperature and humidity. i wanted to show more. i want to display a graph on the UI which logs the temperature and humidity every 20 minutes, plotting the average of 20 mins. ive known about plotwidget and matplotlib, but i still cant figure out on how to get the data and draw out the graph. im kinda new to this whole thing. please do be patient with me im just a kid that needs help thanks in advanced !

this is the code i currently have

import Adafruit_DHT
import time
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtCore import *
from pyqtgraph import PlotWidget

sensor = Adafruit_DHT.DHT11
pin = 4

class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(634, 428)
        self.lcdNumber = QtWidgets.QLCDNumber(Dialog)
        self.lcdNumber.setGeometry(QtCore.QRect(220, 40, 271, 131))
        self.lcdNumber.setObjectName("lcdNumber")
        self.lcdNumber_2 = QtWidgets.QLCDNumber(Dialog)
        self.lcdNumber_2.setGeometry(QtCore.QRect(220, 200, 271, 131))
        self.lcdNumber_2.setObjectName("lcdNumber_2")
        self.label = QtWidgets.QLabel(Dialog)
        self.label.setGeometry(QtCore.QRect(26, 42, 161, 131))
        font = QtGui.QFont()
        font.setPointSize(16)
        self.label.setFont(font)
        self.label.setObjectName("label")
        self.label_2 = QtWidgets.QLabel(Dialog)
        self.label_2.setGeometry(QtCore.QRect(30, 190, 161, 131))
        font = QtGui.QFont()
        font.setPointSize(16)
        self.label_2.setFont(font)
        self.label_2.setObjectName("label_2")
        self.widget = PlotWidget(Dialog)
        self.widget.setGeometry(QtCore.QRect(510, 40, 391, 131))
        self.widget.setObjectName("widget")
        self.widget_2 = PlotWidget(Dialog)
        self.widget_2.setGeometry(QtCore.QRect(510, 200, 391, 131))
        self.widget_2.setObjectName("widget_2")
        self.timer = QTimer()
        self.timer.setInterval(5000)
        self.timer.timeout.connect(self.DHTread)
        self.timer.start()
        

        self.retranslateUi(Dialog)
        QtCore.QMetaObject.connectSlotsByName(Dialog)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Dialog"))
        self.label.setText(_translate("Dialog", "Temperature :"))
        self.label_2.setText(_translate("Dialog", "Humidity :"))
        
    def DHTread(self):
        humidity, temperature = Adafruit_DHT.read_retry(sensor,pin)
        print('Temp =', temperature,'*C Humidity =', humidity)
        self.lcdNumber.display(temperature)
        self.lcdNumber_2.display(humidity)


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    Dialog = QtWidgets.QDialog()
    ui = Ui_Dialog()
    ui.setupUi(Dialog)
    Dialog.show()
    sys.exit(app.exec_())

jsulm · 2 Nov 2020, 07:08

@helloworldddd What exactly does not work? Is DHTread(self) called? If so, what does it print?

helloworldddd · 2 Nov 2020, 07:12

@jsulm i cant figure out on how to plot a graph and display it with PlotWidget and pyqtgraph with the values taken from the sensor !

jsulm · 2 Nov 2020, 08:04

@helloworldddd I never used PlotWidget or pyqtgraph and those are not part of Qt.
You should consider reading some documentation/tutorial like https://www.learnpyqt.com/courses/graphics-plotting/plotting-pyqtgraph/
Or check https://doc.qt.io/qt-5/qtcharts-index.html which is part of Qt.

helloworldddd · 2 Nov 2020, 08:12

@jsulm ive also read up on using .csv files to plot the graph by using the values recorded. the examples shown were only fixed values. how do i plot the graph with values that just being recorded ?

jsulm · 2 Nov 2020, 08:15

@helloworldddd said in DHT11 Sensor with RPI:

how do i plot the graph with values that just being recorded ?

Well, use the recorded values instead of the values from csv. I really don't get what exactly the problem is! Can you please be more specific?

helloworldddd · 2 Nov 2020, 08:18

@jsulm how do i get the recorded values and put it into a list and limit the list to like in 2 hour intervals with 20 mins as every point. and the time, which is the x axis to self increment?

jsulm · 2 Nov 2020, 08:27

@helloworldddd said in DHT11 Sensor with RPI:

how do i get the recorded values and put it into a list and limit the list to like in 2 hour intervals with 20 mins as every point

What is your level of experience with programming? Do you know how you can add values to a list in Python? Please don't forget that this is Qt forum not Python... "limit the list to like in 2 hour intervals with 20 mins" - this is simple math to calculate how many elements the list should contain (max).

You never answered my question: "Is DHTread(self) called? If so, what does it print?" Can you please answer it?

helloworldddd · 2 Nov 2020, 08:31

@jsulm like i said im just a newbie with programming. was hoping to find some help here. which incase guess i came to the wrong place. DHTread(self) is called. it just shows the value onto the UI through lcdnumber display

jsulm · 2 Nov 2020, 08:41

@helloworldddd said in DHT11 Sensor with RPI:

DHTread(self) is called

That is good. Now you can add the values to a list (myList.append(myValue)). But it is better to use https://www.oreilly.com/library/view/python-cookbook/0596001673/ch05s19.html in your case as you want to have a list with fixed max size and remove old values if you insert new values into full list.

helloworldddd · J jsulm 2 Nov 2020, 08:31

@jsulm ahhh u could have started with that but thanks so much for your help !

helloworldddd · 3 Nov 2020, 06:03

@jsulm hello, sorry to bother u again. do u know how to use plot values to time, time as x axis on pyqtgraph? im using the command self.widget.plot() i would like to input the x axis value as time instead of a list of number like below. Thanks in advance !

hour = [1,2,3,4,5,6,7,8,9,10]
reading = []  #this is the reading from the sensor

self.widget.plot(hour, reading)

jsulm · wrote on 3 Nov 2020, 06:03

@helloworldddd said in DHT11 Sensor with RPI:

do u know how to use plot values to time, time as x axis on pyqtgraph?

Sorry, I never used pyqtgraph. Did you check its documentation?