In this lesson we show how to detect light levels with a Raspberry Pi and a photoresistor. The photoresistor is connected in a voltage divider to the ADC0834 AD converter, which then connects to the Raspberry Pi. The schematic of the circuit is below:
In this video lesson we show how to create a programmable temperature alarm using the Raspberry Pi, the DHT11 sensor, the ADC0834, a potentiometer and a buzzer. The results are displayed on a LCD1602 LCD display with a i2c connection. The device operates in either program mode or monitor mode. Pressing the button puts you in programming mode. In this mode you turn the potentiometer until your desired set temperature is reached. Then pressing the button again will switch you to monitor mode. In monitor mode the current temperature and humidity are displayed on the LCD. When the temperature exceeds your setpoint, the buzzer will release an audible alarm. Below is the schematic for our build.
In this video lesson, we show how to create a dimmable LED on the raspberry pi using a potentiometer. Below is the schematic of the circuit we will be using.
Then we used the following code to read values through the ADC0834 analog to digital chip, and then apply a PWM signal to control the brightness of the LED.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | import RPi.GPIO as GPIO import ADC0834 import time GPIO.setmode(GPIO.BCM) LEDPin=23 GPIO.setup(LEDPin,GPIO.OUT) myPWM=GPIO.PWM(LEDPin,1000) myPWM.start(0) ADC0834.setup() try: while True: analogVal=ADC0834.getResult(0) print('Raw= ',analogVal, 'Vol= ', analogVal/255*5) DC=analogVal*100/255 myPWM.ChangeDutyCycle(DC) time.sleep(.2) except KeyboardInterrupt: GPIO.cleanup() print('GPIO Good to Go') |
We will be using the Sunfounder Ultimate Raspberry Pi kit in all these lessons. You can pick your kit up HERE. In order to use the ADC0834 Analog to Digital converter in your projects, you must have the following library installed on your system. In order to do this, you need to copy the code below. Then create a new program on your Raspberry Pi, and paste the code. Then the code should be saved as ‘ADC0834.py’ in the SAME folder you will be running your main python program from. Also, you may save the program in the default python library file on the raspberry pi. To do this, you can save the file to:
/usr/lib/python3.7/ADC0834.py
Note the above includes the path and the file name. Using this is a better option, as any program on python3.7 should find the library here.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 | #!/usr/bin/env python3 #----------------------------------------------------- # # This is a program for all ADC chip. It # convert analog singnal to digital signal. # # This program is most analog signal modules' # dependency. Use it like this: # `import ADC0834` # `sig = ADC0834.getResult(chn)` # # *'chn' should be 0,1,2,3 represent for ch0, ch1, ch2, ch3 # on ADC0834 # import RPi.GPIO as GPIO import time ADC_CS = 17 ADC_CLK = 18 ADC_DIO = 27 # using default pins for backwards compatibility def setup(cs=17,clk=18,dio=27): global ADC_CS, ADC_CLK, ADC_DIO ADC_CS=cs ADC_CLK=clk ADC_DIO=dio GPIO.setwarnings(False) GPIO.setmode(GPIO.BCM) # Number GPIOs by BCM mode GPIO.setup(ADC_CS, GPIO.OUT) # Set pins' mode is output GPIO.setup(ADC_CLK, GPIO.OUT) # Set pins' mode is output def destroy(): GPIO.cleanup() # using channel = 0 as default for backwards compatibility def getResult(channel=0): # Get ADC result, input channel sel = int(channel > 1 & 1) odd = channel & 1 # print("sel: {}, odd: {}".format(sel, odd)) GPIO.setup(ADC_DIO, GPIO.OUT) GPIO.output(ADC_CS, 0) # Start bit GPIO.output(ADC_CLK, 0) GPIO.output(ADC_DIO, 1) time.sleep(0.000002) GPIO.output(ADC_CLK, 1) time.sleep(0.000002) # Single End mode GPIO.output(ADC_CLK, 0) GPIO.output(ADC_DIO, 1) time.sleep(0.000002) GPIO.output(ADC_CLK, 1) time.sleep(0.000002) # ODD GPIO.output(ADC_CLK, 0) GPIO.output(ADC_DIO, odd) time.sleep(0.000002) GPIO.output(ADC_CLK, 1) time.sleep(0.000002) # Select GPIO.output(ADC_CLK, 0) GPIO.output(ADC_DIO, sel) time.sleep(0.000002) GPIO.output(ADC_CLK, 1) time.sleep(0.000002) GPIO.output(ADC_CLK, 0) time.sleep(0.000002) # ODD # GPIO.output(ADC_CLK, 0) # GPIO.output(ADC_DIO, channel) # time.sleep(0.000002) # GPIO.output(ADC_CLK, 1) # GPIO.output(ADC_DIO, 1) # time.sleep(0.000002) # GPIO.output(ADC_CLK, 0) # GPIO.output(ADC_DIO, 1) # time.sleep(0.000002) dat1 = 0 for i in range(0, 8): GPIO.output(ADC_CLK, 1); time.sleep(0.000002) GPIO.output(ADC_CLK, 0); time.sleep(0.000002) GPIO.setup(ADC_DIO, GPIO.IN) dat1 = dat1 << 1 | GPIO.input(ADC_DIO) dat2 = 0 for i in range(0, 8): dat2 = dat2 | GPIO.input(ADC_DIO) << i GPIO.output(ADC_CLK, 1); time.sleep(0.000002) GPIO.output(ADC_CLK, 0); time.sleep(0.000002) GPIO.output(ADC_CS, 1) GPIO.setup(ADC_DIO, GPIO.OUT) if dat1 == dat2: return dat1 else: return 0 def getResult1(): return getResult(1) def loop(): while True: for i in range(4): res = getResult(i) print ('res{} = {}'.format(i,res)) time.sleep(0.1) time.sleep(1) if __name__ == '__main__': # Program start from here setup() try: loop() except KeyboardInterrupt: # When 'Ctrl+C' is pressed, the child program destroy() will be executed. destroy() |
Unfortunately the Raspberry Pi has no built in Analog to Digital converters for reading analog voltage values. So, what was a very easy task on the arduino becomes a more difficult task on the Pi. However, many applications and projects on the pi require reading analog values. In order to do this, we must interface to a ADC0834 Analog to Digital Converter chip. The video above provides in depth description of how to do this, but the resources below should also help you.
You can click on the image for a closer view of the diagram.
In order to use the chip, you will need to install a python library on the raspberry pi. Create a python file on your raspberry pi, and name it:
ADC0834.py
You must name it exactly that. Note the 0 in the above file name is a zero. Now copy and paste the following code into the file:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 | #!/usr/bin/env python3 #----------------------------------------------------- # # This is a program for all ADC chip. It # convert analog singnal to digital signal. # # This program is most analog signal modules' # dependency. Use it like this: # `import ADC0834` # `sig = ADC0834.getResult(chn)` # # *'chn' should be 0,1,2,3 represent for ch0, ch1, ch2, ch3 # on ADC0834 # import RPi.GPIO as GPIO import time ADC_CS = 17 ADC_CLK = 18 ADC_DIO = 27 # using default pins for backwards compatibility def setup(cs=17,clk=18,dio=27): global ADC_CS, ADC_CLK, ADC_DIO ADC_CS=cs ADC_CLK=clk ADC_DIO=dio GPIO.setwarnings(False) GPIO.setmode(GPIO.BCM) # Number GPIOs by BCM mode GPIO.setup(ADC_CS, GPIO.OUT) # Set pins' mode is output GPIO.setup(ADC_CLK, GPIO.OUT) # Set pins' mode is output def destroy(): GPIO.cleanup() # using channel = 0 as default for backwards compatibility def getResult(channel=0): # Get ADC result, input channel sel = int(channel > 1 & 1) odd = channel & 1 # print("sel: {}, odd: {}".format(sel, odd)) GPIO.setup(ADC_DIO, GPIO.OUT) GPIO.output(ADC_CS, 0) # Start bit GPIO.output(ADC_CLK, 0) GPIO.output(ADC_DIO, 1) time.sleep(0.000002) GPIO.output(ADC_CLK, 1) time.sleep(0.000002) # Single End mode GPIO.output(ADC_CLK, 0) GPIO.output(ADC_DIO, 1) time.sleep(0.000002) GPIO.output(ADC_CLK, 1) time.sleep(0.000002) # ODD GPIO.output(ADC_CLK, 0) GPIO.output(ADC_DIO, odd) time.sleep(0.000002) GPIO.output(ADC_CLK, 1) time.sleep(0.000002) # Select GPIO.output(ADC_CLK, 0) GPIO.output(ADC_DIO, sel) time.sleep(0.000002) GPIO.output(ADC_CLK, 1) time.sleep(0.000002) GPIO.output(ADC_CLK, 0) time.sleep(0.000002) # ODD # GPIO.output(ADC_CLK, 0) # GPIO.output(ADC_DIO, channel) # time.sleep(0.000002) # GPIO.output(ADC_CLK, 1) # GPIO.output(ADC_DIO, 1) # time.sleep(0.000002) # GPIO.output(ADC_CLK, 0) # GPIO.output(ADC_DIO, 1) # time.sleep(0.000002) dat1 = 0 for i in range(0, 8): GPIO.output(ADC_CLK, 1); time.sleep(0.000002) GPIO.output(ADC_CLK, 0); time.sleep(0.000002) GPIO.setup(ADC_DIO, GPIO.IN) dat1 = dat1 << 1 | GPIO.input(ADC_DIO) dat2 = 0 for i in range(0, 8): dat2 = dat2 | GPIO.input(ADC_DIO) << i GPIO.output(ADC_CLK, 1); time.sleep(0.000002) GPIO.output(ADC_CLK, 0); time.sleep(0.000002) GPIO.output(ADC_CS, 1) GPIO.setup(ADC_DIO, GPIO.OUT) if dat1 == dat2: return dat1 else: return 0 def getResult1(): return getResult(1) def loop(): while True: for i in range(4): res = getResult(i) print ('res{} = {}'.format(i,res)) time.sleep(0.1) time.sleep(1) if __name__ == '__main__': # Program start from here setup() try: loop() except KeyboardInterrupt: # When 'Ctrl+C' is pressed, the child program destroy() will be executed. destroy() |
This file, ADC0834.py, should then be put in the following directory:
/usr/lib/python3.7/
Moving or copying the file to that directory might require use of Sudo if you get a permissions error.
Now the following code will allow you to read the analog value coming from the potentiometer in the above circuit diagram:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | import RPi.GPIO as GPIO import ADC0834 import time GPIO.setmode(GPIO.BCM) ADC0834.setup() try: while True: analogVal=ADC0834.getResult(0) print(analogVal) time.sleep(.2) except KeyboardInterrupt: GPIO.cleanup() print('GPIO Good to Go') |