Detailed explanations added
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README.md
119
README.md
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@ -7,15 +7,128 @@ In order to make her happy, I decided to make an automatic watering system using
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## List of items needed for the project
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- Raspberry Pi -> any model would work, but for convenience I would choose one with WiFi
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- Raspberry Pi -> any model would work, but for convenience we would choose one with WiFi
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- Breadboard -> a small solderless 400 points one
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- MCP3008 ADC -> as I'm using analog moisture sensors
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- MCP3008 ADC -> as we're using analog moisture sensors
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- Capacitive soil moisture sensors -> the resistive ones would corrode over time
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- 5V Relay module -> one channel per pump is needed
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- 3V-6V Submersible water pump ->
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- Power supply -> I'm using an old AC adapter (12 V, 2 A) that I already had with a female DC adapter
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- Power supply -> we're using an old AC adapter (12 V, 2 A) that we already had with a female DC adapter
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- Fish tank tube -> Several meters, depending on your plants layout, 4 mm diameter transparent tube
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A schematic of how all parts are connected is below:
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<img src="figures/watering_system.png" width="60%" />
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## How the system is connected
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### Moisture sensor
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As the capacitive sensors are not digital, we'll need to transform their analog readout to a digital one, as the GPIO pins on the Raspberry Pi only support digital inputs (distribution of GPIO pins in the raspberry is explained [here](https://pinout.xyz/#)).
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In order to convert digital signals into analog ones, we'll need and ADC, analog-to-digital converter. MCP3008 is a cheap solution for this problem.
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This chip is placed into a breadboard (assuming you know how a breadboard works) to facilitate the input/output of other components. Carefull must be taken positioning the chip, remembering its orientation (chip's pins diagram can be found [here](https://microcontrollerslab.com/mcp3008-8-channel-10-bit-adc-converters-with-spi-serial-interface/)).
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Once the chip is hooked up into the breadboard, we'll proceed to connect it to the GPIO pins in the raspberry:
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- VDD pin is connected to the power rail on the breadboard
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- VREF pin is also connected to the power rail on the breadboard
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- AGND pin is connected to the ground rail on the breadboard
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- CLK pin is connected to GPIO11 (pin #23, a.k.a SPIO SCLK) on the raspberry pi
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- DOUT pin is connected to GPIO9 (pin #21, a.k.a SPIO MISO) on the raspberry pi
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- DIN pin is connected to GPIO10 (pin #19, a.k.a SPIO MOSI) on the raspberry pi
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- CS pin is connected to GPIO5 (pin #29) on the raspberry pi. You could choose any other GPIO pin that has no other function, e.g., GPIO 6, GPIO 17, GPIO27, ...
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- DGND pin is connected to the ground rail on the breadboard
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Still, there is no connection between the chip and raspberry. In order to do so, one has to connected both, power and ground grails to the raspberry pi:
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- Ground rail can be connected to any of the ground pins on the raspberry pi. In our scheme, we chose pin #34
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- Power rail can be connected to any of the 3v3 power pins on the raspberry pi. In our scheme, we chose pin #17
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With all those steps done, now it's time to hook up the moisture sensor into the breadboard. The three outputs of the sensor need to be connected as follow (jumper cables are used for convenience here):
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- The black cable (ground) is connected to the ground rail on the breadboard
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- The red cable (VCC) is connected to the power rail on the breadboard
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- The yellow cable (signal) is connected to any of the MCP3008 chip channel inputs. In our scheme, we chose channel #5 for no particular reason
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That's it for the moisture sensor!
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### Relay and water pump
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If we want to water the plants according to the signal readout by the moisture sensor, we'll need a mechanism that allows a water pump to start and stop watering. This is what a relay allow us to do.
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The relay is connected directly to the raspberry pi as follows:
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- JDVCC pin can be connected to any 5V power pins on the raspberry pi. In our scheme, we chose pin #2
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- VCC pin can be connected to any 3v3 power pins on the raspberry pi. In our scheme, we chose pin #1
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- Ground pin can be connected to any ground pins on the raspberry pi. In our scheme, we chose pin #39
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- In1 pin can be connected to any GPIO pin on the raspberry pi. In our scheme, we chose GPIO21 (pin #40)
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The relay could be tested and you should hear a "click" sound everytime the circuit opens/closes (every second if you use the script `test_relay_on_off` below).
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Once tested, you can attach the water pump to the relay. This step is fairly straighforward (see picture above):
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- The red cable (power) from the pump is connected to the rightmost input of the relay
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- The black cable (ground) from the pump is connected to the negative input of the female DC adapter (which is connected to the power supply)
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+ The positive input of the female DC adapter is connected to the central input of the relay, closing the circuit
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At this point, everytime the relay closes the circuit, apart from the "click" sound, the water pump will start to pump some water until the circuit opens :)
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### Testing the moisture sensor
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Notice that we're using GPIO5 in the board when creating the `cs` object and channel #5 on the MCP chip when creating the `analog_ic` object, respectively:
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```python linenums="1"
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import adafruit_mcp3xxx.mcp3008 as MCP
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import board
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import busio
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import digitalio
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from adafruit_mcp3xxx.analog_in import AnalogIn
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def test_sensor_in_out_water():
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# create the spi bus
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spi = busio.SPI(clock=board.SCK, MISO=board.MISO, MOSI=board.MOSI)
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# create the chip select
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cs = digitalio.DigitalInOut(board.D5)
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# create the mcp object
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mcp = MCP.MCP3008(spi, cs)
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# create an analog input channel on pin 5
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analog_ic = AnalogIn(mcp, MCP.P5)
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try:
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while True:
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print(f"ADC Voltage value: {analog_ic.voltage:.3f}")
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time.sleep(.5)
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except KeyboardInterrupt:
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return
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```
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By running this function, we're getting the following values:
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- Air: 2.153 V
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- Water: 0.677 V
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### Testing the water pump
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```python linenums="1"
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import RPi.GPIO as gp
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import time
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def test_relay_on_off(rly=None):
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# use GPIO numbering
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gp.setmode(gp.BCM)
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gp.setup(rly, gp.OUT)
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gp.output(rly, gp.HIGH)
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try:
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while True:
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gp.output(rly, gp.LOW)
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print("Relay 1 ON")
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time.sleep(1)
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gp.output(rly, gp.HIGH)
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print("Relay 1 OFF")
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time.sleep(1)
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except KeyboardInterrupt:
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gp.cleanup()
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```
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