Essential Parts of Simple Automatic Control Devices
Any device made with Arduino can be considered a simple automatic control device. There are three essential constituent parts for a simple automatic control device. They are as follows:
An input unit for collecting signals An output unit for sending out signals A control unit for processing the signals received
Let’s draw an analogy between an automatic control device and a human being. In a human being, all signals are imported through sight, hearing, taste, touch and smell, and then transmitted to the brain which outputs responses to each. In this case, the output signal would be actions of the human being.
An Arduino can output responses as well. Output responses that the Arduino is capable of include sound, light and movement (DC Motors, dyanmos, servos etc.)
Here is another way to explain it: imagine someone says “hello” to you, and you immediately reply “hello” in return. In this case, your ear is the input unit; your brain is the control unit and your mouth is the output unit.
How do we carry out this whole process (receiving signals, processing signals and then sending out signals) by using Arduino?
Along with our Arduino, we simply need an acoustic sensor and a buzzer. The acoustic sensor “hears” a sound, the Arduino receives a signal and outputs a signal to the buzzer to buzz. In this case the acoustic sensor is the input unit; the Arduino is the control unit and the buzzer is the output unit.
Can you tell which components in the kit can be used as input units and which can be used as output units?
Input Units - Sensors A sensor (also known as a transducer) is a physical unit whose purpose is to sense or detect the characteristics of its environment (such as light, temperature or moisture levels) and then transmit this data to another device.
Sensor Pin The three categories of sensor pins are as follows: Digital Pin Analog Pin Protocol Pin (Digital)
A protocol pin is also a kind of digital pin. I2C, Serial and SPI are frequently used digital pins.
Control Unit - Arduino The Arduino controller is the control unit. Here we have chosen Arduino UNO as the control unit, which processes signals as if it were the brain of a human being.
Output Unit - Actuators There are various types of actuators. An actuator is a type of device that is responsible for moving or controlling a system or mechanism. It is also the mechanism by which a control system acts upon an environment. It may convert energy into motion, sound or light. A buzzer or speaker can be an actuator that outputs sound.
The Relation Between Code and Hardware The input unit, control unit and output unit mentioned above are all hardware. In the context of our human being analogy, hardware is the body of our device. However, the brain is much more important as it produces ideas and then controls actions every human being takes. Code here functions as the mind of a human being. Both body and mind are indispensable to a human being.
Digital Signal & Analog Signal in the Electronic World The input unit, the Arduino controller and the output unit communicate by signals, which in turn are processed by code. How do input units and controllers communicate with each other? How do controllers communicate with the output units? To answer the above questions, we first need to understand two concepts: digital signal and analog signal.
Differences between Digital Signal & Analog Signal Digital Signal: The digital signal has two states: “HIGH” or “LOW”. “HIGH” is a 5V signal and represents “1” (or on). “LOW” is a 0V signal and represents 0 (or off). Analog Signal: The analog signal can have any value in a certain range. In Arduino’s analog pins, any value between 0V and 5V is mapped to a range between 0 and 1023. For instance, 0 is mapped as 0V; 1023 is mapped as 5V and 512 is mapped as 2.5V.
“Digital” & “Analog” in DFRobot Kit Here are two ways to tell whether sensors in your DFRobot Kit are digital or analog:
(1 )If a sensor has a green wire it uses digital signal; if a sensor has a blue wire it uses analog signal.
(2 )Letter “A” or “D” may be marked on the sensor’s board. “D” represents “digital” and “A” represents “Analog”.
IO Extension Board V7.1 Now let’s take a look at the I/O extension board. A function diagram of the extension board is shown below. We mainly use the I/O extension board to connect sensors.
Analog and digital pins are marked on the extension board. The area with “A” is for analog sensors, and the area with “D” is for digital ones.
The advantage of the I/O extension board is that there are more power and ground pins on the extension board than those on the Arduino board. This way you’ll have enough power pins for connection to various sensors at the same time.
On the extension board, there are a row of power pins in red and a row of GND pins in black below the digital pins.
Different colors shown in our DF Kit have different meanings: Green = digital signal Blue = analog signal Red = power Black = ground