Smart Gardening #2: Concept Design by drawing Block Diagram

Last time, we studied the fundamental data to collect by a commercial Three-way meter (last Smart Gardening blog post). So, let’s review it again and start a DIY concept design in a smarter by drawing a block diagram.

Recap: Three-Way Meter, weblink

This three-way meter device can measure three different type of data and display them on an analog meter with a switch. One good thing about it is a battery-free device.

  1. Light Sensor
  2. Moisture
  3. pH
  4. Analog Display

Here is a smarter way to measuring gardening data with Arduino. Arduino is a low-cost micro-controller which can control sensors electrically and monitor the live data.

This is a list of components as the first prototype. We would like to design this with very minimal knowledge of electronics.

  1. Arduino Micro: Arduino Micro with headers
  2. 4-line display: SunFounder IIC I2C TWI Serial 2004 20×4 LCD Module Shield
  3. Light Sensor: Digital Light Intensity Photosensitive Sensor Module
  4. Soil Moisture Sensor: DFROBOT Gravity: Analog Capacitive Soil Moisture Sensor- Corrosion Resistant
  5. Temperature and Humidity Sensor: BME280 I2C or SPI Barometric Pressure and Altitude Sensor

This time, I decided not to use pH meter because there is not a low cost pH meter and we don’t measure pH very often. However, I may be wrong, so I will try to include it in the next version. In addition, as the three-way meter is a battery free device, it is good to add a small solar panel to charge the device in the next version.


Engineers usually draw block diagrams to share ideas as a Proof-of-Concept prototype. Microsoft Visio is a good software tool including business flowcharts and electronics block diagram as part of the software package.

This block diagram is very simple, and it shows that Arduino Micro is the brain of this smart gardening prototype ver 1.


I2C is a standard bi-directional two-line communication between a micro-controller and sensor including SCL (Clock) and SDA (Data).

SPI is another standard three or four uni-directional wires including SCLK (clock), MISO (Master Input Slave Output), MOSI (Master Output Slave Input), and CS (Chip Select).

Analog voltage is the voltage level that the sensor outputs to a microcontroller, so microcontroller’s ADC (Analog to Digital Converter) can quantify the voltage level which is based on sensor’s quantity (ex: soil moisture level and light luminance).

Next, I would like to start wiring and soldering to connect all components.

green scientist
Love travel, running, engineering, and gardening. Exploring new parks.

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