Basic Aquatic Shield

The Basic Aquatic Shield senses the general settings of a small habitat. This can be a fish tank, an indoor greenhouse or a large aquaponics setup. My shield uses some lower-end sensors and outputs the data to an LCD screen.

The concept was combined by me after i started to adjust another led-growth-experiment. I was trying to grow some of the easiest aquatic plants in a tropical open water aquarium. The setup was quite complex and potentially dangerous as light levels increased.

I searched for a way to monitor all the basics “ the easy way “ After looking around the web i found a plant care concept from seed studios. Tried to duplicate the system, but found some errors in the code. The hardware also made me second ges myself a couple of times. Testing each component gave me a better understanding but i left this system before expensive parts were needed.

Going over the components gave me more details and that lead to the B.A.S. It’s made up around a arduino Nano and uses a ‘ old style ‘ nokia LCD. The sensors include a moisture sensor, a humity / temperature sensor and a light sensor. Extra components are used to increase the stability and protect the MCU.

This is a DIY project so costs were kept low and some parts like the sensorwires were recycled from old computers, Most parts however were ordered from small webstores that provid good support and fast services.
These are the major components ;

• USB Nano V3.0 ATmega328 16M 5V Micro-controller
• 84*48 LCD Module Blue backlight adapter pcb for Nokia 5110
• Soil Hygrometer Detection Module + Moisture Sensor
  
• DHT11 - Digital Temperature and Humidity Sensor
• TEMT6000 Light Sensor

2 september 2016

Step 1: Part 1 - Soil Hygrometer Detection Module

The moisture sensor that i used was a standard type that consist of a probe and a amplifier board. This board increases the analog sensitivity from 8 to 10 bit. The board needs a 5V supply voltage and has both a analog and digital output. But in my setup i used the analog port that simular hygrometers have. I connected the unit to A1.

In my application the probe is used as a water level detector. More information and references can be found in the pdf that i made.

During testing i noticed that the grey-metal layer of the probe started to corrode. This lead to unstable readings after about 2 weeks. To overcome this problem I soldered two metal pins on the probe. This modification also failed because the roods were also corroding.

Step 2: Another Sensor to Add

Getting more details from the conditions surrounding my Leds was also one of the goals. For this I didn’t go for an analog option and chose to use a familiar digital sensor. The DHT 11 from D-Robotics is a very good option. It includes a resistive-type humidity measurement component and an NTC temperature measurement component, and connects to a high-performance 8-bit micro controller.There are many pro’s to this sensor and there is plenty of data out there to increase the usability. The sensor is connected to D7

Data from the sensor is sent over a one-wire protocol and has to be processed via a library.

More information is listed is the pdf that i made.

Step 3: Getting It Out There .. and the Libs

Using a display played a big role in the initial testing. I used to love my old Nokia ‘ mobieltje ‘ and again, many pro’s. Unfortunately it came with a lot of coding issues. The big pro of this LCD is it’s very low pin count vs resolution. I took some time to transfere the ADA fruit demonstration sketch to the standard SPI – 2 connections. One can call this a 4 + 3 wire configuration including 1 for backlight. The hardware was also adapted for pulse wise powering the display with 3 volt.

For proper programming you have to install these libs ;

• Adafruit P8544 Nokia LCD

• Adafruit GFX

• DHT

• SPI

Using libraries keeps the coding simple and clean for further use..Just follows the trail from the PDFs

Step 4: One More Sensor

Sensing light sounds easy but is quite unique. One should know that sunlight has a large spectrum and our eyes are sensitive to certain wavelengths. All plants have special ‘ tools ‘ that process light of other wavelengths in the bleu and red area.

If one wants to detect light from an artificial, single point source it’s important to know that the source has a mechanical apex angle. Lights with a low apex angle, like halogen bulb, can produce higher lux levels. This is also the reason that our eyes can get damaged by these sources.

Detecting light with a lux sensor is quite simple under normal condition but my goal was simple to have a general value of the strength. So i went for a small ambient light sensor from Vishay semiconductors.

My version of the TEMT6000 sensor had a analog output and operates at 5V. ( 3 connections )

Please feel free to look at the code again.

Step 5: Playing With Parts

If you want to copy my design you'll need to buy the following mechanical parts ;

• 1 x 6x8cm Double side Protoboard Circuit Universal DIY
• 2 x 16 Pin Single Row Female Straight Header Strip 2.54mm Pitch
• 7 x 4 Pin Header Male 2.54 mm Pitch
• 1 x Dupont female - female 4 pins header cable
• 1 x Dupont female - female 8 pins flatcable
• 1 x Switch for LCD background
• 1 x 9V battery clip

And the smaller parts that are in the schematic design.

I'm Beta testing the second PCB and the layout will be reveiled..
The code is available via mail..

Some details :

• The resolution of the DHT 11 is 1 degree celsius
• Use a flatcable for the LCD screen
• SPI lib is needed for the LCD
• The CS pin from the LCD is connected to ground

Step 6: The PCB

This is the layout that i came up with. The PCB is working fine but the readings from the moisture probe are not reliable. I'm still testing a second modification.