Difference between revisions of "Team:Newcastle/Circuitry"
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Revision as of 09:15, 13 September 2018
Alternative Roots
Circuitry
Stage One
Powering
There is two options for powering this device via the mains or from a battery source. I have designed it so both can be used if the other isn’t available. However I would recommend using the mains as batteries need to be replaced regularly. Since the Arduino and LED lights need a constant 5V supply once the batteries have drained to roughly 3.5V the lights start to fade and do not operate as designed. Also we used 4 cheap AA 1.5V which totals to 6V, meaning a voltage regulator is needed to protect the circuit. This regulator can get hot after sustained use, I believe this is due to the lights drawing 1.5 Amps. However for a small demonstration this is sufficient. Therefor a more permanent and reliable source would be the mains. Taking a regular phone charger which safely steps the voltage down to 5V we have a power source for the Arduino to use. I would not recommend building your own. Usually there is live (Vdd), ground (GND), and two data lines (-D, +D) the latter two are not necessary for our application. When powering the Arduino a capacitor is needed to put in parallel, this protects it from surges in voltage which could otherwise damage it.
ROUGHLY
AMPS ARE PULLED
FOR THE WHOLE SYSTEM
APPROXIMATELY
KWH OF POWER ANNUALLY
USED TO POWER SYSTEM
PROVIDES UP TO
LUX OF LIGHT
TO GROW SEEDS
CONTAINS
INDIVIDUALLY ADDRESSABLE
LOW-POWER LED'S
Stage Two
Control
Having identified the design parameters for the system, the next stage was to begin ordering parts and putting it together. The system was divided into three independent, functional sub-systems to make the task of assembling the system more manageable and allowing team members to focus on the sub-system that most suited their specialty. These three sub-systems were hardware, software and biological aspects.
The function of the hardware is to contain the electronics and organisms, power the LED’s/microcontroller and maximise the light available to the plants. Containment is through the use of a sealed box, with a detachable lid for access. This box is glued with tin foil and sprayed black to minimise exchange of light with the environment. Powering the LED’s proved to be more difficult, taking our engineers many days to find the optimal solution. You can find all the grizzly details on this process here. However, essentially the system is powered from a 5V 2.1A AC adapter that plugs straight in to your mains power supply. Alternatively, you can use 4 AA batteries to power the system for short periods of time if necessary. The LED’s are wired in parallel so the same light is provided along the length of the container. This can be seen from images in the Gallery.
The purpose of the software is to control the LED’s, by allowing the user to easily adapt features such as light intensity, wavelength and also specify the length of the day/night cycle. For our design, we use the Arduino UNO microcontroller to control these characteristics as it offers a user-friendly interface and is well-suited to our design. You can find all the code laid bare and a guide to the Arduino here.
The engineers, hard at work trying to troubleshoot issues with the system.
The finished product, set to a rainbow function that cycles through various wavelengths of light
Stage Three
LED Wiring
Substantial time was spent carrying out extensive research, both inside and outside the lab, in order to optimise the system for the target audience. This included speaking with organisations and individuals in industry who are involved with hydroponics-based systems or those who may be interested in working with such a system in the future. Some of the individuals we liaised with include Chris Tapsell, the Research Director of KWS UK, one of the biggest seed companies in the world, and Richard Ballard, co-founder of Growing Underground in London where they hydroponically grow micro greens and salad leaves 33 metres below the ground. These potential clients helped us focus our product so that it can better meet the needs of our clients.In addition to gathering external opinion on our system, we also did our own tests on system performance. This included tests to verify the optimal light intensity, wavelength and positioning. The graph below illustrates how the light intensity (measured in lux) varies over time (in seconds) when the system is operated under various wavelengths of light. The black line indicates the system running with the rainbow function loaded which cyclically varies the light wavelength. As the results showed that blue, red and purple light and provided the most lux we are currently using these in the system but plan to use the rainbow function too in future to see how this affects growth or the aesthetics of the plant.
