Difference between revisions of "Team:Newcastle/Circuitry"

 
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                        LED wiring
 
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                <p class="about-para">Once the project idea was finalised, the team began looking for cheap, efficient and standardised methods for growing plants in iGEM. The hope was that such an item existed that would meet these specifications as well as being a closed container to prevent contamination and also providing a high throughput of plants. It was soon established that such an item did not exist to meet our specifications. Therefore, to combat this issue, it was decided that the best way forward would be to design our own hydroponics system. This would allow us to grow large amounts of Arabidopsis in a controlled setting for the purposes of our project. Several team members were assigned to this “sub-project”.</p>
 
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                <p class="about-para">Before getting hands-on in building the system, the team as a whole established a few design parameters. For example, the system needed to be cheap and easy to build from scratch. This is so future iGEM teams are able to construct the system for their own needs and even build upon our design, as necessary. Additionally, the system must be versatile, open-source and easily adapted for various conditions such as light intensity and wavelength. By adopting such an open and adaptable design the intention is that the end-user is able to effortlessly match the system to their needs, without getting entangled in streams of code.</p>
 
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                <p class="about-para">Several weeks were spent modifying the design until a design was found that met all the above criteria, the specifications of the design can be seen below.</p>
 
  
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                <p class="about-para">When creating an electrical circuit there needs to be a decision made for as to how this system is powered. There are two options available: mains (AC), or battery (DC). To increase the flexibility of the system it was designed to be able to use both power sources; however, we recommend the use of mains power due to the limited capacity of batteries. The Arduino and LED lights draw a constant 5 V, therefore the system requires at least four 1.5 V AA batteries, giving a nominal 6 V. To protect the circuit this would require a voltage regulator, which can overheat with a sustained 1.5 A current drawn for the LEDs.  Given the constant drain on the batteries, the system does not perform well when the supply voltage drops below 3.5 V. To address this problem, we adapted a regular USB phone charger, which safely steps down mains to 5 V. We do not recommend building your own version of this!<p>
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<p class="about-para">In a phone charger cable there are usually four wires; live (Vdd), ground (GND), and two data lines (-D, +D). The latter two are not necessary for our application due to their voltage rating, shown in Figure 1A (2.76V, 2.06V). Therefore, these wires can be either trimmed shorter than Vdd and GND or taped up, to avoid a short circuit in the system. For the example shown in Figure 1B; red is power, black is ground, white and green wires are the data lines, however it is good practice to confirm this is by checking the voltage from Vdd, D+ or D- to ground with a multi-meter.</p>
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                <p class="about-para">When powering the Arduino, a capacitor is needed in parallel to protect it from surges in voltage, which could otherwise damage it. In order to protect the LED lights, there needs to be small 330 Ω resistor on the data line. A circuit diagram can be found in Figure 1C, which details the correct set up.</p>
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                    <p class="about-para">The LEDs used also took a 5V DC power supply, which was one of the justifications for using this particular product, as it means that they can be powered from the same source as the Arduino.</p>
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                    <p style="text-align:center"><br>Figure 1A. Schematic of a standard USB cable [1].</p>
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                    <p style="text-align:center"><br>Figure 1B. Above is 4 exposed wires. Red is power, black is ground,white and green are the data lines [1].</p> 
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                    <p style="text-align:center"><br>Figure 1C. Schematic demonstrating how to power the Arduino and the LED's, made on fritzing [2].</p>
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                 <h5>UP TO</h5>
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                 <h5>ROUGHLY</h5>
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                 <div class="stats__count">1344</div>
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                 <div class="stats__count">2</div>
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                 <h5>SEEDS CAN BE GROWN</h5>
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                 <h5>AMPS ARE PULLED</h5>
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                 <h5>IN HYDROPONICS</h5>
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                 <h5>FOR THE WHOLE SYSTEM</h5>
 
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                 <h5>LUX OF LIGHT</h5>
 
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                 <h5>TO GROW SEEDS</h5>
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                 <h5>TO GROW SEEDLINGS</h5>
 
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                 <h5>LOW-POWER LED'S</h5>
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                 <h5>LOW-POWER LEDS</h5>
 
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<p style="font-size:100%">Stage two of the build was to be able to control the day and night cycle (16-8 hours) to allow proper plant growth. One method to implement this would be to break the circuit from the ‘Vdd’ line (power line). We decided to pursue this method as it would reduce the power consumption when the night cycle was in effect.</p>
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                    <p style="font-size:100%">In order to break the power line there needs to be two pin outs, pin 11 for the data line and 12 for the switching circuit. 11 determines the light intensity and function of the lights. After a 16 hour cycle pin 12 is written to ‘LOW’ (logic zero), which turns a N channel power MOSFET off for 6 hours. This sequence would repeat every day.
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                    <p style="font-size:100%">We encountered  some issues when implementing this design, which appeared to be caused by the Arduino’s pin out voltage of 3.3V. Despite the MOSFET’s threshold voltage being between 1-2V [3], it should be adequate. However, the voltage at the source (MOSFET output) was measured to be 3V,  and the LEDs need at least 4.2V.</p>
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                  <p style="font-size:100%">This meant that we had to go back to the drawing board. Our second iteration was based on a NAND gate; the truth table shown below illustrates the function of the gate.</p>
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                <p style="font-size:100%">Highlighted in red are the two functions we are interested in. Since ‘Vdd’ will always be read as ‘high’, 5V, we can eliminate the first two states. The basic operation is inverting P12 logic. When implemented in our device, the logic worked as predicted; however, the 2A current demand of the LEDs caused the gate to heat up and become unstable in its operation. Iteration three involved the implementation of a relay switch; however, this was also limited in terms of the current drawn and overheated. In our final iteration we discovered we could achieve the desired result through the code. Changing the brightness from a defined integer, to an 8 bit integer, allowing a range between 0-255. Setting the brightness to ‘0’ would turn the LEDs off. The code can be seen<body link="blue"><a href="https://2018.igem.org/Team:Newcastle/Software/NH1" class="black"> here.</a></p></body>
  
  
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                    <p style="font-size:100%">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.</p>
 
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                    <p style="font-size:100%">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.</p>
 
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                    <p style="font-size:100%">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.</p>
 
 
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                     <p style="text-align:center"><br>The engineers, hard at work trying to troubleshoot issues with the system.</p>
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                     <p style="text-align:center"><br>Figure 2A. The engineers, hard at work trying to troubleshoot issues with the system.</p>
 
                      
 
                      
 
                      
 
                      
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                     <p style="text-align:center"><br>The finished product, set to a rainbow function that cycles through various wavelengths of light</p>
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                     <p style="text-align:center"><br>Figure 2B. The finished product, set to a rainbow function that cycles through various wavelengths of light</p>
 
                      
 
                      
 
                      
 
                      
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                    <font size="4" font face="verdana" font color="green">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.</font><br><br>
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                    <font size="4" font face="verdana" font color="green">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.
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                  <p><font size="4" font face="verdana" font color="green">The final device has 5 LED strips spaced equally across the lid to give a constant light level for the seeds. These strips are connected in parallel to one another, which means they are in sync with one another. From the point of view of the LEDs the data line (pin 11) appears the same. In order to allow the lid to be removable we fed the wires through a hole on the side of the lid, which was soldered onto a vero-board where a crimp housing was connected. Allowing us to unplug the lid and remove it when the hydroponic solution was added. This reduces the potential for water damage to the lid. As an extra precaution, we insulated the exposed metal contacts on the LEDs and vero-boards, with a hot glue gun which also adds structural security.</font></p>
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          <p style="text-align:center"><font color="green"><br>Figure 3.0; Image of parallel wiring layout and insulated contacts</p>
 
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<p class="about-para"><font size="3"><b>Attributions: Luke Waller, Umar Farooq</b></p>
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                  <p><font size="3"><b>1.</b> Ada Fruit, "icharging", 5 Aug 2010; 'https://learn.adafruit.com/minty-boost/icharging', 5 Aug 2010.</p>
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<p><font size="3"><b>2.</b> Arduino Basics; 2 Jul 2015, https://arduinobasics.blogspot.com/2015/07/neopixel-playground.html </p>
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<p><font size="3"><b>3.</b> Rapid; 'https://www.rapidonline.com/pdf/162663_da_en_01.pdf' </p>
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Latest revision as of 00:15, 18 October 2018

Alternative Roots/Circuitry

Alternative Roots

Circuitry

Power Control LED wiring

Stage One

Powering

When creating an electrical circuit there needs to be a decision made for as to how this system is powered. There are two options available: mains (AC), or battery (DC). To increase the flexibility of the system it was designed to be able to use both power sources; however, we recommend the use of mains power due to the limited capacity of batteries. The Arduino and LED lights draw a constant 5 V, therefore the system requires at least four 1.5 V AA batteries, giving a nominal 6 V. To protect the circuit this would require a voltage regulator, which can overheat with a sustained 1.5 A current drawn for the LEDs. Given the constant drain on the batteries, the system does not perform well when the supply voltage drops below 3.5 V. To address this problem, we adapted a regular USB phone charger, which safely steps down mains to 5 V. We do not recommend building your own version of this!

In a phone charger cable there are usually four wires; live (Vdd), ground (GND), and two data lines (-D, +D). The latter two are not necessary for our application due to their voltage rating, shown in Figure 1A (2.76V, 2.06V). Therefore, these wires can be either trimmed shorter than Vdd and GND or taped up, to avoid a short circuit in the system. For the example shown in Figure 1B; red is power, black is ground, white and green wires are the data lines, however it is good practice to confirm this is by checking the voltage from Vdd, D+ or D- to ground with a multi-meter.

When powering the Arduino, a capacitor is needed in parallel to protect it from surges in voltage, which could otherwise damage it. In order to protect the LED lights, there needs to be small 330 Ω resistor on the data line. A circuit diagram can be found in Figure 1C, which details the correct set up.

The LEDs used also took a 5V DC power supply, which was one of the justifications for using this particular product, as it means that they can be powered from the same source as the Arduino.


Figure 1A. Schematic of a standard USB cable [1].


Figure 1B. Above is 4 exposed wires. Red is power, black is ground,white and green are the data lines [1].


Figure 1C. Schematic demonstrating how to power the Arduino and the LED's, made on fritzing [2].

ROUGHLY
2
AMPS ARE PULLED
FOR THE WHOLE SYSTEM
APPROXIMATELY
70
KWH OF POWER ANNUALLY
USED TO POWER SYSTEM
PROVIDES UP TO
1700
LUX OF LIGHT
TO GROW SEEDLINGS
CONTAINS
120
INDIVIDUALLY ADDRESSABLE
LOW-POWER LEDS
================================================== -->

Stage Two

Control

Stage two of the build was to be able to control the day and night cycle (16-8 hours) to allow proper plant growth. One method to implement this would be to break the circuit from the ‘Vdd’ line (power line). We decided to pursue this method as it would reduce the power consumption when the night cycle was in effect.

In order to break the power line there needs to be two pin outs, pin 11 for the data line and 12 for the switching circuit. 11 determines the light intensity and function of the lights. After a 16 hour cycle pin 12 is written to ‘LOW’ (logic zero), which turns a N channel power MOSFET off for 6 hours. This sequence would repeat every day.

We encountered some issues when implementing this design, which appeared to be caused by the Arduino’s pin out voltage of 3.3V. Despite the MOSFET’s threshold voltage being between 1-2V [3], it should be adequate. However, the voltage at the source (MOSFET output) was measured to be 3V, and the LEDs need at least 4.2V.

This meant that we had to go back to the drawing board. Our second iteration was based on a NAND gate; the truth table shown below illustrates the function of the gate.

Vdd Pin 12 Output
0 0 1
0 1 1
1 0 1
1 1 1

Highlighted in red are the two functions we are interested in. Since ‘Vdd’ will always be read as ‘high’, 5V, we can eliminate the first two states. The basic operation is inverting P12 logic. When implemented in our device, the logic worked as predicted; however, the 2A current demand of the LEDs caused the gate to heat up and become unstable in its operation. Iteration three involved the implementation of a relay switch; however, this was also limited in terms of the current drawn and overheated. In our final iteration we discovered we could achieve the desired result through the code. Changing the brightness from a defined integer, to an 8 bit integer, allowing a range between 0-255. Setting the brightness to ‘0’ would turn the LEDs off. The code can be seen here.


Figure 2A. The engineers, hard at work trying to troubleshoot issues with the system.


Figure 2B. The finished product, set to a rainbow function that cycles through various wavelengths of light

================================================== -->

Stage Three

LED Wiring

The final device has 5 LED strips spaced equally across the lid to give a constant light level for the seeds. These strips are connected in parallel to one another, which means they are in sync with one another. From the point of view of the LEDs the data line (pin 11) appears the same. In order to allow the lid to be removable we fed the wires through a hole on the side of the lid, which was soldered onto a vero-board where a crimp housing was connected. Allowing us to unplug the lid and remove it when the hydroponic solution was added. This reduces the potential for water damage to the lid. As an extra precaution, we insulated the exposed metal contacts on the LEDs and vero-boards, with a hot glue gun which also adds structural security.


Figure 3.0; Image of parallel wiring layout and insulated contacts





References & Attributions

Attributions: Luke Waller, Umar Farooq

1. Ada Fruit, "icharging", 5 Aug 2010; 'https://learn.adafruit.com/minty-boost/icharging', 5 Aug 2010.

2. Arduino Basics; 2 Jul 2015, https://arduinobasics.blogspot.com/2015/07/neopixel-playground.html

3. Rapid; 'https://www.rapidonline.com/pdf/162663_da_en_01.pdf'