This is a final year project I am working on with cooperation with Grobotic Systems. The project aims to design and built the first iteration of an open source plant growth chamber that would give the opportunity for Grobotic Systems and university students to develop and reiterate.
Although there are some similar projects that are out there in the open source community, this project will focus on having a lower cost of manufacturing as well as some aspects that are missing from other projects such as heat insulation, multi-spectral lighting system with wall-reflectors and an automated watering system. It will also include the use of an Arduino for data logging to Google drive and controlling chamber conditions.
Ultimately, I aim to create this initiative in the university for other students to develop on the project so that it can reach the initial project I aimed for but could not complete.
The project aims to design and built a plant growth chamber with data logging and a control system with Grobotic Systems, to the open-source community and The University of Sheffield students for further development of the chamber.
Conduct thorough research on how plant growth chambers operate, what are technologies used and potential materials to be used
Design the body of the chamber and HVAC system
Build prototype and test system as well as control system
As mentioned in Chamber Body_3 log, the chamber walls will consist of 3 mm acrylic, 25 polyurethane and 6 mm plywood. Unfortunately, due to the current situation (Covid-19) its not possible to obtain acrylic and plywood and cut them under the designed measurements.
However, as I have obtained polyurethane sheet before the events caused by the corona virus, I was able to assemble the chamber using only polyurethane.
The edges of the base were cut to be 6 mm in thickness, this caused the edges to collapse and therefore i used cardboard to glue the parts together.
to cut properly through polyurethane, hand tools would not be accurate so using water jet cutter could be tried as laser cutting would be dangerous
when cut thin, as shown in the last picture, the material is week and can collapse so thicker cuts must be made allowing at least 10 mm of material thickness
The next steps would be:
operate axial and centrifugal pumps, as well as the thermoelectric cooler through the arduino controller
attach these components to the chamber interior
glue the edges together to close gaps
test the components and the effect of ventilation, stirring fans and insulation
As per the concluding point in Lighting Systems_1 log, the reflective material has been selected ( see Chamber Body_3 : Materials log ). However, the beehive design has been omitted due to its unnecessary complexity but can be adapted in further iterations of the chamber.
After consulting with Grobotic Systems, it was decided that a more basic design of a lighting system should be adapted. Consisting of only 4 LEDs, 2 Far red 730 nm and 2 Full white light, the lighting system should be sufficient to provide the necessary radiation for plants to grow in.
Before the events of the COVID-19 outbreak, the lighting system was halted because of the following:
Other open-source chamber manufacturers don't have issues with the design or operation of lighting systems (except with using reflective surfaces)
Other systems such as HVAC has a higher priority to develop and test
After researching other open-source growth chambers, I concluded that most of them do not use proper insulation. The disadvantage of that is, that the heat transfer from inside the chamber to the atmosphere would be relatively high and thus maintaining a constant temperature would be difficult.
On this basis an insulating material had to be used and fitted inside the walls, base and ceiling of the chamber. Polyurethane foam was chosen because of its wide commercial use, has a high r-value per cm and can be easily cut using sharp tools.
Another important aspect is the reflective properties of the inner side of the walls. Having a high reflective index would mean that the distribution of radiation to the plant would be greater, and therefore the plants would have a better environment to grow in.
Because polyurethane can not be used for this purpose another material had to be chosen; white acrylic. It has the suitable reflective characteristics as well as it is easy to shape using laser cutters.
Finally, for the outer side of the wall, polyurethane alone would be weak and vulnerable against the outer environment and therefore plywood would be used as the an outer shell because of its rigidity, low cost and ease to be shaped.
In conclusion, there would be three layers in the walls, base and ceiling of the chamber:
As concluded in the last Chamber Body log (Chamber Body_1), it would be better to have a design that would have its walls and base lock onto each other instead of having a third component locking them together. On that basis, another design was created as shown in the figures bellow.
The concept of locking the structure is now simpler where:
Both walls are attached to each other in a similar manor to a jigsaw puzzle
Both walls are attached to the base by being slotted in their respective positions
These connections can be supported using glue
Tolerances of manufacturing might affect the assembly of the components
Hope you are all well. Due to the current situation imposed by the COVID-19 virus outbreak, the university has closed all facilities and the government has laid new rules for everyone to stay at home. On this basis, some aspects of the project would not be able to progress, thus the project would now focus more on the development of a HVAC system, testing all the components and insulating material. If the progress of this aspect was fast and I was able to obtain other components, i would be able to develop an irrigation system as well.
However, I will add every component that I would have used before the current circumstances to the Components list on the project page to be available for you.
For the body of the chamber, I decided that I would build it by manufacturing the walls and design them in a way that they would interlock together to form the box-like figure of the chamber.
I came up with different designs and decided to go with the one shown in the figures bellow. Basically, the walls would have cuts at their edges where they would house the shuriken-shaped structures. The shuriken structure, has similar cuts in the edges to interlock with the cuts in wall edges. The shuriken has 4 of these cuts at its 4 edges. The reason for this is to allow the shuriken to be connected to different walls at the same time acting and holding the walls together. The aim was to have the ability to build several chambers at the same time using the shuriken structures.
After the building a small scale prototype, I was able to test the following: 1) ease of assembly, 2) interlocking strength of the shuriken structure, 3) how the box encloses together.
The results where as follows:
1) There was an excessive tolerance between the shuriken and the walls at the cuts/locking area, which made it hard for the whole structure to hold together without tumbling over itself
2) This also made it harder to assemble and was not user friendly at all
3) After connecting it with glue there was spaces between the edges in the corners making the boxes not completely enclosed
1) It would be best to abandon the shuriken structure for holding the box together.
2) It would be better to allow for some sort of glue to be added to the assembly process
3) It would be smarter to connect the walls together without having a third structure facilitating it
I'm currently searching for LEDs specifically full white light, 455 nm blue, 660 nm red and 730 nm far-red LEDs. I got these wavelength values from multiple papers and communicating with Grobotic Systems, which is a smart growth chamber manufacturers. The design in mind is a similar to a beehive, where LEDs of different wavelengths are placed next to each other, each contributing to the total radiation output.
Next I'll be looking for reflective surfaces to attach to the walls to increase the overall light intensity of the chamber.