Hello World! This is our initial status report, roughly one month into the semester. You can click read more below to get the full scoop:
Realistically, the project has been going on for around two weeks at this point (plus a week of preamble), since we grouped up a week later than most of the other teams. The first week we joined up was dedicated to choosing a project, writing up the abstract, and getting the project proposal slides together. The following week, we presented our project proposal and began refining the concept. This past week has been dedicated towards tightening our project requirements and MVP as per feedback from the course staff.
The MiGroBox team started this week still quite behind on the concept phase of the project. We had not truly settled on an MVP target design nor had we adequately defined our project requirements.
First and foremost, we tackled the overall target features we wanted to include in the project with the goal of slimming down the project concept into an achievable MVP. Automated watering and lighting were a given, so those two features were kept. Temperature and humidity control was cut down to just monitoring. Seeding was kept and slightly expanded to include long term seed storage. Automated harvesting and packaging were entirely removed.
By tightening and better defining our list of features, we were able to much more easily conceive of what specific parts would be required to accomplish each goal. As with the feature list, we slimmed down our parts list practically to the bare essentials.
First on the chopping block was an entire axis of our CNC! Originally, the MiGroBox concept had been a 3-axis CNC design. After discussing what benefits moving in two planar directions provided, we decided it was altogether unnecessary and would only serve to complicate the mechatronic design of the machine. As the MVP now stands, it will only move vertically up and down and horizontally left to right.
Next, we cut down on the number of sensors and actuators needed for the climate monitoring and control requirements. We realized that direct temperature and humidity control was generally unnecessary for the MVP and reduced this requirement down to a single combination temperature and humidity sensor. We kept the requirement for providing ample airflow via PWM fans and realized this feature would also provide sufficient humidity control. Room temperature would be totally acceptable for the MVP as the MiGroBox was being designed for primarily indoor use anyway. We had been discussing water pH sensing and control – a feature that likely would greatly improve yields and plant health – but cut from the MVP. If the initial results with regular tap water prove to be less than acceptable, water system pH control will likely be the primary feature to add later down the line. We also considered adding light sensors but realized they were wholly unnecessary.
Finally, we considered the big ticket features: seeding, harvesting, and packaging. These would be the major aspects of the design that would set it apart from the myriad of “grow boxes” already out on the market. We realized, however, that these features could not all be adequately implemented over the course of just one semester. Rather than trying to do everything poorly, we decided to focus on one of these major features and execute it effectively. We selected seeding, as automating this task seemed to be the most achievable and useful of the three.
Our concept for the “seeding feature” includes a long term seed storage hopper which will actively dispense a single week’s worth of seeds (based on weight) into a smaller distributor hopper. This smaller hopper will hold the seeds as they are rinsed and soaked overnight and will then distribute them over the top of the grow tray. Our MVP seeding feature set does not include replacing the grow medium, as that would drastically overcomplicate the design.
With the featureset tightened, the current list of actuator and sensor parts includes:
- CNC:
- (2) Nema 17 stepper motors (1 per axis, unless that’s too weak)
- (0/2) Endstops (0 = tmc drivers, 2 = minimums with software max)
- Water system:
- (1) Water pump motor
- (1-2) solenoid water manifolds/splitters
- (1) Soil/grow medium moisture sensor
- (>=2) loads cells (1 for feed reservoir, 1 for waste water reservoir)
- Seeding/distributor:
- (2) continuous servo motor
- (3) load cells (1 for big storage hopper, 1 for seeding hopper, 1 for grow tray)
- Air flow/climate control:
- (2) PWM motor fans
- (1) temperature/humidity sensor
- Lighting:
- Full spectrum led strip light strips
Additionally, we will need a main microcontroller (likely an ESP32), a power supply, and a custom main board. A relay board will also be needed if relays are not included in the custom main board.
With nearly 20 actuators and sensors (not to mention the firmware, website, and custom circuitry required), this MVP is pretty involved. Still, we feel this design is achievable and represents the most effective balance between project complexity and feature requirements.
We also received constructive feedback concerning our “wage” requirement metric – namely that it’s a bit over-the-top:
Our TA felt that involving sale prices and profitability into the technical evaluation of the project was a bit unnecessary and recommended we stick to more concrete metrics. As such, we have settled on primarily evaluating our automated results against the manually-grown controls through wage hours and yield ratios (seed weight vs. produce weight). We feel that the overall wage metric is still useful to include as it combines these two measures and also includes insight into the economic and quality factors at play. However, it is fair to say that this metric is a bit too muddy to use as the primary measure of evaluation.
Current Risks and Mitigation:
The most pressing risk currently facing the project is schedule slip. This project started later than most others this semester and we have still not laid down a solid enough system design. Re-working the MVP and slimming down our feature set and parts list has helped get the project moving to pace, but it is still not quite there. We are actively mitigating this by crunching to wrap up the concept and refinements phases of the project within this upcoming week.
What we need to do next:
We are actively wrapping up the MVP system diagrams and will have those ready by the end of this upcoming week. We are also working on trade studies for the various part selections and aim to conclude all such studies within this week. Having reworked our MVP project design and requirements, we will also need to rework some of the specifics of our project schedule and timeline – this too will be settled this week. Finally, we want to get some tangible work done and are thus aiming to kick off the first of many weeks of growing microgreens! We will be submitting our first purchase orders by Monday. These will include orders for seeds, grow medium, and trays as well as some initial electronics that we are confident we will use such as the ESP32 microcontroller and temperature/humidity sensors.