Skip to content

Procedures Description

Jump to bottom Edit New page
fruby edited this page Jun 19, 2013 · 13 revisions
  1. [External part] (https://github.com/hsgr/pom/wiki/Procedures-Description#external-part)
  • Open and close of covers
  • open and close of PVPs
  1. [Plants Cycle] (https://github.com/hsgr/pom/wiki/Procedures-Description#plants-cycle)
  1. [Electronics] (https://github.com/hsgr/pom/wiki/Procedures-Description#electronics)
  1. [Energy] (https://github.com/hsgr/pom/wiki/Procedures-Description#energy)

Plants Cycle

The plants cycle starts from the planted seeds inside the selected material (rock-wool, hail cubes or clay pebbels) in each pot.

The temperature and the humidity are checked by sensors and can be stabilized. The resistance, placed on the cylinder, regulates the temperature in a range between 10 and 20 degrees Celsius. Dehumidifier controls the humidity at most up to 75%.

The plants, under the right environment and provided with CO2 and water-droplets, grow and produce new seeds and oxygen. When they are fully grown (45 days for spinach), the [razor harvest] (https://github.com/hsgr/pom/wiki/Procedures-Description#harvest) them in order to be dried and keep the produced seeds in a good condition.

Aeroponics

TODO: write it

Watering

Water, mixed with ingredients, transforms into micro-droplets and feeds the roots of the plant inside the spiral container. The ratio of mixed fertilizers (NPK and micro-nutrients), hydrogen peroxide (liquid oxygen) and pH-up or pH-down is monitored and controled by the auto-doser system and the inputs that gets from the several sensors and the arduino.

Starting from the water tank, the water is pumped and pushed into the spiral tube at the dome. The created pressure enable the sprinklers that shape and let micro-droplets (5-50μm) in the spiral container. The inclined surface of the spiral container drives the water at the center spiral. There the water goes through the hole and the connected tube back at the water tank by completing the cycle.

Oxygen Harvest

Collection and storing of the oxygen produced by plants is performed by means of a VPSA oxygen concentrator. The absorption system mainly consists of a tower filled with zeolite molecular sieve absorbents and piping valves, etc. Air enters via the top of the tower and passes through the absorbent layer where CO2 and moisture are absorbed by molecular sieve. Oxygen passes through the absorbents freely, concentrates at the bottom of the tower and ends stored in an oxygen tank under pressure. The pressure within the tanks is monitored by using manometers.

Plant Harvest

TODO:write it!!

CO2

The CO2 serves three different functions in our system. The first one is to participate at the photosynthesism the second one is to help pneumatic system to open and close the covers and finally the third use is to clean the PVPs from the dust.

Electronics

The main component of our system is a AVR ATmega2560 in custom PCB.We selected this hardware unit, firstly to be able to use as many input and output pins as we need, secondly because of it's low-power consumption. The big community that supports it (AVR-Arduino) is also an advantage.Another option would be to use a micro-processor for all that functions which will through an operating system will provide us extra security in functionality. It will also Provide flexibility in programming different situations and functions.A possible operating system will be a real time Linux system.

The subsystems are the sensors that mostly communicate via I2C protocol, the actuators which are controlled either with the PWM method or with simple I/O pin and the power distribution system which supplies 5 Volts and 3.3 Volts and has an input of 12 Volts (Solar panels and batteries hybrid system).

Actuators

Actuators are used to function the doser system (5 parts),the pneumatic system of shell movement (8 parts) and 7 more for air and water valves whose function described in other section. They use the PWM communication method and simple I/O (ON-OFF) to be controlled. Three identical circuits ,shown in the schematic, drive the three modules. Each circuit consist of a power MOS transistor, a diode for the protection of the circuit and a capacitor to minimize the noise. The specs for the components of doser system are shown here: http://www.ebay.com/itm/Marine-Magic-Replacement-Aquarium-dosing-pump-head-/281030701506?pt=LH_DefaultDomain_0&hash=item416ebc31c2.

For the pneumatic air and other valves we need 12 Volt DC operation voltage and low-power consumption.

The Fan, which is a simple computer one, is connected directly on 12 Volt supply as it functions continuously.

The pin mapping for coding with arduino IDE is shown here: http://arduino.cc/en/Hacking/PinMapping2560.

Dosing Pump (x5)
-PWM:2,3,4,5,6

Pneumatic Air Valve 12V DC (x8)
-I/O:29,30,31,32,33,34,35,36

Other Air and Water Valve (x7)
-I/O:22(water),23(air),24(air),25(air),26(air),27(air),28(air)

Fan
-Connect direct in 12V

Heating Resistor
-I/O:37 (Drive 2N2222 which drives a relay or drives a power MOS transistor with ID > 50A)

Sensors

IMU (MPU-6050)
Description: It measures the pitch and the roll angles of the capsule.
URL:https://www.sparkfun.com/products/11028
PIN Mapping: PIN20(SDA),PIN21(SCL), PIN3(INT1)
Input voltage:3.3 Volts
I2C protocol

Barometric Pressure Sensor (BMP085)
Description: It measures the pressure inside the capsule.
URL:https://www.sparkfun.com/products/11282
PIN Mapping: PIN20(SDA), PIN21(SCL)
Input voltage:3.3 Volts
I2C protocol

Humidity and Temperature Sensor (HIH6130)
Description: It measures the humidity and temperature inside the capsule.
URL:https://www.sparkfun.com/products/11295
PIN Mapping: PIN20(SDA), PIN21(SCL)
Input voltage:5 Volts
I2C protocol

Light sensor (VCNL4000)
Description: It measures the luminosity, to sense if it's day or night.
URL:https://www.sparkfun.com/products/10901
PIN Mapping: PIN20(SDA), PIN21(SCL)
Input voltage:3.3 Volts
I2C protocol

CO2 Sensor (K-30)
Description: It measures the CO2 inside the capsule.
URL:http://www.co2meter.com/products/k-30-co2-sensor-module
PIN Mapping: PIN20(SDA), PIN21(SCL)
Input voltage:5 Volts
I2C protocol

EC-Meter sensor
Description: This component is not our preferable one as it does not connect  through i2c.
We prefer i2c in order to have all the sensors on the same bus. We would use another one,
but we couldn't find any till now.
URL:http://www.practicalmaker.com/documentation/ec-shield-documentation

Radiation sensor (to do list)
Description: we use part of the sensor described above to fulfill the sensing of radiation
of our system.
URL:http://www.cooking-hacks.com/index.php/documentation/tutorials/geiger-counter-arduino-radiation-sensor-board#intro

PH-Sensor (pH-Stamp)
Description: It measures the PH to control the dosing pumps for aeroponics.  
URL:https://www.sparkfun.com/products/10972 
PIN Mapping: pin14(RX3), pin15(TX3)
Input voltage:5 Volts
Serial protocol

Terminal MicroSwitch
Description: It is useful for the control(closing) of pneumatic air valve of shell movement.
URL:https://www.sparkfun.com/products/9414  
PIN Mapping:36,37,38,39
Input voltage:5 Volts
I/O

The reason for selecting the I2C protocol for the communication of our subsystems is that it's a usual selection of NASA for such space applications (so it is tested a lot) and that the specs of the protocol highly cover the requirements of our system without spending resources.

Power Source System

This system consists of two voltage regulators. The first one has an input voltage of 12 Volts and an output of 5 Volts with maximum current of 500 ma (http://www.onsemi.com/pub_link/Collateral/MC78M00-D.PDF) and the second one has an input of 5 Volts (from the first) and an output of volts with maximum current of 150 ma (http://www.micrel.com/_PDF/mic5205.pdf).

Energy

Consumption

TODO: write the table with the needs of everything

Production

TODO: write about the efficiency of the PVP+++ calculations

Automatic Systems

Startup

Assuming working temperature in the beginning, the capsule is good to go in normal operation mode, as soon as its landing is complete.

Normal operation automation

  • Day/Night detection and system cycling

The day or night state is determined according to the daylight sensor measurements, with an algorithm tolerant to short-timed lighting or occlusion events According to the day/night state detection, the outer shell of the greenhouse opens or closes as needed, and the desired oxygen levels and O2 management (storage of oxygen surplus, release of oxygen during night) are adjusted.

  • Aeroponics nutrient solution management

The nutrients doser pumps fertilizer to the nutrient/water solution according to its current pH value.

  • Atmosphere humidity management

In case of low humidity, the aeroponics nutrient solution sprinklers are activated. In case of excess humidity, the dome atmosphere’s humidity is reduced by gradually replacing the internal earth-like atmosphere with Mars' dry CO2 atmosphere, thereby removing the need for a dehumidifier. If, due to atmosphere replacement, the O2 concentration is too low, the O2 composition management system inhibits the dehydration procedure until the oxygen composition is safe again

  • Atmosphere O2/CO2 composition management

The O2 management. depends on the day/night cycle state. During the day: -When the O2 level is too low, the dome valve is blocked until is is safe to open again -When there is an O2 surplus, the VPSA is activated to store it in the O2 tank, taking care to clean the VPSA filter before each use

  • Aeroponics dome pressure control

If there is no dehydration sequence running, the external dome valve is set to deflate or inflate the dome according to the atmosphere pressure measurements

  • Master heating control

The whole mission capsule is kept at a stable temperature range, appropriate for spinach growth(20 to 23 deg. Celsius) by means of a heating resistor and the automation microcontroller’s role as a thermostat.

After complete spinach growth

After a predefined amount of time (about when the plants are fit for harvesting) the harvester mechanism is enabled, and when harvesting is finished, the dehydration phase begins.

Dehydration The temperature, daylight detection, pressure control and shell control systems keep working, the humidity control system is set to alternately replace the internal air with the martian atmosphere, and adjusting the dome pressure with the external valve(atmosphere composition no longer is an issue). The other aeroponics systems(doser, sprinkler, O2 tank and valve) are disabled. Eventually, the capsule atmosphere ends up as mostly CO2 at earth-like pressure and temperature, so the seeds are properly preserved until a human or robotic operator comes to retrieve them later in the future. Also, the capsule systems are kept in operational condition to facilitate a new plant growth and harvesting cycle, in a possible later stage of the space project the PoM greenhouse is part of.

Implementation

The microcontroller code implementing the required automatic mechanisms is located in the project's 'arduino automation directory'; a port of the code to a more efficient platform (a TI MSP430 microcontroller based solution, for example) is also supported, as the high level automation logic code is separated from raw I/O code. Additionally, a detailed description of the implementation is provided in the project's 'diagrams' directory in the form of flowcharts, so non-technical people can also easily study the logic and suggest improvements or extensions.

Add a custom footer
Add a custom sidebar
Clone this wiki locally