Incubator

Clent/Contact: David Hale of Windy Meadows Farm
Project: Large-scale incubator to hatch several thousand eggs in various developmental stages

Hatching Cells:

Assumption: The hatching cells will be located in a building which will allow people to enter for interaction, monitoring, repair, etc. Some form of environmental control is possible which may assist the hatching cells. It is not thought that the hatching cells would contain sufficient control headroom to allow them to be operated in a completely independent environment exposed to the elements from a hardiness standpoint. That is, building a weatherproof and tolerant system may be cost prohibitive. Also, though the hatching cells are intended to be autonomous, manual intervention and monitoring is desired for independent and inexpensive redundancy for reliablility and failsafe checking in emergency situations. It is envisioned that a modular, self-contained, and autonomous hatching cell of capacity ~1000 eggs could be built to provide a uniform, conditioned environmnet capable of efficient hatching. Each cell would consist of sensors to monitor multipoint temperature & humidity; and actuators to control hot/cold air inlet, humidity, auxillary heater(s), and fans to provide uniformity of conditions.

Requirements

Considerations

Priorities

DesignProcess

Notes

question: Do some form of corrosive environmental factors need to be considered?

Safety

System safety is defined as keeping the envoronmental conditions in the hatching cell within those bounds which ensure egg viability. Note that this is not necessarily the optimum egg hatching conditions. Excursions of the environmental conditions outside of those required for safe operation constitute alarm situations and invoking of fail-safe mechanisms.

Requirements:

Notes

Requirements

1. Stable and uniform temperatures in egg environment


1. Stable: [98,100] deg. F in normal operation
2. Uniform: +/- 1 deg. F temperature variation throughout the egg environment. This implies some form of air distribution and mixing control (i.e., fan).
3. Maximum Temperature Range: [80 degF for x minutes, 103 degF for 20 minutes] Preference will be given to keeping the eggs cooler than optimal in system failure modes. This will keep eggs viable, but possibly extend the hatching period and/or reduce hatching efficiency (# hatched eggs/ # eggs total). Cooler temperatures will probably extend the battery life and meet its design goal which should be considered subservient to this requirement.

1. Fresh Air exchange: [2,3] /hour is considered adequate. Fresh air must be provided to the eggs to allow for oxygen and waste gas exchange during the growth process. This can be accomplished by turning on a fan to draw fresh air in from the external environment through a baffle.
2. Humidity control: [40,60] %RH


3. Egg turning control: 1 rev/day. A tilt mechanism over an x deg. range may be considered adequate.
4. Reliable (i.e., low MTBF, failures are immediately detected and alarmed, repair w/o bringing down system (hot swap capability) or max system outage X min.
5. Minimize operational expenses


6. Consistent: All data should be easily accessed and displayed to effect effective manual consistency checking. Historical data should be easily accessed for comparison. Consistency checks should be incorporated to validate all data and to detect failed sensors/actuators at the earliest possible time. System diagnostics should be incorporated as a part of normal operation.
7. Safe: Multi-level, multi-redundant arcxhitecture to insue that eggs remain viable.

Considerations

1. Multipoint, distributed temperature sensing
2. Freescale MC9S12NE64xx microcontroller to allow monitoring and PV control via a Web Browser.
3. External temperature monitoring to effect feed-forward conpensation, improve setpoint control, and reduce operating costs. This might also contain seasonal inputs, time of day, and insolation.
4. Adaptable to changes in the configuration of the hatchery (i.e., additions or rearrangement of the facilities and equipment) (flexibility)
5. Battery backup and capable of running X hours on batteries. This implies operation of the cell at the battery voltage and the use of an inverter to convert offline power to charge the batteries. The cell can operate on this inverter while the inverter is operational. This would imply, also, that heaters and fans would operate at the batter voltage.
6. Muliple, modular, self-contained hatching cells w/in large facility vs. single, large, open facility (this might lower operating expenses, allow for improved environmental control in the cells, and make facility modifications easier).

Design Process

1. Requirements


2. System Diagrams

file:///C|/Documents%20and%20Settings/Alvin%20Schatte.FAMILY-R03JP2TL/My%20Documents/Digi-Key-Freescale%20Design%20Contest/Design/System1.eve - This is the system diagram which will invoke the EVE editor file:///C|/Documents%20and%20Settings/Alvin%20Schatte.FAMILY-R03JP2TL/My%20Documents/Digi-Key-Freescale%20Design%20Contest/Design/System%20Diagram.svg - This is the Scalable Vector Graphics (SVG) file which can be specified in an HTML document.




3. Operational charts and screens


4. Define process variables (PV) and measurements

ContestEntry : Submitted 8-15-2005

9-23-2005- Received package indicating that we had been accepted as a finalist in the design contest.

Priorities

Notes

1. Mechanical thermostat override (ultimate failsafe: mechanical thermostat controls power to electronics)
2. Dual uC redundancy with third uC acting as a System Monitor
3. Unanimous voting algorithm with Timeout


4. Independent self-check with System Monitor to override unanimous vote failure (?)
5. Continuous consistency checking


6. Continuous self-diagnostics


7. Assertion testing with abort levels (DBC)
8. Jump to logged reset in unused program space
9. Zoned Watchdog timer (HW?)






1. Serial link between uC


2. RTOS with RTC


3. DO-178B, Misra-C, Code Standards (Jack Ganssele) principles
4. Raw data logging (this will allow failure replay and test recursion via simulation)
5. Trace file


6. Calibration to improve raw sensor accuracy.
7. System hardware operation with recorded raw data (simulation mode)
8. Lantronix design contest for Wireless interconnect (follow on)
9. Oversampling principle to reduce data uncertanty:
confidence interval = x' +/- a*variance/sqrt(n)
where

a - depends on confidence level desired (e.g., a=1.96 for 95%) x' - is the data mean (average)

variance - data variance

n - number of samples in the data