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Environmental Management. Environmental Needs. Maintain internal temp within operating temp of components. Optics: 10 Mp cameras -40 < 0 < 70. Electronics (all temps in C) FPGA 0 < T < 85 Connector Board 0 < T < 70 D3 supplied OEM Board -40 < T < 85
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Environmental Needs Maintain internal temp within operating temp of components Optics: 10 Mp cameras -40 < 0 < 70 • Electronics (all temps in C) • FPGA • 0 < T < 85 • Connector Board • 0 < T < 70 • D3 supplied OEM Board • -40 < T < 85 • Electronics Range • 0C < T < 70C
Environmental Needs • Allow for standard Environmental conditions as defined by MIL-STD-810G and DO-160 Temperature Range: -32C to 45 C (on ground) Humidity: 90%
Power Requirements of Devices MAX POWER= 102.78W
Environmental Management: Heat • Major sources of heat generation inside chassis • Hard drive • about the half the heat produced comes from this • Voltage Regulator • FPGA • DSP • Net Heat generated by system can be estimated using the net power input to the system
Environmental Management:Heat Transfer analysis Heat Transfer model: assuming a steady state • Radiation • Least efficient mode • Model as black body • From electronics to chassis • From chassis to external environment • Model dependant primarily on surface area of components q rad • T Chassis • TAmbient
Chassis wall T chassis T ambient q chassis T chassis q board Board stack T boards Environmental ManagementHeat Transfer: radiation model • Treat enclosure as a black box radiating heat to the outside air • Neglect Convection • Protected from moving air • Neglect Conduction • Temperature at surface of chassis = temperature inside of chassis • Heat radiating from chassis is 50% of heat radiating from boards (qc = .5qb)
Environmental ManagementHeat Transfer: radiation model Used a ‘double’ radiation model • Radiation from electronics to chassis wall • Radiation from chassis wall to outside environment • Combined the two models into one by assuming an efficiency between the heat transfer rate of the electronics and the chassis wall
Environmental ManagementHeat Transfer: radiation model ‘Safe zone’ between ~ 10 and ~ 30 W
Environmental Management : Humiditydew point: should we be concerned with condensation? • Temperature at which water will condense on a surface • Function of ambient temperature and relative humidity • Used to determine whether additional steps should be taken to control temperature/ humidity inside the chassis. • Conclusion: Condensation will not be a big problem • May run into trouble at very high humidities (above 80%) • Dew point is very close to air temperatures
Environmental Managementdew point: should we be concerned with condensation? • Some environmental management techniques may be valuable to prevent condensation at high humidities • Main options: • include a heating system to keep temperature inside the chassis above dew point • reduce humidity inside the chassis to lower the dew point inside the chassis • a common method : silica gel packs
Appendix: Radiation • Assumptions: Treat enclosure as a black box • Neglect Convection • Neglect Conduction • Temperature at surface of chassis = temperature inside of chassis • All Power consumed by electronics is output as heat radiating out • = .89 • qc = .5qb
Appendix: Humidity • Dew point temperature is given as: • Constants defined as follows: • Variables: • Td - Dew point (C) • T - Ambient temperature (C) • RH - Relative humidity (%) • m - Temperature range dependant constant (non-dimensional) • Tn - Temperature range dependant constant (C)
