Audible altimeter part 2

Below is notes about the components chosen for the first version of the altimeter and some notes.

• Air pressure changes approximately 1.44kPa / 100m
• Sensor interface: i2c
  • SPI would be easier to interface with, but I2C is better learning experience
  • The USB library I’m planning on using has also I2C module (¹)
• MCU: atxmega128a4u
  • 1.6V-3.6V
  • max 32MHZ @ 2.7V
  • max 12MHZ @ 1.6V
  • max 12mA @ 32MHZ @ 3.0V + 0.5mA from 32MHz internal OSC
  • I/O max 20mA per pin
  • 4.5€ @ Digikey
• Barometer: Freescale: MPL3115A2 (²)
  • Pressure, temperature and altitude
  • 20bit
  • 50kPa – 110kPa (= >4000m – 0m)
  • 0.3m resolution
  • 0.1kPa relative accuracy (changing temperature)
  • Probably not very good for this purpose, but is cheap (2.5€) and gets the project started
  • 6ms-512ms / sample
  • 8.5µA-40µA-265µA@3.3V 1Hz update rate
  • I2C
  • 2.9€ @ Digikey
  • 2V – 3.6V
• Barometer2: Measurement Specialties: MS5805-02BA01
  • 1.8V – 3.6V
• Acceleration/heading: InvenSense MPU-9250 (³)
  • Just for the fun of it
  • Barometer data might be little bit boring while developing
  • 5mA max?
  • I2C
  • 11€
  • 2.4V – 3.6V
• GPS: Linx FM Module
  • http://www.linxtechnologies.com/resources/data-guides/rxm-gps-fm.pdf
  • 3.0V – 4.3V
• GPS: SIM33ELA ?
• GPS antenna: Pulse W3011A
• Hymidity sensor: Silicon Labs 336-2540-1-ND
  • I2C
  • 1.9V – 3.6V
• Clock: Microchip MCP7940M (⁴)
  • MCU could do everything this chip can do, but why not just add another i2c chip?
  • 1.2µA@3.3V timekeeping
  • 0.69€ @ Digikey MCP7940MT-I/MNY MCP7940MT-I/MNYCT-ND
  • I2C
  • 1.8V – 5.5V
• Crystal Oscillator
  • 0805
  • 0.9€ @ Digikey CM315D32768EZFT 300-8816-1-ND
  • +-20ppm
• Display: LS013B4DN04 / LS013B7DH03
  • 32mm x 28mm x ~1.5mm
  • 2.7V – 3.3V
  • 12µW dynamic display @ 1Hz
  • 15€ (Mouser)
• FPS connector
  • SFV10R-2STE1HLF 609-4306-1-ND – Top contacts
  • SFV10R-1STE1HLF 609-4305-1-ND – Bottom contacts <- Use this for 180 bent (under PCB)
  • 0.55€ (Digikey)
  • 0.5mm pitch
  • 0.3mm FPC thickness
  • 0.7€ @ Digikey
• Buzzer
  • CSS-0575A-SMT-TR 102-2201-1-ND
  • 3.7€ (Digikey)
  • 5mm x 5mm x 2.4mm
  • Drive with NPN BJT + 180 OHM + protective diode
  • 3.2€ @ Digikey
  • 2V – 4V
• USB charging IC
  • MCP73831 http://www.digikey.fi/product-detail/en/MCP73831T-2ACI%2FOT/MCP73831T-2ACI%2FOTCT-ND/1979802
  • Sparkfun
  • 0.4€ @ Digikey
• USB connector
  • Micro B
  • 0.4€ @ Digikey 609-4616-1-ND or 609-4618-1-ND
• Micro SD card slot
  • 1.1€ @ Digikey 101-00660-68-6-1-ND
• Flash memory
  • S25FL216K
  • 2.7V – 3.6V
  • SOIC-8
• 3.3V supply IC
  • Linear regulator
  • Reasoning: For 3.3V linear offers ~90% efficiency. 2.7V design would not benefit much more. Switching regulator would require board space and add complexity. Maybe next time.
  • Reasonable transient characteristics? (AND9089-D)
  • 0.7€ @ Digikey NCP4681DSQ33T1G NCP4681DSQ33T1GOSTR-ND
• 400mAh battery: 403035
  • 35mm x 30mm x 4mm
  • 7€ (ebay)
  • 3.7V
  • 2.7V – 4.5V
• Current consumption active:
  • 13mA: MCU
  • 0.3mA: Barometer
  • 5mA: 9Axis
  • 0.001mA: Clock
  • 0.015mA: Display
  • <= 20mA (buzzer not included)
  • = 20h @ 400mAh
• Current consumption waiting:
  • 1mA: MCU (MAX) (active 1MHz)
  • 0.01mA: Barometer
  • 0.015mA: Display
  • <= 2mA
  • >= 1 week
• For 9 month battery life
  • 400mAh / 24309h = 62µA
  • 5µA: MCU (32kHZ)
  • ~1µA LDO
  • 1.2µA: Clock
  • = Should be possible

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