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ECE345 Senior Design Project

ECE345 Senior Design Project. Group 8 Ta: Ajay Patel Presentation : Mahlknecht Stefan Michael Brown. Lasermodem. Why build a Lasermodem?. cheap point to point link connecting different buildings cable links not possible everywhere high data rate Internet access over network.

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ECE345 Senior Design Project

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  1. ECE345 Senior Design Project Group 8 Ta: Ajay Patel Presentation : Mahlknecht Stefan Michael Brown Lasermodem

  2. Why build a Lasermodem? • cheap point to point link • connecting different buildings • cable links not possible everywhere • high data rate • Internet access over network

  3. Characteristics of our Lasermodem • Speed • - from 2400 bps up to 115200 bps • Distance • - Up to 400 m without focusing lens at the receiver • - Up to 3 km with 50mm lens and stable mount • Sight contact between modems needed • decrease in reliability under bad weather conditions

  4. Block diagram : +Vcc Laser driving circuit Laserdiode Voltage regulator Transceiver receive/ transmit TXD Photodiode RS232 converter RTS DTR RXD

  5. Voltage Regulator : •Provides stable 5V output from a range of input voltages

  6. RS 232 converter :

  7. Transceiver component:

  8. Laser driving circuit :

  9. Laserdiode :

  10. Photodiode:

  11. Optics : Light (680 nm) Photodetector PIN - Diode Collimator lens Adjustable mount Convex lens (50 mm) Receiver optics and mount : Light(680 nm) Sender optics and mount : Laserdiode

  12. Software : Initialization procedure: Open com port 9600 Set RTS on low = reset Send initialization string Set DTR on low = control Set DTR on high = data Set RTS back on high Close port Set DTR on low = control

  13. RS232 standard : The standard RS232 waveform : Corresponding logical TTL standard :

  14. IRDA Modulation scheme :

  15. LASERMODEM

  16. Alignment & focus • Tradeoff between alignment and focus: • Focused beam --> Much power at the receiver but • very precise alignment required • Unfocused beam --> Only fraction of beam hits receiver but • alignment not so critical. • Combining the best of both: • Place a convex focusing lens at the receiver ! • Power received ~ Area of lens

  17. Cost Overview Student Labor Cost: Unit Cost Hours Multiplier Total $25 180 2.5 $11,250 Machine Shop Cost: Unit Cost Hours Total $20 10 $200 Cost for two modem Parts $166.40 Parts and Labor $11,616.40 Volume cost Parts $79.80

  18. Experience gained from the Lab: • difficulty getting special parts • long way from idea to a working device • teamwork requires a lot of communication • --> good that we have Email nowadays • handling laser diodes requires special care • difficulty making printed circuit boards • organization and time management very important

  19. Conclusion : The experience gained in this class will help those of us starting in industry. It was long hard work to get all the components we needed for this project, but at the end we were able to present a product that would be ready to enter in the market.

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