The Energy Directors Jeremy Nash, Chris Lamb, Kelsey Whitesell, Josh Chircus

Milestone 1  One way digital signal transmission through free space  Simple noise filtering  Show functionality of ADC/DAC/SPI  Basic motor movements Milestone 2  2 way signal transmission with ADC/DAC/Encryption/TDM functionality over short distance  Full motor control  Simple alignment functionality Josh

 Full auto-alignment functionality  2 way optical communication of audio signal with ADC/DAC/Encryption/TDM functionality  Package system in an aesthetic structure  Incorporate telephone handset for users to communicate with Josh

Laser setup: Successfully transmitted analog signal using laser diode and photodiode setup at 1ft Signal encoding: Several circuits, including the audio amplifier, summers, laser diode driver, and transimpedance amplifier have been implemented and debugged Motor control: Pseudo code for motor alignment complete, awaiting motor testing PCB layout: Schematic complete. PCB design almost complete. PCBwill be ordered within the week to implement a faster MCU for encoding Josh

Parts Bought Free Parts PartCompanyPrice 10 PhotodiodesThorlabs$130 2 Laser DiodesQPhotonics$120 1 Optical FilterEdmund Optics$125 InvertersDigiKey$10 TOTAL$385 PartCompany 2 Laser DiodesIntense (Kevin Caughlin) 8 Low Noise Op AmpsAnalog Devices 5 MultiplexersDigiKey Josh

EquipmentPurposePrice DEPS Funding$2200 UROP Funding$960 Laser DiodesTransmits encoded information-$120 PhotodiodesDetects laser signal-$130 LensesUsed in alignment system-$125 Inverter$10 Money Left$2775 PCB parts (Original Design, Redesign, Components, etc.) Decodes voltage from photodiode and filters noise$200 Motorized Track Actuators Precision adjustment of photodiodes and lasers for automatic alignment $350 TripodsUsed for Mounting Transceivers$100 Items Left to Purchase650 Josh

 Each transceiver will have an AC-DC power adapter to supply power to the board  Easy to implement  All components run on 15V or less  Allows for system portability  The motors will be powered by a separate AC-DC power supply of 24-36V  Decrease noise feedback from motors Josh

Jeremy

 ADC  12 bit samples  200 ksps (1 sample per 5μs)  Used to digitize audio signal  DAC  12 bit input  Used to convert digital signal to audible signal Jeremy

 1 ADC sample per packet  2 8 bit SPI transactions  12 bits for ADC sample  4 bits for checksum STC UCLK SIMO Jeremy

Input Signal Offset Summer ADC Data Serialization AM H/W Laser + Optics Transimpedence Amplifier Decoding H/W DAC Amplifi er Speaker Input Output (No Load) Input Output (Loaded) Jeremy

 Interrupt driven  Receive Interrupt  Transmit Interrupt  Alignment Interrupt  Interrupts are put into a FIFO buffer and processed Jeremy

 Transmitter  Summer and bias circuits for encoding data  Filters  Laser diode driver and laser diode  MCU  LED indicators, selection and on/off buttons (switches)  Receiver  Photodiodes- receiving and alignment feedback array  Transimpedance amplifier  Audio amplifier with volume control  Bandpass filters  MCU Jeremy Chris Josh Kelsey

 12 bit DAC and ADC  Capable of data encryption  Easy to lay down (64 pins)  4 Synchronous SPI ports  116 KB Flash, 8KB RAM  16MHz clock suitable for audio and digital data processing  Three-channel internal DMA for high-speed memory access in video applications  Disadvantage: No available development boards besides target boards Kelsey

Transmitter

 Linear track actuators for X-Y plane control  Motors: Firgelli Linear Track Actuators ▪ 10’’ stroke length ▪ VDC input ▪ Bracket available separately ▪ in/sec speeds depending on load  Motor drivers: two relays for directional control from the MSP 430; opto-isolators  Pulse-width modulation input Kelsey

 Stepper Motor for tilt control  Use stepper motors from Lin Eng. ▪ High resolution: 0.45 degree step size ▪ High torque ▪ 4 Leads  Pre-assembled motor driver from Lin Engineering ▪ Max. step frequency 2.5 MHz ▪ Optically isolated I/O ▪ See schematic Kelsey

 X-Y control  If receiving photodiode has no current: ▪ check to see if any photodiodes on array have current ▪ If so, PWM linear actuator driver to move transceiver unit a pre- calibrated distance in the x-y plane (positions of diodes stored as 1x2 vectors) ▪ If not, scan up and down in a 5x5 ‘’ window until current is seen in one of the diodes. If no current seen still, scan a 6x6’’ window… then adjust transceiver position  If receiving photodiode has current, no adjustment is necessary Kelsey

 Tilt control (sideways)  Used when one photodiode is receiving and the other is not, indicating a tilted transceiver ▪ Clamped transceivers should help reduce the chances of this problem ▪ Optical encoders cannot be used alone since only one transceiver has a motor and if misaligned, the other transceiver cannot communicate its tilt to the other ▪ Use similar scanning technique as for x-y control  Forward-backward tilt control not possible in our design Kelsey

 Photodiodes – Thorlabs FDS100  nm  High Responsivity in red (650 nm) range  Fast recovery time (35MHz)  Laser Diodes – QPhotonics QLD S  Single mode Fabry Perot laser  1 mW to 14 mW operating range  Pulsed operation with 0.5ns rise time easily allows 5 to 10 MHz modulation bandwidth  Low threshold current (~60 mA) and high slope efficiency  657 nm, +/- 1nm  Operating temperature range -40 o C to +40 o C  Laser Diodes – Intense  5mW - 10mW operating range  650nm, +/- 10nm  Low threshold current (~20 mA)  Operating temperature range 20 o C to 25 o C  Provided free of charge by Intense  Optical Filter – Edmund Optics NT  655 nm center wavelength, 40 nm bandwidth  93% or better transmission  1.25 mm (1 inch) diameter  UV Grade Fused Silica (low reflectance)  Collimating Kit – Optima Precision Inc. LDM-3756  Small, compact size (2 cm), focusable  Low divergence  High transmission of collimated beam, greater than 93%  Simple built-In heat sink Chris

 LIV Curves  Non-ideal nature in power drift may be due to temperature drift. Chris

 IV curve  Linear nature of IV curve suggests that resistance of Laser Diode remains constant throughout operating range. Chris

 Linearity Implies that resistance of photo diode is essentially a constant at all power levels. Chris

 Profile agrees well with the laser diode LIV curves, indicating that the photo diode is detecting the laser diode correctly. Chris

 The shift in responsivity suggests that the wavelength of the laser diode is decreasing due to power shift. Chris

 Op-amp  Must have > 112 V/μs slew rate for 16MHz Operation (LF356N is 12 V/μs)  Must be low noise to preserve digital signal integrity  Speaker Driver  Needed for drawing sufficient current  Optical Issues  Power loss and noise  Difficulties with the beam divergence  Mechanical awkwardness  Awkwardness Chris