IoT enabled sensor node

The goal of the project is developing a low-power Internet-of-Things (IoT) enabled smart sensor node that is capable of generating, processing, and storing locally generated sensor data (i.e. position, identification, sensory info, etc.) and communicating through optical means to an optical wireless communication (OWC) hub.

=Problem Definition=

event 5G will provide extended wireless connectivity and capacity, it is expected that massively deployed IoT devices will require data traffic that would not be met by only RF based wireless technologies. The wireless connectivity based on wide optical bands, termed as Optical Wireless Communication (OWC), is considered to be promising solution for the development of high density and high capacity 5G and IoT networks of the future. In comparison to RF-based networks, OWC-based network technologies offer unique advantages such as high data rate, low latency, high security, and low energy consumption without interfering with RF communication channels.





=Background= The life of a citizen of the early 21st century takes place simultaneously in physical and cyber space. In couple of years more than 50 billion devices will connect more than 7.6 billion people with exponentially increasing connectivity demand. As the demand for data heavy wireless applications and services are increasing, the RF spectrum will get more congested resulting in slower wireless browsing or worse. This necessitates communication service technology to shift from fourth generation (4G) to fifth generation (5G). It is expected that the 5G will be deployed many part of the world by 2020. Comparing with the 4G, the 5G will offer new services with high quality of services (QoS) and quality of experience (QoE), high user capacity (1000x), higher data rates (100x), lower power (10x), and lower latency.





=Deliverables=

Figure 1. Envisioned IoT enabled sensor node with Optical Wireless Communication (OWC).

Minimum expectation is to design and verify a compact IoT enabled optical transceiver sensor nodes that could respond to commands received from OWC hub in visible spectrum, achieving up to 10m optical wireless communication (OWC) distance and more than 100Kb/s upload data rate with less than 10-3 BER as shown in Figure 1. Transmitter unit has to be able operate with off-grid power sources (i.e. battery) for extended period of time (i.e. weeks), and should be compact enough to be deployed remote locations. The unit should have smart processing (i.e. MCU), storage (i.e. store sensory data every hour for a month), and integrated sensor(s) (i.e. temperature, humidity, etc.). Available development

=Specifications=

=Design Solution=


 * System Diagram


 * Component Selection & Sizing

System Diagram
Algorithm


 * Transmitter




 * Receiver




 * Summary



Component Selection & Sizing
LED


 * [[File:2019_Flash-IoT_Copy_of_LEDS_example_and_material_(1).pdf]]





Lens holder





Operational Amplifier


 * [[File:2019_Flash-IoT_opa2846.pdf]]
 * [[File:2019_Flash-IoT_MT-037_opamp_offset_voltage.pdf]]

Photodiode


 * [[File:2019_Flash-IoT_opt101.pdf]]
 * [[File:2019_Flash-IoT_Copy_of_Two_example_data-sheets_of_Photodiodes.pdf]]
 * [[File:2019_Flash-IoT_BPX_61,_Lead_(Pb)_Free_Product_-_RoHS_Compliant-318809.pdf]]





Details in the TIA module



LED driver
 * The goal of the LED driver is to switch LED at high frequency(>200kHz).
 * An inverter was used as the LED driver to optimize the digital signal.





Photodiode receiver


 * The goal of the photodiode receiver is to amplify the signal of photodiode by 100dB and suppress the noise from the ambient room light


 * The circuit contains:
 * Transimpedance Amplifier
 * Ambient Light Filter
 * Sallen-key Filter
 * Schmitt Trigger Inverter

Initial circuit design



Output of TIA/AMF



Output of TIA/AMF



Final output



Photodiode receiver
 * We tested our photodiode in serial with a 100k Resistor
 * The voltage across the resistor can roughly indicate the magnitude of photodiode current
 * The inverter is used to digitalize the signal





=Project Equipment= Photodiode





LED





Lens Holder





=Project Learning=

Literature interview



Engineering analysis

Tests



Software Learning



Circuit design problems
 * LED driver
 * The inverter can not drive high current if we use high power LED
 * PD receiver
 * Nulling voltage offset is an issue
 * Noise from wire connection and break

Design problems
 * Very short communication range(2cm)
 * High power LED maybe not affordable and efficient in terms of power

Picture





Transmit signal with different duty cycle
 * Input




 * Output



=Final Design=

Final design block diagram





Final schematic for TR module







LED Transmitter
 * Changes we made in our final design:Connect multiple inverters in parallel to drive more current

Photodiode Receiver
 * Changes we made in our final design:
 * 1) Use a TIA module existed in the market
 * 2) Adjustable Gain:from 100dB to 141dB
 * 3) Gain Bandwidth: 1 MHz
 * 4) Voltage supply:+/-5V--15V
 * 5) Remove Ambient Light Filter
 * 6) Implement a bandpass optical filter at 450nm
 * 7) Implement the similar function using a subtractor

Sketch



=Validation=

=Team Members=

=Additional Documentation= Budget



Client Interview



Circuit Design



Project Schedule



Project Equipment


 * Photodiode


 * 1) [[File:2019_Flash-IoT_opt101.pdf]]
 * 2) [[File:2019_Flash-IoT_Copy_of_Two_example_data-sheets_of_Photodiodes.pdf]]
 * 3) [[File:2019_Flash-IoT_BPX_61,_Lead_(Pb)_Free_Product_-_RoHS_Compliant-318809.pdf]]


 * OPAMP


 * 1) [[File:2019_Flash-IoT_opa2846.pdf]]
 * 2) [[File:2019_Flash-IoT_MT-037_opamp_offset_voltage.pdf]]


 * LED


 * 1) [[File:2019_Flash-IoT_Copy_of_LEDS_example_and_material_(1).pdf]]

Meeting Minutes



References


 * PD circuits


 * 1) [[File:Single-supply_opamp_design.pdf]]
 * 2) [[File:Design_of_visible_light_communication_receiver_for_on-off_keying_modulation_by_adaptive_minimum-voltage_cancelation.pdf]]
 * 3) [[File:Applsci-07-00670-v2.pdf]]
 * 4) [[File:An-photodiode-parameters-characteristics.pdf]]


 * Other


 * 1) [[File:Ultra-wide_coverage_VLC_system_with_alignment-free_receiver.pdf]]
 * 2) [[File:Performance_Comparison_of_MIMO_Techniques_for_Optical_Wireless_Communications_in_Indoor_Environments_.pdf]]
 * 3) [[File:Indoor_Optical_Wireless_Systems_Technology,_Trends,_and_Applications_.pdf]]
 * 4) [[File:Indoor_Optical_Wireless_Communication_Potential_and_State-of-the-Art.pdf]]
 * 5) [[File:Improvement_of_the_Transmission_Bandwidth_for_Indoor_Optical_Wireless_Communication_Systems_Using_a_Diffused_Gaussian_Beam.pdf]]
 * 6) [[File:Cellular_Indoor_OWC_Systems_with_an_optimal_Lambertian_Order_and_a_Handover_Algorithm.pdf]]
 * 7) [[File:Aligning_the_Light_Without_Channel_State_Information_for_Visible_Light_Communications.pdf]]
 * 8) [[File:4.5-Gbs_RGB-LED_based_WDM_visible_light_communication_system_employing_CAP_modulation_and_RLS_based_adaptive_equalization.pdf]]