ELEN4012A · FINAL-YEAR CAPSTONE
Sending data through power lines and light. We’re exploring the bridge between the wiring in a room and a beam from an LED.
POWER LINE COMMUNICATION × VISIBLE LIGHT COMMUNICATION
Existing wires. A small buffer. A different last hop.
THE PROBLEM & OUR APPROACH
Our prototype explores a practical question: can existing power wiring feed a local light-based data link, with a buffer managing the handoff?
PLC brings data through mains wiring to a gateway. An LED then carries the data across a local optical link to a photodiode receiver. Combining them gives us a wired backhaul and a visible-light last hop to study, without running a separate data cable along the PLC path.
PLC can deliver data in bursts or pause under interference. The optical transmitter has its own limited rate. A direct handoff can lose a burst that arrives faster than it can be sent, or leave the light link with nothing to send during a gap.
A finite buffer holds arriving data until the VLC transmitter is ready. It absorbs short bursts and can keep the transmitter supplied through a brief PLC pause, while queued data remains. Pacing and feedback are still needed when input stays faster than output.
Compare a six-packet burst with and without storage. Each step represents a VLC opportunity to send up to two packets; these are teaching units, not measured hardware rates.
Send a burst to see the gateway hold data while the light link sends at its own pace.
0 packets lostA buffer buys time; it does not increase VLC capacity, remove electrical interference, or cover an indefinite outage. Once storage fills, excess input is lost in this model. In the real system, backpressure or retries must be handled by the transport and gateway.
Explore buffer size and interference ↓FROM WALL TO LIGHT
PLC brings the data in. A buffer helps manage the handoff. VLC carries it across the optical link.
PLC adapters use the mains wiring as a communication path. Interference can make delivery uneven.
Queued messages wait at the gateway until the optical transmitter is ready to carry them.
An LED carries the encoded message. A photodiode and receiver electronics turn it back into data.
A CLOSER LOOK
Explore the PLC path and gateway through project illustrations, alongside the actual receiver circuit drawings. Tap any image to inspect it.
Two PLC adapters bridge the router and gateway over existing mains wiring. This is a conceptual layout, not a bench photograph.
The gateway holds incoming data and releases it as the optical transmitter becomes ready. Queue sizes here are illustrative.
The photodiode input stage.
The receiver amplifier stage.
PLC equipment, gateway, LED transmitter, and complete setup photographs are awaiting team contributions.
02 / TRY THE IDEA
Explore the tradeoff between buffer size and burst losses before trying the message studio.
The power line stalls, then releases a burst. Find the smallest buffer that keeps simulated losses under 1%.
Illustrative data, not bench measurements. Each interference level uses the same trace for a fair comparison. This simulator never controls the rig.
03 / FROM THE BENCH
Local optical image tests recorded on 12 October 2026. These results describe the USB → light test route.
32 × 16 PIXELS
0.797s64 packed image bytes
64 × 32 PIXELS
2.547s256 packed image bytes
128 × 64 PIXELS
8.110s1,024 packed image bytes
Source: the project’s high-resolution image acceptance report. Source and received pixels matched exactly. Times include host pacing and receiver feedback; they are not optical flight times. The PLC → VLC route and this web portal still require end-to-end verification.
04 / MAKE IT YOURS
Prepare something on your phone, preview what the receiver will see, and explore the transmission journey.
THE PEOPLE BEHIND THE LINK
School of Electrical and Information Engineering
University of the Witwatersrand
Team names, supervisor details, and contact information will be published once supplied.
View the project on GitHub ↗
Internet of Light