@misc{rr-2026-0618,
  title = {Engineering an E-Waste PPG Heart-Rate Monitor: A Technical Report on Photoplethysmography, E-Waste Reuse, and Prototype Development},
  author = {Ruben David Roy},
  year = {2026},
  url = {https://idx.ruben-roy.com/p/2026/rr-2026-0618},
  note = {Technical design report}
}