Pembuatan Model LTSpice dari Komponen LED untuk Rangkaian Transmitter Visible Light Communication (VLC)

AGUNG SETIA BUDI, Dzuhri Radityo Utomo, S.T, M.E., Ph.D; Dr. Dyonisius Dony Ariananda, S.T., M.Sc.

2026 | Skripsi | S1 TEKNIK BIOMEDIS

Pemodelan komponen Light Emitting Diode (LED) yang akurat di LTSpice merupakan dasar penting bagi simulasi rangkaian transmitter Visible Light Communication (VLC), namun model SPICE untuk LED komersial sederhana yang umum tersedia di pasar lokal masih jarang dipublikasikan, sementara instrumen karakterisasi presisi sepertis ource-measure unit umumnya mahal dan sulit diakses. Penelitian ini bertujuan mengembangkan model dioda LTSpice untuk lima warna LED 5 mm (merah, kuning, hijau, biru, dan putih) yang diperoleh di area Yogyakarta, sekaligus merancang sistem pengujian otomatis berbiaya rendah yang dapat direplikasi menggunakan komponen umum. Sistem dirancang berbasis mikrokontroler ESP32, DAC MCP4725 12-bit, serta rangkaian Voltage-Controlled Current Source (VCCS) yang memanfaatkan op-amp LM358P, transistor 2N2222, dan resistor sense 10 ?, sehingga arus LED dapat dijalankan otomatis sebanyak 256 langkah dari 0 hingga 53 mA. Validasi sistem dilakukan dalam tiga tahap: akurasi DAC (gain error ?1,89%), validasi pengukuran menggunakan resistor referensi 47 ?, serta tracking rangkaian VCCS dengan error rata-rata ?1,14 mV (standar deviasi 0,37 mV). Karakterisasi V-I dilakukan terhadap 25 sampel LED (lima sampel per warna), kemudian parameter dioda SPICE (IS , N , RS ) diekstraksi melalui regresi multilinear pada bentuk linearisasi persamaan Shockley + RS pada rentang fitting 5–25 mA. Hasil menunjukkan ideality factor N berkisar dari 2,10 ± 0,09 (LED kuning berbasis AlGaInP) hingga 3,44 ± 0,49 (LED biru berbasis InGaN), resistansi seri RS dari 0,48 ? hingga7,39 ?, dengan rata-rata Root Mean Square Error (RMSE) sebesar 0,65 mV untuk seluruh 25 sampel — jauh di bawah ambang batas fitting yang dapat diterima. Penelitian ini menghasilkan file LED_measured.lib yang dapat langsung digunakan dalam simulasi LTSpice, sekaligus menemukan bahwa LED hijau yang dijual di pasar lokal cenderung berbasis material AlGaInP/GaP, bukan InGaN.

Accurate LTSpice models of light-emitting diodes(LEDs) are essential for simulating Visible Light Communication(VLC) transmitter circuits, yet published SPICE parameters for the simple commercial LEDs commonly available in local markets remain scarce, while precision instruments such as sourcemeasure units are typically expensive and inaccessible. This paper presents a low-cost, replicable automated characterization system for extracting SPICE diode parameters from 5 mm commercial LEDs, together with extracted models for five colors(red, yellow, green, blue, and white) sourced in Yogyakarta, Indonesia. The system is built around an ESP32 microcontroller, a 12-bit MCP4725 DAC, and a Voltage-Controlled Current Source (VCCS) implemented with an LM358P op-amp, a 2N2222 transistor, and a 10 ? sense resistor, sweeping the LED current automatically across 256 steps from 0 to approximately 53 mA. System validation was carried out in three stages: DAC accuracy (gain error ?1.89%), measurement validation using a 47 ?reference resistor, and VCCS tracking (mean error ?1.14 mV, standard deviation 0.37 mV). V–I characterization was performed on 25 LED samples (five per color). Diode parameters (IS , N , RS ) were extracted via multilinear regression on the linearized Shockley + RS equation over a 5–25 mA fitting range. Extracted ideality factors N ranged from 2.10±0.09 for AlGaInP yellow LEDs to 3.44 ± 0.49 for InGaN blue LEDs, with series resistances RS from 0.48 ? to 7.39 ?. The mean root-meansquare error (RMSE) across all 25 samples was 0.65 mV, well below the practical fitting threshold. The study additionally finds that green LEDs sold in the local market tend to be based on AlGaInP/GaP material rather than InGaN.

Kata Kunci : Light-Emitting Diode, model SPICE, Visible Light Communication, karakterisasi V-I, regresi multilinear