The free, offline-first Electrical Engineering & RF lab in a single file — from schematic to H(s), Bode, root locus, state-space, SPICE-grade transient physics, and back to a suggested circuit topology.
🌐 Live app: eerflab.com · runs 100 % in your browser · no install · no account · works offline
Phòng thí nghiệm Điện – Điện tử – RF miễn phí, chạy hoàn toàn offline trong trình duyệt: từ sơ đồ mạch → hàm truyền H(s) → Bode / quỹ đạo nghiệm / không gian trạng thái → mô phỏng vật lý thật → và gợi ý ngược lại topology mạch.
How complex can it get, and can you still find anything? The complete Arduino UNO Q — all 24 schematic sheets transcribed onto one canvas, ≈3 800 parts, every chip pin carrying the PDF's own name — and the app points at its own entry points: the programmable MCU and the power input glow, and a 🔦 finder bar names them in words so you never hunt. · Mạch phức tạp đến đâu, mà vẫn tìm được? Toàn bộ 24 trang sơ đồ của Arduino UNO Q trên MỘT canvas, ~3 800 linh kiện — và app tự chỉ vào chỗ cần: MCU lập trình được và nguồn vào phát sáng, thanh 🔦 gọi tên chúng bằng chữ.
 |
 |
Double-click the MCU on any sheet and an Arduino-style IDE opens right there. Write setup() / loop() with pinMode · digitalWrite · digitalRead · analogRead · analogWrite · delay · Serial — and:
- the sketch runs on simulation time, not wall-clock (
delay()yields, so the solver stays in charge); analogWrite()is a real 490 Hz PWM the oscilloscope in the app can actually see — not a DC average;Serial.printstreams to a live monitor beside your code;- ▶ Upload hot-swaps the code while the circuit is still running. No stop, no reset, no reload — you edit, upload, and watch the waveform change.
- A sketch that doesn't compile is refused, and the running simulation keeps running.
Two real part families, both with per-pin FUNCTION labels printed on the symbol (PB5 · D13 · SCK · LED) — because a pin number alone teaches nothing:
| Part | What it is | Honest behaviour |
|---|---|---|
| eerfLab-M1 | Friendly 3.3 V teaching MCU, self-powered 3V3 pin, PWM on every D pin |
Branded as ours — an honest fiction, never sold as a chip we don't model |
| ATmega328P | The Arduino UNO's real chip | 5 V logic; you must power VCC/AVCC; below the 2.7 V brown-out the sketch holds in reset; PWM only on D3/5/6/9/10/11 like a real UNO; RESET pin is live; ≈25 Ω drive; 40 mA/pin absolute max is warned |
VN — Nhấp đúp vào MCU: một IDE kiểu Arduino mở ngay trong app. Sketch chạy theo thời gian mô phỏng, analogWrite là PWM 490 Hz thật nhìn thấy trên scope, Serial in ra màn hình bên cạnh, và ▶ Upload thay code khi mạch đang chạy. Hai họ linh kiện: eerfLab-M1 (3.3 V, dễ dùng) và ATmega328P (chip UNO thật — phải cấp 5 V, có brown-out, đúng 6 chân PWM). Chức năng từng chân ghi thẳng trên ký hiệu.
 |
 |
 |
 |
On a board with thousands of parts, "where do I program this?" and "where does power come in?" are the only two questions that matter first. So the app answers them without being asked: the programmable MCU and the power source carry a neon halo sized in screen pixels (unmistakable even at the fit-view of the whole UNO Q) plus a caption naming the action — PROGRAM HERE — double-click → IDE / POWER IN. A 🔦 finder bar lists every key part in words; click a chip and the view flies straight there. The bar tracks the page scroll, so it is still on screen when you scroll into the board. A sheet author can flag any part with their own bilingual caption and colour, saved with the sheet.
VN — Trên bảng mạch hàng nghìn linh kiện, app tự chỉ: MCU và nguồn vào có quầng neon (đo bằng pixel màn hình nên luôn nhìn rõ) kèm chú thích nói rõ HÀNH ĐỘNG. Thanh 🔦 gọi tên từng phần quan trọng — bấm một chip là bay thẳng tới đó, và thanh này bám theo cuộn trang.
 |
 |
 |
 |
A synthesised cascade used to be checked stage by stage — and stage-by-stage "✓ exact" proves nothing about the chain. Now every section is normalised to unity at its own reference band before any gain is placed on it, gain is only assigned to a stage that provably carries it (the built circuit is read back and measured, because a unity-gain Sallen-Key throws K away entirely), and whatever no stage can carry is declared as a leftover instead of vanishing.
The visible result: a 3rd-order Butterworth stage that asked for R1 = 403 µΩ — not a resistor, less than the wire you'd solder it with — now reads R1 = 15.9 kΩ, and the drawn chain multiplies back out to H(s) exactly (it was off by ×3.9 × 10⁷ at 3rd order, ×1.5 × 10¹⁵ at 5th). Polarity is derived from the count of inverting stage templates rather than from a magnitude, so a 180° flip no longer demands a pointless unity-gain op-amp. Pinned permanently by 112 gates that multiply every preset's drawn stages back against the target.
VN — Cascade bây giờ đúng bằng TÍCH của những gì nó vẽ ra: mỗi tầng được chuẩn hoá về 1 tại dải tham chiếu của chính nó, độ lợi chỉ đặt lên tầng thật sự gánh được (đo ngược lại từ mạch đã dựng), phần còn dư được KHAI BÁO chứ không biến mất. R1 = 403 µΩ → R1 = 15.9 kΩ.
- The UNO Q power section actually powers up — a real 12 V on the barrel jack through modelled LMR51440 + two TPS62A02A bucks lands 4.989 / 3.742 / 3.318 V, the 47 ms power-good delay gates the USB host handover, and the green power LED draws 3.88 mA.
- Indexed geometry (E58) replaced the all-pairs scans: netlist 978 → 73 ms, lint 3696 → 151 ms — pan and zoom stay interactive with the whole board mounted.
- Save/load keeps your sketches, block pins and declared clocks (E59); double-click works during a live run (E57).
Most tools give you one link of the chain. eerfLab gives you the whole loop, in both directions:
| Step | What you get | Công cụ |
|---|---|---|
| 1 · Schematic | Drag-and-drop schematic editor: sources, passives, diodes/zeners/LEDs, BJT/MOSFET/JFET, transformers, machines, pots/trimmers, relays, fuses, speakers, programmable MCUs — plus a library of 95 exact, datasheet-verified ICs picked by real MPN | Vẽ mạch kéo-thả, linh kiện thật theo mã |
| 2 · Simulation | One click ▶ — DC operating point, AC → H(s), and a real time-domain transient engine: exponential Ebers-Moll BJTs (SPICE pnjlim convergence), switch-level power MOSFETs, coupled-inductor transformers, dq-model electric machines, I²t & power-rating "boom" physics, honest refusals when an op point is non-physical |
Mô phỏng ⏱ vật lý thật, linh kiện quá tải nổ như đời thực |
| 3 · Analysis | Exact H(s) (MNA nodal analysis + minimal rational fit), factored poles/zeros, Bode with GM/PM markers, step, Nyquist + encirclement criterion, root locus, closed-loop step, state-space ẋ = Ax+Bu (controllable canonical) with one-click MATLAB / Python export, Monte-Carlo tolerance envelopes and pole clouds, noise, FFT/THD, PCB trace calculators (IPC-2221/2152) | Phân tích H(s), Bode, Nyquist, quỹ đạo nghiệm, không gian trạng thái, Monte-Carlo, xuất MATLAB/Python |
| 4 · Suggested topology | Type ANY H(s) and the studio designs circuits for you: cascade of first/second-order op-amp stages with concrete E-series R/C values, KHN state-variable biquads, lag/lead compensators, and the full analog-computer integrator chain — each stage openable back in the Circuit Lab. Unrealisable gain is declared, not hidden; RHP poles are flagged honestly ("needs a stabilizing loop") | Nhập H(s) bất kỳ → app tự đề xuất mạch: cascade op-amp, KHN biquad, chuỗi tích phân analog computer — mở ngược lại vào Circuit Lab |
That loop — circuit → math → circuit — is what makes eerfLab a studio, not just a simulator.
- ≈3 800 parts on one canvas — the complete Arduino UNO Q (ABX00162), all 24 schematic sheets, every chip pin carrying the PDF's own name, every net a label, the 104-LED matrix, both 60-pin FFCs, the Arduino headers, 58 DNP, 51 testpoints — and it still pans and zooms
- 95 exact ICs — datasheet-verified, pin-for-pin, picked by MPN (NE555P, TL431, LM358/LM324/LM741, LM393/LM339, TL08x, CD4000 & 74HC logic families, CD74HC4046A PLL, MAX4374, MC34063, TL494, UC3842, SG3525AN, LMR51440, TPS62A02A, ATmega328P, …) with per-part golden tests and refusal diagnostics (floating pins, missing supply, out-of-range VCC)
- 60 + generic component models — R/L/C/pots, diode family with breakdown & thermal ratings, BJT/MOSFET/JFET, transformers (incl. tapped), machines, relays, fuses, thermistor/LDR/varistor/varactor, speakers, crystals…
- 13 auto-running live examples — the complete Arduino UNO Q, its cycle-true power close-up, the programmable-MCU sketch lab, battery protector (MAX4374), 180 V boost (MC34063 + IRF644), SG3525 inverter, 3φ motor, 3φ generator, DC motor, 555 blinker, TL431 regulator, LM358 swing lesson, HC4046 PLL lock — each with a bilingual engineering walk-through in the hint
- 51 headless regression suites / 2 000 + individual checks run green before every release — solver math, IC golden tests, preset physics, cascade synthesis, UI lint — plus a browser smoke run against the exact bytes production serves
- 4 integrated labs — Circuit Lab → H(s) · H(s) → Circuit · Block Diagrams & Mason's gain formula · RF Lab (Smith chart, S-parameters, matching, stability circles)
- 1 file, 0 servers — the whole studio ships as a single offline HTML file
Real chips, real physics · Chip thật, vật lý thật
 |
 |
 |
 |
 |
 |
Analysis you can trust · Phân tích đáng tin
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
More from the bench · Thêm từ bàn làm việc
 |
 |
 |
 |
- Students — see why the textbook Bode plot looks that way; drag a slider and watch poles move; write a sketch and watch the PWM on a scope
- Educators — every live example is a prepared lecture: real chips, real failure modes, honest limitations
- Practicing engineers — quick H(s) sanity checks, compensator sketches, state-space export to MATLAB/Python, PCB trace-width math
- Hobbyists & makers — build the inverter or the 555 blinker exactly like the web schematic — except this one has been debugged for you
No account. No cloud. Your designs stay on your machine.
free online circuit simulator · transfer function calculator · H(s) from circuit · Bode plot online · Nyquist plot · root locus tool · state-space realization · controllable canonical form · MNA nodal analysis · SPICE alternative in browser · Arduino simulator online · ATmega328P simulator · Arduino IDE in browser · MCU PWM simulation · Arduino UNO Q schematic · op-amp filter synthesis · KHN biquad designer · Sallen-Key · lag lead compensator · Monte Carlo tolerance analysis · Mason's gain formula solver · signal flow graph · Smith chart matching · S-parameters · SG3525 inverter simulation · MC34063 boost converter · class AB amplifier design · 555 timer circuit · PLL CD4046 · three-phase induction motor simulation · DC motor transient · power electronics lab · electrical engineering education — mô phỏng mạch điện online miễn phí · hàm truyền · đồ thị Bode · quỹ đạo nghiệm · tổng hợp mạch op-amp · mô phỏng Arduino · mạch nghịch lưu SG3525 · động cơ không đồng bộ 3 pha · phòng thí nghiệm điện tử ảo
→ eerflab.com — press Load example, pick the 🧩 Arduino UNO Q, follow the 🔦 finder to the MCU, double-click it, and upload a sketch into a board that is already running.
Built with an obsession for honest physics: if the model can't simulate something faithfully, it says so — in English and Vietnamese.
Free to use, but not open source. The hosted web application is free for personal, educational and professional work. The source code is proprietary and is not published here — copying, redistributing, modifying, reverse-engineering or creating derivative works requires prior written consent. See LICENSE.
Miễn phí sử dụng, nhưng không phải mã nguồn mở. Mã nguồn không được công bố ở đây; xem LICENSE.
— Hai (Steve) Nguyen · Electrical Engineering, CSULB · LinkedIn