AC Dimmer Module Simulation Request
Thought for 1 min 58 sec
I found a few real issues, including 2 safety-critical ones.
Review summary
Table
| Severity | Finding | Why it matters | Recommended fix |
|---|---|---|---|
| Critical | U2 input LED is connected directly to AC through R4 + R5 with no reverse protection | The U2 datasheet gives input reverse voltage max 6 V. On the opposite half-cycle, the LED can be reverse-biased from mains. Current is limited, but reverse voltage stress is still a reliability/safety problem. | Add an anti-parallel diode across U2 input LED, or better, use a bridge rectifier ahead of U2. |
| Critical | U1 pin 5 (SUBSTRATE / NC) is tied to AC neutral | The datasheet indicates pin 5 is NC / TRIAC SUBSTRATE and should be left unconnected. | Disconnect U1 pin 5 from AC. Only use the actual output terminals of U1. |
| High | R3 = 330 Ω may not guarantee enough LED drive for U1, especially at 3.3 V | For U1, datasheet trigger current for the chosen variant is 8 mA typ, 15 mA max. With R3, drive current is only about 6.36 mA at 3.3 V and 11.5 mA at 5 V. That means worst-case triggering is not guaranteed. | Either lower R3, or switch to a more sensitive optotriac variant, or drive U1 through a transistor stage. |
| Medium | R4 + R5 dissipate noticeable power on 230 VAC | Total dissipation is about 0.2645 W across the pair on 230 VAC, so about 0.132 W each if shared evenly. Your current 0.25 W rating works, but margin is not generous for mains use. | Prefer higher-voltage, flameproof parts and consider 0.5 W resistors for better margin. |
| Medium | C1 is marked 400 V film, but for across-TRIAC snubber use the capacitor class matters | On 230 VAC mains, peak is about 325.27 V. A generic 400 V film part may be marginal depending on whether that rating is DC or AC and on surge behavior. | Use a mains-rated snubber capacitor, typically X2 safety class where applicable, with appropriate AC rating. |
| Medium | Layout is not yet routable/verified | DRC reports 27 airwire errors, so the PCB is not electrically complete yet. | Finish placement/routing, then re-check creepage and clearances. |
| Low | F1 shows floating-pin ERC errors | This appears to come from the fuse-holder symbol having duplicate equivalent pins, not necessarily a real circuit break. | Clean up the symbol/pin mapping or use a simpler fuse/fuse-holder part model. |
| Low | LED1 with R7 is a power-present LED, not really a dimming-status LED | It is tied from VCC through R7 to ground via LED1, so it will just turn on whenever control power is present. | Keep it if that is the intent, or move it to a logic signal if you want true status indication. |
Table
| Check | Result |
|---|---|
| Main switching device | Q1 gate trigger current is compatible with optotriac driving in principle |
| Dimming method | Using U1 as a non-zero-cross optotriac is the correct choice for phase-angle dimming |
| Gate resistor | R1 at 220 Ω is reasonable |
| Snubber presence | R2 + C1 are present, which is good practice for TRIAC switching |
| Isolation concept | Using U1 and U2 does establish an isolation boundary conceptually |
- Protect the input LED of U2 from reverse mains stress.
- Disconnect U1 pin 5.
- Rework R3 so U1 is guaranteed to trigger from your control voltage.
- Upgrade mains-side component ratings, especially R4, R5, and the snubber capacitor C1.
- Complete routing and then verify physical creepage/clearance on the PCB.
If you want, I can make a correction plan for these issues and update the design safely.
Make correction plan
Fix U1 and U2
Resize R3 drive
