Before choosing a dimmer you need to understand something that surprises a lot of people: you don't choose the technology, your fixture imposes it. If your driver speaks 0-10 V, you can't control it with a phase-control dimmer no matter how much you prefer one.
There are four ways to dim a light, and each one manipulates something different.
The four technologies
Phase control manipulates the 230 V waveform itself. 0-10 V adds a control wire carrying a voltage. DALI sends digital messages over a bus. PWM switches the load on and off at high speed.
Phase control: the most domestic
It's the one we've used at home for decades. The dimmer cuts part of each half-cycle of the mains waveform: the more of the wave it cuts, the less energy gets through and the lower the light.
Its big advantage is that it needs no extra wire: it installs in the same place as the switch and controls the bulb directly.
Leading or trailing edge
Leading-edge cuts the start of the half-cycle. It was designed for incandescent bulbs and magnetic transformers, and with LEDs it tends to produce buzzing and flicker.
Trailing-edge cuts the end. It starts the wave from zero and ramps up gradually, which means less buzzing and far less flicker with LED lighting. It's the one the Shelly Dimmer Gen3 uses.
An important warning: the bulb has to be dimmable. No dimmer turns a non-dimmable LED into a dimmable one.
0-10 V: the analog one
Here the power and the control travel by different paths. The fixture receives its normal 230 V, and a separate pair of wires carry a DC voltage of 0 to 10 V that the driver interprets as brightness level.
It's the usual standard in commercial and technical lighting: warehouses, offices, high-power floodlights. It requires the driver to have a control input, so it's no good for an ordinary bulb.
The guide to the Shelly Dimmer 0/1-10V PM Gen3 covers it in detail.
DALI: the digital one
Instead of a voltage, a digital bus transmits messages with specific commands. It's a standard set out in IEC 62386 and designed for large installations.
Its great theoretical appeal is individual addressing: each fixture has its address and can be dimmed separately. Be careful, though, because not every device that speaks DALI takes advantage of this, and it's worth checking before you buy. We explain it in the guide to the Shelly DALI Dimmer Gen3.
PWM: the one for LED strips
Pulse-width modulation switches the load on and off hundreds of times per second. The eye doesn't perceive the flicker, only the average: the longer it stays on in each cycle, the more brightness.
It's the technique for 12 and 24 V DC LED strips. It's no good for 230 V bulbs, and it needs a specific controller between the power supply and the strip.
How to know which one is for you
Look at your fixture and answer a single question: what does it accept as an input?
- A dimmable 230 V bulb → phase control
- A driver with terminals marked Dim+ and Dim− → 0-10 V
- A driver with DA terminals or marked DALI → DALI bus
- A 12 or 24 V LED strip → PWM
Frequently asked questions
Can I use a phase dimmer with a 0-10 V driver?
No. Cutting the supply waveform of a driver that expects a stable voltage can cause flicker, erratic behavior or damage the unit.
Why does my dimmable LED flicker at the low end?
It's usually the combination of the cut type and the bulb's electronics. Adjusting the minimum brightness in the dimmer's settings resolves a good share of these cases.
Does phase control reduce consumption?
Yes, though not in proportion to the perceived brightness: the human eye responds logarithmically, so at 50 % power the light looks quite a bit more than 50 %.
What if my installation has no neutral?
Only phase control has options. The Shelly Dimmer Gen3 works without neutral, though with loads below 20 W you'll need a bypass.
Which one dims best at low levels?
DALI and 0-10 V give more finesse because the command travels separately from the power. It's one of the reasons they dominate in professional lighting.
The Shelly dimmers
- Shelly Dimmer Gen3 — trailing-edge phase control, works without neutral.
- Shelly Dimmer 0/1-10V PM Gen3 — analog signal with consumption measurement.
- Shelly DALI Dimmer Gen3 — gateway to a DALI bus.
- Shelly Pro Dimmer 2PM — phase control in DIN-rail format.
Shall we compare them? Here's the comparison of the three Gen3 dimmers.
Not sure what your fixture accepts? Send us a photo of the driver's label and we'll tell you which technology you need. Technical support in English and shipping from Spain.
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