Dimming LEDs: TRIAC, DALI or 0–10 V – Which to Choose?

Brightness control only works when the luminaire, its power supply and the controller all support the same dimming method: TRIAC (phase-cut) suits 230 V luminaires with a compatible power supply, PUSH-DIM suits a plain push button, and 0–10 V and DALI suit professional systems. This guide explains how these methods differ, where each fits, why flicker appears and what to check before you buy.

How the dimming methods differ

Dimming changes the luminous flux (lm), and with it the power the luminaire draws from the mains. Brightness can usually be lowered from 100 % to a few per cent, although the lowest level depends on the luminaire and the controller. The main difference is how the controller passes on the command: by cutting part of the 230 V sine wave, over a separate signal wire, or through a digital protocol. The table compares the most common methods.

TRIAC: the usual choice for homes

A TRIAC dimmer cuts part of each half-cycle of the 230 V supply and so lowers the average power. It is the simplest method because no control wire is needed: the dimmer replaces an ordinary wall switch, which makes it particularly suitable for refurbishing a flat where you do not want to run new cables. Keep in mind that one dimmer controls the whole circuit equally.

Why LED luminaires need a compatible power supply

TRIAC dimmers were originally designed for incandescent bulbs, which are a purely resistive load and run steadily from a few tens of watts. The power supply of an LED luminaire is electronic, so both the dimmer and the luminaire must be marked as suitable for phase-cut control. There are two kinds: leading-edge and trailing-edge dimmers. Trailing-edge types usually suit modern LEDs, but the manufacturer's compatibility table always has the final word.

Minimum and maximum load

Every dimmer has load limits, for example from 3 W to 100 W. If the circuit draws less than the lower limit, the light may flicker or fail to reach a low level. Add up the total power of the circuit, not of a single luminaire, and keep about 20 % headroom below the upper limit.

PUSH-DIM and 0–10 V: the simpler methods

PUSH-DIM

A PUSH-DIM power supply is controlled over the same 230 V wire that feeds it: a short press switches it on or off, and a long press changes the brightness. You need an ordinary momentary push button and a luminaire that supports the function. It suits a single circuit but cannot create scenes, and the manufacturer limits the line length and the number of buttons.

0–10 V

In a 0–10 V system the power supply receives a control voltage over two separate wires. Brightness changes from the minimum to 100 %, and switching off is usually done with a separate switch or relay. The system is simple, but dimming curves differ between manufacturers, so it is best to use power supplies from the same series on one circuit.

DALI and smart controls

DALI

DALI is a digital protocol: every power supply has an address, so a single two-wire line can control individual luminaires or groups and create scenes. The standard allows up to 64 devices on one line, and digital commands are less sensitive to interference than an analogue signal. More about the protocol is on the DALI Alliance website. DALI needs a controller and careful design, so it is most often used in offices, shops and larger homes that need several scenes, such as “work”, “evening” or “cinema”.

Smart controls: Tuya and Zigbee

Smart control works as an extra layer: a module or smart bulb does the dimming, while a phone or voice assistant sends the commands. Zigbee devices connect through a hub and form a network that stays stable even with many devices, while Tuya usually runs over Wi-Fi or a Zigbee hub. A smart module installed upstream of the luminaire must still match its power supply on the same principle: a TRIAC module controls a TRIAC-compatible luminaire, while a 0–10 V or DALI interface must be built into the luminaire itself.

How to check before buying and avoid flicker

Most problems come not from the light itself but from incompatibility. Before buying, it is worth taking these steps:

1. Check which dimming method is stated in the luminaire specification, and do not buy a dimmer until you know it.
2. Add up the circuit power and compare it with the dimmer minimum and maximum limits.
3. Check whether the manufacturer lists compatible dimmers.
4. Avoid mixing luminaires from different manufacturers on one TRIAC circuit.
5. Confirm the power supply choice in our guide How to choose an LED power supply.

Flicker and humming usually come from too small a load, an incompatible dimmer type, or long cables picking up mains interference. If the problem persists, try changing the dimmer before the luminaire. It is also worth checking whether the low-end limit can be set on the dimmer itself, as many models have an adjustable minimum level. If you are unsure about compatibility, you can ask us for advice.

How this looks in our range

The dimming method is listed in our catalogue under the attribute “Light flux dimming method”. In pendant luminaires TRIAC is the most common, with some DALI, stepped and touch models, and part of the range has no dimming. Ceiling fixtures come in TRIAC and DALI versions, while magnetic track is mostly DALI, with TRIAC and PUSH models too. For track systems the attribute currently shows no dimming.

Frequently asked questions

Can any LED luminaire be connected to a TRIAC dimmer?

No, only one whose specification states TRIAC or phase-cut dimming. A non-dimmable LED luminaire on a dimmer may flicker, hum or fail. If the luminaire is dimmable, also check the dimmer minimum load, whether it is leading or trailing edge, and the manufacturer compatibility list, because even two dimmable products are sometimes incompatible with each other.

How does DALI differ from 0–10 V?

DALI is digital, so every device has an address and can be controlled individually, while 0–10 V is analogue and controls the whole circuit equally. DALI allows scenes and groups but needs a controller and design work, so 0–10 V is more often chosen for simpler solutions where one signal for the whole group is enough and individual control is not needed.

Why does a dimmable luminaire flicker at low brightness?

The usual cause is too small a total load or a dimmer that does not match the luminaire power supply. Increase the circuit load, choose a trailing-edge dimmer or use the model recommended by the manufacturer. Flicker can also point to a poor contact in a connector, so check that the wires are properly tightened in the terminals and that the dimmer is not overheating.

Does smart control replace a dimmer?

Not always. A smart module acts as a dimmer but must still match the dimming method of the luminaire. First establish whether the luminaire is TRIAC, 0–10 V or DALI, and only then choose a module or hub. Also check the maximum load of the module, which is often lower than that of a wall dimmer.

Summary

Dimming works reliably when the luminaire, power supply and controller match in dimming method. For homes TRIAC is usually enough if load limits are respected, PUSH-DIM suits simple circuits, and DALI is worth choosing for scenes and individual control. Smart controls add convenience but do not remove the compatibility requirement. Read the specification first, then calculate the load, and only then buy the dimmer. If a circuit mixes several different luminaires, it is better to ask a specialist than to swap components by trial and error.