How to choose lighting control for a smart home – on/off, push dim, triac, or DALI?

Introduction

In practice, we often run into changes to the lighting plan during installation. The change is usually initiated by the homeowner, but sometimes also by the designer or the fixture supplier. A typical example is a situation where, after the wiring has already been pulled, the owner says they want specific lights to be dimmable. In a classic installation, you simply pick a suitable fixture and dimmer in that case. But once you want to add smart features and remote control, things start getting complicated – and it's good to know that in advance. This article will help the average builder get oriented in the current types of fixtures, their capabilities, and where they're best used when building smart lighting, including the cabling and wiring for a smart home that's worth planning already at the first-fix (rough-in) construction stage.

Basic Ways to Control Lighting

Classic On/Off Switch

The gold standard of lighting control – the most common and simplest way to turn a light on or off. Best suited for practical spaces such as a hallway, entryway, staircase, utility room, garage, cellar, pantry, closet, workshop, or outdoor lighting. In a classic installation, the switch directly opens/closes the 230V circuit leading to the fixture. You can have a single switch, a double switch, and so on.

An existing classic installation can, in individual cases, be "upgraded" with one of the smart switches – a Wi-Fi switch module behind the switch, for example the Shelly 1 Mini, which can switch the light remotely and adapt to how the physical switch is operated (Toggle or Edge modes). At the same time, it has its limitations – mainly its dependence on Wi-Fi (connection dropouts), the usual requirement for a switched neutral wire in the switch box, and a relay that stays permanently live behind the switch. If you had fifty such switches in your house, the risk goes up and management becomes unwieldy. An alternative is a smart bulb with a built-in Wi-Fi/Zigbee module, though in that case the wall switch has to stay permanently on. You can also use a dual relay* or a resistive dimmer – in the case of a dimmer, it's better to replace the switch with a push-button.

*Relay? A relay is essentially an electrically controlled switch. When you feed a control signal into a relay, a coil inside it energizes, pulling in a metal contact that closes (or opens) the main electrical circuit – for example, the 230V feed to a light bulb – without anyone having to physically press anything. The electronics do the work.

Tip: In truly smart homes, though, buttons without a fixed on/off state are used instead of classic switches. Pressing the button is simply a pulse: turn on, turn off, dim by holding, double-click, and so on. So that the buttons stay universal and their function can be changed at any time, they're not wired directly into the 230V circuit – instead, they typically just pass along a signal over some kind of bus. In our PiHome system specifically, the buttons carry only 5V, and the signal switches against ground (GND) over a single UTP cable (4 twisted pairs) – so we can typically wire up 4, but easily even 7 buttons (7× signal vs. shared ground GND). It's safe, you can take it apart yourself even as a layperson, and kids can touch it even with wet hands. On top of that, everything can be controlled via automation or from a phone.

Dimmable Lighting

Why dim at all? Dimming lets us regulate the light output to fit the situation. During the day we want plenty of light, while in the evening we appreciate lower intensity and a more pleasant atmosphere. Dimming is handy for things like watching a movie, relaxing, or evening lighting, when you don't want the whole house lit at 100%.

Dimming makes the most sense in places where we spend more time and where atmosphere matters – for example, in the living room, dining room, bedroom, children's room, home office, bathroom, or on the terrace.

Rule: ON/OFF = function. Dimming = comfort and atmosphere.

Dimming often comes with another request as well – changing the color of the light. It's not just about intensity, but also about adjusting the white color temperature (Tunable White) or colored RGB/RGBW lighting. How the light is dimmed therefore significantly affects the price, the options for future expansion, and the way it's installed.

TRIAC Dimmers – Phase-Cut Dimming

TRIAC, i.e. a triac dimmer, is the classic way of dimming 230V lights using phase-cut dimming. This principle worked very well with older incandescent bulbs and halogens. A TRIAC could even be built right into a switch and regulate the circuit directly. It can be installed into a classic electrical installation.

With LEDs, the situation is more complicated. Not every LED fixture or LED bulb is suitable for TRIAC dimming. You need to watch LED compatibility with the dimmer – specifically between the triac dimmer, the LED source, and the fixture itself. With an unsuitable combination, you can end up with LED flicker, a limited dimming range, or an audible buzz.

TRIACs are the cheapest option price-wise. For classic bulbs and halogens, a resistive dimmer built into the switch is enough. For LEDs, you need to check which LED you'll be dimming, and for LED panels you may need to choose a TRIAC driver. The price of a TRIAC driver for an LED panel starts at around € 20. 

Tip: In truly smart homes, we can also use TRIAC. In PiHome, we use the Shelly Pro 2PM for smaller numbers of lights (up to 16 pcs), which each controls up to two independent circuits, up to 160W/channel. The buttons are universal, so we get to choose whether repeated presses should dim the brightness or switch between scenes. From there, it's entirely up to us how we want it to work. 

PUSH-DIM – Button Dimming

Push-Dim is the simplest form of digital dimming. There's no classic dimmer on the wall, just an ordinary button. A short press turns the light on or off, while holding it down changes its intensity. Releasing the button stops the dimming. You need at least a 4-conductor cable, so this is best suited for new builds and renovations.

The button itself is cheap and can be any classic type. The "intelligence" sits in the LED driver, which has to support the Push-Dim function. The advantage is therefore very simple control and the ability to use the same button design throughout the whole house.

Push-Dim drivers are more expensive than TRIAC ones price-wise. Today they're often combined with DALI functionality. The advantage is that you don't need any extra hardware for it, even within a classic electrical installation.

Tip: In truly smart homes, we can also use PUSH-DIM. In PiHome, we use it for small to medium numbers of lights. In PiHome, pressing the button sends a pulse to the relay. A short press → on/off. A long press → dimming. The 2PM each controls up to two independent circuits, up to 160W/channel. The buttons are universal. The advantage is that we can also control the lights via automation and remotely through the relay. The downside is that the driver remembers the last setting, so at night, for instance, you can't jump straight to 50% or 25% brightness right away – there's always a jump from 100% intensity if the last setting was 100%.

DALI 

If you're planning a larger number of colored and dimmed circuits in your home – by that I mean dozens – it starts to pay off to deploy professional addressable dimming over the DALI protocol (Digital Addressable Lighting Interface). DALI supports up to 64 fixtures by default. In a smart home, the foundation is a quality master gateway, which typically costs around € 800. On top of that, keep in mind that DALI fixtures contain DALI drivers, which are also more expensive than classic dimmers. Similar to DALI, larger smart homes can also use the KNX bus system for lighting, which combines lighting control with other home automation elements.

Another specific requirement is the buttons – you need a DALI Input, for example for 4 buttons, so the system recognizes them as DALI and can dim through them, or you need special DALI buttons. DT6 handles white light, while DT8 also handles color. DT8 devices are usually the most expensive. The +DA and -DA wires on the terminal block then form what's called the DALI bus, over which the signal travels to all fixtures and controllers.

Tip: In truly smart homes, we can also use DALI as the most expensive option. In PiHome, we recommend it only for larger numbers of lights and a lot of RGBW – that's where it makes the most sense. In PiHome, pressing the button sends a command. A short press → on/off. A long press → dimming, scenes, and so on. The buttons can be universal or special DALI buttons in the case of RGBW. 

PWM 0–10V and Other Analog Systems 

These are mainly used in commercial spaces, and we won't be covering them here.

Summary and Recommendations

A summary of the main characteristics of each type of lighting control and dimming – approximate price, the wiring needed, and whether you can deploy the technology into an existing classic electrical installation or need to plan for a renovation or new build.