Category Archives: Lighting

PIR Sensors for Lighting Control in the Outbuildings

Posted on by
Reply

The house has PIR sensors to control lighting in the hallways / landings and bathrooms. These are Danlers PIR Occupancy Switches; model CEFL PIR in dry locations and CEFL PIR SEALED in bathrooms. These take a 230V live input and switch that with a relay for the output. They’re intended to directly switch 230V lighting (and are rated for 6A of resistive load) but they’re wired to a KNX ‘Binary Input’ bank which senses the switched 230V and is configured to control the relevant (DALI-dimmable) lights.

A key reason for adopting this approach was the limit of 20 KNX devices within an installation imposed by the (relatively) affordable KNX ‘ETS Lite’ software license used to program the home automation system – there’s only one KNX device (the Binary Input sensor), whereas there would have been 12 if these had been native KNX presence sensors. The Danlers sensors are about £45 each, whereas native KNX presence sensors are getting on for double that.

In the Ground Floor Hallway, which is relatively long and thin and is typically approached from the Front Door / Living Room (at one end) or the Kitchen / Family Room (at the other end) there are two sensors – about 1/4 the way from each end. These effectively operate ‘in parallel’ and the first one to trigger switches the lights on. This configuration works well.

While they function as intended, slight niggles with using the 230V Danlers PIR switches include:

  • Despite the Danlers units being a well-regarded, British-made product (with a 5-year warranty) roughly 1/3 of them have failed. Two were repaired under warranty – but failed again (and were then replaced under warranty) and two more failed outside warranty.
  • They operate with a very distinct ‘click’ from the 230V relay, which in some cases is A Good Thing – e.g. visitors using the windowless downstairs bathroom hear the ‘click’ as soon as they open the door, while they’re looking for the light switch – but it can be annoying in other rooms.
  • Since there’s no manual switch to choose to press (or not), the sensors always trigger when they sense movement – whether or not that’s intended or desirable
    • In en-suite bathrooms it’s annoying to have the lights come on at full brightness in the middle of the night – but they need to be bright at other times of day
    • The basic sensors can’t do anything different at night, so there’s an Automation rule in Home Assistant which reacts to the Binary Input sensor and does different things depending on whether it’s considered ‘night’ or not – which means some of the lighting is reliant on Home Assistant working correctly and is hence less robust than native KNX operation would be

For the Outbuildings, there’s a rather more modest requirement for automated lighting control than in the House – just the Shower Room and the Plant Room, both of which receive no natural light and which have Switched (rather than Dimmable) lights. Now the KNX device limit is higher (up to 64 devices in a single installation, using the ‘ETS Home’ license tier), using native KNX presence sensors seemed a better way to go – avoiding the need for a ‘Binary Input’ module (which have a high cost-per-input in small sizes). Since the Shower Room sensor needs to operate in a humid environment that needs to be ‘sealed’ to some extent, which limits the choice of MDT-brand sensors to pretty much just the MDT SCN-P360L2.03 which provides 360-degree coverage with two PIR sensors and is IP44-rated. (The Plant Room sensor is identical, even though it doesn’t need the IP44 rating.)

These sensors offer a range of additional flexibility:

  • They can take an input to specify Day versus Night, and do different things depending on the setting, without needing to rely on an Automation rule in Home Assistant
  • They can be adjusted in terms of their sensitivity threshold for presence / occupancy
  • They can provide logic to maintain overall lighting levels, taking advantage of natural light where that is available (and running artificial lighting at reduced brightness) then adding more artificial light when the natural light level reduces
  • They can provide an output to a HVAC system, with different configuration settings from the lighting outputs
    • For example, in the Shower Room, this could be used to change the fan speed on the MVHR system – either via a switched output or a ‘dimmable’ 0-10V controller

It remains to be seen how well the KNX PIR sensors operate in practice but so far I’m impressed by their specification, their small size, and the configuration options available. While it would be difficult to retro-fit these into the House (since the existing sensors use 230V Twin&Earth cabling, which would need replacing with KNX Bus cabling) I’d be inclined to use native KNX sensors in the House if starting again.

Dimmable LED Bulb Experiences

Posted on by
Reply

LED lighting has definitely come of age and all of the lighting in the property uses LED technology. Where the lights are purely functional (e.g. the outdoor floodlights) or offer low-intensity feature lighting the fittings are simply switched with a relay but most of the internal lighting is controlled via dimmers.

In general, the dimmable light fittings have embedded LEDs for the actual light output and separate LED drivers (i.e. control electronics) – typically mounted remotely. These all work very well and offer great dimming performance using DALI control. DALI is a a great way to control lighting dimmers – a digital signal is transmitted over a dedicated control bus directly to the LED driver which then sends the appropriate low-voltage waveform to the LED itself.

There are a handful of exceptions:

  • The outdoor light on the balcony is a Nordlux Canto Maxi which takes 2 x GU10 bulbs. While this is installed on the balcony it’s close to the big sliding glass door into the main bedroom and hence it effectively counts as one of the bedroom lights and deserves to be dimmable.
  • Some of the bedrooms and living rooms are wired for dimmable bedside or table lamps, controlled together in sets. (These are connected via round-pin 5A sockets to prevent other appliances being connected by mistake.)

Dimming for these circuits is via Aurora AU-DATR400 dimmer units which take a DALI signal and generate a “dimmed” mains waveform. It should be a simple case of installing a dimmable LED bulb into the light fitting.

The only big disappointment with the lighting control on the whole project was with the GU10 bulbs for the balcony light. Recognising that dimmable LEDs are still problematic it seemed sensible to stick with the big brands so I opted for some Sylvania GU10 bulbs which appeared to be high-quality (made in Belgium) but which did not perform at all well. The main issue was that the light level would oscillate between the two bulbs a few times a second. They were OK at near full brightness but dimming was a disaster.

Lesson learned and with more caution I waited a few months before looking for dimmable bulbs for some bedside lights. These were going to be very visible within their light fittings and I settled on some golf-ball-style bulbs from Philips Lighting, with their “warm glow” feature (where they dim to a lower colour temperature):

These worked perfectly and look good. Dimming performance is excellent. I still can’t get used to the fact that they don’t even get warm.

I then decided to try swapping the GU10 bulbs in the balcony light for Philips units with equal success.

Conclusion: I’m going to be buying dimmable LED bulbs from Philips from now on.

Different brands and models of LED bulbs react in different ways and the control technology is still developing rapidly so where multiple dimmable LED bulbs are installed on the same circuit (e.g. several table lamps in a living room) it’s likely to be necessary to buy and replace bulbs in batches – same manufacturer, same model, bought at the same time.