LED Pendant and DALI...do I need to use a relay?

Hi, I'm new to the forums so please excuse any ignorance.

We are are building a new house and have a c-bus certified sparky who has been very helpful. I have a reasonably good understanding of how the C-bus lighting works. I'm not a sparky but have an electronics background.

The question I have relates to some LED pendants we purchased. They have a Mean Well power supply (LPV-35-24) 35w 24v constant voltage and a DALI PWM driver (DALI6001). So 230v to the power supply and DALI to the driver connected to the LEDs in the pendant.

My question is should the power supply be switched by a relay channel in addition to the driver being controlled by the c-bus DALI gateway? Or can the power supply be constantly powered (isolated at the board with a MCB)?

If the power supply is switched by a relay is it easy to commission c-bus to both switch the relay and set the DALI dimming with one switch/button? I presume this configuration would require the use of 2 groups in the lighting application. If the power supply is not switched, i.e. permanently powered, will that waste energy and shorten the lifespan of the power supply?

The power supply and driver all reside in the base(rose) of the pendant. TPS and control cable has been run to each of the 3 pendants we have purchased.

Graphically:

230v -> power supply -> 24v -> PWM DALI Driver -> LEDs

Thanks in advance for any advice.

Marty.

 

If you are worried about saving power perhaps you could use just one relay to power all 3 pendants...

Not sure on the programming side, but it would save the cost of 2 relays and still provide most of the energy savings.

Best to check with the pendant supplier as to how much standby power is used by the transformer and driver or if there are issues leaving it always powered on.

You could always get an electrician to test the standby power use if you already have the pendants.

 

Hi Rik,
Thanks for the response. We have 3 pendants, all close to each other, so using one relay channel seems like a good idea.

One pendant on one DALI channel, and the other 2 on another channel/address.

I just wonder how easy it is the have the relay turn on and send the DALI commands from one saturn switch for example (hold to dim).

Marty.

 

This is pretty simple using logic in the relay. Set the channel to "OR" logic with the two pendant groups. As soon as either group is > 0 the relay channel will turn on. These two groups will also be mapped to the appropriate DALI groups to control the dim level.

 

Paul,
That's great to hear. Sounds like it should be fairly easy to do. We are about 4 weeks away from wiring off the lights. So I'll update any progress.

Thanks for the advice.

Marty.

 

DALI should usually be permanently powered without a relay.

There is a common misconception with DALI that installing a relay will save you power, this depends on the product you are installing, quality DALI drivers use almost no power when off.

I suggest you do the maths by comparing the standby power of the DALI driver that you are using when it is off vs the power required to drive the relay, this information should be readily available on its data sheet. You will probably be using more power to drive a relay, not to mention the additional costs of purchasing the relays and programming them.

The artical below maybe useful;
http://www.dali.net.au/DW/2013/08/02/dali-and-standby-power/

 

Hi Jaied
Good link.
I agree.

I would like to add.
On my only Dali job so far.
After 4 years I have had zero fluorescent lamps and one out of 60 ballasts fail.
I'm a bit anxious about changing it.
My best advice to everyone, make sure you document the Dali fitting address.

 

Hi jaied. Thanks for the response.

I checked the link. It's not so much the DALI bus power I'm concerned about. It's more the standby power of the transformer in the 3 pendants.

The pendants have a meanwell transformer (230vac to 24vdc 35w) and a DALI controller. The transformer (lpv-35-24) is not DALI driven, just the controller. It would be like leaving an iPhone charger permanently plugged in and powered on.

I gues the best thing would be to find out how much power the transformer uses with no load. I can't work it out from the specs. Just 0.25mA leakage current and 85% efficiency.

Marty.

 

Hi mminehan,

I wanted to do this properly so I got the largest power supply I could for this purpose from Tridonic, being a 150W (LCU150/24E 020 - 24166333) LED power supply. Just like in your situation this is NOT a DALI power supply, it is a 24V constant voltage power supply to drive the LEDs, that would be used with a DALI-PWM dimmer to dim constant voltage LED lights using something such as a DALI K210.

To test the standby wattage draw of the power supply I put it on a Watt meter and plugged in with no load. A photo of this can be found at the link below;

http://imgur.com/XqQQNCG

As you can see the Tridonic 150W LED power supply draws 0.9W when it is in standby. Calculating this out to the worst case scenario, if we left the LED off for entire year we would have waisted 365*24*0.9 Watts of Power, which is 7,884W.

Assumming 0.25c per kW for 150W of LED, our maximum waistage is $1.97 per annum.

Does this use more power than the relay? Probably not, but lets take this further and assume that our relay uses zero power.

Lets say our DALI LED setup lasts five years because a lot of LED products are now rated for around 50,000 hours. Lets also say the cost of power increases by 10% each year. We would then get the following annual costs (Year1 - $1.97, Year2 - $2.17, Year3 - $2.38, Year4 - $2.62, Year5 - $2.88).

Over this five year life of the LED, as a worst case scenario of having the LED lights on standby for every hour for five years, assuming that power goes up each year starting from 0.25c, we would waiste $12.03 in lost power over the life of the product.

Can you buy the necessary equipment and get it installed and programmed for less than $12.03? Probably not.

We don't know how much power the meanwell power supply draws in standby and I would be curious to know what it is if you measure it. Hopefull this excercise shows that it is worth doing the calculation.

I think this also shows how installing quality equipment when using DALI usually saves the customer in the long run. Hopefully it helps dispell the myth that some people preach that having a relay with every DALI system will result in a saving.

Good luck with your LED project and I hope this helps.