Dimming Pierlite Starburst

Hi All

I am trying to dim these using a Din Mounted Universal Dimmer, however they dont appear to dim until the dimmer has dimmed by at least 30%.

Any ideas?

Thanks
David

 

The Starburst has a small dead-band at the top of the dimming range so that they always deliver maximum power to the lamp across varying mains voltages and all kinds of dimmers, many of which don't give a full mains cycle to the lamp even when set to maximum.

To dial this effect out, try setting the maximum level of your dimmer to about 80%. You can tweak it from there so that the Starburst just hits maximum brightness as the C-Bus group hits 100%.

 

Thanks, Ill give that a shot. Whats the feeling on LED's etc? In NZ, we appear to only have two options... the Starburst, or the Philips MR16 Replacement. The philips seems to work excellent on a Leading Edge dimmer, except when ramping up, it appears to come on bright, drop back, then ramp up...

The Starburst appears to be ok (subject to this diming issue). One thing that does bug me with it however, is that if I ramp from say 50% to full, it peaks at a higher light level, then drops back to its 100% level.

They also seem to be a little slower than the philips when turning on, with the philips, hit the button, and there is light, with the Starburst, there is a slight delay...

 

I haven't tested either the Philips MR16 replacement nor the Starburst in this regard, but I suspect due to its small size, the Philips can't store much energy between cycles. That means it is likely to 'strobe' at 100Hz when powered with a 50Hz 12V ac supply. The Starburst has sufficient capacitance in the driver to reduce the ripple of the current to the LEDs. This capacitance would take a little while to charge and could explain the difference.

I've tested a number of replacement LED solutions, and those with small capacitance I've seen do result in strobing of the LED light. I prefer the solutions which attempt to smooth the LED current.

 

It would be interesting to see if this effect occurs on all kinds of low-votlage transformers. From my experience, this sort of thing is usually a result of the transformer being unstable and sending high current spikes to the LEDs at low dimmer settings. The kinds of transformers that the Philips MR16's are typically connected to were never designed to run LEDs so the Philips lamps are employing tricks to try and keep the transformer operation stable. This usually works when the lamps are just switched, but not so well when they are dimmed.

As you're dimming them up the increase in current stops very suddenly. There's no soft roll-off of the LED current as you hit maximum brightness. The LED current doesn't overshoot, it just stops suddenly when you hit the max. I suspect what you're seeing is the split-second it takes for your eyes to adjust. To test this theory, try dimming them at a slower rate. You probably won't perceive any overshoot.

The Starbursts have quite a bit of output capacitance and it takes a few moments for this to charge up enough to reach the turn-on voltage for the LEDs. The trade-off is very low ripple DC for the LEDs and low ripple means less heat in the LEDs, higher efficiency and longer life.

 

Thanks Guys.

Any one tried the D900 against the Starburst? I see they have pulled some interesting antics (BrightGreen that is) on these forums... but wonder if the product is as good as they say it is - and appears to be winning a few awards.

Cheers

 

The D900/D1000 seems like a good product. On the plus side I've tried one on quite a few dimmers and it worked well on all but 1 of them. It's definitely a warm white and they do seem a fraction brighter than the Starburst when cold, although the difference is nowhere near as great as it should be given the "numbers on the box" for both products. It worked just fine on the C-Bus dimmers.

On the minus side the lamp driver isn't particularly clever. There's no integrated thermal management, so you might need to be careful installing them in hot spaces. The maximum brightness was definitely affected by the different dimmers I was using. The minimum brightness is a lot higher than the Starbursts and on one dimmer I tested the D900 wouldn't turn on if I flicked the switch with the dimmer set to minimum. I can just see a 220uF capacitor inside the driver next to the output terminals, which is bugger all when operating at these sorts of currents. The light output also dropped noticeably as the lamp warmed up so I think the heatsink design, for all it's CPU-heatsink-like design and colossal size, isn't actually very effective.

To test the effect of the dimmer on minimum and maximum current I hooked it up to both mains and a dimmer. Connected directly to mains I measured 698mA of LED current. I then hooked it up to a Clipsal Universal dimmer (non-C-bus) and measured 623mA at max and 177mA at min, so that's dimming from about 28% to 91%.

After that I hooked up a Starburst and a D900 and connected them both to a C-Bus Universal dimmer and left them on the bench to warm up and came back an hour later. I honestly couldn't pick the difference in terms of light output.

 

Thanks for your comprehensive test report, Newman!

I tried several times to purchase one of these and was either told that they were not yet in stock, or "we've never heard of that" (from the recommended distributors). I suspect living in NQ is part of the reason

Anyway, now I don't need to keep trying to get one to test it!

 

I've set up a 8ch dimmer on a test bench with some pierlite starburst led 12w connected

From what I've heard and everyone I've spoken to I keep getting the same answer, use universal dimmers for LEDs.
I wanted to see this for myself.

Despite the approved dimming sheet saying the the pierlite is starburst compatible on the L5508D1A, the dimmer has some noise when the light is on dim.

I've also tried 2 of the brightgreen d900, d700 , dr700 with viper transformer per channel and they all do the same thing, noisy dimmer whilst dimming. The d900 is much louder when under dimming on the L5508D1A compared to the rest of the fittings.

All in all they dim,Verne better than others but the starburst probably dims the best on this dimmer

I then connected the same fittings to a universal dimmer.
Sure enough they all dim well with no noise coming from the dimmer at all.

Has anyone else tested something similar??

Also the starburst is approved for use with the L5508D1A, how do they justify approved?

And in terms of the pierlite starburst, will using it on the L5508D1A cause any damage to the dimmer itself of the light fitting over a prolonged period?

 

Hello alepore

If it comes to making a dimmer purchase decision then the Starburst specifications should allow a much greater number of fittings per channel on the universal dimmer.
The universal dimmer should be quite cost effective.
It's also easier to plan for universal dimmers than wonder where you are going to fit 2 x 4 channel dimmers to replace the 8 channel dimmer at a later stage.

I've been using an early version of the Pierlite Starburst for 2.5 years now on a leading edge dimmer without any problems.
Cant find the model or specs right now but at the time it had a datasheet with various CBus dimmers and recommended fittings per channel which was a nice touch.

Identical to these as far as I know.
http://www.crompton.com.au/catalog/...ucts/kled12-xl-led-performance-downlight-kits

My leading edge dimmer is in my office and it has always buzzed a bit when dimming, even when there was electronic transformers and halogens connected.
It is not a problem but you do need to keep in mind to locate it somewhere the noise is not going to annoy.
I am very happy with the lamps themselves and their operation on the 8ch dimmer.

Thanks for passing on your experience with the universal dimmer and lack of buzzing.
I think it was Ashleigh who suggested this to me some time ago but it has not been enough bother for me to act on it.
The slight buzzing is greatly reduced once the dimmer is in an enclosure and the door shut.

You definitely do need to consider the CBus board location as clicking relays could be just as annoying.

Regards
Daryl