Who's the Guru on Dimmers + LEDs & Electronic Transformers now days?

Hi all - I am a C-Bus oldie, back here after a FIVE YEAR break!

I've been working in Energy Efficiency consulting and some other stuff, and have just started a new role with a supplier of LEDs.

The challenges of dimming LEDs (either with dedicated drivers or using ELV transformers) is still a problem. I am currently trying to fix up a number of projects where our Trailing Edge drivers have been used with C-Bus in pubs and restaurants, and they are acting pretty strangely. Unhappy clients ahoy!

I know about and have posted a fair bit here about the general issues surrounding electronic loads, but I've been out of the Clipsal fold for a long time now and I've lost track of the current status quo. Worse, I no longer have access to C-Bus devices to play with in the office!

So I want to try and get some help with troubleshooting. Identify are the typical symptoms of various issues, and learn how to work through and solve them.

Capacitance problems
Flashing and flickering
Insufficient load on channel
To much load on channel (? capacitance)
Triac misfiring at low dim settings
etc

32EIND
31CAP
Bottom Loads
Adding Halogen lamps
Adding Iron-core transformers (with no lamp)

So who are the experts who know all this stuff, and who can assist me?

Is there a "troubleshooting dimmers for dummies" guide already printed?

Thanks in advance

 

I have installed a XL-LED (KLED12FW4K) 12W. It is a Crompton product (part of the Gerard Lighting Group). This was a trial before replacing remaining halogen lights on the site.

The products matches all my expectations. Smooth dimming over the full range. Looks like a well made product, but not cheap.

 

Yeah, I have finished doing that. It's just the same old stuff as 5 years ago with CFLs, and 10 years ago with Electronic Trannies on halogens LOL

Yep, and there are 2 separate issues... new builds and retrofits. Under the various Carbon Trading schemes (NSW and VIC) a heap of LEDs get installed into legacy projects. I currently have 3 projects that I have to troubleshoot - restaurants and pubs. Flickering, flashing, instability, etc.

If you were building a NEW project, you wouldn't want to use "dimmers" on LEDs anyway. There are 0-10V and DALI drivers that work far better, so there's no excuse to try and kludge together a phase-cutting dimmer for LED loads. But that is what people do, unfortunately.

I know - and most people don't realise that C-Bus is basically just a communication protocol, not a dimming system. It doesn't help that all Triac dimming systems get all manner of issues of "ringing" and misfiring when they are connected to these dirty loads (like LEDs). I've compiled a lot of good info from people like Lutron, who are facing the exact same challenges but on an even more massive scale.

What makes it really hard is when the dimmer/LED combo is fine on one project, then on the next one the exact same hardware will be acting strangely. There is a lot more to it than just saying "C-Bus compatible" hardware, because even the load cables and config seem to have a bearing. I'm reading reports of mains ripple switching and voltage spikes causing instability as well... so many external influences!

Yes I saw that, and I know who they are. They have a big following those guys, they do very well selling their Bright products on the Whirlpool forums.

 

The Chinese will tell you anything to make a sale. And the people selling this stuff is almost certainly not from any form of lighting background, so they don't have any practical experience with all this stuff.

However there is also some very clever new driver chips coming along that do all sorts of trickery to make them work with phase cutting dimmers.

They are now monitoring the phase angle and then switching in resistive, capacitive and inductive loads in as needed to present a "triac friendly" load profile. Active Power Factor correction, and modification of the driver's output to better replicate the dimming curve of halogen (ie removing that dead band at the top and boittom of the dimming range).

But it's not really the LED guys who are solving this, but the control chip manufacturers like Cirrus Logic and Texas Instruments.

It's sad that there is such a frenzy about these LEDs yet many consumers get let down because the practice just doesn't match the hype. I cannot imagine how frustrating it must be for a normal householder to try and deal with this stuff.

 

ANYWAY...

What I am hoping to do is make up some form of "flowchart" that lists the problems, and the solutions.

For example this afternoon I was testing various low power LEDs with a 32E450LM dimmer mech. There was various problems, and it was possible to get one LED flickering and that would induce flicker in another, whilst the third one wasn't effected. These were different brands, chosen at random from our samples.

But what was very interesting was that almost all the problems were solved with a simple resistive "bottom load". We got this sample from China, and it's just a a 11k Ohm resister witha heatsink on it. It draws about 5W, but it really helped the triac to not go silly.

Apparently the exact some solution can be done from adding a standard wire-wound TM-50 transformer across the channel. Surely all this drama couldn't be THAT easy to solve? Anyway, that is the kind of info that I am trying to compile - For example:

a) Leading Edge, Flickering at low levels --> Add resistive load
b) Not dimming enough (like stuck on) --> Add more load
c) Snap on --> ?
etc, etc

Something simple to lead people through the process of solving things. Because right now, nobody seems to actually know what to do!

What are the common issues anyway?

How do the Clipsal Tech Help Desk guide users through this mess?

 

Yeah, that is OK, that's exactly what our company does - develop products and get them safety approved. EVERYTHING we sell is fully tested and approved and certified. The dummy load device is earthed, plus double-insulated as well - it's a proper commercial-grade product, not some dodgy thing.... but right now I am just testing them.

The sample unit is pretty massive, maybe 80-90mm diameter and covered with round "pins" (like a porcupine) about 25mm tall, and it didn't even get particularly warm after a whole afternoon plugged in.

The thing is, at 5W it dissipates less power than a stock standard Atco TM50 wirewound transformer. I think that they both do the same job, so might as well just tell the electricians to leave an old tranny in the circuit.

These are the types of tricks I want to learn about.

 

Welcome back!

Hi JohnC
Welcome back!
I concur with your sentiments. IME C-Bus dimmer + Electronic Tx + LED lamp = Headache.

I did one project where we used Osram AR111 LEDs (because they supposedly like leading edge dimming) on Existing C-Bus D2A's and unknown electronic Tx's (concealed in the ceiling space due to fancy flush plaster finished recessed down lights where you could not access the gear without cutting the luminaire out of the ceiling). We did a trial of one and for 3 weeks it worked fine. Roll out the other 70 and every scenario happened. Some failed, some flashed, some were just dim and some glowed and the odd one worked fine. In the end we went back to the halogens.

Sleep easy Ashleigh, I can assure you John would not be that careless.

This is an interesting question.....

 

I just leant something new today

New Clipsal "load correction" device: 31LCDA

Brochure: http://updates.clipsal.com/ClipsalOnline/Files/Brochures/A0000268.pdf

Installation: http://updates.clipsal.com/ClipsalOnline/Files/Brochures/W0001577.pdf

Very interesting - claims to solve all the various minimum load issues!

Does this work with C-Bus, and if so how well does it work?

(NOTE this probably doesn't solve the excess capacitance issues on Leading Edge dimmers, where a 32EIND is needed in series to prevent dimmer overload)

 

OK - here's my current "bottom line answer", but haven't tested much of it.

Any feedback or comments very much appreciated...

----------------

OVERVIEW

Dimming problems are primarily caused because the domestic dimmers were never intended to work with LEDs in the first place. Furthermore, the dimmers are generally manufactured as cheaply as possible, which might be fine for incandescent and halogen, but not great for LEDs or CFL lamps.

It is very important to understand that it?s not actually the LED?s fault that the dimmer misbehaves when a halogen lamp is removed and an LED is added in its place. This is fundamental in understanding what?s happening? it is the DIMMER that is making the LED flash and flicker, not a fault of the LEDs themselves. Furthermore it is literally impossible to manufacture a LED that will dim perfectly on every dimmer that has ever been made in every country in the world.

Many LEDs are very good, but they cannot make a bad dimmer into a good one. Also note that some problems simply can?t be solved ? an alternative lamp and/or dimmer combination will need to be selected. All brands of Dimmers and LEDs have dimming problems to some degree, however changing the brand of dimmer or LED can often result in a solution.

START HERE

The first step is to KNOW (not guess) what brand, model and type of dimmer is being used. This must be physically checked by removing the switch plate ? the dimmer type is then determined by online search of the part number. As a very general rule, if it doesn?t specifically state ?Trailing Edge? or ?Universal?, then it will be Leading Edge. If it?s old, then it is almost certainly Leading Edge.

Most consumers don?t even know what dimmer brand and type they have already, and each room might have a different model. So nothing can be assumed. A list of dimmers and the quantity of lamps on each must also be compiled.

Any part numbers specified below are from Clipsal only because I know about the range, not because they are better. It is certainly not a recommendation. This info generally relates to domestic wall-plate dimmers (under 500VA), and NOT to C-Bus, Dynalite, stage lighting, large commercial dimmers, etc.

LEADING EDGE DIMMERS

Excess Capacitance (dimmer overload) > Clipsal 21EIND in series (400VA max per inductor)
- blocks capacitive effect from overloading the dimmer triac.

Insufficient load > Atco TM50 transformer in parallel (don't fit a lamp)
- adds more inductive load, stops triac misfiring

Dimming issues generally > Clipsal 31LCDA in parallel
- adds a complex and optimised correction to the load

TRAILING EDGE DIMMERS

Insufficient load > Clipsal 31CAP in parallel
- adds more capactive load (note this may NOT fix anything)

Dimming issues generally > Clipsal 31LCDA
- adds a complex and optimised correction to the load

UNIVERSAL DIMMERS

These units switch between Leading and Trailing edge, depending on the load type they detect at power-on. So, the solution will depend on what load is connected... probably easiest to just use the Clipsal 31LCDA

NOTES

The above are just things to TEST, not solutions. Do not roll out any solution without testing first. You will need to test each and every sub-circuit separately and individually...
- What works on one site may not work on the next.
- What works for one dimmer model may not work for the next.
- What works for one LED driver may not work for the next.
- What works for 3 lights on a circuit may not work for 4 lights on an identical circuit.

More than one TM-50 transformer may be required to stabilise a circuit. The transformer draws about 5-6W at 100% (less when dimmed), and remains cooler than if fully loaded with a halogen. Adding too many won't hurt a leading edge dimmer. But adding these transformers may actually make the situation worse - if so, then try something else.

LINKS

Clipsal 31LCDA - Leaflet and installation manual
http://updates.clipsal.com/ClipsalOnline/Files/Brochures/A0000268.pdf
http://updates.clipsal.com/ClipsalOnline/Files/Brochures/W0001577.pdf

Clipsal 32EIND ? Product page
http://updates.clipsal.com/ClipsalOnline/ProductInformation.aspx?CatNo=32EIND&ref=

Clipsal 31CAP Installation manual
http://updates.clipsal.com/ClipsalOnline/Files/Brochures/W0001507.pdf


PHEW

 

Hi John,

It looks like you have been researching this topic extensively for some time now. I would like to add the following major road block;

There is a lack of lighting standards that specify how an LED fitting is to be made.

Take halogen globes, their are standards that define how that globe must function and work. Therefore it is possible to make a good phase dimmer that can dim halogens globes with consistent success. Halogen globes that do not meet the standard are not sold and are not accepted.

Above you mentioned "good" and "bad" phase dimmers being the fault for the LED. There is no one accepted way to build a circuit to light up and dim an LED, and unfortunately it seems any LED that will turn on and light up will be imported and accepted. So if there are no standards for LEDs, how does one determine that a phase dimmer is "good" or "bad" for LEDs? How can standards be written when the technlogy is still changing so rapidly?

While I agree with your quote "it is literally impossible to manufacture a LED that will dim perfectly on every dimmer that has ever been made in every country in the world", I would say it would be an even harder task to manufacture a phase dimmer that can dim perfectly with every LED.

I think you hit the nail on the head earlier when you said the following:

It is easy to acquire DALI LED Downlights, and if you get the right brand its the safest way to have a consistent CBus dimmable LED solution that will work without any LED flickering issues.

 

rhetorical question

Hi John
It appears you have answered your original question " Who's the Guru on Dimmers + LEDs & Electronic Transformers now days?"

Thanks for a very informative post.