Dimmers getting dimmer and dimmer and I'm not sure I can see the light any more

The problem is that all the decisions are interrelated, and it's very difficult to make one without having already made several others. Change one and the whole house of cards comes tumbling down and needs to be built up again.

Having given up on the idea of the great low-voltage series cable light system and chosen some LEDs that will dim, I then had to go back to find a suitable dimmer and power supply. The site that sells the LED was very insistent that I needed a magnetic dimmer switch and a magnetic transformer. I did a little research into these and found that they are difficult to find in Japan. Where I could find them, they were for hundreds of watts, while I'm looking at around 20 watts for each of my circuits. This may or may not be a problem in terms of delivering reliable low current and low voltage, but it seems like using a pneumatic drill for dental surgery, and may lead to a system that hums but doesn't dim. 

Because the dimmers work on mains voltage, I would need two of these transformers, each one literally more highly rated than all the lights in the house.

Kingdom of consumer electronics that it is, in Japan wire-wound transformers are like antiques, and difficult to find among the slim and efficient switching transformers on the market here. They are at a premium, perhaps due to all the copper in the wire windings.

It seemed a much better bet, and around 10% the financial risk, to go back to AudioQ and get one or two of their constant current power supplies, sending it straight to the row of lights but this time putting them in parallel. While they had nothing for 36 volts, they do have some adjustable power supplies for 1400 mA, between 5 and 25 volts, which should get the LEDs going.  

I wanted to get some idea of whether this would work or not with the circuit inside the LEDs, which are from Earth Leds and I even emailed them for technical support. I asked a couple of times about their Leds with their wonderful and trademark Lumiselect dimming technology, and whether it would respond to a variable current signal.

The only answer I got, in increasing tones of frustration, was that I needed a magnetic dimmer and a magnetic transformer, and everything would be fine. 

And perhaps they were right, and everything would have been fine if I'd spent over the odds for their LEDs, a transformers and dimmer switches, which I may also have had to import from the US.

As for the transformer, copper's quite valuable at the moment, so it might have been a good investment. 

But we'll see. 

Or not, if the lights don't work at all.

Further Reading for the Link-Lustre

Here are a few of the magnetic dimmers I was looking at, but didn't buy. Click at your own risk.

http://www.amazon.com/blahblahblah

6613 PLW

http://www.leviton.com/blahblahblah

 

Reading the reviews reveals that some of these switches are very delicate, or perhaps they guy runs a karate school. This is a really good one. I should spend more time reading product reviews on Amazon:

http://www.amazon.com/Lutron-DVLV-600P-WH-600-Watt-Low-Voltage-Single-Pole/product-reviews

http://www.hankselectric.net/pdf/Lutron/Diva/divaSpec.pdf

Lutron 

http://www.amazon.com/Lutron-Magnetic-Low-Voltage-Dimmer-Switch/

Diva DVLP 600P

http://www.lightology.com/blahblahblah

Maestro family

http://www.lutron.com/blahblahblah

29.99 on Amazon

http://www.amazon.com/Lutron-MAW600H-WH-Electronics-Maestro-Dimmer

In Japan:

http://www.akaricenter.com

info on them

http://denko.panasonic.biz/Ebox/lightcontrol/knowledge

Low-voltage tension cables. Back to parallel not series

The electrician has been correspondeding with Nayuta, manufacturers of constant current power supplies, and they had the perfect model, with the right voltage and the right range of currents that could be varied. The problem was, they did not know how to vary the current. The power supply has a screwdriver trimmer wheel on it, and there are terminals to connect something to vary the current, but they do not have the something, nor could they, or the electrician, find one. If you can understand that, please explain it to me, because it does not make sense.

I also found some power supplies from AudioQ (Japanese only), with volume controls, which looked promising. They put out up to 350 milliamps, which should be about right for a 12 volt, 4 watt bulb, between 2 and 26 volts.

We want 3 bulbs on one circuit, which at first I thought would be no problem--they would just not come on at full brightness. Then I remembered the VI curve for LEDs and that the D is for diode. If there is much less than 12 volts going through each LED, or 36 volts total, then they will not come on at all, however many amps are available.

So this would only work if we had two bulbs on each circuit. Also, the electrician seemed much happier with something in a box, rather than having to install a bare circuit into the wall.

There is another nagging worry though. Even if the current could be adjusted, and the voltage kept at suitably high, would the bulbs actually respond properly, or would their circuits mess things up?

I'm sure the parts must be out there somewhere, but after a few months of searching we haven't been able to find them, so it's time to go to plan B, which is to use a standard voltage dimmer switch, get LED bulbs that work with dimmer switches and hope for the best. The danger with this is incompatibility between dimmer and bulbs, leading to flickering. As there are three bulbs, one of them may flicker at any level, and we'd be left with an elaborate on/off switch. 

I'm about to order some lumilux fully dimmable LEDs from EarthLED, which apparently work with magnetic transformers and dimmer switches. These seem to be available, although the electrician's first suggestion was a switching power supply and a pulse wave modulation (PWM) dimmer switch. As each of these, and no doubt the controller within the dimmable LEDs, are electronic circuits, each with their own frequencies, the chances of interference, harmonics or beats is quite high.

Not at all relevant, but  here's another constant current, non-variable, power supply.

Dimmable bulbs

I visited Hisashi's bar, Oread, in Tatsuno the other day, and he was saying he wanted to change his lights to LEDs, but had been told it was impossible. He puts on live music in his bar and would like to use LEDs for his stage lights, and adjust them with the row of dimmer switches.

So, if all you need to do to dim an LED is change the current, then why would any LED NOT be dimmable?

The problem is that whenever an LED is packaged into a bulb or fitting, some electronics are added. This is essential to put a cap on the current or voltage and stop a melt down. So the question is whether the bulb has a one-size only approach, and will only send a specific current through the LEDs, or whether it has a cap, and will allow any current to go through, as long as it is no more than the limit.

If the electronics will only send the designated current, then all bets are off regarding dimming. If there is not enough power going into the light, the required voltage will not be reached and no current will flow. LEDs may not obey Ohm's law, but they do obey P = V I. The power will always be the product of the voltage and current. This is sometimes erroneously referred to as Watt's law, but Watt actually had nothing to do with electricity, and the unit we use for electricity was given his name posthumously. P = V I is actually a Joule's law, or a combination of P = I2 R with Ohm's law, V = I R. Back to the LEDs with fixed current internal power supplies, either there will be enough power, and the voltage will be high enough for the full current to flow, or there will not be enough, and no voltage will flow. However fancy the dimmer circuitry on the outside is, dimming won't happen.

If, on the other hand, the electronics put a limit on the current and will only allow current to flow below the meltdown level, then we're in with a chance.

Anyway, there are plenty of dimmable LEDs, in the sense of dimming with a conventional dimmer. Here's one from the US:

I'm only really looking at MR16 GU5.3 bulbs at the moment. These are low-voltage halogen types that I need for the tension wire system.

I got some E17 bulbs for around eight or nine hundred yen to play around with and try out in various appliances we already have. On the bulb instructions, it said we should not, under any circumstances, use the bulb in a fitting with a dimmer, so we tried it in a desk light with a dimmer. Nothing really exciting happened.

As we turned the switch up, first of all, nothing at all happened. Then the light came on, flickering very quickly, almost too quickly to notice, a little below full brightness, then it flashed in one pattern, then flashed in another fashion, then came on at full brightness. What seemed to be happening is that the dimmer on the desk light was interfering with the circuit inside the bulb.

Sharp have a regular lightbulb-like LED, left, which will apparently change brightness.

This site from KC Lightech  also boasts dimming LEDs, in GU5.3. It looks like Cree LEDs inside. They recommend a Panasonic power supply. I wasn't sure how I could actually buy them so I called. They have no stock and will ship an order of a hundred. I only want six!

 

There is a Philips light here for 6,384 yen a throw, 10W, which can dim, depending on the power supply. They don't always work, but do with Maxray, Daiko, Endo and Koizumi.

This 5.5 W light from Decolight is only 1,200 yen. although it doesn't mention which power supplies it will work with, and careful inspection reveals that it is 100 volts AC. And I thought MR16 GU5.3 was a 12 volt DV size.

 

Flickering lights? Damn those dumb dimmers!

Mark from Yamagata writes:

Dear Sir
After reading the latest doses of your blog, I have a question for you. We have LED down lights in a number of rooms, and at a certain brightness they flicker, usually only intermittently. We have been told this is an irresolvable issue, a clash of LED vs dimming technology Comments?

LEDs are diodes. Diodes are semiconductors and this means that sometimes they conduct and sometimes they don't. A regular diode will conduct if you send electricity one way, but not if you send it the other. As their full name "light emitting diodes" suggest, LEDs emit light if you send current through them one way. I heard a company in Korea is developing diodes that will light up whichever way you send current through, which is a good idea in the world of AC power supply.

Anyway, there's a threshhold, usually 2 or 3 volts, at which they'll turn on. Since they are diodes and conventionally it only matters whether they pass electricity or not, on or off has traditionally been sufficient for conventional LED uses on displays. LEDs will produce more light with more current, but only above a voltage threshhold, and if there is too much current, the diode will start melting.

Dimmers traditionally work as variably resistors, so the more you turn them, the lower the resistance gets, and the less voltage there is across the dimmer and the more voltage there is going through the light. Conventional Edison-style incandescent lights also work like resistors, so the current is proportional to the voltage (as I'm sure you can remember from Ohm's law) and the amount of heat and light increase accordingly. This kind of old fashioned dimmer may work with light emitting diodes. Alternatively, it might work really badly as the LED will not turn on until the voltage is high enough, and may not dim the light; just turn it on or off.

The problem with resistors is that the current going through them is turning into heat all the time. More recent dimmers work by rapidly switching the electricity on and off. You can see more here on how stuff works dot com. The AC comes in as a sine wave, and each time the sine wave crosses the zero volt line, then switch a little later. If you're only dimming the lights a little, they will switch on very quickly. If you're dimming a lot, they will switch on just before the voltage goes to zero again. This kind of dimmer should work well with an LED as it will switch it on for a shorter or longer part of the cycle.

LEDs use direct current (DC), not alternating current (AC) so within an LED "light bulb" there may a row of LEDs adding up to 100V, and a ring of diodes known as a wheatstone bridge which sends the input AC voltage in the right direction so that one output is always positive and the other is always negative. Or they may have a step down transformer inside them. AC-DC power adaptors usually work by switching the AC to a much higher frequency, then converting it to DC. They may just be switching the voltage off when it's at the top of the sine wave, and far higher than is needed.

The flickering problem with the LEDs may be caused by a number of things. It could be that at a certain level, the voltage is close to the threshold for the LEDs to come on, so they are switching on some cycles and not switching on other cycles. Anything switching on and off 50 or 100 times a second is going to appear to be on all the time. Depending whether it's a US-based system or a UK based system, TVs change their pictures 25 or 30 times a second without appearing to flicker, but if you get down to about ten times a second, it's going to be obviously flickering. Apparently, this is known as the flicker fusion threshold.

By the way, the difference between the 25 frames per second in the US and 30 frames per second in the UK depends, in turn, on whether the voltage is at 50 Hz or 60 Hz. The eastern half of Japan is 50 Hz while the western half is 60 Hz, apparently because in each half generators were introduced from the US and Europe respectively. This means that Japanese electrical appliance are generally made to work at either frequency, which has probably been an advantage in their international marketing. However, I digress.

Another possible cause of the problem is that there are two systems both chopping away at a sine wave, and there is some interference going on, resulting in a lower frequency flickering. If this is the case, and the LED lights have their own devices for chopping 100V AC into lower voltage DC, it may be that an old style variable resistor dimmer would work better.
I asked Mark for more details and found that the "certain brightness" at which they flicker was usually at about two points on the dimmer scale, say 1/3 and 2/3, but not exactly the same for each light, and the nature of the intermittent flickering was that they flicker for a few seconds, then stop, then flicker for a few seconds again, then stop, and so on.

As a solution I suggested he could just try avoiding the level at which they flicker when he dims them, apologising that this was both obvious and not very helpful as the level at which they flicker is clearly the level he wanted! He went on to say:

We have several types of dimmer down lights. The ones that are flickering have replaceable LED bulbs which are not built into the unit. The second type are unreplaceable (as opposed to irreplaceable--a good English lesson there--and built in. They apparently have 200,000 hours in them which will outlive me (though I think the max is really 40,000). These never flicker. At least not yet.

The life expectancy is usually 40,000 hours, but that's 40 years at 3 hours a day, which I think will probably outlive us anyway! In my opinion, irreplacable lights should be unreplaceable.

The ideal solution for dimming LEDs would seem to be a dimmer power supply that will output the correct voltage and current for a DC LED. This is available, even in Japan, for example here on Rakuten. But in the worst case, there is an LED light bulb screwed into a conventional fitting, connected to a dimmer switch, and the dimmer switch and the electronics inside the bulb are left to fight it out.

LEDs may be an irresolvable clash between electricians and new technology.

You can see more about how diodes work here on how stuff works dot com. The graphs above came from this website.