An LED lighting project

[ddrueding]

This thread started as a PM from me to jtr, inquiring about him doing some work. I figured others here might be interested, so here it is.


My wife brought over an antique chandelier home from Moscow. Ok, it isn't an antique, but it is a family heirloom of sorts. In fact, it is new enough that it is electric with fake candles. 10 fake candles to be precise. This thing was built in the '60s, and designed to run on 220v. It has no certifications, no safety ratings, and would likely void my homeowners insurance if I used it as-is.

My thoughts are to have a certified AC->DC power supply in a junction box in the attic, then make everything in the fixture low voltage (so no certification is needed, and there is no risk of fire/etc).

Mission #1 - Minimal wiring:
This actually hangs from the ceiling from a hook, and has a chain section. Minimizing the number of wires leaving the ceiling would be great. There is some space in the fixture itself for a circuit board/logic/power distribution board.

Mission #2 - Candle-like appearance:
Originally it had some plastic tubes with incandescent bulbs sticking out the top, improving on that would be great. Some option for flickering might be neat, but it would have to be switchable.

 

[ddrueding]

(JTR's response)

This sounds like an interesting project. It should be fairly straightforward also. Basically, I would make one or more regulator boards to drive the LEDs. I should be able to use the same boards I'm using for another product. They fit in a 1" square potting blox. Flicker, dimming, or anything else you may need is easily done via the control pin on the board. For the greatest number of possibilities I could use a microcontroller for the functions. I've already done some simple microcontroller programming.

 

[ddrueding]

Excellent. What dimensions do you require to confirm what you have will fit?

Will this be dimmable from a standard 120v dimmer, or will it require it's own special controls?

 

[jtr1962]

Excellent. What dimensions do you require to confirm what you have will fit?

Do you have space inside the chandelier to fit a couple of 1" x 1" x 1" boxes? That's all we'll need for the internal electronics. All you'll need coming out of the top is a pair of wires to hook up to the power supply.

Will this be dimmable from a standard 120v dimmer, or will it require it's own special controls?

This will need its own controls. A standard lamp dimmer will only work with a 120VAC LED ballast specifically designed for it. In this case, since you're using an AC-DC power supply, there's no way to make it work with a standard lamp dimmer.

Would the controls be mounted on the chandelier, or elsewhere? If elsewhere, then we should be able to get by with running only three wires ( two to power the controller, and one for the PWM signal back to the LED drivers ). The wires are low voltage, low current, so a very thin cable similar to phone wire will work just fine.

On/off can be controlled by separate 120VAC wall switch which simply cuts off the power to the AC-DC supply.

Stuff to think about:

1) How many lumens would you want out of this?

2) Do you want dimming and/or flicker?

3) What color temperature?

4) Would you want to also add in amber LEDs to enhance the "flickering candle" effect?

5) Knob or push-button dimming control?

6) If push-button control, do you want the chandelier to remember the previous light level when turned back on, or should it always start at full brightness?

 

[ddrueding]

We could easily fit a bunch of 1" cube boxes in there, or a larger circuit board.

Building the dimmer into the fixture would work fine, so long as it remembers its last setting when power is restored (flicker and brightness).

1. Representative of candles is fine, there are also recessed lights to back it up if needed.

2a. Dimming - Yes.

2b. Flicker - if it isn't too complex. In order to make it look good, I think the 10 would need to flicker independently, which might mean different controllers for each? Would also need to be able to disable this feature.

3. Representative of candles is fine, 3500K? Something like that.

4. Sounds good, but how would multiple LEDs be integrated into a "candle flame" head unit?

5. The dimmer can be in the fixture itself, so any kind of slider would work. Remembering the previous setting/config is a must.

 

[jtr1962]

We could easily fit a bunch of 1" cube boxes in there, or a larger circuit board.

Building the dimmer into the fixture would work fine, so long as it remembers its last setting when power is restored (flicker and brightness).

That shouldn't present a problem.

2b. Flicker - if it isn't too complex. In order to make it look good, I think the 10 would need to flicker independently, which might mean different controllers for each? Would also need to be able to disable this feature.

I agree you probably need to have all ten light sources flicker randomly and independently for good effect. I'll have to think whether and how this can be done with minimal complexity.

3. Representative of candles is fine, 3500K? Something like that.

Actually, probably closer to 1900K.

4. Sounds good, but how would multiple LEDs be integrated into a "candle flame" head unit?

The idea of using both amber and white would be to use only the amber for simulated candlelight since it's closer to the color of candles, and use only the whites when using the chandelier for illumination. Basically, the "candle mode" would be a decorative special effect. This way the controller for the ambers could be something relatively simple since the amber LEDs would be running at fairly low power.

5. The dimmer can be in the fixture itself, so any kind of slider would work. Remembering the previous setting/config is a must.

If we use a slider potentiometer to control the dimming, then we won't need a microcontroller. By definition a slide pot will start in the previous setting. Maybe all we need to add is a switch to go between illumination and "candle" modes.

 

[ddrueding]

That all sounds great. Let me know of you need any additional info.

 

[jtr1962]

If you can take a few pictures of it that would be nice. I basically want to get some idea of how much space I have to work with where the emitters will go. Also, this will let me figure out heatsinking options ( i.e. size, shape, etc. ).

 

[ddrueding]

For the controller, heatsinking shouldn't be an issue; the whole thing is about 70lbs of cast brass. For the LEDs it might be more difficult. At the moment there is a plastic tube that looks like a candle with the light on top. Not sure if we need to make these out of aluminum and paint them white?

It is still in pieces in a box, so I'll get it stuck together and send the pictures off when I can.

 

[jtr1962]

The controller shouldn't need heatsinking. Typically my LED drivers are 90% to 95% efficient, depending upon how close the LED string voltage is compared to the input voltage. As such, you're usually talking about a watt or so of heat in the controller.

Making the candles out of aluminum rod painted white is one way to go. You would need to get one end smooth enough to be able to attach the LED with thermal epoxy. This setup probably won't be able to dissipate a huge amount of heat, but I'm guessing we could probably run the LEDs at 500 mA maximum. Using the best bin XPGs, you could get about 200 lumens per LED, 2000 lumens total. We may even be able to increase the current further if we used rods with small fins.

 

[ddrueding]

No need to go crazy on the illumination. This chandelier, combined with a pair of 5" 75W cans, is responsible for illuminating the dining area (10'x15'), and still has support from the lights in the kitchen area and the french doors. There is even talk of having a pair of wall sconces made to match the chandelier that would also be in the room.

 

[Gilbo]

Cool .

 

[ddrueding]

Just some neat pictures from a previous project JTR has done for me; LED lighting embedded in the bottle racks light the bottles from below. These pictures were taken during the day, and I'm not so good with a camera, and the chair was moved during an exposure, but you get the idea.

Images on my Flickr page.

Thanks JTR for a fantastic job!

 

[jtr1962]

I'm surprised how bright the bottles look even with the sun lighting the room.

BTW, I found a nice dimming ballast for this project which will make our lives worlds easier:

http://www.newark.com/roal-electroni...ver/dp/69R7347

It works on a standard lamp dimmer. A little pricey but well worth it for the time it'll save. I have three chandeliers in the house I plan to convert to LED eventually. This ballast is just the ticket.

 

[ddrueding]

That does look ideal. Now that the sheetrock is up, we can start to worry about this again.

After looking more at the chandelier, I'm thinking it might be a better idea to put all the controls and electronics in the attic and feed power down to the LEDs in the unit. Would the extra wire length (1.5m?) complicate things significantly? How many wires and of what gauge would be needed?

 

[jtr1962]

After looking more at the chandelier, I'm thinking it might be a better idea to put all the controls and electronics in the attic and feed power down to the LEDs in the unit. Would the extra wire length (1.5m?) complicate things significantly? How many wires and of what gauge would be needed?

No, shouldn't be an issue. The LED ballast is sending DC to the LEDs. There aren't an RF or other issues with DC. You can probably put the ballast a mile away from the chandelier without any problems. The only issue is for the wires to be heavy enough to carry the current without heating significantly. That's a non-issue for us since standard house wiring carries up to 20 amps. Here it's only be asked to carry 1 amp. BTW, only two wires are needed, and any wire gauge suitable for house wiring will do.

Now some things to think about. OK, simulated candle flicker is probably out now since we're using this ballast. We'll basically have dimmable constant-on lighting here. Next step is picking which LEDs we'll use ( color temperature, CRI ) and figuring out the heatsinking. Replacing the plastic tubes with a round finned aluminum extrusion of some sort in a similar length/diameter should work well while being aesthethically pleasing. The trick is running the wire from the LED into the chadelier body so it can connect to the next LED. Maybe run it right along the tube? If we paint everything white, and hide the wire towards the inside of the chandelier, it shouldn't be overly noticeable. We can get by using thin wires for the internal chandelier wiring anyhow. I'll have better suggestions once I can see some pictures of it.

 

[ddrueding]

Ah, yes, pictures. I'll do those tonight if I can.

If we were using aluminum tubes for the candles, couldn't we run the wire inside the tube? The fixture is designed to take the wires inside the tube and then through the inside of the fixture to the top, if we can use small enough gauge.

 

[jtr1962]

If we were using aluminum tubes for the candles, couldn't we run the wire inside the tube? The fixture is designed to take the wires inside the tube and then through the inside of the fixture to the top, if we can use small enough gauge.

Umm, yeah. The only issue with hollow tubes as opposed to solid rods is worse heat dissipation. I probably need to experiment a bit here to see how warm the LED would get. A tube with 1/8" walls might be good. We can mount the LED on a circular piece of aluminum ( or even a copper penny ) on top of the tube. If we use copper tubes we can even solder the penny on top! Remember here we're talking about only ~3 watts of dissipation per tube. That shouldn't represent a big heat problem.

 

[ddrueding]

I gotcha. You mentioned the flickering being out because of the dimmer. Could we make the flickering a seperate light mounted to the same fixture with an independent on/off switch?

 

[jtr1962]

I gotcha. You mentioned the flickering being out because of the dimmer. Could we make the flickering a seperate light mounted to the same fixture with an independent on/off switch?

You could do that. Perhaps put another set of LEDs next to the high-powered primary ones, and wire those to a small flicker control board which is placed inside the chandelier. You could probably also fit the power supply for this ( small 120 VAC to 5VDC or 12 VDC converter ) inside the chandelier. You then just connect the 120VAC inputs of the power converter to an external wall switch. This way you can have illumination, flicker, or both.

Incidentally, this phosphor-converted amber LED perfectly mimics candlelight if you ask me. A little pricey though ( $6.72 at Future ).

 

[ddrueding]

I'm fairly certain I want everything in the chandelier to be low voltage DC, which would involve even more equipment in the attic and even more wires heating into the fixture.

 

[jtr1962]

I'm fairly certain I want everything in the chandelier to be low voltage DC, which would involve even more equipment in the attic and even more wires heating into the fixture.

Not a problem. You could just run a pair of wires from the low-voltage flicker control board to wherever you have the power supply. Total wires coming from the chandelier for both flicker and illumination would be four-all low-voltage.

 

[ddrueding]

Really? If we were to have the flicker LEDs flicker independently, wouldn't we need an independent wire to each of them? How many and what gauge for the power LEDs?

 

[jtr1962]

Really? If we were to have the flicker LEDs flicker independently, wouldn't we need an independent wire to each of them? How many and what gauge for the power LEDs?

Yes, you would need an independent wire for each LED, but you could mount the control board inside the chandelier. The ten wires would run to the control board. The only thing which needs to run outside the chandelier is the pair of wires supplying power. Everything inside the chandelier is low voltage. In fact, to turn on the ten LEDs independently and randomly, a 4 or 5 VDC supply would be ideal. You could power both the control logic and LEDs with the same voltage. I'm thinking a microcontroller can be programmed to do the flickering. That makes the control board pretty simple-one chip, and ten transistors to control the LEDs. If you want to get really fancy you could even run one or two or three control lines to the microcontroller. Those could be controlled by an external rotary switch to give several flicker patterns ( one line = 2 patterns, two lines = 4 patterns, three lines = 8 patterns ). Probably overkill, but I'm just showing how much can be done while running only a few wires.

 

[jtr1962]

Regarding the wire gauge for the power LEDs, probably 18 gauge is fine. The controlling factor is more having the wire physically strong enough to pull through the attic without breaking. I'd say 18 gauge is good enough for that. 22 or even 24 gauge would handle the current just fine, but such thin wire easily breaks when you're trying to run it through walls.

 

[ddrueding]

I wouldn't worry about the wire strength, the electronics box will be in the attic directly overhead and I'll have complete access.

 

[jtr1962]

To update this thread I've completed the project. We decided to simplify it, doing away with the flickering LED idea. I made 10 "candles" from 1.125" copper pipe as follows:

Here are all the parts needed for one candle:

This ring is a spacer needed because the copper cap is a little to small to fit inside the copper pipe:

Here is the spacer being inserted, and in its final location:

Here is the copper cap inserted:

Here are the rest of the parts:

The outer ring is used to hold a plastic C7 cap in the shape of a flame tip. The LED is mounted on the inner ring. I put soldering flux on all the joints, and then soldered everything together over the stove. This is the end result:

Here are a bunch of candle assemblies all cleaned up:

And here they are painted:

Closeup of the LED:

C7 green cap with slots for clearance for wires to LED:

Two pictures of everything lit up:

And here is how they look with various colored C7 caps in place:

They were out of stock on the clear C7 caps which will be used most of the time. The colored ones are for festive occasions.

I used Cree XP-Gs (bin R4, 5B1). These are in the low 4000K area, which is a nice balance between too warm and too cool. The ballasts can be dimmed with a standard triac dimmer. I tested this, and it works. Output on full is roughly 3000 lumens, and power draw from the AC line is 34 watts. Te ballasts drive the LEDs at 1000 mA. The copper candles get warm, but not too warm (I'd say approximately 45°C).

I'll leave it to Dave to post pictures once everything is together. I'm redoing one of my chandeliers also, and will post pics once everything is done.

 

[Stereodude]

You have a thermal chamber in your basement?

Pretty cool project.

For the rest of us these look like an interesting replacement bulb. There was an interesting article in Wired on them.

 

[ddrueding]

Looks awesome, thanks JTR. Can't wait to get it put together and tested.

 

[timwhit]

For the rest of us these look like an interesting replacement bulb. There was an interesting article in Wired on them.

Doesn't look like they're available yet. If you get one, let us know how it works and where you bought it.

 

[ddrueding]

For the rest of us these look like an interesting replacement bulb. There was an interesting article in Wired on them.

Those are the first LED screw-in bulbs that I would consider acceptable.

1. Decent brightness
2. Decent Color
3. Dimmable

Not an option for my chandelier, though. This fixture was brought in from Russia and does not have a UL sticker. Therefore I needed to keep the whole thing low voltage.

 

[Stereodude]

Doesn't look like they're available yet. If you get one, let us know how it works and where you bought it.

No, they're not available yet. I'm tempted to get a 75W equivalent when available for the light over my kitchen table, though the prospect of paying $30 doesn't exactly get me real excited.

 

[ddrueding]

Of the ~50 cans in my house, 9 of them are used enough to make even $50 bulbs worthwhile. I'm just not sure how the light of these would appear next to the halogens.

 

[timwhit]

I'm tempted to get a 75W equivalent when available for the light over my kitchen table, though the prospect of paying $30 doesn't exactly get me real excited.

Looks like I'll be sticking with CFLs in my cans for a few more years.

 

[BingBangBop]

I agree! When LED's start competing in price to CFL's then I'll consider them. As far as I can tell, people currently buying LED's are paying a very large premium for a dimming capability and no mercury. CFL's have long life and if you try you can get good quality light for a premium that is far less than LED's.

 

[ddrueding]

I honestly don't care about the mercury (the amount is trivial, even in large numbers, compared to other sources), but dimming is a must. New technology should not cause me to lose features I already have.

 

[Stereodude]

I agree! When LED's start competing in price to CFL's then I'll consider them. As far as I can tell, people currently buying LED's are paying a very large premium for a dimming capability and no mercury. CFL's have long life and if you try you can get good quality light for a premium that is far less than LED's.

CFL's don't have a long life in many situations (enclosed fixtures where they get hot or applications where they are turned turned back on while still hot) and most have terrible spectral color output.

At least per the Wired article the Switch bulbs are at least equivalent to an incandescent in light quality and perhaps better (per the summary of blind tests done by the makers at various exhibitions / shows).

 

[Bozo]

Dumb question...why copper pipe and not plastic?

 

[time]

CFL's don't have a long life in many situations (enclosed fixtures where they get hot or applications where they are turned turned back on while still hot) and most have terrible spectral color output.

Most enclosed incandescent light fixtures in this country are limited to 60 or 75W. Exceeding this can damage the fixture or make it brittle enough to crack. Given that you only need about one fifth of the power for a CFL (or less because of the superior color temperature), I've never found heat buildup to be a problem.

It's true that color rendition varies - I just make sure I stick with good brands. But they're all supposed to have a CRI of at least 80 anyway. On what basis do you expect the phosphors on white LEDs to provide better color rendition than those on fluorescent tubes?

 

[jtr1962]

It's true that color rendition varies - I just make sure I stick with good brands. But they're all supposed to have a CRI of at least 80 anyway. On what basis do you expect the phosphors on white LEDs to provide better color rendition than those on fluorescent tubes?

The spectra of LEDs are continuous, not spiky like fluorescent spectra. To me anyway if you have an LED and CFL with a similar CRI, the LED generally makes colors look better. CRI isn't a particularly good predictor of which light source people will prefer. There's an ongoing discussion about this on CPF.