# Quantum Dot LED Lighting



## neumahrs (Jan 12, 2010)

They also sell Par 38 bulbs that are 18 watts and put out almost twice the lumens of the Par 30s you mentioned and they come in 6000k and 5000k.

I think another nice little benefit you didn't mention is the fact that they can be dimmable. That would be really useful if you want to do a dawn/dusk effect 

Only drawback.....price


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## stevesmallcombe (Feb 11, 2009)

Nexxus offers a number of different bulbs in their Array lighting line, but last I looked, only the PAR 30 is available using the quantum dot technology that gives the nice broad spectrum white light/high CRI.

You are certainly right about the dimming however, it is a very nice feature of the nexxus bulbs that I have yet to use and should have mentioned. One issue dimming LED bulbs is that they may not draw enough power to meet the minimum wattage requirements of the dimmer. I have that problem elsewhere in the house. Any clues?

Thanks,

Steve Smallcombe


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## Hoppy (Dec 24, 2005)

Very interesting! Thanks for offering this Steve, and especially, thanks for investing $300 and testing them. Now, when competition comes along, especially if it is from Chinese manufacturers, these may drop in price enough to be extremely interesting.


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## mistergreen (Dec 9, 2006)

A bulb will last you 30 years. How many T5HO bulbs have I bought in the last 2 years? 
I bought 3 at the cost of ~$25 each ($75 total) ... and will have to buy more in the future.

I don't see the cost being all that bad.


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## neumahrs (Jan 12, 2010)

30 years is pushing it. Assuming 12 hours use a day its about 11 years but will lose quite a bit of its brightness in about half that time. So realisticly about 5 years... Still an impressively long life span. 

My comment about the price is more to do with the upfront price. In the long run they are definitely cheap.


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## DarkCobra (Jun 22, 2004)

stevesmallcombe said:


> One issue dimming LED bulbs is that they may not draw enough power to meet the minimum wattage requirements of the dimmer. I have that problem elsewhere in the house. Any clues?


I think a dimmer made to work with inductive loads like fans, rather than a common lamp dimmer, should work properly. I can go into the electronic details of why if you like.


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## neumahrs (Jan 12, 2010)

DarkCobra said:


> I think a dimmer made to work with inductive loads like fans, rather than a common lamp dimmer, should work properly. I can go into the electronic details of why if you like.



There are a lot of dimmer switches out there that have low load minimums that work with bulbs like these. The fan ones you're talking about are usually made for DC voltage and not AC.


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## mistergreen (Dec 9, 2006)

DarkCobra said:


> I think a dimmer made to work with inductive loads like fans, rather than a common lamp dimmer, should work properly. I can go into the electronic details of why if you like.



or it can use pwm?


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## DarkCobra (Jun 22, 2004)

neumahrs said:


> There are a lot of dimmer switches out there that have low load minimums that work with bulbs like these. The fan ones you're talking about are usually made for DC voltage and not AC.


I haven't seen the low-load dimmers you're talking about. Do you have an example?

And the ones I'm talking about are AC, like this or this, not DC.

A regular incandescent dimmer briefly triggers the main switch (TRIAC) once per AC half cycle, then relies on the current through the TRIAC to keep it on until the current drops below a threshold, typically when the AC voltage drops to near zero. If the current is too low, the TRIAC turns off prematurely.

An AC dimmer made for inductive loads can't rely on current through the TRIAC to keep it on, so it triggers it repeatedly to ensure it stays on for the proper length of time.


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## stevesmallcombe (Feb 11, 2009)

Interesting information on dimmers. Do the fan speed dimmers use triacs? Do they let through full half cycles? I do have a ceiling fan into which I have placed two sets of 3 3 watt LEDs (up and down lighting) and the dimmer that comes with the fan control seems to dim them just fine, so obviously low wattage dimmers do exists. To find one that I can remotely control is another matter.

As to the life of the LED bulbs, phosphors have a finite lifetime and I certainly know of "white" LEDs that change their color significantly as they age. I hope the the quantum dots don't age the way phosphors do and the 50,000 hour lifetime spec on the bulb is close to real. 

Thanks for all the input.

Steve Smallcombe


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## neumahrs (Jan 12, 2010)

DarkCobra said:


> I haven't seen the low-load dimmers you're talking about. Do you have an example?
> 
> And the ones I'm talking about are AC, like this or this, not DC.
> 
> ...



I was thinking small fans not ceiling fans. I've seen dimmer switches made specificly for LED lamps and low wattage application such as this one


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## DarkCobra (Jun 22, 2004)

stevesmallcombe said:


> Interesting information on dimmers. Do the fan speed dimmers use triacs? Do they let through full half cycles? I do have a ceiling fan into which I have placed two sets of 3 3 watt LEDs (up and down lighting) and the dimmer that comes with the fan control seems to dim them just fine, so obviously low wattage dimmers do exists. To find one that I can remotely control is another matter.


Fan speed dimmers do also use triacs, they just trigger them differently. The schematics I've seen for both fan and incandescent dimmers work by passing a portion of each half cycle, and have a continuous adjustment range.

But now that you mention it, I recall seeing some fan speed controls that instead have discrete settings (low/medium/high), which could at least theoretically be done instead by passing some full cycles and skipping others; though I've never seen a schematic describing this scheme, or had opportunity to examine this style of speed control in person. Obviously such a scheme, if used, would introduce flicker in a LED light.

Also, some incandescent dimmers may work at low currents better than others. It depends on the specifications of the triac used.

As for remote control, have you looked into X10? It's not the most advanced system out there, but it's cheap and sufficient for many tasks. I use it to run all my aquariums and a few other things under computer control, with multiple RF remotes.



neumahrs said:


> I was thinking small fans not ceiling fans. I've seen dimmer switches made specificly for LED lamps and low wattage application such as this one


The linked item is a dimmer for inductive loads, similar to the ones I posted; as it's intended to connect to a transformer that supplies power for low-voltage lighting.


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## mistergreen (Dec 9, 2006)

does chopping out the AC voltage waveforms also lowers the voltage?

I bring this up because I've played with dimming LEDs by reducing voltage and it's doesn't work very well. THe dimming is not smooth and turns off abruptly.
It might work great for other devices but not LEDs if that's that case.


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## Lance Uppercut (Aug 22, 2009)

pics please?


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## stevesmallcombe (Feb 11, 2009)

I had hoped to avoid pictures so that you guys would not see how bad off my plants are, but here they are:

Again, this is a temporary quick and dirty test fixture and I will build a more furniture quality canopy and base cabinet when I move the tank upstairs to its permanent location. 

As you can see in the picture of the top back corner of the tank, I have run two cords down to the Neptune controller so and can turn on the lights in stages.


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## macclellan (Dec 22, 2006)

Nothing to be embarrassed about - plants look fine. Those LEDs are far to yellow for my taste though.


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## stevesmallcombe (Feb 11, 2009)

Back to the subject of dimmers. It seems that there are two types of “low voltage” dimmers, the ones meant for magnetic transformers (MLV) that start power somewhere in the line cycle and let the rest of the cycle through (standard phase), and the ones meant for so called electronic transformers (ELV) that start at a zero crossing and chop the cycle off part way through (reverse phase). Lutron recommend the MLV dimmers for inductive or resistive loads and the ELV dimmers for capacitive loads. How do the fan controller/dimmers fit into this picture? 

While the LED lights I am using are not low voltage, they use 115V, the way the dimming is done may have an effect on how low currents are passed as has been mentioned.

I also checked the specs on the dimmers that were recommended and they mention that loads below 40 watts may not work properly. Most all the dimmers I have looked at seem to have a 40 watt minimum load specification or at least mention the potential for erratic operation below this point. I think it is a matter of trying them out.

BTW, some time ago I designed and built a load controller for a water heater on our boat that passed whole half cycles using a zero crossing detector opto-triac to control the power triac, and while I didn’t have to worry about the water heater flickering, all the rest of the lights on the boat would flicker if I wasn’t careful about time scales.

As to X10, in a previous house I had the home theater lighting set up with scenes, etc. using X10 as well as control of the lights and CO2 in the fish tanks. I used this system for about 10 years, but basically found it to be fairly fragile in that plugging in various appliances or even laptops could suck the X10 signals out of the wiring and the signals would be lost forever. Yes, one can use filters to isolate capacitive loads, but it was a pain and not as reliable as I would like for controlling CO2. I have X10 signal strength meters and various controllers, but would hope to never use X10 again.

In the house we are moving from, I have tried an Insteon system for lighting automation, and it is much better than in that signals are repeated until they are received and signals travel between phases using RF. Unfortunately Insteon is not compatible with the URC remote control system I am using in the home theater so this next time I’ll probably so with a z-wave (and URC) compatible system by Lutron or Leviton for lighting automation.

For the fish tank I am using a Neptune AC3 controller for lights, heater, air, pumps and CO2. The system is currently programmed to turn off the lights if the tank gets too hot, but now with the much cooler LED lighting, that may not be necessary.


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## mistergreen (Dec 9, 2006)

yeah, a bit yellow for my taste but should grow plants and algae 

I'd put more plants in that tank or algae will take over.


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## stevesmallcombe (Feb 11, 2009)

One does have to be careful judging color or color temperature from a photo. The tank really does not look yellow in person. 

I was hoping the existing plants would grow back fast enough to keep the algae down, but I think you are right and I should add a few more plants before it is too late.


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## mistergreen (Dec 9, 2006)

Can you hold up a piece of white paper next time you take pictures of the lights/tank too away from the light?

That'll give us a reference for the light color (if we can't trust the camera).

thanks.

ps. throw in some fast growing plants like stems and hygros.


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## DarkCobra (Jun 22, 2004)

mistergreen said:


> does chopping out the AC voltage waveforms also lowers the voltage?
> 
> I bring this up because I've played with dimming LEDs by reducing voltage and it's doesn't work very well. THe dimming is not smooth and turns off abruptly.
> It might work great for other devices but not LEDs if that's that case.


Chopping AC can lower the voltage if it chops out the peak.

And dimming LEDs by controlling voltage, as you've found, is inaccurate. The correct way is to control current rather than voltage.

But you can't run 120VAC directly into LEDs, so there's a current limiter built-in. At simplest, a few passive components; in something as expensive as the Nexxus, probably a dedicated IC. All can produce a current to the LEDs that varies with the input voltage.


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## DarkCobra (Jun 22, 2004)

stevesmallcombe said:


> Back to the subject of dimmers. It seems that there are two types of “low voltage” dimmers, the ones meant for magnetic transformers (MLV) that start power somewhere in the line cycle and let the rest of the cycle through (standard phase), and the ones meant for so called electronic transformers (ELV) that start at a zero crossing and chop the cycle off part way through (reverse phase). Lutron recommend the MLV dimmers for inductive or resistive loads and the ELV dimmers for capacitive loads. How do the fan controller/dimmers fit into this picture?


Fan controllers with a continuous adjustment range are definitely MLV-type. I haven't heard of the ELV-type before, but I understand the concept from your description. By turning on when the voltage is near zero instead of in the middle of a peak, it avoids sudden inrush of current into a capacitor. I'd consider the typical limiting circuitry on 120VAC-powered LEDs to be capacitive in nature, and an ELV-type dimmer might be gentler on them in the long run. Although a MLV-type dimmer should still work, just the way an incandescent dimmer does (both chop in the middle of cycles).



stevesmallcombe said:


> As to X10, in a previous house I had the home theater lighting set up with scenes, etc. using X10 as well as control of the lights and CO2 in the fish tanks. I used this system for about 10 years, but basically found it to be fairly fragile in that plugging in various appliances or even laptops could suck the X10 signals out of the wiring and the signals would be lost forever. Yes, one can use filters to isolate capacitive loads, but it was a pain and not as reliable as I would like for controlling CO2. I have X10 signal strength meters and various controllers, but would hope to never use X10 again.


Yes, that is a possible issue with X10. Some people never have problems, other people do. Everything works great for me, except for one aquarium in the living room that has an issue with receiving signals only sporadically, and I've never been able to track down the cause. My solution was to not control X10 devices directly from the remotes. Instead, the computer receives commands from the remotes, then forwards them over the line. By doing so, it can remember what state a device should be in. I can mark specific devices as "unreliable", in which case it resends commands for them at intervals. The troublesome devices always end up switching within a few minutes at worst, which is good enough.

I'd love to have one of the more advanced, two-way communications control systems, but they're too expensive for me. Each device only controls one AC plug. What I'd really like is a single device with six plugs, which would be much more cost efficient since you need one RF/line interface and microcontroller for them all. Current monitoring would be a bonus, since you could remotely detect if a filter isn't running. This may be something I'll eventually build myself, but I have too many other projects on my list right now. I'm still struggling through the build of my dimmable X10-controlled T5HO hood. Wood finishing is apparently not my strong point, I have to sand down and try again. :hihi:


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