Practical LED Lighting for Fun and Profit

LEDs have finally begun to surpass compact fluorescents (CFLs) in effeciency (lumens per watt) signaling the perfect time to move beyond crappy LED throwie projects to real, practical LED home lighting. This instructable presents a method to make an LED replacement for the low voltage halogen bulb pendant you currently have over your kitchen countertop or island just like everyone else who has watched trading spaces or extreme makeover home edition in the past 10 years.

Step 1: Gather your materials

LEDs have been making big strides in terms of luminous efficiency and cost recently. The current champion in terms of efficiency is the the Philips Luxeon Rebel line of power LEDs. The Rebel is not only tiny at about 3mm by 5mm, it is available in models with >100 lumens per watt. For comparison, typical incandescent bulbs hit the 15 lumens per watt and fluorescents the 75 lumens per watt range. The best source for power LEDs is www.ledsupply.com which sells a variety of LED products for all your LED needs. The item we are interested in here is their "Endor Star" which is a thermally conductive but electrically insulated package with up to 3 Rebel LEDs mounted on it. I used the 3x90 lumens/watt star with 480 lumens of output at 700mA drive. This is pretty much equivalent to a typical 50W halogen bulb that puts out 600 lumens that you might have in your low voltage lighting system. This LED array will cost in the neighborhood of $30 but will last as long as $25 worth of halogen bulbs while using 7W versus 50W for a $50 lifetime operating cost versus $375 operating cost for the halogen.

Besides the LED you will also need a driver circuit. Since the plan is to build an LED replacement for a low voltage lighting bulb, we need a driver that can handle an AC input. Low voltage lighting uses a transformer to reduce the typical 120VAC power to a "low" 12VAC level. www.ledsupply.com conveniently sells an AC capable "buckpuck" that will accept 12VAC input and output a regulated 0-700mA output current for driving strings of LEDs.

So go ahead and shop at LEDsupply or equivalent to get the electronics parts. If you want to be able to dim your LED bulb you will also need a potentiometer. The Endor Star will need to be mounted on a heat sink, such as a section of aluminum angle or channel extrusion. This will require holes to be drilled and tapped as well as screws, heat sink compound, and some wire.

Materials:

1. Power led such as a 3-up Endor Star with 3 Luxeon Rebel 90 lumen LEDs
2. Constant current LED driver with AC input ability such as BuckPuck 03021-A-E-700
3. 1.25" section of aluminum extrusion for heatsink
4. 4-6 screws fro mounting LED to extrusion, 6-32 works great
5. Tap for threading holes for screws, 6-32 tap works great
6. Heat sink compound for mounting LED to heat sink. Since the LED is isolated, you can use a metallic based heat sink paste like molybdenum anti-sieze
7. Some wire to hook everything up
8. Soldering tools and a clue

Comments

[lancruz]

I just made my first LED lamp. I used 13 3 watt Luxeon Rebel LED's. They are very bright? My question to you is where is the profit. I had fun making, I'm just curious about your thoughts in this direction. Is it the set up for accent lighting that you are speaking of?

[jmengel]

These days, the profit is in reducing your energy bills. Back when I wrote this, the available LED bulbs were pathetic, none of which used the cutting edge high-brightness high efficiency LEDs. You couldn't find a good LED bulb replacement at nearly any price. FYI, the Rebel LEDs are totally old school now, with many better LEDs available (Such as Cree XML). In the meantime, manufacturers are now cranking out a large number of LED bulb replacements, some of which are decent. Nothing yet that is a slam dunk, but progress is being made and as prices come down further I fully expect LED to replace CFL and halogen in most applications. Not in the easy bake oven though. The limitation currently is the fixtures. Houses and buildings have legacy fixtures designed for easy replacement of a glass bulb. In the future, LEDs will be built permanently into purpose design fixtures that will look much different than what we are used to. For all practical intents and purposes, the LEDs will never fail so replaceability in most applications is a waste and since the LEDs make up such a sizeable portion of the cost, the fixture rather than the light element will become "disposable". I've moved on to making purpose built custom LED fixtures along these lines since Philips and the like can handle the bulbs. For example, I've done several moped and motorcycle headlights and am building a set of linear LED arrays for low profile closet lighting, and so forth. Commercialization is another story as safety testing is a must. UL listing will be required and the resulting costs have kept me doing one-off work for myself, friends, and family. The future is bright.

[GeekTinker]

"Not the easy bake oven though" - Even the Easy Bake has dumped the light bulb: http://abcnews.go.com/blogs/business/2011/09/easy-bake-oven-loses-light-bulb-gets-20-makeover/

[fretted]

Yea they dumped the light bulb and the ovens don't work very well my sister had one when we were kids with the light bulb they worked great we bought one for my daughter when she was a child i don't think the cake ever baked right not once my wife ended up putting them in the real oven to make the cakes bake that was way before i joined we ended up trashing the easy for a Violin that worked out better anyway lol

[mcarrell]

This article could really use an update. I recently replaced this very same pendant light in my own kitchen with a 4-LED Feit Electric bulb. it is both attractive, and required no modification to install, just screw in place of the conventional bulb or CFL. It's also brighter than a 60W bulb in my opinion. Say good-bye to Mercury!

[jmengel]

Certainly this is an old instructable with LEDs that are no longer state of the art, and I've written new ones that use newer LEDs with higher efficiencies (http://www.instructables.com/id/Improved-high-power-LED-bike-head-light-with-integ/) such as the Cree XP-G line-up. Additionally, I've revamped the pendant light design detailed here with a better heat sink and cheaper driver so that the the total cost is now around $20 with a top of the line XP-G and around 100 lumens per watt. The concepts are the same however: a good heatsink, a constant current driver, and a top of the line LED.

As old as this instructable is, the Feit bulbs that I have seen are still poor performers in comparison. The efficiencies are miserable, at around 40 lumens per watt. This is in line with a bad CFL. The majority of commercial bulbs are not up to snuff yet, especially the cheap no-name ones coming out of China. There are some good bulbs being made by TESS (and sold through FIRST robotics teams) that are approaching 80 lumens per watt using Cree LEDs in a nice package at $20 subsidized by Google, and Philips has a good bulb with similar specs for $40 (http://www.amazon.com/Philips-Ambient-Dimmable-Replacement-Light/dp/B004IUMGV4).

Thanks for reading.

[jmengel]

I forgot, I wrote up the improved bi-pin bulb:

http://www.instructables.com/id/Replace-Low-Voltage-Bi-Pin-Halogens-with-LEDs/

Since then, I have made similar bulbs with the Cree XP-G stars which are significantly brighter at the same power. The pictured bi-pin has a couple thousand hours under its belt of trouble free operation. It is the most used light in the house.

[4Blades]

(removed by author or community request)

[jmengel]

Yes there are other solutions out there, with more coming every day. The linked $60 bulb is not bright enough for anything but accent lighting (240 lumens) and is less efficient than a CFL which can be bought for $5. My system is pretty pricey too ($45) and not ready for wide use in a home. With ~500 lumens the light is bright enough for a task or reading lamp with a good reflector but not for general lighting. Pumping it up to 500 lumens also decreases the efficiency (~70 lumens per watt) to that of CFLs. When run at max efficiency (~90 lumens per watt) the setup I show will only put out ~300 lumens which is marginal. For now the lamp I put together is just a proof of concept, too expensive and not bright enough for many uses but as efficiencies improve through 120 lumens per watt and costs drop due to mass fab this type of lighting will find more and more application. I am in the process of building the shown LED lamp into a small portable reading light that can be plugged directly into the wall (120VAC). This will be more useful to me than pendant lights. Stay tuned.

[Rusdy]

You'll be glad to know that there is a 120VAC LED now in the market (or 230V for those in the 'other' part of the world)

Unfortunately, I only managed to find one distributor (Farnell) so far: Order code is 1734729 from www.farnell.com

No driver required, literally plug and play. (Oh, must use heatsink of course :) ), so to make LED light bulb is now even easier!!

PS: Just type '230V LED' on the search box of Farnell's website if you can't find it

[jmengel]

Thanks for the tip.  Interesting product.  As far as I can tell these use a built in rectifier of sorts and a current set resistor rather than a constant current driver.  The result is a nicely integrated solution with poor performance and sensitivity to voltage fluctuations.  Looking at the specs and assuming the LED light engine is their top of the line and capable of 100 lumens/watt the integrated drive electronics are cutting the efficiency in half.  The resulting overall performance is ~50 lumens/watt for cool white and ~35 lumens/watt for warm white.  Not very good.  Low part count is attractive, but I'll wait until something a bit more efficient comes along.   CFL's are cheaper and better than these for most applications.

[Rusdy]

 Good point, I was wondering how they do it. I should have known better a diode is a diode (i.e. DC voltage naturally). After looking at the PCB myself (just got it today), I can't see any fancy circuitry on it. It's simply an RC circuit.

I haven't tried how it works in practice. Will probably flicker like my other 'cheap' 230V LED. Looks like cheap LED lighting is just simply not there... yet :)

[Svartalf]

However, having said that all, one should realize that the CFL, while "more efficient", will not last as long as the LED system would, nor does the LED have the mercury that the CFL does. The thing, while more expensive, is cool, fun to do (Heh...we're all part of that "maker" crowd- why else would we be here on Instructables?), and much more green than the CFL is in the big picture sense of it. Nice intro into this insanity the LED junkies have gotten ourselves into... ;-)

[jmengel]

The amount of mercury in a CFL is less than you think. Snopes lists the mercury in a CFL as around 5 mg (link below). The average fish these days has about 1 ppm of mercury. This means that by eating 5 kg of fish, you consume the same amount of mercury as in a typical CFL. I don't know about you but I have eaten a lot more than 5 kg (11 lbs) of fish since the last time I chomped down a whole CFL bulb. Your mileage may vary.

http://www.snopes.com/medical/toxins/cfl.asp

[Svartalf]

The only problem is the number of CFLs and the fact that while snopes is right, it methylates so easily and causes all kinds of cumulative toxins that most people don't think about- in the fish is only part of the problem. :-) Mercury is your friend, contrary to the stories otherwise, yes. CFL's are part of the solution, yes. But, for me, I've already elevated mercury levels from all the amalgam fillings in my mouth- I would rather like to avoid any more exposure to mercury if possible as we just don't know what the trace amount increases would do to things. The thing is, what you have done is liable to outlast most of the CFL designs, does something that a CFL is less able to do, and doesn't expose yourself to any mercury and less phosphor than the CFL would if it got busted. This doesn't even get into the differences between stated lifespan and actual on the CFLs (I've been using CFLs for some 5+ years now in almost every application to avoid heat and power consumption for reasons I won't get into...)- the bulbs flatly don't last as claimed; I'm always changing the things out and most of the ones I'm changing out aren't in 24 hour service settings.

[rj44319]

Hi, I finally got the stuff in the mail and unpacked it. I tested one and it worked. But i am having problems getting the wires soldered to the pads i am using 60/40 solder and a 25 w soldering iron what is wrong?

[jmengel]

I assume you are talking about the solder pads on the LED star? 2 things make soldering to the star board difficult. 1. The circuit board is of a high thermal conductivity design and heat from the iron is quickly drawn away. 2. The solder used on the board is lead-free and of a higher melting temperature. To solder to the star with 60/40 lead solder you need to get the pb-free solder liquid which might take a stronger iron. I find that I need to use my adjustable 60W high power iron, turned up a bit past where I usually use it and a coarser tip to get the joint done right. Using my 60W temperature controlled Weller does not work well since the temp set point is fixed at 60/40 type temps. Using a 25W may not work at all.

Here is the station I use:
http://store.sra-solder.com/product.php/6266/26

[rj44319]

how many could put together? should it be series or parallel?

[jmengel]

It depends. Both. You can do either or a combination, such as 3 parallel strings of 3 LEDs in series for 9 total. Depending on your available voltage and the current capability of the driver and LEDs one approach may have an advantage. In most applications with moderate available voltage or a boost type driver, it is preferred to use series strings since all LEDs will get the same current. If in parallel, small differences in the forward voltage (Vf) of the various LEDs will result in differing currents through each. The good news is that Vf increases with increasing current so that the parallel strings will stay in the same range of currents. The bad news with parallel is that if one of the LEDs fails in an open state that the rest of the LEDs will have increased current and may fail as well. For example, if you had 3 LEDs in parallel with a 600mA total current then each would be getting about 200mA. If one LED fails, the other two will now be getting 300mA. In a series example with the 3 LEDs, if one fails the whole string turns off, but the other LEDs are unharmed. Another factor is that most buck type drivers are more efficient the closer you run to supply voltage so with higher available voltages (e.g. 12V) you would typically use a buck driver with series LEDs. However if the series combination of Vf's is higher than your supply you need to switch to a boost driver or go parallel LED arrangement. If you have only a small available voltage (e.g. 3.6V) then you will probably have to use a boost driver and stick to LEDs in parallel. OK, enough, I think you get the point. You can do whatever works best.

[alah]

Hi, jmengel. I´m working on a LED fixture and I have almost decided to use LUXEON Rebels. I can´t buy one or two to test the light output. I´ll have to import them. So I´d like to know: At 700mA, would the light seem as white as fluorescent? I wouldn´t want bluish or yellowish light. Thanks.

[jmengel]

Just like fluorescent there are different light qualities depending on the design. Both LEDs and fluorescent bulbs emit white light by exciting a collection of phosphors which actually emit the light. The mixture of phosphors determines the color and quality of the light. So to answer your question, LED light can be as white as fluorescent light. If you are concerned about the light being too bluish, then I would stay away from the "cool" LEDs and focus on the "neutral" or "warm" ones. These are typically less efficient in terms of lumens per watt, but the color of light more closely approximates traditional lighting.

[lavert31]

I see that on the star toy have three -,+ connectors as for each led. but you connected only one of them. is this enough to power all three LEDs?? Is it matter to which pair you connect the input voltage? etay

[jmengel]

The star board has 0 ohm resistors, or shorts, across the other LED terminals so that the 3 LEDs are in series. Thus you need only connect the power across the single unwired + and - pads. It does matter how you connect the input voltage, it will only light up one way.

[lavert31]

O.K. Thanks for your answers. :-)

[lavert31]

Hello, First of all thanks for the comprehensive tutorial. my question is how did you calculated the power consumption and efficiency. Etay

[jmengel]

Measure input voltage, measure current at the input voltage. Multiply together to get power. For example, 750mA at 10.3V is 7.7W. Efficiency can only be calculated by measuring the output light intensity. Since I don't have the instruments to do this, I use the manufacturer reported numbers.

[arirang777]

Great project. I love it. If you wouldn't mind to enlighten this poor noobie: Does a "low-voltage" setup consumes less energy than (comparable in light) regular incandescent bulbs? I mean, if I use LED + transformers/drives and an incandescent bulb (like one of a xmas light for example) without no transformers at all, will I still save energy with LEDS? I guess my question is if those drives/transformers will consume the energy that the LED is "saving". Thanks in advance!

[jmengel]

No, I don't think low voltage lighting consumes any less energy than 120V lighting per lumen output. Both are incandescent in that they rely on a heated metal filament for light output. The difference is that low-voltage lighting is typically directional and tailored for an application. Thus the bulb delivers more useful light and allows a smaller wattage bulb to be used. So rather than turning on a 100W bulb in the middle of the room to read by, you turn on a 50W low-voltage light. The transformers can be efficient (>90%, the higher the current capacity the better efficiency under load), and good LED drivers are also very efficient (>95%). I would say ~90% efficient for the electronics for a well designed LED light. If your 1000 lumen LED array consumes 12W, then the fixture as a whole consumes about 13W. Compare that to a 1000 lumen incandescent that consumes 60W and you can see that there are still savings with LEDs.

[arirang777]

Thanks for the prompt reply. I was concern about transformers after reading about "VAMPIRE POWER" and wanted to make sure I was not actually creating more of those. The application I see for your wise device is to replace those night lights in staircases and corridor walls for LEDs installed in the ceiling instead. I could easily use less of regular night lights, free some wall contacts, and have a lower maintenance cost. I think they will even look great than those night lights plugged into the wall and work better if I add to the circuit a motion sensor and a dusk-to-dawn sensor as well. I am actually ordering few LED modules as we speak to do some test. Your project is neat, green and cool. Thanks!

BTW, do you know why is that low voltage lamps works with its 12VDC transformers, but not with for example a CAR battery with also 12VDC? Cheers!!!

[jmengel]

The transformer in a low voltage system will not waste power constantly like a plugged in wall-transformer because there will be no power to the transformer when it is off, the wall switch disconnects the power. Additionally there are both AC and DC low voltage lighting systems, so it would be worth your while to check yours before implementing. The bulbs will work on AC or DC. The LED drivers may or may not work on AC, depending on the driver design. In many cases, the only difference is the addition of a diode bridge (and sometimes including ripple capacitors) rectifier between the AC source and the LED driver circuit.

[arirang777]

opppppppppssssssssss. You are 100% right: They will be switched off when not in use. I missed the wood by the trees. I am sooooooo doing this. Thanks jmengel!! I already subscribed. Keep the good work!

[shams]

IT is simple to make it to sevarel mhz.just dig out the pcb of a ccfl then hook it with led rope

[WardXmodem]

Some people are sensitive to flicker. I noticed when using things like LED rope light, they seem to flicker a lot - because they run off the 60 cycle as a diode, and thus some are on half the time, perhaps? Or even if run through a full-wave rectifier, they have 120Hz flicker. SO I am wondering if the circuit module you say adjusts current while changing the output to say 30KHz or something which won't be noticed? Alternatively, does anyone know of a circuit that would do 110/120V 50/60Hz to 110/120 but at 30KHz, so you could "plug in existing" LED devices, but they'd not flicker? By the way, I bought a Kill-a-watt meter (EZ or whatever the latest is that allows you to put in electric rates then it totals cost as you use what is plugged into it), and the LED rope light wouldn't even REGISTER, i.e. was under the 0.00A it was measuring!!! It MIGHT measure correctly by "summing" but it would depend upon how many digits of (hidden) resolution it works on in amperage. Anyway, Nice post, thanks for sharing.

[netbuddy]

Check the capacity and voltage on the capacitors that are connected to the rectifier, if these capacities are not high enough then flicker can be caused because the capacitors that filter and smooth the power stage is fluctuating and the capacitors are discharging faster than the charge is being replaced. The idea of a capacitor is to provide a supply with a top up of power when needed. This means the voltage drop between the rectifier stage and capacitor stage can only be down for a very short time if your capacitors are small value but longer with larger values. The result is less ripple and more stable supplies. Theirs many other reasons for flicker and this will most likely be the cause of it, other causes will be appliance like a TV or Washing Machine for example that are already plugged in and themselves a cause line noise that leads to flicker. For this you would need line suppression.

[jmengel]

The circuit module I used adjusts the voltage to maintain a constant current. The module can also be PWM controlled to reduce effective brightness at high frequency that will not register as flicker on your retina. If you want your rope LED to not flicker you need to run them off of DC. You could make a simple linear supply without a x-former, direct to a rectifier, and some caps to get >120VDC with some 120Hz ripple. You are not able to see 120Hz flicker so that should suffice. Some of the LED light strings have a power supply box, you would have to investigate that if you had one before messing around with the power supply. -J

[WardXmodem]

Thanks, yah, DC is a simple way to do it, I kind of didn't see that "hand in front of my face" ;-) But actually I'm thinking pulsing give you more light per watt - I saw a curve once, with frequency and amps, and putting a crazy # of ma thru an LED but only for a millisecond every so often was the brightest perceived light.... I'd have to dig that up again. Thanks for replying!!

[viacin]

and profit? dude, this thing looks awful. We gotta dress it up some, cuz it works great :D

[curlyfry562]

Sweet I am glad to see someone finally put this on Instructables. One recommendation though, it would be a lot simpler to use thermal adhesive instead of screws, it will also help to reduce the risk of shorts, because the screw heads are very cloce to the soulderpads. Thanks for posting!

[3toedSloth]

This is excellent! Plenty of light in a very do-able low-cost setup. thanks for the good write-up. My only reservation about this setup is that it uses cool white temperature LEDs. If they were available in warm or neutral I'd be all over this.

[jmengel]

The problem with the neutral and warm LEDS is that the efficiency falls off. For example, if the cool white (6500K) units have 100 lumens per watt, the neutral (4100K) would have 80, and the warm white (3100K) 60.