Build LED Under Counter Lighting that ROCKS!

Background:
I admit it, I am a geek when it comes to LED's and LED lighting. The fluorescent under counter lighting that came with my hose wasn't cutting it. Time for an upgrade! With a background in physics and surgical lighting, I knew I needed a good Color Temperature and Color Rendering Index (CRI). So what are Color Temperature and Color Rendering Index? They are two measures of what light looks like and how it makes things look when it illuminates them. Color Temperature can be read about here, and Color Rendering Index here. Color Temperature is the main “color” of the light based on the temperature of a black body radiator. It is measured in degrees Kelvin (Which is “zero” equals absolute zero and the same per degree increase as Centigrade.) A lower Color Temperature, say around 3700-3500K is considered “warm” light and a hotter one such as 7000K is considered “cool” because it is bluer. Yes, it is backwards from what you would think. There is a lot of debate going on about Color Rendering Index as it is more subjective than people realize. It also depends on Color Temperature, so a CRI of 90 at 3700K will look different than a CRI of 90 at 6700K. Why is this important and why do I care??? Well, when it was just incandescent lighting vs. fluorescent you kinda knew what you were getting into.

For me to achieve success with my kitchen counter lighting project I needed one key thing: wife approval factor. As much as I liked LED's my wife has a different opinion. I first had to prototype a 4 foot section and do a side by side comparison. The LED's won!

There are a lot of power LED's available these days from Nichia, Cree, and Seoul Semiconductor. All are available in warm or cool Color Temperatures. The LED's I used, I lucked into. I got a bunch of 1 watt Nichia emitters that have a color temp of 4400K and a high CRI. Unfortunately for me, they were bare emitters, not mounted on a star PC board.

Another piece of the puzzle I needed to figure out was: How much light do I need? Light gets measured in “Lux” which relates to “Lumens” by means of one lux = one lumen per square meter. Check here for more info: Interestingly, there is a push to have light bulbs listed in lumens instead of watts as that measurement is more relevant to what you see. There are also recommended levels for the amount of light that should be present in living and working spaces. Check that out here  OK, with all this background info I was ready to start... 

Step 1 Design Phase

I really wanted to improve on the current light output and provide a nicer quality light. To answer this I needed to figure out how much light was there to begin with. First I researched the light output of typical fixtures and came across this great info: 
So I looked under my counter and found a random assortment of fluorescent lights. I have a lot of counter space including two five foot stretches of cabinets on a 24 foot counter that includes the sink and stove. The five foot stretches were different, one had a four foot fluorescent and one had a two foot and a one foot. I guess they were “what ever was on the back of the truck” designed... I now had the chance to even things out. I measured that available space and came up with 16.5 feet of total space broken down into sections of 5, 3, 1.5 an 1 foot. Based on the light output I wanted I came up with a need for about 400 lumens per foot. My LED's were 70 lumens per watt driven with 350ma (About 1 watt). At 440ma I determined I could get 90-100 lumens. After modeling this in excel I figured I needed an LED every 2.7 inches. I rounded down to 2.5 inches.

How to mount these was my next thought process. I came up with using 1.5” angle aluminum that would also act as a heat sink. There are many IC's designed to drive LED's and LED strings with boost convertors etc but I went old school. White LED's have a voltage drop across them of about 3.5 volts. If I put 8 of those in series I would need 28 volts. This worked for what I was going to use as a power supply. I had several 24VAC transformers from other unfinished projects that could supply 2 amps and I wanted to be able to use these. They are also readily available. One of these could run 3 strings of 8 LED's with a margin of safety. Check out schematic 1, because the 24 VAC is an RMS value the peak value of the voltage is 1.4 times larger. So after rectification and charging a filter capacitor there is about 35VDC available at no load. Under load of about 1.5 amps we drop to just over 30 volts. I planned on using a simple current regulator based on the LM317. They are well known, robust, can supply 1.5 amps and, are not expensive. Because the LED's I had were not mounted on a PC “star” board I had to source those and figure out how to solder them to the boards. The following is my experience with all of this with a very good outcome. You can use as much of this as you need to build your own LED lighting system. Lets start building!

Materials:
LED's

• http://ledz.com/?p=led.power
• mouser search for LED, power, white
• Digikey search for LED, power, white
• ebay search 1 watt led
• Star PCB for the emitters (you need a bunch of these unless you are lucky to have your LED already on a Star) http://www.dealextreme.com/p/star-connection-board-for-cree-led-emiters-5-pack-4512

Aluminum Angle:

• (Prototype) Lowes
• Final Source Onlinemetals.com

Mounting Hardware:

• 4-40 nylon screws Digikey H544-nd 
• 4-40 nuts Digikey H216-nd
• Transformer, 24VAC Jameco
• Wire 22 gauge, white and black. I used Black for ground and white for +DC
• Wire nuts Lowes
• 5 Dual gang J-box 2 1/2” height to contain the power supply and connect to LED strings Lowes
• Covers for J-boxes (should be right next the the J-boxes)  Lowes 

 

Comments

[meyer_lanski]

Thanks for the great tutorial! It inspired me to do something similar for my kitchen but I have a small problem. I purchased a 5m strip and when connecting to power supply the light at the end of the 5m is not as bright as the beginning. As though power is lost. What could be the cause of this?

Any help would be greatly appreciated!

I have the following:
5m rgb smd 5050 LEDs (300 leds total) (12v 1.2amp/m)
1 24 IR Remote
1 12v 7amp power supply

Here are the links to what I have purchased:

LEDS:
http://www.ebay.ca/itm/160703608361?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

REMOTE:
http://www.ebay.ca/itm/390379498690?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

POWER SUPPLY:
http://www.ebay.ca/itm/220915150719?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

[DJJules]

It sounds as if you have a voltage drop across the LED strip. I would run an additional power wire for the +12 volts and ground to the end of the strip also. Or, split the strip into meter segments and run separate power to each. The challenge you have is that strip draws 1.2 amps per meter and it is basically a PC board with the LED's mounted on it. (I have a couple of those I just picked up that are RGB leds!) So, a 5 meter strip draws 6 amps and there is bound to be voltage drop across it.

Jules

[meyer_lanski]

Hi DJJules,
Thanks for such a quick reply. I didn't think of adding an additional power wire to the other end, great idea! However my LEDs are RGB so Where would I connect the negative wire to?

The positive goes to the '+' but the R, G, B, are all negative (ground) so If I connect to only one of r, g, or b, then only the color i connected to will light up brighter and if i connect the negative wire to all three r, g, b then the strip turns white in color since current flows through all three.

Remote Box (control colors) End of strip
+ ------------------------wire--------------------- > + wire goes to additional power
R ------------------------wire--------------------
G -------------------------wire------------------
B -------------------------wire-------------------


My current power supply is 12v 7amps. Would it help if I tried a 12v 10amp power supply? Trying to thing of a way to fix the voltage drop problem.

This is becoming more of a headache than i expected!

Thanks again.

[Ian+Siobhan]

whats the overall cost of this project?

[DJJules]

This one ran more than I expected for sure even though I had the LED's already. plan on a couple hundred bucks. You will never have tor replace a light bulb again though!

Jules

[phettsack]

How is the color reality?
Does a steak look like a steak or more like a cleaning sponge?

[DJJules]

The color is fantastic. these LED's have a great CRI and look good.

[woodNfish]

Nice project, but I have a problem with your AC wiring connection to your power supply - it is exposed. It should be inside the connection box that your power supply is in, or inside another connection box to shield them from anyone touching them.

So here is my suggestion to fix the problem: Mount the power supply box where your AC comes in so all your wiring is inside and then mount your lighting strip to the power supply box. It still won't meet code because your lighting strip has exposed connections too, and you are pumping 4 amps through it which is more than enough to kill you.

[DJJules]

Yea, I need to put the wire nut connections inside a J-Box. I also plan on putting a cover over it to diffuse the light. I'll make sure that it encloses everything. They do not draw 4 amps. each LED string has about a tenth of that at 440ma. And there are no exposed voltages above 30VDC.

Thanks,

Jules

[woodNfish]

Hi Jules, I was looking at your power supply schematic that shows 4amps at 100 volts. I figured that was for all the strips total, but I could be wrong. Still, it is a very nice project and you do good work.

[Ninzerbean]

The Xenon lights under my kitchen cabinets are so hot I turn them on to heat my kitchen in the winter, they melt chocolate in the cupboards above, and I got a second degree burn once by accidentally touching the glass in front of them. I hate them, I thought I had no choice because everywhere and everyone I asked about LED's said they were not available for this purpose. Ha! I loved reading your 'ible and though I can't make these myself I will look into the sites some commenters suggest. Thank you!

[vishalapar1]

Wierdly cool, how did you add the PDF file and the excel file to this instructable??

[DJJules]

Easy, when you are adding pictures for each step, select the pdf or excel file instead of a picture.

Jules

[atzonkov]

Great Instructable. What was your over all cost?

[DJJules]

Thanks! It was about 200 bucks for everything not including some tools I bought. Remember though I was given the LED's these are about $1.50-$3.00 each so add that in there too. Once again, not cheap but results well worth it.

[atzonkov]

Thanks for the info. I am trying to decide between doing this myself (for the fun) or going with some commercially available LED under cabinet solutions.

[backdraft999]

Great instructable!
I know it sort of defeats the purpose of an instructable, but you could probably save a lot of time/energy and definitely a lot on money by buying led light strips or light bars from here: http://www.oznium.com/.

[chrwei]

How much power do the 24 LEDs actually use, including transformer inefficiencies?

[DJJules]

Each LED string draws 440ma and the voltage steady state on the capacitor is about 30 VDC (Which includes the drop across the regulator) I am estimating that the string of 24 draws about 40 Watts which is what the 4 foot fluorescent that one of my counter sections used. But. I am getting 500 lumens at the counter top with the LED's and was 350 lumens with the old lighting. And, that was the brightest spot.

[Ugifer]

Nice looking project - I might just try something similar.

Two minor points in your instructable - the Kelvin scale uses the same increase in temperature per degree as the Celsius scale (not Fahrenheit), and also I don't think the output from your bridge rectifier in the picture should be 63V AC. Rectifiers should give you a DC voltage, and as you say in the text, the maximum you would expect is about 35V under no load. Otherwise a beautifully presented entry. Thanks.

[DJJules]

You are absolutely correct on the Fahrenheit. Kelvin is the same increase as Centigrade. Rankine is the the one starting at absolute Zero and increasing the same as Fahrenheit. The Capacitor in my schematic is rated for 63V. it actually sees about 35 as you mention. Wanted to ensure no one under rates theirs should they build this. I have seen several manufactures do this. Say, use a 35V rated cap that works at 50 (for a while anyway...) then they start seeing failures in the field.

Thanks for this nice comments and for reading it. (i'm going to edit the temp comment in the instructable)

Jules

[Ugifer]

Edit - maybe the 63V is the voltage-rating of the capacitor - in which case pls ignore the above.

[mattthegamer463]

Nice job! At 3.5V per LED, you could string 35 of them in series and run it off the 120VAC from the wall, with no other components required (except a fuse for safety) and place more 35 LED strings in parallel with the first for additional lighting.

[chilloutdocdoc]

You cannot run these LED's merely by constant voltage in the way you are suggesting. LED's are to be driven with a Constant Current source of power.

Running them in a constant current configuration provides multiple benefits.
* Protection from providing too much current
* Prevents Cascade failure if one LED goes out

This idea is great overall. But I'd just be careful running 350mA LED's at over 350mA as the author is.

[DJJules]

I am running them above 350 ma but max on these form their data sheet is 700ma. I also made sure that nothing get too hot. The star PCB hits about 41C max which means the die temp is still less than 50C. Max form data sheet is 80C

You are correct on the current limit. I have seen other instructables that do not have any current limiting. recipe for disaster.

Jules

[DJJules]

The problem with that is without running them form DC, they will turn on and off 60 times a second and you can notice that slightly kinda flickers. Then there is still current limiting to deal with. I thought about running them all in series with a higher voltage DC supply. but for safety kept it lower.

[adamazing]

Epic instructable, and brilliant project! But the title is confusing, especially since the reflected light in the thumbnailed main project image makes it appear as if the light is shining up from beneath what I think of as the kitchen counter/counter top. I have no idea what you'd call that space, but calling it a counter just seems weird to me. :)

[edwardchen]

I hadn't noticed until you said it, but it should be Under Cabinet lighting to be similar to other products out there.

nice instructible, btw!!

[WVvan]

Great Instructable! Well documented and informative. Learned some new stuff.

[Ricardo Furioso]

It's really Under Cabinet/Over Counter lighting.
Brilliant.
Especially with found LEDs.
I was wondering about dimmers as well.
I don't understand your flickering issue.
So far we have old-school christmas lites in our kitchen and my wife loves them.
Thanks for the ideas.

[surrealdreams]

Very impressive instructable. You bring up an important point that many other instructables neglect: wife approval factor. I will present this project to my wife with this carefully applied. Thanks!

[xxev75]

Has anyone tried tackin up just some regular LEDs lights like xmas ones? just and idea

[KT Gadget]

It would work because X-mas lights are getting cheaper, however, there are 2 problems; if you were to just plug them in as is, like DJJules mentions below, the string would cause flickering when you move around due to the AC (alternating current) power line. Another problem would be is that the amount of light from 1 string of lights is a lot less than the LED string in this instructable, so if you wanted to get close to the above equivalent light output, you may have to get around 3 strings to get close to the same amount or make a diffuser to spread the light more.

Other than that if you don't mind the flickering (or run it through a bridge rectifier and rewire the X-mas string), then it should work. And I'm not saying it won't work, but it requires some modifications to get an equivalent result.

Some material that works great as a diffuser is the plastic and diffuser material of the backlights in LCD Monitors/screens. They worked great when I made a LED lightpad for sketching.

[eblisster]

Thanks so much for this!! I always want to get brighter light on my counters and hate some of the lighting options out there because they're so very HOT! I will be looking into this project some more after I move into my next house. Up until this very moment, I didn't think you could get this kind of brightness with LEDs.

[DJJules]

You are welcome! You can get massive brightness out of them these days. As a reference the ones I am using are about 70 lumens per watt and were state of the art 2008. Newer ones are 100+ lumens per watt and they get better everyday. BTW they really make colors pop when lit by them.

Good luck when you go to build yours

Jules

[mikeasaurus]

Looking good, nice and bright!

I suggest cutting a length of diffuse plastic to place over the LEDs to soften the light some and eliminate the mirrored reflection seen on your counter tops. That may just be my personal taste. Good luck with the dimmer addition.

[DJJules]

Yea, that is on my list of things to do. My wife wants it diffused too.