Instructables

How to Make an Improbably Bright LED Task Lamp

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Picture of How to Make an Improbably Bright LED Task Lamp
Fiat Lux!  The rallying cry of every scientist, engineer, handyman, or anyone that has to work on small fiddly bits.  You can never have enough light when working on some things.

I wanted a replacement for my 250 watt halogen--a lamp which, while sufficiently bright, was so hot that it was impossible to work with for any length of time.  Enter the world of high-powered LEDs.

In this Instructable I'll show you how to construct a 50-watt LED lamp.  50 watts doesn't sound like a lot compared to 250, but LEDs are around 5-6 times as bright as incandescent per watt.  The 250 watt halogen puts out 3600 lumens--this LED puts out over 4000!

The materials should be less than $100, depending on what you can scrounge together and how exactly you construct it.

The hard parts--the machined mount for the LED--I did on the manual mills at TechShop.  TechShop has everything you need for this entire project, even soldering irons and the like in case you don't have one.  Most of you probably don't have access to a mill otherwise, so sign up today!

WARNING: Parts of this Instructable require experience with AC line power.  If you're uncomfortable with this, get someone to help you out!  If you make this at TechShop, just ask around and someone can give you guidance.
 
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Step 1: Gather your materials

Picture of Gather your materials
The first step is to gather your materials.  In the picture is everything you need.  Starting from the left, you'll see:
- An old CPU cooler.  LEDs need cooling, and you'll want a pretty beefy heatsink and fan to keep things cool.  Almost any model will do.
- A reflector.  This part is optional--you can use it if you need a bit more directionality to your light.  This one I got from Deal Extreme, part number 39963, "20~100W Silver Plated Plastic Smooth Reflector (58mm)", $2.10.
- A machined mounting plate.  I'll show you later how to make this at TechShop.  You'll want a (approximately)  2x2x0.5" block of aluminum for this part.
- The LED plate!  Deal Extreme part number 157806, "50W 3000K 5000lm 50-LED Emitter Warm White Light Plate (32 ~34V)", $16.00.
- The LED driving circuit.  This is a constant-current circuit that takes AC input and converts to ~34 V output at 1.5 A.  Deal Extreme part number 132902, "JR-50W LED AC Power Driver for 50W LED Light Lamp Bulb", $18.80.
- Some miscellaneous screws.  I needed 4x 3 mm screws and 1x 4 mm.  The exact screws don't matter much, but you'll need taps for whatever thread you choose.
- The mount itself.  I used a "Photo Studio Lighting Light Stand Magic Clamp" from eBay for $14.99, but you can use whatever you think works best.
- Some 2 watt resistors, approximately 400-500 ohms.  This is to reduce the 34 volts of the power supply down to the 8 or so the fan needs.
- An aluminum case.  Aluminum is good because it dissipates the heat of the driver circuit.  
- 22 gauge wire.  Not too critical; just make sure it can handle 1.5 amps.
- Rubber grommets.  For the cabling holes in the aluminum case.
- A GFCI plug.  I cut this one from a $9 hair dryer on Amazon!  Standalone cables were closer to $20, so this seemed like the better option.  I highly recommend a GFCI plug for safety!

Step 2: Machining the mount

The mount is the hardest part of the project since it requires specialized equipment like a mill.  Don't worry, though, it's not too bad!

The basic idea is that you will have 4 tapped holes for the LED mounting screws to screw into.  These holes are 34 mm apart on my LED plate; make sure to measure if yours are the same.

The first step is to square off your block.  The dimensions aren't too critical as long as it's around 2x2x0.5".  You need enough area for the LED plate to mount onto and enough thickness for the mounting screw to come in from the side.

I used the face mill available at TechShop San Jose for the facing step.  It makes for a very clean surface.  Ask the front desk to borrow it, and ask someone if you need help on using it.

The next step is to drill the holes.  There should be 4 small diameter holes which you will tap out to the desired screw type.  Make sure to pick the right drill size for the tapping step--look it up in a table if you need.  Otherwise, you are very liable to break the tap.  Tap each hole very carefully, since these will be fairly small holes.

The exact position of the holes is not too critical as long as they are exactly 34 mm from each other and square.  You should definitely use the Digital Read Out (DRO) available on all TechShop mills for this part.  And use lubricant!  I almost had to start over when I broke a drill because the aluminum had fused to the bit.  A little spritz of lubricant solves this.

After drilling the holes for the LED plate, you will need a mounting hole for the heatsink.  There are two steps--use a drill, or even better, an end mill (to keep a flat bottom), to create a hole that the head of your center screw can go into.  Don't drill all the way through--leave 1/8" or so  of remaining material.  Then, drill the rest of the way through with a drill just larger than your outer thread diameter.  Done correctly, your center screw will slide in nicely with no part of the head above the surface, but with sufficient thread on the underside.

The last step is to drill the mounting hole.  I used a 1/4-20 tap, as this is the same as the standard camera tripod mount.  It gives reasonable flexibility in mounting choices.  First, drill with the correct drill size all the way through to the center hole.  Then tap all the way through.  It's generally wise to tap in through-holes if you can as it allows the cut material to fall away more easily.

And that's it!  You should end up with a block like shown in the last pictures.

Step 3: Attach the mounting plate, heatsink, and LED plate together

Picture of Attach the mounting plate, heatsink, and LED plate together
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The next step is to attach the main lamp components together.  You'll need the LED plate, your mounting block, the heatsink, some thermal paste, screws, and a drill/tap combo.

First step is to drill and tap the center bottom of your heatsink.    Most likely, this will be a "blind hole" meaning it doesn't go all the way through (since there is a fan in the way), so be extra careful with the tap.

Spread some thermal paste on the heatsink surface (the thinner the better, as long as you cover everything), place the block on top, and screw it into place tightly using the center hole.

Spread some more thermal paste on the block again and put the LED plate on top.  Screw it in tightly and you're done.

Step 4: Assembling the electronics box

Picture of Assembling the electronics box
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Now for the LED driving circuit.  The aluminum box is one I picked up at Fry's; just about anything the right size will do.

Drill some holes on the end, clean up the sharp edges, and insert some rubber grommets.  Insert the AC power cable, tie a knot in it to prevent it from slipping, and solder it to the circuit board.  Make sure that the live and neutral wires are hooked to the right place.  I had to check which wire was which on my multimeter--the "fat" prong on the plug side goes to neutral while the thin prong goes to hot/live.  Also make sure to get a very solid soldered connection--you don't want this coming undone!  The GFCI will help if anything goes seriously wrong, but you don't want to get to that point.

You'll need three wires for the other side--one for ground, one for LED positive, and one for the fan positive.  Insert the wires through the grommet and tie another knot.

I don't have a picture here, but for the interior connection you'll want ground to go to the black wire from the board, of course, as well as LED positive to red.  For the fan wire (yellow, here), you'll want to tie it to a reasonably beefy resistor (2 watt, 470 ohm is good).  The other side of the resistor goes to the normal positive lead.  Make sure to shrink-wrap everything.

When you finally test this, make sure to wear safety glasses the first time and stand back a ways.  Nothing should go wrong if you've been careful, but in the worst case a component could explode and send shrapnel out.  Be careful, and as before ASK FOR HELP if you aren't sure about the wiring.  AC wall power is nothing to play around with.

I used Kapton double-sided tape to attach the board to the case, but you may want something more robust.  The board had a large metal plate on the bottom that you can tap and screw into if you like.  I may just go that myself, but for now the tape is sufficient (Kapton is strong and heat-resistant).

By the way, this circuit board handles any input voltage from 85 to 265, so it will work equally well anywhere in the world if you have the right plug.

Step 5: Final Assembly

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We're almost done!  You now need to finish the wiring on the lamp side.  Solder the ground wire and the fan negative to the minus tab of the LED.  Wire the positive wire to the plus side of the LED, and finally attach the fan positive to the fan wire.  Use a generous amount of solder for the best connection.  Make sure everything is nice and secure with zip ties, and use heat-shrink tubing for any wire conenctions

I've left the electrical tabs bare here since 34 volts is not too dangerous, but if you're at all worried about shorting anything, you should paint over the tabs with urethane conformal coating, available at any electronics supply.  It will insulate and protect the connections.

Once the lamp head is done you can screw it into place on the flexible arm.  Again, use zip ties to keep the wires secure.

Step 6: Done!

Picture of Done!
And we're done!  The lamp really is absurdly bright--the background in this picture looks dark but is really normal room lighting.  There is so much light that everything else is underexposed.

Good luck, keep safe, and feel free to ask me if you have any problems.

By the way, Deal Extreme sells 100 watt and even 200 watt version of this LED emitter and driving circuit--that's more light than even I need but you might need more!

And don't forget: I made it at TechShop, and you can too.  Go to www.techshop.ws to find one in your area.
cwalker386 months ago

i have an old 36 volt Li-ion drill battery, which does fluctuate a bit sometimes up to 40v on a full charge. Do you think it would power the led or fry it? the battery seems to only be able to power 2 12v car bulbs (incandescence, xenon etc). Not sure, still a little iffy on my electronic skills and my multi reader does not want to give me any info except voltage. It can only read up to 200ma so im assuming its higher than that.

pfred21 year ago
You're into your task lighting. I don't want to sound mean or anything but the most likely reason you snapped a bit is because the drill bit walked on you when you started it. Lubricant had nothing to do with it. You have to be doing super high speed production for lubrication to be a factor with aluminum. If you insist on using your DRO method use a center bit before you use a little twist drill. Better yet just use transfer punches and skip all of that measuring entirely. But then don't drill out on the mill with a vise bolted down. Small twist drills should be run into divots or they'll walk, flex, and snap. Not every time, but enough that common practice is to punch the work before drilling it.
spcutler (author)  pfred21 year ago
Don't worry at all about "sounding mean"; I'm a beginning machinist and I know it.

However, I don't believe that bit wandering was the problem here.  That was in fact my first theory behind the breakage (even though I've never had a problem before on a very smooth, freshly face-milled surface), and so on the next hole I used a center bit (actually, a really beefy sharp-tipped chamfering mill).  I then drilled down just a little ways and inspected the bit before going further.  The aluminum had completely galled to the grooves, and I had to dig it out with a sharp object.

A little spritz of lubricant solved the problem completely, giving me nicely-shaped chips instead of long strings that would gall to the bit deep inside the cut.  The last two holes I stopped using the center drill, and I had no problems at all.

You're probably right that I should always punch or center drill first, but the fact is that I'm lazy :-).  That said, I've been meaning to pick up a set of shorty bits, which would also improve matters. 
In light of the new information I wonder if you were running high enough RPM? Aluminum surface speed is high, about 300 surface feet per minute. Also, you know you are supposed to raise the bit out of the hole often to chuck the chips don't you? You can't expect the twist helix to completely clear the hole for you. You have to start raising after you've gone about the depth of the diameter you're drilling.

I have seen materials stick to bits working it though. That can be because of poor tool finish. In which case then you would have to use some kind of a coating to overcome the deficiency, or buy better bits.

For laughs I figured out what RPM you should have been running for the size hole it looks like you drilled and no milling machine can go that fast. It is slightly over 9,000 RPM. If you were going that fast the chips probably would have flown off the bit don't you think?

I don't know what the top speed of the machine you were using is but I'd be surprised if it is over 4,500 RPM so being as you could only run about half of the speed you should you would have to adjust your technique some.

I just got done running some little jobs here where I had to center drill start a number of holes. It is a pain. Works though. I made bearings brackets and lead screw lock collars for a CNC machine I'm making. The machine has 2 sets of double lead screws too so it added up to 8 of each. On the bearing brackets I drilled for 3 8-32 set screws a piece too. Oh, and I made a couple of extras in case I messed one up (I didn't but I felt better setting up different operations having made extras). So for the brackets alone I had to do about 30 chuck changes just for the center drill. Then another 30 to mount the bits. I'm striving to be lazy, so far it hasn't worked out for me yet though.

P.S. Being lazy always ends up costing me extra work, materials, tools, time, etc. machining.
spcutler (author)  pfred21 year ago
You're probably right about the spindle speed; I was at about 3k (machine didn't go much higher), and I think your 9k figure is the right ballpark.

I was using peck drilling but a single diameter seems like overkill; I was going about 3 diameters at a time. Maybe shorter pecks would have prevented the break, but adding lube solved the problem equally well (this is starting to sound dirty...). The chips were actually being cleared well enough that I doubt I needed to peck drill at all.

Sounds like a cool project you've got going. I have a mini mill at home that I've thought about converting to CNC. That's kinda on hold since TechShop has a nice Tormach CNC that's better than any home conversion that I could do.
I clear chips to stop birds nests from forming as much as for any other reason. There are too many variables to make any specific statements as to when chips should be cleared other than they need to be.

As far as surface speeds go they are all known at this point. I use variations of this formula

SFPM = PI * Dia. * RPM / 12

294.5 = 3.1415927 * 0.125 * 9000 / 12

Aluminum working surface speed is between 250-300 SFPM but small diameter tools should be run faster to stress them less. The additional speed translates into less torque on the tool.

There is a metric analogue to this formula but I am not very familiar with it. Whenever I need to work in metric units I convert to imperial measurements.

Speeds and feeds is intermediate machining magic so it pays to become familiar with the topic as best as you can. For aluminum it is less important, when you work with harder materials like steel it becomes more critical. Perhaps this is because the relative hardness of your tools, and materials gets closer to one and another. Then you must rely less on sheer brute force, and more on finesse to get the job done.

P.S. I didn't bother to look up what drill was used for your tap but just guessed it was about an eighth of an inch (0.125). I was only looking for a ballpark figure and knew you likely weren't even close. Calculating machining speeds is one of those rare places where math is really cool. heh
lutam1 year ago
I did a similar setup for a SAD Light. I have problem with the power driver or the led array. It seems to be overheating after some times, only the strip of leds in the middle of the array stay lit.
spcutler (author)  lutam1 year ago
What kind of heatsink setup did you use? A good rule of thumb is that the LED should stay cool enough to touch without burning your finger. If that's not happening, you need a bigger heatsink or one that's in better thermal contact with the LED. A very smooth surface, thermal paste, and a reasonably high clamping force are important.
I checked a local supplier (Germany), and while they sell 50W LEDs, they cost 80€ and above (~100$)... I wonder where the price difference comes from...
Ebay is your friend, I found a supplier once that offered 5 of these 50 watt ones for about $40-50.
Interresting. I wonder whether their quality would be an issue, i.e. whether you would notice the extra money spent or not... At that price, I'd call it a bargain...
spcutler (author)  Dominic Bender1 year ago
I'm not sure. Your local source may be higher quality, but the $16 unit I used seems perfectly good for my purposes. My source has even larger emitters but they start at $66 for 100W, so the 50W version is the best deal.
Tomdf1 year ago
You sir, are improbably talented at naming projects. Nice work.