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.
Step 1: Gather your materials
- 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 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
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
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
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!
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.