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Electronics: Fun and Fundamentals — LED Photo Lights

Often I have to take photographs of small objects–for example, when I’m selling items on eBay. Electronic flash is overkill for this kind of work, and video lights are bulky and hot. I decided to build miniature photo lights from small, efficient LEDs.

On eBay I found complete LED reflector bulbs for just $3 each. They are plug-compatible and identical in size and packaging to the little 12V quartz-halogen spotlights often used in track lighting (although the LEDs have a cooler light temperature of 6,000 Kelvin–very similar to cloudy daylight). All the distributors were in China, but I’ve never had any problems ordering components from Chinese sources. Sure enough, within 10 days I received my lights.

Since each unit was rated at 4W, I needed a 12VDC AC adapter rated to supply at least 40W. Fortunately this kind of switching power supply is commonly available as a power source for laptops and LED displays. I found a 50W unit for $5.

(Caution: Some adapters of this kind deliver much more than 12VDC when they are not fully loaded. Therefore, avoid powering just one light at a time.)

How to mount the lights? I wanted to use them in two sets of five, so that I could position each set on opposite sides of a subject. The angle of each individual light had to be adjustable, so that I could focus their combined beams around a small object, or point them at a larger object from farther away. I also wanted to be able to angle the lights up and down, or backward toward a reflective photographic umbrella if I needed diffuse, shadowless illumination.

The design that I came up with uses jointed arms, made from 3/4″ oak and small aluminum angle brackets. Originally, the lights push-fitted onto a 3/8″ brass peg. I later changed the design so that they screwed onto a ¼-20 threaded stud, which is a more common termination on a photographic light stand (plus it fits on a tripod). If you don’t have light stands or extra tripods, you can easily improvise something from a vertical 1″ dowel screwed into a plywood base.

I chose oak as my construction material because I wanted to use wood screws to make the joints in the articulated arms. The screws would tend to work loose in softer wood. You can get an affordable piece of 3-1/2″ x 3/4″ oak from The Home Depot, where you’ll also find a length of aluminum angle, to make the brackets.

Download the cutting and drilling template.

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Steps

Step #1: Cutting and Drilling

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Electronics: Fun and Fundamentals — LED Photo Lights
  • Download the drill diagram PDF from above. The diagram is to scale, so you can use it as a template to mark your holes and lines if printed at 100% scale.
  • The drill diagram shows how to take the wooden parts for one set of lights from a 3-1/2" oak strip. The dimensions do not have to be precise, so I didn't bother to allow for the thickness of the saw cuts.
  • I used a chop saw, but this requires great care when cutting relatively small pieces. A band saw is much safer. If you must use a hand saw, this will entail some work, as oak is not easy to cut.
  • To fabricate the yoke section, make two parallel cuts, then a series of angled cuts to remove the center area in little triangular fragments. A band saw or jig saw is good for this. A hand-held keyhole saw will work if you're persistent. A chisel won't do it, as the oak is too tough.
  • A drill press will insure that each hole is precisely 90 degrees to the wood. If you use a hand-held drill, secure each section of oak with a clamp or vise. The toughness of the oak, and the smallness of the pieces, will encourage them to spin out of control if you try to hold them by hand. Countersink each hole to accept the flat head screws.

Step #2:

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Electronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo Lights
  • Light stands come with many different mounting types. Our stand uses a ¼-20 threaded stud for which the light could screw onto. To put threads into our lights, we're inserting a tee-nut into the yoke.
  • Measure the outer diameter of tee-nut (ours is 5/16") and drill a hole of that size into the yoke.
  • Hammer in the nut with a scrap piece of wood in between the nut and the hammer to prevent the nut's flange from warping from the impact.
  • Secure the nut from the other side of the yoke using the matching bolt and washer. Since the tee-nut and the bolt are both 1/2" long and the wood is 3/4" thick, they will roughly have a 1/4" connection in the middle (minus the thickness of the washer).

Step #3:

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Electronics: Fun and Fundamentals — LED Photo Lights
  • Mark lines in 1 ½" increments on the 1/2" inner-side of the aluminum angle. These are spaced for the 10 brackets for holding the lights.
  • Drill two 3/16" mounting holes from each end of the line that's spaced ½" from each end.

Step #4:

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Electronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo Lights
  • Mount the aluminum angle onto a piece of scrap wood using #8 screws and clamp it into a bench vise to make it easier to cut.
  • Again, mark a line every 1 ½" for cutting out the brackets. Mark two lines that are 3/8" appart in the center of each bracket for cutting out the notch. Cut each bracket out and then cut the sides of the notch.
  • Make each notch by using pliers to bend the section between saw cuts to and fro until it breaks off. Remount individual brackets to the vise to file the bottom flat.
  • If there are grooves molded into the base of each light, the notch would hold them in place. If there are no grooves, don't worry, just epoxy the lights onto them. Adjust the notch width to fit the base of your lights if they are wider.
  • File all edges to debur them.

Step #5: Assembly.

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Electronics: Fun and Fundamentals — LED Photo Lights
  • In the following steps, drill 7/64" relief holes for the #10 and #8 screws that will hold all the pieces together. Use the same 11/64" drill bit that was used on the arm-pieces to transfer their centers by poking through the holes.
  • Attach the cross-piece to the stem. The screws are offset to avoid fouling the hole through the stem below them.
  • Place one of the arm pieces over the top of the cross piece to use it as a drill template to transfer their centers.

Step #6:

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Electronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo Lights
  • Drill 3/16" holes through the yoke as shown and countersink one hole.
  • Use a 2" bolt, washer(s), and wing nut to attach the yoke to the stem as shown. Pack with washers if necessary, on one side only, so there is wood-to-wood contact (providing friction) at the other side. The assembly should feel sticky when you turn it around the bolt.

Step #7:

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Electronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo Lights
  • Round the ends of the arms and use 5/8" screws to attach a bracket to each, and to the central cross piece.
  • The spotlights that I used are not sensitive to polarity. If you buy different lights, check their polarity with a 9V battery and battery carrier terminating in stripped wires. Touch the wires to the pins very briefly.
  • Insert the lights into the brackets (with the same polarity facing the same direction if your lights are polarized), adding epoxy glue if you want to secure them or if your lights don't have grooves.
  • Attach the wooden arms to the central cross piece as shown. This lighting set is now ready to be wired.
  • Repeat these steps to make the second set.

Step #8: Wiring.

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Electronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo Lights
  • If you're using heat-shrink tubing to insulate each joint, remember to slide the tubing onto the wires before soldering them!
  • Your 12VDC power supply almost certainly has a plug on the end of its output wire. Chop it off and strip the wires as shown.
  • Add solder to each set of wires, then slide heat-shrink tubing over them, as shown. Melt the solder to join the wires, then slide the tubing over the joints and apply a heat gun.

Step #9:

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Electronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo Lights
  • In the wiring diagram, the lengths have been abbrevated so that you can see the pattern of connections. The actual lengths are up to you. See the photos for actual wire usage.
  • If your spotlights only work with positive voltage on one side and negative on the other, the molded pattern on one side of your dual-conductor wire will help you to maintain consistent polarity throughout the circuit.

Step #10:

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Electronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo Lights
  • Tin the pins. Attach a copper alligator clip to each pin before adding solder to it. Make sure the solder melts fully, and sticks.
  • Add solder to a wire, then melt it onto the pin as shown.
  • Using a chisel head soldering tip is recommended for heating these thick wires.
  • Solder the lower row first so wires won't be in your way.

Step #11:

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Electronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo Lights
  • Test the light, then slide heat-shrink tubing over the wired pins.
  • Your wired lights should look something like this.

Step #12:

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Electronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo LightsElectronics: Fun and Fundamentals — LED Photo Lights
  • If you want the option of adding a photographic umbrella, drill a 5/16" hole in the front edge of the stem section, and insert the shaft of the umbrella. Alternatively, you can diffuse the light by shining it through a piece of textured transparent lighting panel.
  • By the time you read this you may be able to buy LED reflector bulbs that are more powerful than the ones I found. Just be sure that your AC adapter is appropriately rated (or use a separate adapter for each set of lights).
Charles Platt

Charles Platt

Charles Platt is the author of Make: Electronics, an introductory guide for all ages. He is completing a sequel, Make: More Electronics, and is the author of Volume One of the Encyclopedia of Electronic Components. Volumes Two and Three are in preparation. makershed.com/platt


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