Desk Lamp 01

Overview

This desk lamp is a fairly simple project that uses a combination of repurposed materials and a couple of inexpensive specialty items. It provides quality task and reading light in a very flexible yet minimal package. A full list of materials and complete build instructions follow the pictures.

desklamp01 finished1

desklamp01 finished2

desklamp01 finished4

desklamp01 finished3

desklamp01 finished5

Skills and Tools

This is designed to be an introductory level making project and thus does not have pre-requisite skills. It will go a little faster if you have soldered before and especially if you have worked with epoxy casting, but it really doesn’t require any previous experience to complete in 2-3 hours of working time.

Tools required include some basic hand tools, a soldering iron and heat shrink tubing, a multimeter for checking wire polarity, a hot melt glue gun with glue sticks, and a drill with bits sized to the holes to be drilled. Suggested, but not required,  tools include a drill press with a step bit (which makes much cleaner holes with less metal deformation than the common twist bits), a rotary (Dremel) tool with grinding bits, and a bench vise.

In addition to the material listed for the lamp below you will need some disposables. These include Superglue or thread lock compound, masking or painter’s tape, plastic cling wrap, disposable mixing bowl, plate and stirrers, and medium and fine sandpaper. Thin double-sided tape will be useful but is not necessary

Lamp Materials

The following items are required for the lamp, although similar substitutions can be made in many cases.


 

The gooseneck for the lamp neck is the hardest item to find, especially at a reasonable price. The gooseneck used here is a 8mm wide by 500mm long item in black. These are sold as a pair for $17 (including shipping) on Aliexpress. The specific item I purchased is item #16 from this vendor. Expect up to 4 weeks delivery to the US. You can use the second gooseneck to make a second lamp or just save it for another project.

 

desklamp01 gooseneck


 

A 12 or 24 volt LED panel for the light. I suggest item G20038 or item G20251 from Electronic Goldmine. G20038 operates at 24 volts while G20251 operates at 12 volts. They are the same size and put out the same quantity and quality of light. These $4 panels provides ample light at a 3500K color temperature, which is mostly pure white with a slight bluish tint. They fit perfectly in the mint tin used for the lamp head. They take 12 or 24 volts DC directly with no need for additional driver circuitry. The panels distribute the heat generated by the LED elements sufficiently to not require an additional heat sink. This project described here uses the 12 volt panel. The whole line of these LED panels offered by Electronic Goldmine are great plug and play units. You do not want to look directly at these panels when they are on, they can definitely hurt your eyes.

desklamp01 led panel


 

A 12 volt or 24 volt DC adapter to match the voltage of your LED panel. This is a good opportunity to use one reclaimed from old electronics. You will want a long (2 meter, about 6 foot) cord and enough amperage to drive your LED panel. The 12 volt LED panel only uses 300 milliamps so an adapter rated at 300 milliamps or more should work. There are many types and quality of adapters out there and the actual voltage output of adapters rated at 12 volts can likewise vary. The one I used measured 16 volts at no load. Fortunately the LED panels seem pretty voltage tolerant. Still, you will want to measure the output of your adapter with a multimeter and pick one that is as close to 12 volts as possible if you are using a 12 volt LED panel.

desklamp01 adapter


A mint tin for the lamp head. The Altoids mint tins work great and some other brands us the same tin size. You can purchase unfinished tins in this size (but you wont get any mints to enjoy).

desklamp01 mint tins


 

A nut can for the lamp base. I used a Blue Diamond almond can that holds 6 ounces. These tins have a bottom that is gently rounded over rather than the usual crimped seam–which makes for a more attractive lamp base when inverted. The almonds are pretty tasty also. You can certainly use other cans. Don’t go with something smaller as it wont hold enough weight to keep the lamp standing up. Select a new can with no dents. You will need the lid during the assembly process, so don’t lose it.

desklamp01 nut can


 

A switch. I used a single throw toggle switch with a through-hole panel mount. The power is here is low enough that you can use almost any switch, however a panel mount switch is much easier to install as it only requires a single drilling operation. Don’t use a momentary contact switch as that won’t work.

desklamp01 switch


 

At least 800 grams (28 ounces) of conformable weight material that will easily fit int the nut can. I used steel BBs (a 28oz package of 2400 goes for about $5). It may be tempting to use lead weights, but don’t. Lead is an environmental toxin and is not necessary for this project.

desklamp01 BBs


 

At least 6 fluid ounces of resin or metal glue to bind the weight material together. This is a good chance to use left over resin from other projects–such as Bondo, casting compound, or other polyester or epoxy resin. A single part glue could be used, but make sure it is suitable for metal (non-porous materials) and will fully harden on its own inside the nut can. The best choice would be a thick but pourable resin compound that gives you at least 10 minutes of working time before it gels.

desklamp01 resin


 

Something to make a power cable protection part from. The power wires from your 12 volt adapter will enter the nut can through a thin and sharp opening. If you do not protect them from the metal edge of the nut can they will be cut through and short out in no time. Over do the protection here. I used the thick hard plastic from the barrel of a discarded pen. This was cut down to a very small part that had a flange at the back to glue to the inside of the can and a small hard tube than extended through the opening to about 6mm (1/4″) past the hole in the can).

desklamp01 pendesklamp01 protect


 

About 1 meter (3 feet) of two conductor wire. Since the current is very low the wire gauge doesn’t really matter. However a thick plastic insulating layer will be helpful for durability and multistrand wire will be a better choice than solid core. Use some salvaged wire here.


 

Finally, you’ll also want some spray paint for metal. Since the gooseneck is already black, gloss black paint is the easiest choice to live with. It would be harder to get paint in all the little flexible joints on the gooseneck but probably not impossible if you really want a different color.


 

Assembly

Remove the wrappers from the mint tin and nut can. Clean both out with a damp cloth. You will need the plastic lid to the nut can later in the assembly process, so don’t lose it. Carefully remove the lid from the mint tin box by prying the tabs outward with a small flat-tipped screw driver. You can recycle the mint tin lid. Flatten the tabs back into the slot they were punched from the best you can. Hammering them against the corner of a bench vise works well, but be gentle and avoid smashing the lip at the top of the tin, as I did in Figure 1 (fortunately I had a spare tin and started over).

Figure 01. Don't do this! Flattening tabs on the mint tin too aggressively has smashed the lip.
Figure 01. Don’t do this! Flattening tabs on the mint tin too aggressively has smashed the lip.

 

The thin metal bends very easily–you can remove much of the distortion caused to the box by flattening the tabs using your fingers or gentle tapping. The tabs should fit almost perfectly back into their slots. You should seal any remaining gap from the inside to prevent light leakage later on. A piece of reflective metal foil tape works best, but you can also glue a strip of aluminum foil into place instead.

Measure and drill the hole for the gooseneck in the mint tin. Center the hole on one of the narrow ends of the tin. Check the width of the small end of the gooseneck before you drill. The outside of the threads on mine measured 7.5mm. You want a tight fit here so match the bit to the actual size of the threads. Although it is difficult, try to prop the inside of the tin where you are drilling against a piece of wood if you are using a twist bit. The metal is very thin and distorts easily. If you have a step bit, this is an excellent time to use it as it will be much gentler on the metal and leave a cleaner hole. A step bit is shown drilling this hole in Figure 2.

Figure 02. Drilling hole in the mint tin for the gooseneck using a step bit in a drill press. The bit is taped to indicate where to stop drilling.
Figure 02. Drilling hole in the mint tin for the gooseneck using a step bit in a drill press. The bit is taped to indicate where to stop drilling.

 

Always wear safety glasses when drilling metal, and use the slowest setting on your drill. Clean up the inside of the hole the best you can with files or sandpaper. Remove distortion from the surrounding metal with your fingers–but be careful not to cut yourself.

Drill three holes in the nut can. Mark a line across the center of the bottom of the nut can (at it’s widest spot) and continue the line down one side.  The side with the line down it will be the back of the lamp. Mark a spot about 12mm (1/2″) up from the bottom on this line. This is where you will drill to bring your power cord in through the power protection part.  As shown in Figure 3, mark a spot about 12mm (1/2″) in from the back lip of the base on your first line for the gooseneck and another one about 12mm (1/2) in from the front lip for your switch. It’s a good idea to label these so you use the correct sized bit for each, as shown in Figure 3.

Figure 03. Back view of nut can marked up for drilling.
Figure 03. Back view of nut can marked up for drilling.

 

Measure the outside diameter of the threads for the switch, large end of the goose neck, and whatever you are using for for the power protection part and drill the appropriate sized holes.  Again, a step bit will give the cleanest results. If you are using a twist bit try to support the metal with a block of wood on the bottom side of the hole while drilling. Clean up any rough edges.

Prepare the tin and can for painting by removing any labels or label glue and lightly sanding the entire outside of each with 220 grit (or finer) sand paper. You want a clean yet dull surface for the paint to adhere to.

Next, solder up and assemble the electrical components. Replace the short leads on the LED panel by soldering in their place one end of a 1 meter (3′) two conductor wire. The solder on the LED panel leads melts very easily and you can unsolder the original leads and solder your new wire in place with little effort. Make sure you can identify the positive (red on the original LED lead) and negative (black on the original LED lead) conductors on your new wire before your remove the original leads as there is no polarity marking on the LED panel. You will also want to make sure there is no possibility of the soldered ends of your wire shorting out against the tin. New wire soldered into place are shown  in a latter stage of assembly in Figure 4, below.

Attach the LED panel to the center of the inside bottom of the mint tin. Use thin double-sided tape or a heat resistant glue (such as Super glue). Do not use hot melt glue in the lamp head as the heat from running the lamp (about 71 Celsius or160 Fahrenheitwill melt the hot melt glue. Using the same tape or glue secure the wire that has to run around the outside of the LED panel to reach the gooseneck against the side/bottom crease of the mint tin.

The gooseneck does not usually come with washers. If you can find lock washers or even flat washers that fit, use them. Assemble the lamp head in the order shown in Figure 4.

Figure 04. Lamp head assembly order.
Figure 04. Lamp head assembly order.

 

Slide the nut onto the wires down to the LED panel. If you have a washer, slide that one next. Insert the wires through the hole your drilled in the mint tin. Slide the free end of the wires all the way through the gooseneck from the small threaded in out through the large threaded end. Liberally apply a heat resistant glue (such as super glue or epoxy) or thread lock compound to the threads on the end of the gooseneck that is going into the mint tin. Insert the gooseneck into the tin and tighten the nut down as tight as you can get it with pliers. You want this connection very tight and glued down so it doesn’t work loose.

The other end of the gooseneck, with the loose ends of the wire protruding from it, goes into its hole at the back of the nut can. Align the gooseneck so that the LED panel in the lamp head is facing toward the front of the nut can and then glue and tighten down the nut on the gooseneck as tightly as possible. When the lamp is finished you will want the lamp head bending over the front of the base for balance and thus you want to align the part the light comes out of with the front of the base when you tighten down the gooseneck. Add some glue to your power cord protector and insert it into its hole from inside the nut can. The power cord protector is shown glued into place in Figure 5.

Figure 05. Power cord protection part glued into place.
Figure 05. Power cord protection part glued into place.

 

The rest of the wiring is very straightforward. Power comes from the adapter, goes across the switch leads, and up to the lamp head. Ground comes down from the lamp head and out to the adapter. Before you start soldering this wiring, cut the plug off of your adapter and strip the leads. Plug the adapter into an outlet and use a multimeter to make sure you know which lead from the adapter is positive (usually black with a white stripe, but check).  After unplugging the adapter feed the leads from the adapter through the power cable protection part into the nut can. Once you have enough inside to solder to the switch (about 75mm or 3″), tie a loose nut in the power wires against the inside of the power protection part to keep the wire from pulling out.

Put some heat shrink on the positive lead from the adapter and solder it to an outside lead on the switch. Put some heat shrink on the positive lead from the lamp head and solder it to the center lead on the switch. Heat shrink the tubing. Add heat shrink tubing to the unsoldered lead on the other side of the switch.  You need to thoroughly cover all exposed electrical connections and prevent resin leaks, so add hot melt glue around the bottom of the switch. Put some heat shrink on the ground lead from the adapter (usually pure black, but you should have checked). Solder the ground lead from the adapter to the ground lead from the lamp head. Heat shrink the tubing. Finished, heat shrunk and glued wiring is shown in Figure 6.

Figure 06. Wiring, heat shrinking, and glue covering finished.
Figure 06. Wiring, heat shrinking, and glue covering finished.

 

Install the switch into its hole on the nut can tightly and with glue or thread lock. You probably want the switch to flip left and right or forwards and backwards, so align it to your preference on the nut can base as your tighten it down.

You are going to be filling the inside of the nut can with highly conductive steel BBs floating around in resin that is looking for a way to leak out. So you want to make sure all of your electrical connections are well insulated and there are no leaks in the can. It’s a good idea to cover your ground connection with tape over the heat shrink. Fully encase the switch, nut around the gooseneck and power protection part with hot melt glue. It may take more than one layer to make sure nothing electrical is exposed and all holes are sealed. Fill the hole in the center of the gooseneck and the hole in the power protection part with holt melt also. Take your time and be thorough. It doesn’t have to look nice, just be leak and electricity proof. A fully glued up lamp base is shown in Figure 7.

Figure 07. Base with finished wiring in place and hot glue set up.
Figure 07. Base with finished wiring in place and hot glue set up.

 

Test the lamp to make sure it is functional before proceeding to add the weight. Make sure you are not looking into the LED panel when you plug it in as the switch may be on.

Prepare to cast the BBs and resin into the base in order to weight the lamp. Resin gets very sticky and usually sets faster than you want it to, so careful preparation a head of time will reduce panic during the process. Figure 8 illustrates good preparation for casting.

Figure 08. Preparing for resin casting.
Figure 08. Preparing for resin casting.

 

In this example I used some leftover casting epoxy, which worked but was really thinner (and thus more leak prone) and longer setting (24 hours!) than would have been optimal. Do your resin work in a well ventilated area that you can afford to get messy.  You will be pouring your cast through the bottom of the assembled lamp and then inverting it (after temporarily sealing the bottom) so that it cures with the weight at the bottom. You will want a plastic plate with a sizable lip to set the lamp on after pouring and inverting (in case you have leaks). It is also a good idea to cut a circle out of a piece of thin cardboard about half the diameter of your nut can. Put the circle on the plate and center the lamp over it when its time to invert. The circle keeps a rounded bottom from forming at the center of your lamp base that would allow it to rock when finished.

You need to firmly support your lamp base upside down while pouring about  900 grams (2 lbs) of resin/BB slurry into it. The slightly open jaws of a bench vise work really well, as shown in Figure 9.

Figure 09. Base in vise.
Figure 09. Base in vise.

 

If you don’t have a vise a couple of sturdy blocks of wood or bricks will work. Make the support strong and stable. Don’t set the lamp base up on flimsy or tip-prone supports if you don’t want 2400 BBs epoxied to your floor!

Mix the resin per directions on the container, you will need about 6 fluid ounces of mixed resin or glue. Resins need to be very completely mixed to cure correctly. So mix it up really well and then mix it again and then mix it a while longer. Once it is completely mixed, pour the BBs into the mixing container and then stir everything well to coat the BBs. The mixture can be poured into the lamp base. The mixture should mostly, but not completely, fill the nut can.

The most critical operation to finishing the whole process with minimal grief is sealing the opening at the bottom of the base. Start with a taught piece of plastic cling wrap to make it waterproof. Run masking tape around the nut can tight against the bottom of the lip to hold the cling wrap tight to the can. Make this masking tape seal as tight as you can against the nut can. Put the original plastic lid from the can firmly back on and tape it down tightly and completely. A completely taped up base is shown in Figure 10.

Figure 10. Lamp based sealed and taped up after resin/BB pour and before inverting.
Figure 10. Lamp based sealed and taped up after resin/BB pour and before inverting.

 

Invert the lamp so that it is right side up and center it over your cardboard circle on top of your plastic plate, as shown in Figure 11.

Figure 11. Lamp upright during resin cure.
Figure 11. Lamp upright during resin cure.

 

If you find that any of the resin has leaked through the switch or gooseneck opening it is much easier to clean it off now (paint thinner works well on uncured epoxy) than after it has cured. Allow your base to fully cure per the instructions for your resin.

Once the resin has cured you can clean up the base in preparation for painting. The thin casting epoxy I used led to some leaks which resulted in hardened resin around the outside bottom of the base. This required about an hour of careful grinding with a grinding bit in a rotary tool, sanding with medium grit and then fine grit sandpaper, and cursing, to remedy. Thick resin and more careful taping could have prevented much or all of this work. If you do have to clean resin leaks from your base, remember that any flaws you can see or can feel with your fingers will show through your paint. Go slow and do a careful job.

The final step is spray painting in a well ventilated area. Before painting, tape over the lever on the switch and very carefully tape around the inside of the lamp head, as illustrated in Figure 12.

Figure 12. Lamp head taped up for painting.
Figure 12. Lamp head taped up for painting.

 

Your lamp won’t work if you paint the LEDs black. You also want to keep the reflective properties of the inside of the tin intact.

Two or three thin coats of spray paint for metal should do the job. After the paint dries and the tape is removed the lamp is finished and ready to use.

If you would like to dress things up a bit you can glue a felt bottom onto the base and consider a small bit of diffusion or tinting in the lamp head. The mint tin should protect your eyes from the direct output of the LEDs under normal use. However, a slightly frosted piece of flexible plastic or paper could be cut to sit inside the lip of the mint tin if you want some diffusion. The more opaque you make this, the lower your light levels will become, so you can’t add strong diffusion.

Likewise, a slightly orange tinted gel or diffuser can be used to warm up the color of the light, if you prefer. A good choice would be a 1/8 CTO (color temperature orange) gel. This material is heat resistant and available from photography suppliers in small sheets.

The lamp head will operate at about 71 degrees Celsius (160 Fahrenheit) so it will be quite toasty to touch but not hot enough to burn you from casual contact or to ignite paper. Test the heat resistance of a plastic diffuser before you permanently glue it into place.

 

 

 

Leave a Reply

Your email address will not be published.

bill@robot50.net