Desklamp With a Concrete Lamp Base

This is a guide how to build a desk lamp with LEDs and a concrete lamp base. I build this with stuff that I found at various places in the house during a clean up. The only things I bought are the two LED modules that are needed as the main light source.

To build the lamp you need an empty plastic pot, an aluminum rod, leds, an old power supply, concrete and some other small items. The lamp base is made of concrete resulting in a solid stand. To add some colour I have added some blue, green and yellow leds. The lamp uses two 1 Watt LED moduls and nine 5 mm colour LEDs. The power supply was lying around in a drawer for some years, so its new duty is to provide some proper light for my desk.

I used an old yogurt pot. The one I found is nice because there were no prints or labels on it. But any old pot will do as far as it is not to big or to small.

The lights were fitted into a plastic tube I found. I don't really know where that one comes from originally, but it is solid enough so don't bent when mounted to the aluminum rod and a bit flexible so the LED modules can be squeezed in. If you don't have such a plastic tube you could use a more rigid tube made of acrylic. With that you need to consider the in diameter of such a tube, it must be little larger then the width of the LED modules. The modules have a width of 28 mm, so I guess a acrylic tube with 30 mm of inner diameter will work.

Electronics

• 2 LED Modules 1 W
• 5 mm leds: yellow, blue, green(3 of each colour)
• 1 power supply 6V or 5V, 2.5W or bigger (you can use a 5V power supply as long as it has enough power, mine just happened to be a 6V one)
• 1 Si diode, in case the power supply has 6 V output voltage
• 1 switch
• 1 plug with socket, 5.5x2.1 mm
• 3 x 220 Ohm resistors
• some wires

other parts

• Aluminum rod 360 x 10 mm
• plastic tube 380 x 25 mm
• 30 x 3 mm screw
• 5 nuts 3 mm
• 2 capsules from 'Überraschungseier'
• some tape
• 900 gr concrete
• old plastic pot for the lamp base, 500 ml
• shrinking tube
• some wool or cotton
• cardboard

The picture shows the circuit used for this project.

My power supply happened to have 6V output voltage instead of the more useful and common 5V. Therefore I put a Si standard diode before everything else. The diode yields in a voltage drop of 0.8 V. This gives me an input voltage of 5.2V for the rest of the circuit, which is good enough for me.

Three colour diods are put in parallel and share one resistor. For all colours I used the same value 220 Ohm. That is not optimal but it works. If you like you can extend the circuit so that each LED has its own resistor and calculate the proper value for each colour. You can find some information on that here.

First of all we test if all LEDs work as expected. This can be done by using a breadboard
and some wires. With that set up we check how hot the LED module get, turns out not so hot. So, everything fine now, we can start solder everything according to the test set-up.

What goes inside the lamp base

First we must prepare the capsules so that they can hold the switch and the the socket.

My power supply had the wrong pluck, so I removed it and soldered a different one to it. No it fits nicely with into the plug. Always remember, check the polarity! The plug gets some long wires, so that we can trim them later to the correct length.

The socket is mounted on the side of a capsule, because that way it fits easier in the lamp base container. The capsule is mounted in a upright position later on.The container gets it hole somewhere in the middle. Now the wires are soldered to the socket. Leave the wires a bit longer, shortening is easily done afterwards. Now put the socket in the hole of the container and then in the capsule and screw both tightly together. Close the lid, the two wires are now outside the container. We seal it with a little bit of tape. Now one of these wires must be connected to the switch.

At this time we only solder the plug and the switch, as these to components are placed in the pot with concrete. Make sure the wire are long enough so we can easily solder them to the LED holding plastic tube afterwards. I would strongly recommend using black and red wires so the polarity is recognized easily.

The switch is mounted in the top lid of a capsule, so we drill a hole in the top and fasten the switch. The capsule is then sealed with some tape. The capsule with the switch is later strapped to the aluminum rod.

We have two long wires that will connect the lamp base to the lamp coming out of the capsule with the switch.

What goes inside the plastic tube

The LED modules and the colour LEDs get wired according to the schema. Cut the wires to the length you wish they should have. Once everything is soldered it is time for another test. The connection from the stuff of the lamp base the to LEDs can be made by using some crocodile clamps. That way we can test the hole set up, from power supply, switch and the lights. If everything is still working we need to prepare the modules and the colour LEDs for being moved into the tube. That is done by using some tape. Wrap the tape around the wires of the colour LEDs and also between the two modules. Bare in mind how the colour LEDs should be placed in the plastic tube and wrap accordingly. This wrapping makes the complete lightning set a bit stiff so it is easier to shove it into the tube later on.

Again, make sure that the wires to connect the lamp base are long enough.

The aluminum rod needs a 3.1 mm hole where the plastic tube gets mounted. In this build that hole is placed 55 mm from the top. A 3.1 mm is used because that makes it easier for mounting with a 3 mm screw.

Next is the plastic tube, the holes for the mounting screw and the aluminum rod are placed 50 mm away from one end. We need holes for the rod with 10 mm diameter and for the screw with 3mm. This time I use these exact values for the holes as the plastic is a bit flexible so we won't get much problems in putting all together.

To get these holes perpendicular to each other I used a piece of paper, pencil and a scissor. Wrap the paper around the tube and mark the place where the paper starts to overlap. Now cut very carefully at that line the paper. The paper should now exactly wrap around the tube without any overlap. Next step is to fold this paper in half. After this is done fold from the outside to the just created middle line of the paper. The paper has now three folding lines. Wrapping it around the tube again we have now four points where we can mark the points where the holes must be drilled.

The light section needs something to defuse the colour LEDs and to disguise the wires and all the taping that was done. With some wool we try to wrap all the wires and the colour LEDs. The downwards pointing LED modules should have the wool only on top and not on the downward pointing part where the main light is coming from. This is now pushed into the plastic tube. The LED modules are a bit wider then the plastic tubes diameter. Squeezing the plastic tube makes it easy to shove everything in. Bare in mind how the plastic tube is mounted to the aluminum rod so that the light is really pointing downwards.

Next we need to prepare something that holds the aluminum rod in place when the concrete is poured in. We cut a peace of corrugated cardboard so that it exactly fits into the ground of the pot. In the middle of the board is a hole where the aluminum rod exactly fits in. A second piece of corrugated cardboard is prepared in a similar way only that it now exactly fits in the top of the pot. This second one has some cut-out sections so that the concrete can be poured in.

The plug is already fixed in the plastic pot, next is now to attach the switch in its little container to the aluminum rod. With some tape that is done in now time. We just need to care of the height where the capsule is attached. The switch needs to be outside of the concrete and most of the rest must be inside. I attached the mid of my capsule at roughly 55 mm from the bottom of the pot. The wires from the switch that will connect to the lamp are hold in place at the rod with shrinking tube.

Now the rod is placed in the cardboard placeholder on the ground and in the top one. Again some tape to fix everything.

The concrete is prepared according to the instructions. For this container appr. 850 gr. of concrete was used.

Now the concrete is poured in the pot. Tapping with a wooden spoon removes the small bubbles the concrete is holding. Then this must be dried for a day.

Note: After the concrete is poured in you will notice the rod will get some boost from the attached capsule. Fix the aluminum rod to the plastic pad with some more tape. Use a sounding lead to assure the rod is perpendicular.

After the concrete is set and dried we can mount the plastic tube with all the lights in it.

The two wires from the lamp base are threaded to a hole and then hanging outside the shorter end. Also the wires from the light are hanging on that side. A screw is already partially mounted at the plastic tube with to screw nuts. Next is to put the plastic tube on the aluminum rode and fixing it with the screw and with two additional screw nuts. So we have screw, plastic tube, screw nut for fixing that end. In the middle we got a screw, the aluminum rod and a screw for fixing that middle part. On the other side again screw, plastic tube and another screw. That is a bit fiddly but at the end there ought to be only one winner: a mounted tube.

The last step is to connect the power from the lamp base to the tube. Again with some shrinking tube to prevent a short circuit when pushing the wires into the tube.

A little bit of wool at both ends of the plastic tube so everything looks nice. Now the power supply is plugged in and the lamp is switched on.

Well done, a new desk lamp is borne.