Step 1: What you need
Parts & Equipment:
-One umbrella, preferably light colored (I picked yellow), with a straight handle and with a hollow shaft so that you may pass wires through it. It is very important that the umbrella be simple - none of that spring loaded-automatic stuff! You want the shaft to be hollow.
-64 SMD (surface mount) LEDs in your color of choice. The actual size does not matter except that smaller will look more invisible (preferable) but will be more difficult to work with. I used size 805 (2mm wide) 3.5V white LEDs. White, blue, UV & some greens require 3.5 Volts and won't require additional resistors on each LED, but 1.8V LEDs (red, yellow, green) do (more trouble!)
-A spool of thin single strand, lacquered copper wire. Thin enough to be almost invisible against the umbrella, but thick enough to withstand the occasional stresses/snags. This is what the SMD LEDs will be soldered onto.
-3AA battery holder, preferably compact and arranged in an L shape, as the batteries will have to lie over the umbrella's shaft. 3AAA batteries would work well too, and are more compact, but won't last as long.
-Normal plastic coated multi-strand copper wire, preferably the kind that will not break easily after repeated flexing.
-One 750 Ohm variable resistor with built-in on/off switch for dimming and turning the umbrella on & off.
-Needle and thread (of the same color as the umbrella)
-Solder and Soldering iron/gun
-Wire cutters, wire strippers, scissors, x-acto knife
-Drill and drill bits
-Large board and small nails, to be used for laying out the wires and soldering the SMD LEDs onto the wires.
-Masking tape and double sided tape/carpet tape
-Clear epoxy or Glue, super-glue
Step 2: Solder the LEDs onto the wires
Before starting, measure out your umbrella and plan where each of the LEDs will go. This umbrella will have 16 spokes radiating out from the center, each spoke having 4 LEDs. I chose to have 4 different sets of LED spacing (8 of each set) to make a pseudo random looking pattern. I set the LED spacing set so they're generally closer together towards the outside of the umbrella in an effort to make the LED distribution reasonably even throughout the surface of the umbrella.
Get a large board (wider than the radius of your umbrella) and hammer a bunch of nails along the sides so that you can string up/stretch out your single-strand copper wires (2 wires to each nail). Place masking tape and/or mark off the points at which you will be soldering the LEDs. Leave some extra lengths of wire at each end in case you need some extra length once it comes time to actually install them onto your umbrella.
Place some masking tape under the wires to prevent burning the board (in case you ever want to use it for some other purpose) and more masking tape to hold the wires down in place as you solder. My wire was lacquer coated, so I had to first burn it off at the points where the LEDs will be added with my soldering gun and hot solder. (You may try scraping it off instead, or using a wire stripper to strip it off.) Once the wires are 'tinned' with solder, try to wedge an LED between the two. Be careful to place all LEDs in the same polarity!!
Time to solder your first LED. I tried to apply some masking tape onto the wires so that they pinch the LED in place - makes it easier to solder the LEDs in if they're not always moving around. With a very quick, light touch, touch both sides of the LED with the hot soldering tip and the solder coating the wires and tip will flow into the LED contacts. If you're not sure you got it, hook up 3V (two AA batteries) to the wires hanging off the board and see if the LED lights up! Once you get the hang of it, move on and do the rest of the LEDs. I soldered mine in two sets - half of the wire/LEDs on the board at one time (16 'spokes') and the other half after finishing the first.
After all the LEDs were soldered in, I applied power to the board/wires to see all the LEDs light up in their glory :) This is also a good time to determine how many volts you want your umbrella to run on, and what value variable resistor you want to use for dimming. I decided on 3 AA batteries (4.5 Volts (or 3.6 volts if using rechargeable batteries)) and a 750 Ohm variable resistor.
Step 3: Assemble the central hub for the wires
Make two rings of wire. I used masking tape to hold it's shape while putting it together. The masking tape also served to mark the spacing where each LED string will be attached. The exact size of the rings doesn't matter except that you want it to be fairly close to the center of the umbrella. Do not actually solder the wires into full circle just yet as you will need these to be detached when you fit it into the umbrella later on - just hold the circle together with more masking tape for now and leave lengths of wire long enough at one end to reach the batteries once it's inside the umbrella.
I used the same single strand copper wire as I used for the LED strings/spokes. *THIS WAS A MISTAKE!* Every time you open and close the umbrella, the wires in this hub will flex and this kind of wire will eventually break from the stresses.. bad bad bad. Later on I soldered additional loops of stranded wire onto the hub. These wires are much better at holding up to stresses of repeated flexing. (see photos 7 & 8.)
[edit: The next umbrella I made used *only* loops of wire for the hub - see photos 9 & 10.]
Cut the lengths of wire off the big board (4 LEDs per length). Measure the ends/length/LED placement and start soldering the strings of wire onto the hub. Make sure you get the wire/power polarity right! You can add power to the wires to see if you're getting it right. After all 16 strings are attached, you will have an interesting glowy mess... might be used to make an interesting headpiece or hat, but we're trying to stay focused on making an electric umbrella :P
Step 4: Get the wires and hub into the umbrella
Once everything is roughly in place it's time to attach the open ends of the hub together. Cut, strip and twist the wire ends together. Once tied together, place some newspaper between the hub wires and the umbrella's cloth so that you won't burn the cloth. Solder the wires together. Once that is done, add tape to that new section on the hub so it's shape and spacing matches the rest of the hub. Now you should have two wires coming off the hub. These wires will go to the battery clip / power switch / dimmer.
Cut little bits of double sided carpet tape and start placing them under the hub to keep it in place. Set it down, centered around the spokes with two strings of LEDs between each spine. Once in place, sew the hub to the spokes and cloth of the umbrella.
Step 5: Attach the LED strings to the cloth
Once they're all set in place, remove the masking tape and cut off the excess wire at the ends/edges. Try adding power to see what the umbrella will look like. It's not finished yet, but this is the point where it finally looks like it is and you can see the lighting effect for the first time.
The super glue is not good enough to hold the LEDs in place forever. It's just temporary to keep everything in place while you sew all the wires and LEDs into place. I used small stitches - one on each LED and one on the wire halfway between each LED.
Step 6: Add the ON/OFF/dimmer control
Drill one small hole in the shaft at the top of the umbrella - just large enough to let the fine copper wires through, but don't insert wires yet. Next, drill out the umbrella's handle - carefully drill a hole all the way through the handle and into the metal shaft of the umbrella. Be careful to use a drill bit just slightly smaller than the diameter inside the shaft and drill carefully right down the center of the handle until the bit pushes through. You want the hole to be large enough to let the drill shavings that went up the shaft to fall back out again. Try to get them all out.
Next you need to drill a larger hole in the handle, just deep enough for the dimmer switch to rest inside. I used a 3/4 inch bit for this, and then drilled out one side some more for the irregular shape of the dimmer switch. Again, try to get all the shavings out of the umbrella itself.
Now, it's time to run two single strand copper wires down from the top of the umbrella and out the bottom of the handle. This part is really tricky as the wires could get bunched up inside. Pull them out again if they get stuck and try again. If the wires get too bent up, throw them away and try again with new wires.
Once you get them through, solder one of the wires at the top to your battery clip, and the other to one of the wires leading to the hub/LEDs. The other wire from the hub goes directly to the 2nd wire on the battery clip. At the bottom (the handle end) solder the wires to the switch and dimmer such that you can disconnect power altogether by turning/clicking the variable resistor all the way counterclockwise, and so that the LEDs grow brighter the more you turn it clockwise.
Once you've tested that it all works, glue the variable resistor in place with epoxy or other glue. If possible, find a nice decorative knob to put onto the variable resistor.
Step 7: Finishing up
And finally you can take it out for a spin!
It looks amazing, but is a bit delicate. Don't take it out in the wind - I don't know if it would survive the umbrella reversing itself in the wind! Also be careful opening, closing and transporting the umbrella so as not to put too much mechanical stresses on the fine wires.