Introduction: Analog LED Table

About: See some of my work here and as always accepting orders for custom design and fabrication as featured on Discovery Channel, Wired Magazine, Gizmodo, Engadget, Geekologie, PCWorld, CNet and many more - Pinteres…
This is my instructable on building a simple LED table that works and responds in an analog manner. It was to be built of individual pods with 4 LED's with there own photo-transistor to detect movement, or rather a disturbance in the light/wave patterns above them. It seemed simple at first, hook up a couple LED's & a resistor to a power source that is interrupted by a photo-transistor to act as a switch and voila, right? place foot in mouth here.

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Weeks later of googling, and reading forum after forum I came up with a circuit that I was happy with. Realistically this would have been easier using a micro controller but I was rich on time "or so i thought" and low on cash. Total cost of this panel including the wood frame has been around 35$ Now of course I did have to scrounge, look for freebies and of course use eBay. I live in a quite remote section of Northern British Columbia, so sadly there was no quick run to an electronics supply store. This table was to go to my best friend for a Christmas present but sadly, I ran out of time. He got an radiant ceiling mounted heater for his garage instead. So the LED pods I built, sat in bin being bounced around for a year and a half. They looked so sad and neglected, all they need was a home, some 12V juice and a little love, See what they needed for a happy home on the
next pages

  1. I forgot to mention, this table was built as a panel. That is why the power is on the side. The panel can easily be moved about, it can be placed on my coffee table, kitchen table or even the wall as interactive wall art. I believe this is important as my family likes to be able to mix up our furniture arrangement and may not always want such as large piece to be hard to move around . In pictures and videos the table is sitting on top of my living room coffee table. It would be simple to add permanent legs or even cheat a little and pick up a cheap used table and buck the legs to the desired height
  2. I have added a new circuit diagram in step 4, feel free to comment, give advice and poke holes - its how we all learn, and I have a lot of learning to do!
  3. Added the write-up on building the frame, guess I didn't save it properly when I wrote it the first time.  Live and learn...
  4. See step 11 for some pictures with a paper diffuser added!  This optional but it does soften the look.  This is fire resistant paper, the kind used for lamp shades, I thought this prudent as the power source could potentially spark or heat up
  5. Wife's friend they sell similar tables to parents with children with sensory seeking Autism.

Before building this table, remember your are using dangerous power tools, exposing yourself to potentially lethal doses of electricity, cutting yourself with broken glass, burning yourself with solder, dealing with nasty paint fumes and in general annoying the crap out of those you live with, and danger unto its own! So be warned!


Step 1: Supplies, Supplies, Supplies

Supplies needed

*Most of the panel supplies can be skipped if you all ready have a ready built glass table with enough space below to contain the electronics.

  • One 48"x30" sheet of tempered or laminated safety glass
  • Two eight foot 2"x4"s
  • Four eight foot 1"x4"s or 2 eight foot 1"x1"s if you can find them cheap
  • Two 1/4" thick pieces of wood paneling/plywood one being 48"x30", other one 49"x31"
  • Wood screws, 3/4", 1-1/2", 3-1/2
  • Gorilla Glue
  • Stain & corresponding sealant or paint

  • 240 Leds
  • 300 12v 470 ohm resistors
  • 60 22k resistors
  • 60 3 leg photo transistors
  • 120 transistors (2N 3904 -J05)
  • Spool of bailing wire
  • Small spool of thin non stranded copper wire
  • Ethernet cable or equivalent
  • Simple SPST switch
  • 12v DC bulb and holder
  • Converted computer power supply
  • Electronics grade solder
  • Hot glue
  • Electrical tape or shrink tubing
  • Thins sheets of semi flexible clear plastic, I used the replaceable plastic face inserts from a face guard I no longer had the base for, "waste not want not"
  • black silicone tubing, similar to kind used for fishing gear, or sling-shots
Tools used
  • Table saw
  • Circular saw
  • Drill
  • Router
  • Hand held power planer
  • Soldering iron
  • Other tools used for the wood frame are up to you, its just matter or preference or budget.

Step 2: Building the Panel Frame - Get Out the Gorilla Glue!

Whooooops, for some reason I forgot the write-up for this section.  So here goes!

My glass was 30" by 48", so this dictates the size of the table.  I used safety glass as this is what a friend gave me.  If it was plate or Plexiglas, I would probably choose to make it a little thinner, say 22" by 48".  Safety glass is strong stuff, to layers of glass laminated with a layer of plastic in between.  If it breaks it stays intact, but is tricky to cut. Whatever type of glass you use, don't try to cut tempered glass! unless you like playing 1000000 piece-o-glass pickup!  Its impossible to cut once it has been tempered, sometimes it will have a mark letting you know its tempered on the edge, sometimes not - BE CAREFUL!

Enough on what type of glass, on to the frame.  One of the easiest ways to start is to simply lay your glass on a level floor or work surface, lay down some padding of some kind to protect the glass, a beach towel would work fine.  lay your wood around the glass in the shape of frame and mark it off with a pencil.  The key here is to allow a 2 mm gap between the wood and the glass so later the glass can be made to slip in and out.  Once you have measured and checked to make sure everything is kosher cut your wood.  You should have 4 pieces, two 2x4's at  84 cm long and two 2x4's at122 cm long.  My trick for connecting them is simple.  First pre-drill through holes for wood screws to hold it together.  Then apply gorilla glue to the edges being joined  "make sure to dampen the edges with water first" then I simple screw them together.  The screws provide the temporary clamping pressure.  Wait a couple of hours for the glue to set up hard, "full cure is in 24 hours though".  Once setup you can remove the ugly screws and use a 3/8 drill bit to re-drill the holes.  Go through the one board into the other just like the wood screws to the depth of about 4 inches.  Blow out any sawdust and get your dowel ready.  I simple had a bucket of water that I dipped the tip the end of the 3/8 dowel in to pre-wet it.  Put about a tablespoon worth of gorilla glue in a disposable container and use it for your glue source instead of the bottle to prevent any contamination of your bottle of gorilla glue.  Dip a stick or small brush into the glue and paint the tip of the dowel with gorilla glue.  push it into the hole and with a small saw cut it off flush.  Repeat for the rest of the holes.  Once dry, this joint is rock solid!

I made mine a little out of order as I also fitted it with framing members at the same time I built the basic frame.  This made the setup a little harder, far better to build the basic frame first.  I then chose which side would be the bottom and routered out a edge on the inside of the frame to accept the bottom panel.  This isnt really needed if you choose to use battens on the inside instead.  I used some leftover wood paneling we ripped out of a house renovation.  If you use stronger plywood you could get away with not adding the framing members at the sides and in the middle, but I'm cheap so I needed them for the flimsy paneling.  I attached the framing members the same way as the frame.  Pre-drill, gorilla glue, screw, wait to dry, remove screws and bore out the holes to 3/8 and insert glue covered 3/8 dowel.  Whew- run on sentences!

Once the frame is dry re-measure your opening and cut your bottom board to fit nice and snug.  When you know it fits, remove it an apply gorilla glue to all the edges and re-fit the board.  I used drywall screws to lock it in place while the glue dries.  The screws can then be removed or left in place as they won't be seen.  I removed them just in case they might scratch what ever I was going to place the panel on after.

Next add 3/4" spacers "see picture labeled gorilla glue swelling" running onto the bottom panel inside the frame.  When you put your next panel in with the circuitry this 3/4 gap will be holding all the wiring from view.  Cutting that panel is rather simple, you can measure the glass or simply trace glass right onto your panel.  The glass and panel should be the exact same size to allow easy removal later. 

Before staining or painting the wood determine where your holes need to be cut for the power supply cord and switch.  Cut these out before applying your chosen finish.  I used a mahogany stain/varnish combo.  I am still torn if I like the finish or not, everyone else seems to like it though.

Step 3: Power!

I am not going to go into this too deeply, as a bunch of instructables describe building lab power supplies from computer power supplies all ready.  But here is a basic run down.  One more thing, be very careful, there is enough residual juice in this things capacitors to fry you!!!!
  1. Find your smallest power supply you can use, as your space is limited.  In the first pic the one on the left is from a dell, "pain in the ass to work with anyway".  The non descript one on the left is smaller, that's what we want.  This one drove a mechanical fish robot for a month at our local museum, a couple LEDs will be no problem.
  2. I wanted the guts exposed so for this one I'm taking the cover off, and removing some of the side metal to increase my clearance.
  3. The fan I later replaced for a smaller one as this one was wider the the 2x4
  4. The wires we are concerned about keeping are the yellow ones - 12V, the black ones - ground, 1 red wire - 5V, One green wire - for the on switch and the fan wires of course.
  5. I divided the yellow wires into 5 bunches, as I will have 5 rows of led pods.  I also separated the ground wires, 5 for the pod rows, and one for the green and red wire.
  6. The green and black wire are hooked up to the SPST switch, this turns the unit on and off
  7. The red and black 5V wire goes to the 12V DC  automotive light bulb - this acts as a heavy resistor to provide a small load for the power supply.
  8. The remaining yellow 12V wires and ground wires I tied off and readied to be attached to the LEDs.  All other wires were trimmed short, soldered and capped with electrical tape.

Step 4: Circuits

Ah yes, its pod building time! Now you will have to bare with me as I built the actual circuits over a year and a half ago.  Little embarrassed to say that I never properly learned how to draw a circuit diagram and it is next on my list.  So I have included my bizarre 3d representation of the circuit  picture #8 along with many photos.

ADDITION: I have added a slightly proper circuit diagram, hopefully this makes sense!  Please feel free to comment, add advice, or poke holes, its how we all learn.  Thanks!
  1. Cut your bailing wire into sections about 16 inches long.  Bend the middle of it into a circle about the diameter of a tennis ball, this does not have to be precise.  Where the extra wire bisects bend them down at a 90 angle.  After and inch bend it up 90 degrees and after another inch bend it down 90 degrees more.  Do this 60 times.  Look at the pictures!
  2. Take your LED's and your small resistors 470 ohm.  Most places you buy LED's from will supply you with the matching resistors, you just tell them the power source.  I asked for ones to run them off a 12V circuit.  The Blue LED's are 3.2v, the green ones were a little less.  Twist one resistor around the cathode (shorter wire) and solder in place. Repeat 240 times.
  3. Cut your plastic into 60 strips about 1 inch by 5 inches.  Drill holes to look like picture #7
  4. Trim off the 3 leg of the photo transistor, see diagram.  Or if you have 2 legged ones, your done 60 more steps.
  5. From the picture, insert the 2 transistors and the photo-transistors into the hole you made and solder as per the diagram.
  6. Next insert the 22k resistor and solder to the base of the one transistor and tie it to the emitter of the other transistor.  The other end is soldered to a 470ohm resistor which is soldered to the photo transistor. The other leg goes to the base of the second transistor.  Finally off the emitter of the first transistor you solder a wire that will be soldered to the bailing wire ring.  Do 60 times
  7. get out your hot glue, because the plastic base is so thin the heat of the glue enables you to bend the plastic around the bailing wire, attaching it.  Yep 60 times.
  8. finally solder the anodes of the LED's to the bailing wire circle, look at the pics!
  9. Strip your Ethernet cable, you will have 3-4 sets of wire.  Each set will usually have one colored wire, and one white wire, cut off a 3 foot section for each LED pod.  Solder these on as per the photos.
  10. Repeat until complete!
  11. Patience, I will get around to learning how to write a proper diagram.

Step 5: Laying It Out

This is a simple matter of laying out the LED's in a pleasing manner, mine was 5 rows of 9.
  1. Once the pattern was marked, I simply drilled a small hole for the wire to feed through, and 2 holes for the bailing wire base.
  2. Then the bailing wires were bent, locking the pod in place.

Step 6: Drilling Holes & Installing Pods

Once again drilling holes, attaching pods, feeding the wires.

Step 7: Wirring the Pods

  1. All wires fed through the holes
  2. Bundle the wires into groups
  3. Secure and neat, ready for test run!

Step 8: Power Ups and Initial Testing

  1. Hook the negative leads to the ground.
  2. Hook the positive leads to the 12V
  3. Turn on - success

Step 9: Power Plant Goes Online

  1. Here we have put the power supply in place
  2. Chiseled out a hole for the fan
  3. Drilled the hole for the switch
  4. and drilled a crappy hole for the power cord, covered my error up with an ugly shower ring adapter, whoops

Step 10: Test Run, Curses...

So, got a little cocky but luckily I caught my self.  One of the pods stayed lit all the time.  It took me an hour to figure out what was wrong, I had soldered in one of the transistors backwards.  I had a few spare boards so I popped it apart and put in a new one, its all good!

Step 11: Final Assembly

  1. All is well, final assembly
  2. Fitted the board into the table
  3. Hook up all the wires
  4. Install the fan
  5. And screw in the 1"x1"boards to support the glass
  6. All is not so well!
  7. Discover that the photo transistors are too sensitive indoors  AAAAAAH
  8. Super simple fix, cut 1/2 cm lengths of black silicone tubing used for fishing gear, these slip over the heads of the photo transistors preventing stray darkness from entering from the sides and triggering the LED's in low light situations, nice!
  9. I recently added a paper diffuser under the glass, this softens the leds intensity on the eyes!  If your end intent is to do this, you could skip the steps on hidding the wires as it would not be seen.  Kinda miss seeing the circuits though.  The beauty of using the paper is it can be removed if you change your mind!

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