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
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
*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.
Step 2: Building the panel frame - Get out the gorilla glue!
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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!!!!
Step 4: Circuits
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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!
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.
Step 6: Drilling holes & installing pods
Once again drilling holes, attaching pods, feeding the wires.
Step 7: Wirring the pods
Step 8: Power ups and initial testing
Step 9: Power plant goes online
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
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