Help! Interactive LED coffee table.

L

Langer

Limp Gawd
Joined
Jul 20, 2008
Messages
327
Hello again all.

I'm taking on yet another project, one I couldn't resist after seeing the video below:
YouTube Link

After hunting around on the Evil Mas Scientist Laboratories website I found an example circuit diagram and building instructions.

I was hoping that someone could help me make some sense of the diagram below. Perhaps put it into lamens terms for me. I have a bit of hobbiest level electronics experience, but I've never taken on a project like this before.

Here is the circuit diagram, which I understand for the most part, I was just hoping someone could offer up a wiring diagram to help me better understand.
TableDiagram-2.jpg

The project called for 16 of these circuits in a 1-D topology (whatever that means)
TableDiagram-1.jpg


They took some pics of the circuit as well - simple enough, I just have a bit on confusion identifying which wires correspond with which:
TableBook-5.jpg

TableBook-4.jpg


When complete it should start to look something like this (hopefully I can do a better job of wire management).
TableBook-8.jpg


Any help that you lot can offer would be a great benefit, I don't have much experience with making my own IC circuits... outside of some basic arduino projects.

Thanks in advance.
 
im not sure what "1D" configuration is but they seem to just all be in series... each one connected to the next via the "communications" hookups... like xmas lights :)

really awesome find on that project btw, i think i have my winter project this year :D
 
Thanks guys, I spent some time today examining the circuit and I now grasp it in it's entirety (almost... I'll ask these questions tonight after I post my diagram). Thanks for those who lent a hand.

I'm ordering the parts to begin construction today, should be able to throw it together in <1months time.

My plan is to use frosted glass so that you don't see the circuits and so you'll only see the glow of the lights.

I'd be interested in fabricating these for purchase if there is enough demand.
 
Okay, I've redrawn the diagram to be more user friendly (at least I can understand it better now).
click for big


I have a few questions for the electronic experts among us:
1 - On the Chip there are V+ and V- pins... what voltage do I apply to these when using 15V to power the LEDs?

2 - There is also a demand for a second power source of -15V, what does this mean? How do I get negative voltages?

3 - Can anyone suggest some inexpensive power supply units that can power the +15V, -15v, and the mystery IC voltage pins?

4 - Can anyone see any problems with my diagram, or is it all tickity-boo?

5 - For circuit number 1 in the 16 circuit series, do I simply ignore the "IN FROM NEIGHBORS" section? the same question for the last in the series, do I ignore the "OUT TO NEIGHBORS" output? Or is there something that I need to take into account?

THANKS so much in advance, for helping me realize this vision.
 
To help a bit further here are the specs of the IC's I'll be using:

LF347
Gain Bandwidth: 4 MHz
Channels: 4 Channels
Input OutputType: Vcm to V+, Not R-R Out
Slew Rate: 13 Volts/usec
Supply Min: 8 Volt
Supply Max: 36 Volt
Offset Voltage max, 25C: 10, 5 mV
Supply Current Per Channel: 1.8 mA
PowerWise Rating 2: 450 uA/MHz
Internally trimmed offset voltage: 5 mV max
Low input bias current: 50 pA
Low input noise current: 0.01 pA/SqrtHz
Wide gain bandwidth: 4 MHz
High slew rate: 13 V/µs
Low supply current: 7.2 mA
High input impedance: 1012
Low total harmonic distortion: <=0.02%
Low 1/f noise corner: 50 Hz
Fast settling time to 0.01%: 2 µs
 
The schematic is assuming that you'll use +/-15V as the V+ and V- on the LF347 as well as on the LED strings.

To get a +/- power supply, it's really easier than you might think. Heck, you don't even need a +/-15V power supply. Take a 12V power supply, and put two 1kOhm resistors in series between the 12V line and the GND line. Now, use the point between the two resistors (it'll be at 6V) as the "ground" for the rest of the circuit(s). Use the power supply's GND as the negative voltage, and the 12V line as the positive voltage. Because you'll be dealing with only +/-6V (instead of +/-15), you'll only be able to put around 5 LEDs in each string (instead of 14). However, you are certainly welcome to put multiple strings in parallel in order to light up more LEDs.

As far as the communication network goes, the original diagram shows two inputs from neighbors, and two outputs to neighbors. There's nothing that says you can't add more. If you want each node to talk to four neighbors, you can do it--just make sure that each input from a neighbor has its own 140kOhm resistor. The outputs are even simpler--just go ahead and add connections from the communication amplifier to as many neighbors as you'd like.
 
Wonderful!!!

Thanks so much!

I'm gong to amend my diagram... and hunt down a 12V PSU.

A couple quick questions, just to be certain.

I am to supply the +/- voltage directly to the IC? and the +/- voltage to the LEDs?
The initial design mentioned the use of two PSUs, is this necessary, or will 1 do the job?
What kind of PSU specs should I be searching for?


Thanks again man, you've painted a very vivid picture that caused a light to turn on above my head. It all makes sense now.

Hoorah, cudos!
 
Is this suitable? Will I need to add resistors to the LED array?

The Specifications for the IC state a Min Voltage of 8V. Will the 6V input present an issue?
or does it follow regular math... +6v [SUM] -6v = 12V?




BreeSpree from XtremeSystems has suggested that it be a wall mounted art piece... which I LOVE.

I've decided to make a picture style interactive panel - instead of a table (or perhaps in addition to the table).
I'm thinking of using perforated aluminum with LEDs poking though the holes to accomplish this, detailed in a nice metal frame.

The goal here is to make an interactive picture that will light up when you walk past, and also allow you to stand and play with it.
 
It would probably be a good idea to add resistors to the LED array. Also, what you've done with the LED array is different from what it was in the original, and won't do what you want it to do. You want the output from that last amplifier to go to the middle of the string of LEDs, not to one end. And you'll want to use four LEDs per string between +6V and the amplifier output, and another four LEDs per string between the amplifier output and the -6V.

The minimum supply voltage for the amplifier was something that concerned me a bit, actually. Looking at the datasheet, however, I couldn't find a minimum supply voltage listed. Can you link to the specs you were looking at?

12V power supplies are plentiful and cheap. You've got one inside your computer, for example, that'll do quite nicely. If you've got an old-n-busted inkjet printer, the power supply for that might work just fine. (I have two at the moment, one is 30V @ 400mA, which might not be enough current for the application, since it would only be capable of lighting up about 20 strings of LEDs at a time. Well, that *might* be enough, but I don't know. I have another that is 18V @ 1100mA, which would be capable of lighting up 55 strings at a time)
 
I listed the specs of the IC I'm using a couple posts up - LINK
Gain Bandwidth: 4 MHz
Channels: 4 Channels
Input OutputType: Vcm to V+, Not R-R Out
Slew Rate: 13 Volts/usec
Supply Min: 8 Volt
Supply Max: 36 Volt

As for the LED array, I currently have 6 across and 5 down.
Are you suggesting going 8 down and X across? with the output in the middle of the "down" array?\\

If I'm missing something, a diagram would help.

Thanks mate.
 
Ah, serves me right for not paying attention...

Since the maximum supply is 36V and the datasheet calls that +/-18V, the 8V minimum should work fine with a 12V power supply.

Here's what I meant in reference to the LED array:
Code: 
(+6V)->|-->|-->|-->|--+-->|-->|-->|-->|--(-6V)
(+6V)->|-->|-->|-->|--+-->|-->|-->|-->|--(-6V)
(+6V)->|-->|-->|-->|--+-->|-->|-->|-->|--(-6V)
                      |
                      |
               (output from opamp)
>| is an LED
The idea is that when the output of the opamp is high, one half of the string lights up, and when the output goes low, the other half lights up. And since the circuit oscillates, it switches between the two, creating the 'shimmer' effect. Does that make sense?
 
Langer said:
Is this suitable? Will I need to add resistors to the LED array?

The Specifications for the IC state a Min Voltage of 8V. Will the 6V input present an issue?
or does it follow regular math... +6v [SUM] -6v = 12V?




BreeSpree from XtremeSystems has suggested that it be a wall mounted art piece... which I LOVE.

I've decided to make a picture style interactive panel - instead of a table (or perhaps in addition to the table).
I'm thinking of using perforated aluminum with LEDs poking though the holes to accomplish this, detailed in a nice metal frame.

The goal here is to make an interactive picture that will light up when you walk past, and also allow you to stand and play with it.
Click to expand...

no you only have half your LED's there... and you do NOT tie the output of your opamp to +6vdc... you attach the gnd side of half your led array to -6 and the other half of your led's positive side to +6... then the "ground" in the middle is the output of your opamp... the swing around +/-0v is what causes the different sections to pulsate/fade
 
Thanks a lot guys, BIG HELP.

Is this a suitable way of powering the opamp?
also, will the 12V work, or should I step up to a 16V(or more) PSU. And will doing so mean I need to modify the values of the resistors/caps in the circuit?



Thanks again, please excuse my noob factor.
 
your voltage divider for your psu section is a little less than ideal, at the very least you should add some caps... you might also want to add some caps from your V+ to gnd and V- to gnd very close to the opamp to minimize the possibilities of oscillation

heres some more info on virtual grounds

http://tangentsoft.net/elec/vgrounds.html

one of the nice things about using +/-15v is you can have more LED's in series, that means less current draw from your opamp... you need to keep in mind how much current each of those LED strings is going to draw and make sure your not going to try and pull too much

you can always find a 30v supply (or a more common 24v supply) and split that...

like this:

http://cgi.ebay.com/Meanwell-DC-Pow...=39:1|66:2|65:1|240:1318&_trksid=p3286.c0.m14
 
As an eBay Associate, HardForum may earn from qualifying purchases.
FLECOM said:
your voltage divider for your psu section is a little less than ideal, at the very least you should add some caps... you might also want to add some caps from your V+ to gnd and V- to gnd very close to the opamp to minimize the possibilities of oscillation
Click to expand...
Actually, I think the voltage divider will be just fine. It's used purely as a reference voltage in three out of the four opamps, and in the fourth, the 1kOhm resistors are so much smaller than the 22MOhm feeding into that ground, that any current coming through the 22mOhm resistor won't be enough to noticeably affect the ground level.

FLECOM's recommendation to get a higher-voltage power supply isn't a bad one, though. The 4.5A capacity of the one linked will be way more than you'll need, so you'll be in good shape.
 
One last time, and THANKS again to the both of you:

Are the values all okay for this setup using a 24V PSU in the 4-6amp range.

How's this?
 
One small change: with a 24V power supply, you can put six LEDs on each string instead of four. Other than that, this looks good. Make sure you post pics when you do it!
 
wow i like the LED cube idea.... too bad their whole wiki is in german?... is there a translated version?

I am thinking of building one those...
 
A bit of Googling will reveal many sites on LED cubes. I actually purchased leds to build a 10 x 10 x 10 cube, but haven't had the time to sit down and put it all together... I don't think they are complicated so much as they are just time-consuming to assemble the led matrix.
 
@Mohonri - Thanks man.... updates when the parts arrive.


As for the LED cube, I built a 6x6x6 cube some time ago back in high-school for a Computer Engineering project - it was a bitch to make and I wont be doing another.

The controller involved in a 10x10x10 would be mind boggling, I don't think you guys understand the principle and the work involved... the fabrication of the actual cube is the easy part, its the controller that will cause your headaches.
 
Langer said:
As for the LED cube, I built a 6x6x6 cube some time ago back in high-school for a Computer Engineering project - it was a bitch to make and I wont be doing another.

The controller involved in a 10x10x10 would be mind boggling, I don't think you guys understand the principle and the work involved... the fabrication of the actual cube is the easy part, its the controller that will cause your headaches.
Click to expand...

I guess that depends on perspective and experience... It seems to me that any of these cubes really are just multiple 'planes' of 2D led matrices, where each matrix is driven by addressed high-side / low-side methods. So the driving section is relatively straightforward, albeit laborious to construct. I will say that I mis-spoke earlier and was planning on an 8x8 cube, not a 10x10... but really I do not see a great deal different between the two other than more labor.

Likewise, software control can be whatever your goal is, but really you are just manipulating 'voxels' in a 3D array and passing that information on to the driver section. This can be as simple as addressing individual points in 3D space or more complicated to include vector paths and geometry. Imagine having a 3 dimensional array variable where each location is set to be either on or off. As your manipulate the cube, you are just setting the values appropriately as your math transverses through space. You probably want to deal with these variables at the bit level for best memory efficiency in a ucontroller, but the principles remain the same.

So while I would agree that for a person with lessor previous experience in these areas, yes, it would be complicated. But if you've worked with driving 2D arrays it is just an added extension. There are plenty of 3D algorithm resources on the net. If you have done anything along the lines of graphical lcd projects (or even 2D matrix games, ala Wumpus - man, am I showing my age!) you have much of the thought process down already. That said, this is also not the type of project I would recommend for a beginner to the ucontroller hobby... there is a lot going on and I don't want to downplay the issue entirely.

I wish I could locate a great 8x8 AVR based project from a German forum I discovered some while ago because it had some great schematics that were not overly complicated - if I can find it again I'll post it here. But another good resource I've found is this MIT student project PDF that, while based on much more complicated controller hardware, does discuss the general assembly and driving methods for an 8x8 cube - replace their high end FPGA with a general purpose 8 bit ucontroller of sufficient capability (24 IO ports, internal or addressed [X, Y & Z]) and you're on your way.

edit - Here is another good site (in German - use Google's translation util) on an 8x8 display...

Also, from a controller pov, I think there is more similarity than difference between driving a 3x3x3 cube and a 10x10x10 cube. I very much look more forward to the controller programming than I do the construction of the cube ;)
 
how should the leds of each module be arranged over the table? in a local cluster around the module or what?
 
enzoR said:
how should the leds of each module be arranged over the table? in a local cluster around the module or what?
Click to expand...
However you want. If you put them all in one spot, you'll get something that looks a bit more like a checkerboard, but if you have the strings mix up with each other a bit, it'll look more blended. It's really a matter of taste.
 
if you want, on my blog i have the circuit and coe for a simple LED matrix display using a PIC mcu

http://db.penguinattack.net/mcu

I also go over the basics of electronics and show you how to use PIC mcus.

The circuit you want to use it just using a photo diode and the feedback of several op amps to drive LEDS, With a micro controller, you can make this circuit so much more complex and fun.
 
hello i saw the project for interactive led table and i donwloaded the fist circuit diagram. I made plate schematic according to the diagram and when i turn it on the leds just flash dont blink :(( i will post you some pictures from it in next post.
 
demonce


demonce


i used the capatitators and resistors from the diagram

wirediagram-LOW.jpg


only part is photodiode

can anyone give me advice and help
 
oh man!!! talk about thread resurection... i remember having the idea of doing this myself, until i realized that I would never finish it!

Langer did u ever finish yours?
 
chronic9 can u tell me is this correct schematic ???? i need one more brain for thinking because only mine its not enough. i also would like to read Langer thinkings too if he reads and if he is still present on this forum.

here is the diagram and schematic i made

demonce


demonce


demonce


Big thanks in front
 
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