Illuminated periodic table - multiplexer

Discussion in 'The Projects Forum' started by jhelliar, Mar 21, 2009.

  1. jhelliar

    Thread Starter New Member

    Mar 21, 2009
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    I am trying to create a periodic table wall chart 8' by 4' which has an LED inserted into each element. I would like like to be able to wire this to a control panel and be able to push buttons to light up different LEDS or groups of LEDS. Someone has suggested I should do this using/via a multiplexer. IS this a sensible idea and how would I go about doing it? I have never used one before. What would I need to buy?

    Many thanks in advance for any help received.

    Jack
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    How close is April 1st?
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    It's a reasonable project. What is necessary are the details - what groupings of elements are to be illuminated. Give a lot of thought to the control panel for all this, too.
     
  4. jhelliar

    Thread Starter New Member

    Mar 21, 2009
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    Do you think a multiplexer is a sensible ideas or just use a set of push to make switches?

    Many thanks Jack
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    I can't tell yet - it will depend on the way you wish to arrange the way the various LED's illuminate on the periodic table.

    The periodic table is not easy to lay out in an organized fashion. There are the vertical columns of each Group, there are the metals, semimetals, and nonmetals. The lanthanide and actinide elements get organized into groupings external to the main table.

    The way you wish to be able to light up the LED's is going to be crucial to the project. Can you state what groupings should be controlled in addition to individual elements? Do you wish different colors of LED's?
     
  6. jhelliar

    Thread Starter New Member

    Mar 21, 2009
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    To make it simpler i think i will leave out the lathanides and actanides. The groupings I would like would are:

    Group 1
    Group 2
    Group 3
    Group 4
    Group 5
    Group 6
    Group 7
    Group 8/0
    A period

    If possible:
    Metals
    Non-Metals
    Solids at r.t
    Liquids at r.t
    Gases at r.t.
    Transistion Elements

    I dont mind about the colour of the LEDs

    Thanks for your help

    Jack
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
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    It figures, my chart shows liquid/solid/gas @ 100C, but I can always find another. Have you an example online we can both work from?

    Do you wish the individual elements to illuminate? What resources have you for doing the construction? I can imagine the control panel being a small version of the periodic table applied to a console with switches mounted in each element box and others along the top (or bottom) to control the groupings.

    The parts list will be mostly switches, LED's, diodes, and wire. The wire part gets to be a big expense, even using small stuff. How are your soldering skills?
     
  8. jhelliar

    Thread Starter New Member

    Mar 21, 2009
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    I would like the individual elements to light up. Having spoken to a few people they suggest using acryllic rather than wood for the board but other than that I can order anything I need within reason. I thought ribbon cabling would be good for the main wiring.

    http://www.science.co.il/PTelements.asp?s=MP

    lists all the elements by melting point. Most are solid, Hg and Br are liquid and a few are gases

    Thanks so much for helping with all this
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    Multiplexing is one way to go.

    You might also look at Charlieplexing. Google is your friend.

    Charlieplexing may not work well if you need a lot of LEDs to appear to be lit simultaneously.

    A microcontroller would be the way to go. It would take quite a few logic IC's to implement the necessary functions. It would make things a lot easier if you could set up the table to have either the number of rows or columns divisible by 8.
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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    I need to hit the catalogs for parts and such. Can you work from schematics?

    Pursue SgtWookie's idea if you wish - my technique is pure 1930's level - except for the LED's and maybe a SMPS power supply.
     
  11. jhelliar

    Thread Starter New Member

    Mar 21, 2009
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    Schematics are great. Thanks for all your help can i get you anything for it?

    Many thanks

    Jack
     
  12. beenthere

    Retired Moderator

    Apr 20, 2004
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    You're going to be doing substantial work on this. I have got things worked out, but will have to post it up somewhat later, as other things are pressing right now. I'll get it done this evening or by tomorrow at the latest.
     
  13. jhelliar

    Thread Starter New Member

    Mar 21, 2009
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    That's great. Many thanks again for all your help.

    Jack
     
  14. beenthere

    Retired Moderator

    Apr 20, 2004
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    This project is going to be a lot of work. In fact, you even get to do most of it yourself. The attached files are a blank you can use to do the rest of the elements, and the other three illustrate how to go about it, using hydrogen, lithium and mercury as illustrations. To speak academically, the exercise is left to the student.

    In every case, each element in the wall display will have a green 5 mm LED located so as to act as an indicator. The LED's will individually mount in a so-called clip, which is a push fit into a 1/4" hole. The total thickness of the material must be on the order of 1/8", or a different means will have to be found to do the mounting.

    Each LED will be fed from a common 5 VDC bus. Each LED will have an associated resistor. For high brilliance, use 200 ohm, 1/2 watt. A lower brillance can use 300 ohm, 1/2 watt. The darker the background where the LED is mounted may influence the need for greater intensity. You may also find that a larger 8 - 10 mm LED may be needed for good visibility. Experiment before you buy all parts.

    The LED's in the parts listing are high-output green, as that color is most easily noticed by the eye. Brighter by far are the blue LED's, but the price is greater. Another drawback to blue is that they tend to have narrower dispersion, so they are harder to see off the cone of illumination. Again, experiment.

    Each element LED will have several switches that can source current to it. There will be one so-called ELEMENT switch for each element in the periodic table. From the description, this will be 74. In addition, there can be as many as 4 other switches that will also illuminate the LED. Each switch is able to operate independantly of the others because of the 1N4148 steering diodes that act to isolate each line to the individual LED's.

    Construction must place the necessary diodes at the individual LED's. The lines from the switches are split out to each steering diode as apporpriate. That leads to a figure of 89 switches - 74 for elements, 8 for Groups, 1 for Period A, and 6 for Metals, non-Metals, Solids, Liquids, Gasses, and Transition Elements. Only one wire from each switch needs be led to the display, but several switches will have multiple connections.

    The total number of diodes will depend on the number of elements to display and the connections to the additional switches. The maxumum number should not exceed 445 (5 X 74). These are among the less expensive components.

    Because the location of the display, it might be desirable to have a mirror of it at the control panel - perhaps 3 mm (T1) LED's that will illuminate with the larger LED's in the display. They would use the 5 volt supply, and use 330 ohm resistors to limit current at a lower level. That is significant extra work, but a good visual aid in ascertaining the state of the display.

    Some wiring will need heavier conductors than the 28 ga in the ribbon wiring. The 5 volt line up to the display would be more adequately supplied through 22 ga wire. 28 ga is supposed to be good for 1.4 amps, but it's going to get a bit warm.

    Suggested parts list (all from the current Mouser catalog, may be ordered online:

    Green LED 638-MV6451 @$.16/ea, $.114/100
    Blue LED 604-WP7113QBC/D @$.29/ea, $.18/100
    Clips 351-0004-RC @$.13/ea, $.07/100
    Diodes 512-1N4148 @$.03/ea, $.013/100
    Flat cable 523-191-2801-124 $35.75/100'
    note: the flat cable is 24 wire. That seems to be the most
    ecomonical arrangement.
    Switch 108-1MS1T1B1M1QE @$1.90/ea, $1.24/100

    Power 418-CFM2007S @$20.32
    Note: this is a 4 amp switcher.
    Console 537-MDC15155-01 @$66.98
    Dimensions are 15 x 15 x 4.5
     
  15. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
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    I would favor a linear output method using many shift registers connected in series. Each register can handle 8 LEDs.

    The MCU just clocks the outputs to the shift registers and the LEDs turn ON. The software is simple to develope and takes only several pins of the MCU for all the outputs.
     
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