Searching for electronics today international article. February 1987

Discussion in 'General Electronics Chat' started by Fenris, Jun 8, 2009.

  1. Fenris

    Thread Starter Active Member

    Oct 21, 2007
    Hi all

    I have recently stumbled across a schematic for a solid state LED matrix oscilloscope. I remember the original article my self :D . But does anyone have a scan they could pass on to me please. Mainly to do with the details of using this particular unit when built. I remember wanting to build it back then but the 100 LED's were going to cost an arm and a leg back then! So I fancy doing it now I can afford them :D


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  2. Audioguru

    New Member

    Dec 20, 2007
    If it has a 10V supply then the typical output current from the CD4017 is 17mA.
    Multiplexing will reduce the average current in each LED to only 1.7mA which will look pretty dim. Maybe you can use the 'scope in the dark.
  3. eblc1388

    Senior Member

    Nov 28, 2008
    Hi Audioguru,

    That value of typical current 17mA is quite high. Does any datasheet shows this figure?


    Some high brightness LEDs can provide acceptable brightness at current of a few milliamps. Check them out.
  4. Audioguru

    New Member

    Dec 20, 2007
    The datasheets of Cmos logic ICs from Texas Instruments show minimum and typical output current when the supply is 5V, 10V and 15V.
    With a 10V supply the output current into a 3.5V white or blue LED is 17mA without a current-limiting resistor. The output transistor dissipates 110mW which is slightly above its max allowed dissipation of 100mW. It would be fine with a 9V supply.