methods to incorporate led in a keypad matrix manufacture


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  1. #1
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    Feb 2012
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    Default methods to incorporate led in a keypad matrix manufacture

    hi , i am,looking to incorporate leds into the matrix keyboard design and manufacture of the PET

    the current thought , where the keyboard used mr eds scan rouine where the rows pulled high( 4k7 )change to 1k and then polled low depending on the scan rate

    my requirement is to show a mode led a,b,c constantly , ( led appears on )

    the current thought is to scan the keybaord , and then turn on the low return when the scan is complete for the mode after the scans , i need to change the standard 4k7 pullup to 1k and use the 100R low feed to allow the led to show up when using 3.3v

    this should work ?

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  2. #2
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    Default Re: methods to incorporate led in a keypad matrix manufacture

    Only problem that I see is when you press 2 buttons.
    It will affect leds and put about 17mA thru that printed track. It should be ok, but...

  3. #3
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    Default Re: methods to incorporate led in a keypad matrix manufacture

    forgot about 2 buttons on , but thats no big one

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