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How do i control an led numeric indicator with labview



I guess I am not sure how to search for this.  I would like to display a numeric value on an real life LED indicator by wiring that indicator to an SCB 68 than is hooked into a PCI 6221.  I am looking for an example code that does that, since I can't seem to find it.  I really don't want to have to pull out my books and write one from scratch if possible.


The other problem then becomes this.  Would i need 21 individual lines running to the LED, assuming an array of 7 individual LED lines, each one being driven digitally, and then 3 more ground lines for each number?





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I would consider making a truth table. (see this for an example)


The lines to be enabled for a specific digit are defined in the table, and you select the row. I've provided an example (LabVIEW 8.6) You can use the truth table in this example to set the DIO port values on the 6221.


If you will need additional DIO lines later, you might want to consider using a BCD to 7 segment decoder. This would only require 4 lines per digit. You could even multiplex the 4 lines between segments if you select a BCD decoder than includes a latch. You could control 4 digits using only 8 DIO lines...


I would suggest using a BCD decoder (one per 7 segment display) and an external power supply for the LEDs and only use the 6221 as a control source.

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Google the old reliable "SN7448" and also "SN7447" depending if the display is common anode or cathode, there are probably much more up to date versions of them.



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