OK, wait a minute.
I see that you edited a post a page back (actually, post #48, here: #48), and now you're talking about driving four 7-segment LEDs!
Are you thinking about displaying a time count on there or something?
I hope you realize that the 7-segment displays require a lot more than just four logic lines.
Also, on large 7-segment LED displays like that, usually each "long" segment is made up of four super-bright LEDs that require around 20mA current. You'll have to figure out how much voltage it'll take to get that much current. I have some that are similar to that, and it takes around 11.3v to get 20mA.
Use that LM317 constant current circuit I posted way back to find out what the Vf is.
Note that the decimal points will only have 1 or 2 LEDs in them; they will require much larger resistors to drop the current down.
I see that you edited a post a page back (actually, post #48, here: #48), and now you're talking about driving four 7-segment LEDs!
Are you thinking about displaying a time count on there or something?
I hope you realize that the 7-segment displays require a lot more than just four logic lines.
Also, on large 7-segment LED displays like that, usually each "long" segment is made up of four super-bright LEDs that require around 20mA current. You'll have to figure out how much voltage it'll take to get that much current. I have some that are similar to that, and it takes around 11.3v to get 20mA.
Use that LM317 constant current circuit I posted way back to find out what the Vf is.
Note that the decimal points will only have 1 or 2 LEDs in them; they will require much larger resistors to drop the current down.
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