🚀 go-pugleaf

Doug Heacock (heacock@kuhub.cc.ukans.edu) wrote:
: I was thinking I could connect all of the
: LED cathodes to ground through a single 330-ohm resistor, since only
: one would be lit at a time.

ATTENTION: 	The one current-limiting-resistor-methode can make you 
		troubles, if you power your circuit with more voltage
		than the used LED has maximum reverse-voltage!

		Then the other dark LEDs get reverse-voltage influenced
		from active LED. See follow sheme as example:

			High	     LED 1
		out 1 (12V) >-------->|---------| (~10V)
				    activ	|
						|----- r=330 -----| gnd
			Low	     LED 2	|
		out 2 ( 0V) >-------->|---------|
				    dark
				 LED 2  has a reverse-voltage of
					about 10 V and this is too 
					much.

		Why this consideration? You can supply the digital ic-
		familiy from 3 until 15 VDC, absolute rating 18 VDC.
		If you supply your circuit with 5VDC you will have no
		problems. But in this case, it's better you take the
		hc-family because of better ouput-drivers for LEDs
		(lower output resistance).

So I can help you. Greeting from Thomas