22 Oct
2005
22 Oct
'05
9:56 a.m.
Tony Duell wrote:
Msot common red LEDs have a Vf (forward voltage) of
1.8V. Higher voltage
tend to be the modern low-current ones that you don't want. I'd get the
1.8V one and see what happens.
Except for very speicalised aplications I've never really worried about
the characteristics of the LEDs I am using. Just get a generic red LED
and pick a reisstor to pass between 10 and 20 mA through it.
Well the current does add up, if you are looking at a front panel. Just
remember what you are driving
the led with. A regular TTL gate has only 16 ma of sink current. If you
are replacing a old led, I would
make sure the size of the led is right, and avoid the high brightness
ones. Think what they had in the
70's compared to today.
-tony