Replacing Old LEDs

[woodelf]

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
>  
>