RS-232 Tx / Rx monitoring LEDs?

Chuck Guzis cclist at
Fri Aug 21 10:57:30 CDT 2015

On 08/21/2015 08:36 AM, dwight wrote:
> I was going to add something but it has already been said several
> times. I will add that if using a LED on an AC like signal of high
> voltage, one should use a diode. I recommend using a shunt diode
> rather than a series diode when high voltages are being dropped by
> the resistor. It reduces the need for a high voltage diode but makes
> the resistor hotter. Some red LEDs glow orange when not protected
> from 12VAC. You can ask how I know. Dwight

Ever take a close look at a string of Christmas-tree LEDs?  Most are 
composed of a string of LEDs  hooked directly across the AC line--no 
rectifier diode to be found.

Some seek to reduce the 60Hz flicker by employing two strings to 
illuminate on both half-cycles, reducing the flicker somewhat.   Since 
my eyes react to the flicker (it's like ants crawling over the string), 
I found that simply employing a full-wave bridge rectifier can reduce 
the appearance of flicker tremendously.


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