There is some blinking LED standard for the sensors and
some industrial electronics device. 

NAMUR NE44 is one of them for the chemical plants. 
Normally blinking means some fault conditions there.
Green LED will indicate the power status, yellow LED
will indicate the output status and red LED will 
indicate fault status (often blinking).

We have some in-house indicator standards for our
sensors. They may not be fully implemented depending
on the sensors.
1) green: power-on (static on), short-circuit (4Hz blinking),
under-voltage (100ms-150ms flash)
= operational state of the sensor interface

2) yellow: stable signal indication (static on), unstable signal
indication (4Hz blinking)
= operational state of sensor, signal quality

3) Yellow/Green: human interface indication for teach-in, etc

Regards,
Xiaofan



-----Original Message-----
From: Mike Hord [mailto:mike.hord@gmail.com]
Sent: Friday, October 07, 2005 7:37 AM
To: Microcontroller discussion list - Public.
Subject: Re: [PIC] PIC programmer performance comparison, etc

We have this discussion every few months, it seems.

For a guy like me, red/green (or even yellow/green or
amber/green, or especially orange and red OR yellow)
LED signalling is completely useless.  I usually ignore LEDs,
since I can rarely suss out the meaning.  Unless they're
blinking, of course.

For my money, the ideal LED output is a blink code-
blink three times, then off for the duration of, say, five
blinks, then repeat.  It requires a key to interpret, moreso
than red/green does, but if it only ever blinks in the case
of a failure...

Mike H.

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