[time-nuts] Oncore 1pps driver & LED

[Randy Warner]

Glenn,

You can drive the LED from the DCD line, but along with a series
resistor you need to be sure to include an extra steering diode in
series with the LED. LED's have absolutely no sense of humor about being
reverse biased above a volt or two. This might also affect your 1PPS
pulse accuracy. If you do it this way use a high efficiency LED and draw
as little current through the LED as necessary.

Randy

________________________________________________________________________
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-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Glenn
Sent: Thursday, May 04, 2006 12:35 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Oncore 1pps driver & LED


Could I just drive the LED off the DCD line?

thanks,
glenn


Randy Warner wrote:

>Glenn,
>
>You "should" be alright. You're driving a lot of CAT5, but since the 
>data is only at 9600 baud you should be OK. The 1PPS on the DCD line 
>will be fine too. To blink an LED you just need to buffer the 1PPS 
>signal coming out of the UT+ as it does not have enough drive capacity.
>Just about anything will work: IC buffer or inverter (I use standard 
>74LVC04's in my designs) or just a simple xstr inverter or emitter 
>follower.
>
>Randy
>  
>


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