Hi... Personally, i take great care about the 1PPS timemark output from my GPS receivers. First thing of all: My timemark line drives a single 74ACT04 or 40H69 inverter with short leads to get sure the line is as little loaded as possible without ringing. What happens after is far less stressing: If the line is overloaded, the only component that will "suffer" is the hex inverter, NOT the GPS board!
For the LED, my two GPS boards are a Canadian Marconi (CMC) Superstar and a Trimble Lassen SK8 which deliver VERY narrow pulses. (1ms for the Superstar and something around 10µs for the Trimble (very difficult to see on an analog scope)) These pulses are way too short (especially the 10µs!!) to comfortably drive an LED and give a visible signal. So, i simply woked up an ooooold timer: The famous 555! In a monostable design, i could easily stretch a 10µs pulse up to a much more comfortable 20ms or 50ms and directly drive the LED via a current limiting resistor. (470 ohms for a 5V supply) The PIC solution is not bad either, but personally i prefer the old analog way! Have a good day and 73 de Normand VE2UM. __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
