>Hal Murray hmurray at megapathdsl.net >"Would you please say more? Or post pictures? > >Where did you find a 200 ms PPS pulse?"
The circuitry I added takes the narrow positive going timing pulse (2V/25us) on pin 2 of the surface mounted Lucent 1141 IC (U5) near the DB25 output connector on the main pc board and uses a single NPN transistor to inverts it to produce a negative going 5V pulse to trigger a 555 pulse generator. The generator output is a 5volt positive pulse about 0.2 seconds wide that can drive an LED as well as give a 1PPS rectangular waveform output to an added BNC connector on the rear panel. The reason I used .2sec for the pulse is so it would be long enough to be seen on the LED I mounted on the front panel. The modification only requires one 555 IC that is used to generate the .2 second wide 1PPS pulse, 1 general purpose NPN transistor (2N2222), 6 resistors, 1 LED, and 3 capacitors. All parts used are common and I mounted them on a 16-pin dip socket with 2 stiff resistor leads soldered to pads on the main board labeled ‘J3’ where the right rear corner pad I believe was the +5V and the 3rd pad from the right was ground, but you’ll have to check that to make sure. The circuit board on the front panel already has properly spaced and positioned holes for an LED but there is no hole in the panel so you’ll have to drill one. I have a photo of how I mounted it but you’re on your own making that modification. http://farm8.staticflickr.com/7054/7035510675_fa49693f36_z.jpg http://farm8.staticflickr.com/7251/6889434938_951a57e093.jpg http://farm8.staticflickr.com/7253/7035489479_c0bdb34dbf_b.jpg _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
