Re: [time-nuts] Re-triggerable Monostable?
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Grant, What`s wrong with a diode and a capacitor?.Don C. - Original Message - From: Grant Hodgson [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, October 26, 2007 4:41 AM Subject: [time-nuts] Re-triggerable Monostable? ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I'm working on a synth. project which can take either an external 10MHz reference input or use an internal TCXO. It would be nice if the presence (or more importantly, failure) of the external 10MHz ref. could be detected automatically, and signaled to the user. There are, of course, a number of ways to do this. One is to use a level detecting circuit; simply AM detect the ext. ref. input and apply to a comparator. Lots of circuits to do this, no problem - but requires a number of components, unless there is some magic IC that will do it that I'm not aware of - I suppose a dual op-amp is all that's needed, plus a handful of discretes. Another option might be to use a re-triggerable monostable, which is constantly looking for the presence of (say) a falling edge every 100nS on the ext. ref. input line. It would seem that conceptually, this would be the easiest way, possibly using less components. Does anybody have any favourite circuits for this; or are there any caveats that are not mentioned in the plethora of monostable circuits that are mentioned on the 'web? Mnay (older) test equipments have an int/ext switch on the back, with an indicator on the front, but some newer ones detect the ext. ref. and switch automatically. I suppose that's not a problem on a box, which this synth. is not. The output would simply be a high/low digital line, the ext. ref. input will of course be buffered; I can cope with switching the 10MHz signals. Any ideas appreciated. regards Grant ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Re-triggerable Monostable?
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Don Collie wrote: Hi Grant, What`s wrong with a diode and a capacitor?.Don C. Otherwise known as an AM detector?? Depends if just the absence of a signal is to be detected or if the frequency is significantly different from that expected. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Re-triggerable Monostable?
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY Hi Grant: Your re-triggerable monostable idea has been implemented and is called a missing pulse detector. Have Fun, Brooke Clarke http://www.PRC68.com http://www.precisionclock.com http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam Grant Hodgson wrote: ); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I'm working on a synth. project which can take either an external 10MHz reference input or use an internal TCXO. It would be nice if the presence (or more importantly, failure) of the external 10MHz ref. could be detected automatically, and signaled to the user. There are, of course, a number of ways to do this. One is to use a level detecting circuit; simply AM detect the ext. ref. input and apply to a comparator. Lots of circuits to do this, no problem - but requires a number of components, unless there is some magic IC that will do it that I'm not aware of - I suppose a dual op-amp is all that's needed, plus a handful of discretes. Another option might be to use a re-triggerable monostable, which is constantly looking for the presence of (say) a falling edge every 100nS on the ext. ref. input line. It would seem that conceptually, this would be the easiest way, possibly using less components. Does anybody have any favourite circuits for this; or are there any caveats that are not mentioned in the plethora of monostable circuits that are mentioned on the 'web? Mnay (older) test equipments have an int/ext switch on the back, with an indicator on the front, but some newer ones detect the ext. ref. and switch automatically. I suppose that's not a problem on a box, which this synth. is not. The output would simply be a high/low digital line, the ext. ref. input will of course be buffered; I can cope with switching the 10MHz signals. Any ideas appreciated. regards Grant ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Re-triggerable Monostable?
); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY I'm working on a synth. project which can take either an external 10MHz reference input or use an internal TCXO. It would be nice if the presence (or more importantly, failure) of the external 10MHz ref. could be detected automatically, and signaled to the user. Are you happy hacking low level software? (aka firmware) If so, consider one of the tiny micros. The PIC 12F629 comes in an 8 pin DIP. It doesn't require any external components. (Maybe a socket.) It's got an 8 bit prescaler on Timer0. That would drop 10 MHz down to something you could watch with software. You even have a couple of pins leftover for other hacks. I think there are similar chips available in SOT-3-6 if space is critical. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
