So I've been messing around alot with the 40106 inverting hex schmitt trigger IC and have been trying to figure out a good way to get a sync pulse coupled into it from another oscillator. I had a simple "aha" moment and put a diode between the cap and the schmitt input, and then another diode at that node with a ~9V narrow pulse from the other oscillator. I plugged into LTSpice and it works!...but then I went to build it and nooooope! The basic astable vibrator of course works great, but as soon as I add that diode between the cap and the input it goes CRAZY and oscillates at like 2MHz...
I figured maybe for some reason the 40106 needs some kind of damping between the diode and the input and tried a 470 uH inductor but that didn't help. I also tried some series caps on either side of the diode, which helped, but the whole thing seems unstable and if you just touch the diode it makes strange frequency shifts and couples in some dirty 60 cycle hum or something.
So, my analog guru friends here, do you have any ideas on how to execute this? Atached is a shot of the LTSpice model which is more or less showing what I would like to see in reality. The blue and green waves are the normal square and triangle that you get off the output and input nodes of the astable, and the red is the sync pulse, which you can see creates some sync waveforms.
I figured maybe for some reason the 40106 needs some kind of damping between the diode and the input and tried a 470 uH inductor but that didn't help. I also tried some series caps on either side of the diode, which helped, but the whole thing seems unstable and if you just touch the diode it makes strange frequency shifts and couples in some dirty 60 cycle hum or something.
So, my analog guru friends here, do you have any ideas on how to execute this? Atached is a shot of the LTSpice model which is more or less showing what I would like to see in reality. The blue and green waves are the normal square and triangle that you get off the output and input nodes of the astable, and the red is the sync pulse, which you can see creates some sync waveforms.
Attachments
-
95.5 KB Views: 44