Ring Oscillator Das Blinkenlights
Crap, the original entry I made for this got screwed up somehow. Oh well.
Alan, VK2ZAY, was experimenting with ring oscillators, which make some very nice blinking light displays indeed.
Before this post got mangled, I was experimenting with putting the circuit into LTSpice and analyzing it. My brain was too enfeebled to figure out the relationship that governed the selection of the values for the bias and current limiting resistors and the capacitors, so I figured I’d just code it up. Of course, now that this post is mangled, I’ll have to redo the LTSpice analysis, but what I discovered was that under some conditions, LTSpice predicted very long start times for the ring oscillator, or it simply failed to initialize. This is because I typed exactly the same value for the components. If I varied the value of the components by just 0.1%, the oscillator had no problem firing up.
I’ll redo the schematic and the graphs tomorrow. Stay tuned.
Addendum: Couldn’t wait. Redid the simulation using the values that Alan thoughtfully provided on twitter. Here’s the screen dump: commentary to follow at a later date.