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Issacsutt
modified 5 years ago

A Fun new kind of Oscillator

9
10
424
04:48:13
This is pretty cool cause not only does it oscillate back and forth between two LEDs but its even versatile enough to chain together as many of these circuits as you want and basically create what some people refer to as an “LED chaser”. It’s very simple and easy to understand in operation, however the component count can seem like a lot if you plan on trying to create a pretty long chain of these... Basically all I did here was design a falling edge trigger that does nothing at first when you press a button, but when you release it, a short pulse is produced (or long, or mediocre, or whatever length you want, depending on the size of the capacitors). And then the output of each stage is simply fed straight into the input of the next. Also, something else that’s pretty nice about this special oscillator is that the sizes of the capacitors used directly determines the duty cycle/pulse width of each chain! ***Press the push button to start*** If there’s anyone interested in a more detailed explanation, just let me know in the comments section Here’s a link to one with 3 stages: http://everycircuit.com/circuit/6511405300449280
published 5 years ago
jason9
5 years ago
Looks like a variant of the ring oscillator. However, instead of NOT gates chained together, it’s circuits that convert falling edges to pulses. This has the advantage that the number of units in the chain doesn’t need to be odd. It is also a little more complex though. Additionally, it has a very variable duty cycle equal to the reciprocal of the number of units. So, with 2 units the duty cycle is 50%. With ten units the duty cycle will only be 10%. With many more the duty cycle decreases accordingly.
Issacsutt
5 years ago
Well that’s true, but each one can also have a completely different rise time from the other if the cap sizes are adjusted as so, and the rise time is pretty flexible
jason9
5 years ago
Oh, that’s true.
jason9
5 years ago
I guess this works well to show which stage of a circular cycle something is in assuming a each stage always takes the same amount of time cycle after cycle. So, if it always repeats: 5mS in stage A, 10mS in stage B, 3mS in stage C, 5mS in stage A, 10mS in stage B, 3ms in stage C, and so on forever then this sort of oscillator represents that well.
Issacsutt
5 years ago
Yeah for sure... What’s really peculiar about this circuit though, is with 4 stages (which I actually built on a breadboard), it will actually start oscillating by itself in a weird crisscross fashion where one half will light up alternatively until you hold down the push button for a sec or two discharging the capacitors, and then it will endlessly light up in a ring type of fashion. For example; at first it lights up in a patter like this: A+C -> B+D -> ...A+C and after you hold and release the push button then it’ll oscillate as you’d expect: A -> B -> C -> D -> ...A
jason9
5 years ago
Yeah, those modes of oscillation are possible in standard ring oscillators too. I figured they’d be unstable and decay into the expected oscillation, but I guess experimental evidence says otherwise. I wonder, if the input of the falling edge detector rises, does it force the output to fall immediately, or at least a little sooner than expected? That would stabilize these unwanted modes of oscillation.
Issacsutt
5 years ago
Mmm yes and no, it kinda falls pretty quick but it only snaps off that quick after it goes below about 0.6-0.7 volts do to the npn transistors, one easy fix might be to just lower the load resistors on the PNP’s output, but that could also possibly slow the rise time.... but I have just cleared my breadboard and am working on something else currently so it may be a while before I try that
Issacsutt
5 years ago
I’m probably gonna be posting a VCO pretty soon, it’s gonna use my VCCS circuit and a custom Schmitt trigger oscillator I designed to function... so far, on the breadboard, I have achieved a range of 200Hz - 290kHz with a 100nF cap, and a range of about 150kHz - 500kHz with a 200pF cap, but this is just a rough first design so far. It’s so fun trying to play around with the control voltage, I even replaced the potentiometer with a photocell/LDR sensor and was able to alter the frequency very well just by varying the amount of light that hit it... it was so cool!
jason9
5 years ago
Wow, that’s awesome! Sounds like a lot of fun.
Issacsutt
5 years ago
Yeah it definitely is, thanks!

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