*** Update of March 30, 2019 ***
Well, here is the newest version of he schematic. After looking at my old schematic, in Post #6, and comparing it to the breadboarded circuit, I realized there were two goofs. I was NOT using a pot at the spot where I indicated "VR1". I had a 180K resistor in that spot in the actual circuit. As for my "R1" in the Post #6 schematic, on the breadboard, THAT is where the 100K pot was. I was not using an 18K resistor in that spot on the breadboard. The schematic was drawn incorrectly. Sheesh.
I learned the hard way about the value of drawing the signal flow from left to right, without fail, so I don't become confused about what is what.
Anyway, I re-configured the circuit so that it is much closer to the website circuit in Post #13 by AnalogKid. Instead of using an 18K resistor for R1, I used a 20K pot configured as a variable resistor. Again, I am trying to make the frequency somewhat variable. The R2 in the newly re-configured circuit is a 180K resistor. Here is the schematic for the re-configured circuit:
I tried to follow AnalogKid's advice on drawing out the 4 gates on the CD4011 as well as trying to show the signal flow from left to right. I did have to draw a wire all the way to the left side of the page for the second half of the circuit because I ran out of room on the right side of the page.
The new version of the circuit is nice and stable. I get a smaller range within which to vary the frequency, however, using the new values for R1 and R2. I can only adjust down to about 460 Hz. And I can only adjust up to about 2,000 Hz.
I should have looked to my bookshelf containing my favorite Forrest Mims books. His "Engineer's Mini-Notebook" for "Digital Logic Circuits" has some interesting ideas for CD4011 oscillators on pages 38 and 39:
I notice that Mr. Mims uses a 1 megaohm resistor at the position of R2 in my circuit and a 100K resistor at the position of R1 in my circuit. That is almost 10 times my values for these resistors.
Well, here is the newest version of he schematic. After looking at my old schematic, in Post #6, and comparing it to the breadboarded circuit, I realized there were two goofs. I was NOT using a pot at the spot where I indicated "VR1". I had a 180K resistor in that spot in the actual circuit. As for my "R1" in the Post #6 schematic, on the breadboard, THAT is where the 100K pot was. I was not using an 18K resistor in that spot on the breadboard. The schematic was drawn incorrectly. Sheesh.
I learned the hard way about the value of drawing the signal flow from left to right, without fail, so I don't become confused about what is what.
Anyway, I re-configured the circuit so that it is much closer to the website circuit in Post #13 by AnalogKid. Instead of using an 18K resistor for R1, I used a 20K pot configured as a variable resistor. Again, I am trying to make the frequency somewhat variable. The R2 in the newly re-configured circuit is a 180K resistor. Here is the schematic for the re-configured circuit:
I tried to follow AnalogKid's advice on drawing out the 4 gates on the CD4011 as well as trying to show the signal flow from left to right. I did have to draw a wire all the way to the left side of the page for the second half of the circuit because I ran out of room on the right side of the page.
The new version of the circuit is nice and stable. I get a smaller range within which to vary the frequency, however, using the new values for R1 and R2. I can only adjust down to about 460 Hz. And I can only adjust up to about 2,000 Hz.
I should have looked to my bookshelf containing my favorite Forrest Mims books. His "Engineer's Mini-Notebook" for "Digital Logic Circuits" has some interesting ideas for CD4011 oscillators on pages 38 and 39:
I notice that Mr. Mims uses a 1 megaohm resistor at the position of R2 in my circuit and a 100K resistor at the position of R1 in my circuit. That is almost 10 times my values for these resistors.
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