I agree/disagree. If the frequency is set high enough to start with, then it is irrelevant. High enough does not mean just beyond what we can visible detect. It must go well beyond that for safe, healthy lighting. But my efforts to find the "very stable" version will be helpful for future applications and testing, so a design that "floats" around may not be suitable.If you are controlling LED brightness using PWM then the frequency is pretty irrelevant so the simplest '555 circuit will do the job.
I'm planning to download LTSpice very soon. Are there files you can upload so that I can import your circuit into the program. I have a few low power opamps that I might substitute in the design to see if they work. Don't know the part#s off hand.Hello,
I breadboarded the following circuit based on post #21 and modified it for a frequency of 1Khz.
Circuit worked nicely. I was able to adjust duty cycle from 0% to 100% with no LED flicker.
Oscillator frequency was fixed at 1KHz and did not vary with duty cycle.
One suggestion would be to use a stable voltage reference (or a regulator for the whole circuit) so it doesn't vary with the supply if that's important.
View attachment 169871
Not sure I placed the .lib and .asy files in the correct sub folders but I get an error that states LTSpice can not find pot symbol. The schematic that appears is missing the potentiometer.Attached is my LTspice file, plus the LM339 model and symbol files which do not come with LTspice.
Those must be put in the appropriate LTspice sub and sym directories.
Very much appreciated!Okay forgot that you also need the pot files, below.
Put the .asy file in the sym directory, and the .lib file in the sub directory.
You may need to close and reopen LTspice to get the new models to appear.
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