because its 10k itll take the capacitor too much time to discharge, whats it set on 1/2 hert?

 

because its 10k itll take the capacitor too much time to discharge, whats it set on 1/2 hert?

Hi C,
That does not answer my question.
E

 

t=rc is my favorite law of electricity (and pneumatics) at the moment.

I've been failing electronics at my little desk for about 6-7 years now? And I never got a single osc done, but I do know a fair bit now, but none of it works. Isn't that funny.

I'm another software nut turned to hardware, I know alot about AI and computer vision, so I want to roll it all together into a fully from scratch robot, But I've got really sick smoking cigarettes lately, and I have something I need to abstain from doing, and that pretty much scattered me 254% for the last 6 years, so that didn't help, thats for sure.

 

If you keep thinking you can design an oscillator from scratch without having studied what others have done over the last century, you will keep failing at it. Oscillator circuits, with the possible exception of relaxation oscillators, are not intuitive. Even knowing how they work, it can be tricky to get just the right circuit to work,

If you really want to make a circuit that oscillates, no matter how, build an audio amp with a gain of about 1000, I guarantee it will oscillate.

 

yeh all of its quite unintuitive to me, electricity goes backwards.
it seems the only way to make an oscillator is when you dont want an oscillation.

 

t=rc is my favorite law of electricity

If you know the formula for determining the voltage on a capacitor when it's charging, then you can determine the frequency of the oscillator I showed in post #17.

\( \large V_f=V_i(1-e^\frac{-t}{RC}) => t = -RCln(1-\frac{V_f}{V_i}) \)

Solving for Vf = 0.7V gives a period of 1.5ms for one stage; times 3 gives 4.5ms which yields a frequency of about 220Hz.

 

The multivibrator circuit I posted had equal RC times on each side then the two LEDs alternate equally. If only one LED is used then its on-time can be shortened to make blinks instead of simply on and off.
I would keep the 10k resistor and reduce the capacitance instead.

 

Really, an oscillator circuit IS intuitive. Two things are required, the first being feedback with 180 degrees phase shift, and the second part being enough gain in that feedback loop to exceed all of the losses. So when we look at that collection of parts in post #1 it becomes obvious that there is no gain and no phase shift. So it will not oscillate, but rather it will eventually stabilize.
The various multivibrators that work all have both gain and phase shift in the feedback. So it is that simple. The first part is the gain, and the second is the inverted feedback.
of course, to know if there is enough gain one must be able to see the effect of the input to a portion of the circuit and calculate the output. That math does not need to be precise, just fairly close. But certainly you must be able to understand gain, which is defined as the change in output divided by the change in the input. That can be complicated when one term is in voltage and the other term is in current.

 

I bet I could convert that circuit to be 180 degrees...

 

Really, an oscillator circuit IS intuitive. Two things are required, the first being feedback with 180 degrees phase shift, and the second part being enough gain in that feedback loop to exceed all of the losses.

One should be careful (and exact): A feedback signal with 180deg phase shift (at one single frequency !) is required only in case of an inverting amplifier withn the loop.
But there are many oscillator circuits based on a non-inverting gain stage.
In this case, the feedback path must allow for 360deg phase shift.

In summary: The well-known oscillation criterion (Barkhausen) requires a loop gain of unity which means:
* zero (360) deg phase shift within the complete loop (at one single frequency)
* unity gain magnitude at this frequency (in practice: Slightly above unity to ensure safe start of oscillation) -

 

See if You can wrap your head around this simple Circuit ............
It's even more simple if You use a 555-Timer, only 2-parts, a Resistor and a Capacitor.
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A CMOS logic gate can oscillate with only one resistor and one capacitor. But the champion is the LM7805 regulator IC, which can oscillate with only a single resistor in the supply line, and no capacitor at all. Not an intentional oscillation, but certainly a powerful oscillation.