555 pwm AND frequency controllable? Answered
I've been breaking my head on this for a while now, and still couldn't find a correct solution for this.
I want to be able to adjust the duty cycle (pulse width) with one potentiometer, and the frequency with another potentiometer, using a 555 timer.
Adjusting the frequency shouldn't change the duty cycle! (which is the problem in All of the circuits I find online).
This is an example of a circuit I find online, many of the circuits look just like this one (see picture)
Now, the problem is that when you increase the resistance of the potentiometer for adjusting the frequency,
that makes sure you can never get 0% or 100% duty cycle anymore! or not even close to that.
It's because increasing that resistance, also decreases the 'discharging current' of the capacitor, so it will also increase the discharging time when that's not wanted.
Without R2 it works perfectly, from 0% to 100% duty-cycle; but with the frequency potentiometer it all gets messed up.
It's a little difficult to explain, I'll try it with another example :)
To get 0% duty-cycle (or something close to that, like 10%), you'll need to make sure the path for Discharging the capacitor goes near 0Ohm.
Increasing the potentiometer for the frequency makes that impossible because it's in series with the capacitor's charging and discharging circuit. So that would also increase the discharging time while I don't want that.
When the resistance of the frequency potentiometer increases, the duty-cycle gets variable between just something like 45% and 55% (example) so that's not good.
Is there any way do do this? :/
Thanks in advance,