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I am new to electronics so my question sound dumb.

I am using this diagram to build a 555 timer IC PWM circuit:

enter image description here

The above circuit operates on 9V but I have 5V.

Do I need to change capacitor and resistor values also, or are these values independent of the voltage applied?

From the below picture, it doesn't looks like I need to change a capacitor and resistor values.

enter image description here

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  • \$\begingroup\$ um, what sense do the two diodes make there? This "schematic" (it's not a schematic, really) does not seem to be quite sensible! So, start with a better schematic. The Texas instruments NE555 datasheet has an example "9.2.2 pulse-width modulation", which makes very much more sense. \$\endgroup\$ Jul 26, 2021 at 11:42
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    \$\begingroup\$ @MarcusMüller The diodes allow independent adjustment of the charge and discharge. \$\endgroup\$
    – HandyHowie
    Jul 26, 2021 at 11:58
  • \$\begingroup\$ @HandyHowie but it's but one potentiometer, so these are inherently linked anyways \$\endgroup\$ Jul 26, 2021 at 11:59
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    \$\begingroup\$ How accurately do you need to know? Do you see voltage shown in the equations for T? Well then... to a first approximation, no. But read the fine print in the datasheet ... if you need precision, you may notice a percent or so drift when changing voltage. But then, if you need precision, a 555 is the wrong tool for the job. \$\endgroup\$ Jul 26, 2021 at 12:06
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    \$\begingroup\$ @MarcusMüller This answer explains the diodes - electronics.stackexchange.com/questions/563128/… \$\endgroup\$
    – HandyHowie
    Jul 26, 2021 at 12:12

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The PWM CTRL signal works best from 0.6V to Vdd and is independent of supply voltage for duty cycle as the pulse ratio is determined by the dual thresholds of 1/3 & 2/3 V+ but low side is about 1 diode drop above ground due to Vce(sat) on reset.

This will work the same on 9V as 5V for f and d.c. but if you want full PWM range, I suggest a better way.

For a broad list of dimmer, ESC motor control , read lots more here.

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