Using low pass filter on PWM for voltage

Using Arduino General Electronics
1

Hey, so I'm very inexperienced with electronics, but I'm trying to start a project which requires me to obtain a variable voltage. I've learnt so far that the easiest method to get multiple from the Arduino Uno would be to use a low pass filter on the PWM pins.

I've read quite a bit into these, but there are still some things that I'm struggling to understand. The main point is how to choose the values of the capacitor and the resistor. I know that I want to reduce ripple and settling time, but I don't really understand the cut-off frequency.

I'm going to be using this to emulate joystick potentiometers in a controller, so they will only need 3-4V max.

I've been trying to use the calculator at (Sample)RC Low-pass Filter Design for PWM - Result -, but I really don't know what cut-off frequencies I should be aiming for.

If anybody could give me some advice on this I would be very grateful. Thanks!

2

You can google "arduino RC Low Pass Filter" but most people use 4.7k ohms and 4.7uF. If your load needs
more current, you can increase the cap size to 10uF or even 47uF or 100uF but for analog inputs, they are
high impedance and only draw about 128uA.

3

Thanks for the reply, those values are exactly what I was looking for. So, judging by those values, the aim is to reduce the cut-off frequency?

4

You are taking too much attention to detail!
This is a fixed and single frequency signal.
You just want to integrate the pulses to a
D.C. level. The resistor limits the current
into the capacitor and the cap smooths
the waveform, filling in the gaps with
stored energy.
Herb