Looking for Project Ideas with RC, RLC filters

Hello, as the topic says, I am looking for suggestions that would better help me understand low/high pass filtering, I have an oscilloscope as well to monitor. I am missing extra sensors, I have a servo, DC Motor, Tri color LED, transistor (a transistor radio would be really cool)

Thanks in advance!

The easiest thing would be to filter the Arduino's PWM output to make a (variable) DC signal or to make sine waves.

If you want to so something with music, you could make some high-pass, low-pass, and bandpass filters on the analog inputs and make a color organ where different frequencies affect different LED colors.

If you run audio signals into the Arduino, you need to [u]bias[/u] the Arduino input(s) so it can read the negative half of the waveform (and to prevent the Arduino from being damaged by negative voltages).

You won't often see inductors used at low (audio) frequencies except in speaker crossovers where low impedances are involved. With line-level audio signals a filter would require "impractical" inductors. You'll usually see active filters made with op-amps, capacitors, and resistors.

Radio frequency design is tricky. You could probably build a transistor radio, but in order to build a good one, you have to know what you are doing, and you'd probably need a frequency counter and an RF oscillator in addition to your 'scope.

Thanks for the reply, I think I will start with the PWM to DC since that would just require an RC component and LED I believe.

I like the music idea too. Can you elaborate on the music idea?

and if anyone has a link to a basic transistor radio example that would be awesome, I feel that is part of the EE pilgrimage is to make one.