vicouuntboo said:
Hey
I've doing a project which i've started to build.
The title of my project is Doppler Demostrator for a physics class.
The outcome is to build a small battery powered transmitter embedded in a sponge ball. An audio receiver will receive this signal, measure its frequency and display the result on a digital display.
I've gone about doing it this way but i think i'm totally on the wrong path.
I do not think you will see doppler effect with what you describe.
Your sponge which could be accelerating will transmit but that transmission occurs at close to speed of light. The receiver will receive an un-doppler-distorted(regular) signal and simply demodulate it to recover the frequency. All will look normal unless your sponge was travelling at a significant fraction of the speed of light. lol!
The sound waves would show doppler effect of your moving sponge but only if your sponge sent them into the air (and not the Em spectrum)
Can you do something like the following?
Get one of those hi pitch siren devices like Sonalert etc... and connect this to a portable battery powered circuit that simply keeps the siren running when turned on.
Make another circuit with a microphone, amplifier and filter with an output that will go to an oscilloscope.
Mayby put them both on a rail or track of some sorts where the siren circuit can slide and the microphone circuit remains fixed hooked up the o'scope.
Then when you turn on the siren circuit, you will see a waveform on the scope which is what your amplifier is "hearing" tuned (via the filter) to the frequency of the siren. You can measure this frequency on the scope.
Then slide your siren circuit very fast away from the mic circuit and the scope should show you an expanded waveform indicating that it (and you) are hearing the siren at a lower frequency. Sliding back towards the microphone and the wave gets compressed.
Depending on how fast you can move your sound source, the effects might be barely noticable on the scope but it is measurable and a high speed scope should have no problem showing you that.