Where to put speaker's DC-AC capacitor after adding transistor

Other Hardware Audio
1

Hey Guys,
I'm using a 7.2 Ohm miniature speaker and using the Arduino to generate tones. Previously, I had a 100uf capacitor in series with the speaker (because the speaker wants AC), however, I have now added a transistor (2n2222) to amplify the signal. I don't get any sound out when the capacitor is in the circuit.

This doesn't work:

SpeakerCap2.png
SpeakerCap2.png750×519 3.51 KB

I tried adding the capacitor in series between the transistor and speaker but that didn't work.

This works, however the speaker is now receiving a DC current:

SpeakerCap1.png
SpeakerCap1.png744×529 3.33 KB

Am I right in thinking that the correct solution is to add the capacitor here?

SpeakerCap3.png
SpeakerCap3.png754×519 3.65 KB

SpeakerCap1.png
SpeakerCap1.png744×529 3.33 KB

SpeakerCap2.png
SpeakerCap2.png750×519 3.51 KB

SpeakerCap3.png
SpeakerCap3.png754×519 3.65 KB

2

Please fix your post so that the images are displayed. Instructions

Google will show you circuits that actually work, if you ask nicely.

3

Transistors require a DC bias, speakers should not have DC current. You had the idea of the cap right, but no DC for the transistor, basically.

The circuit jremington gives above has an extra RC filter (C2, R3) - to render the tones less harsh I believe. But R1 is the key to allowing the transistor to function at all.

4

Much appreciated, thank you both.
I've updated my original post, and shared my finished schematic in a new thread: Please Check my Schematic - General Electronics - Arduino Forum