Getting SOUND from your Picaxe (Works with other controllers also).
July 11, 2011
WARNING: If "techie-stuff" makes your head hurt, do not read the following.
To make sound from your picaxe, the manual shows a 10 uF capacitor in series with a 40 ohm speaker.
This will work but gives a very low volume sound.
Now, 10 uF would be 16 ohms reactance at 1000 Hz and less at higher frequencies. So for high pitched tones, the current draw from the picaxe would mostly be limited by the 40 ohms of the speaker and could approach (5v / 40 ohms =) 125 mA. This concerns me because the current drain on any picaxe lead is supposed to be no more than 20 mA. Now admittedly the audio component will be a fluctuating or intermittant value, so it is probably okay.
However, this will still be a very low volume sound. If you are like me you want it to be louder. So some amplification is needed. Consequently, I have drawn up a couple variations of fairly simple audio amps to use with the picaxe to give more volume but lower the current drawn from the picaxe.
The following are not intended to be high quality audio amplifiers, but rather have been drawn for simplicity of construction, using a few commonly available parts.