Connecting a speaker

[Andres Rodriguez]

In Manual 3 page 11 the speaker connection shows:

• One capacitor 10uF
• A 40 Ohm speaker

In the PICAXE CIRCUIT CREATOR http://www.picaxe.com/Circuit-Creator/Sound-Outputs/Speaker/
web page it shows:

• Two Capacitors 22uF
• A 64 Ohm speaker

Assuming that both will work, I'll like to know which is better.

 

[john2051]

Hi
I don't think its a question of better, but I would hazard a guess that the 40 ohm speaker will be louder. I haven't seen the diagram for a while,
but if the speaker is the collector load of a transistor the 40ohm should be louder. If direct from a picaxe, then I would think the higher impedance
would be safer. I thought they'd stopped doing these high impedance speakers, in the 70s you could get them from 2 ohms up to 150ohm!
regards john

 

[JimPerry]

In Manual 3 page 11 the speaker connection shows:
In the PICAXE CIRCUIT CREATOR http://www.picaxe.com/Circuit-Creator/Sound-Outputs/Speaker/
web page it shows:

Assuming that both will work, I'll like to know which is better.

Should be http://www.picaxe.com/Circuit-Creator/Sound-Outputs/Speaker/

 

[inglewoodpete]

The other option is to use a small audio transformer with a primary impedance of 100 to 300 ohms and a secondary of 4 to 8 ohms, with a suitable speaker. Often, you can recover a suitable transformer from an old transistor radio. We're not talking HiFi are we?

 

[Andres Rodriguez]

Pete,
Thank you for the sugestion.

The other option is to use a small audio transformer with a primary impedance of 100 to 300 ohms and a secondary of 4 to 8 ohms, with a suitable speaker. Often, you can recover a suitable transformer from an old transistor radio. We're not talking HiFi are we?

Definitely NOT HiFi

 

[erco]

Try a simple one-transistor amp. Most any speaker is fine, including common 8 ohm types, a 2N2222A transistor and a series resistor (~330-1K) from picaxe to base lead. Works like a champ.

 

[Pongo]

In that Circuit-Creator design, 22 uF seems a very big cap to be putting across the 64 Ohm speaker, that cap is only 18 Ohms Xc at 400 hz, and 7 Ohms at 1 kHz. I could understand a smaller value cap to roll off the higher frequencies (making the square wave sound a bit nicer) but 22 uF with only a 22 uF coupling cap looks excessive to me.