Stop burning speakers with your Picaxe chips

Tip/walkthrough
 
fritsl's picture
By fritsl @ Sun, 2008-03-02 16:06
On Picaxe:

sound 1, (110,3)

is NOT a good idea, you should allways write

sound 1, (110,3) low 1

(you do not need line breaks, just write it as above)

 

Being used to burning things and changing rechargable batteries all the time, I did not really wonder that much that a tiny speaker or two has been fried while having fun with robots and Picaxe over time (mainly 28' these are the only ones this is tested on).

Now I am building a new robot that has a speaker underneath it.. Lifting it up from a test, I felt that the speaker was burning hot!!

Picaxe is leaving the port to "High" after the "Sound" command!!! So the speaker is just getting continious voltage after a "sound".

This means battery drain, and it means burnt speakers after a while, if your robot have just at any point made a small beep!

Crap, Picaxe! (But I still love you) - Must be a bug, no? Or some reason I don´t get??

Your rating: None
By DaveLyons @ Sun, 2008-03-30 20:50

avoiding DC through speaker

Could you put a small capacitor in series with the speaker to block the DC?  I don't know what value would be appropriate, though.
By fritsl @ Sun, 2008-03-30 21:22
fritsl's picture

Sounds like making a brick

Sounds like making a brick wall in front of your teenage-son's car to stop him from drunk driving, no? Would it not be better to take the keys?

get me? :) (or is it me? I know no electronics, I admit!)

Thanks, Dave, hope someone (else?) can work this out :)

/ Frits

By Carsten (not verified) @ Wed, 2008-04-16 09:30

Capacitor in series with speaker!

It is generally a good idea to insert a Capacitor in series with an ordinary speaker, just to prevent DC to reach the coil in the speaker. ( in the range ~22nF upto ~10uF shouild do it) And it should be an ordinary capacitor... The nature in a capacitor is that it allows AC (sound) to pass and blocks for DC (e.g. offset voltages) The other way around an inductor (coil) allows DC to pass through, and blocks for AC. That is why You would use an inductor to reduce noise in AC inlets.. Kind regards
By fritsl @ Wed, 2008-04-16 17:49
fritsl's picture

OOoohhh k-n-o-w-l-e-d-g-e!

OOoohhh k-n-o-w-l-e-d-g-e! Thank you!!

/ Fritsl

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