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Make: Electronics Second Edition.   Experiment 11 NO SOUND!

computerhabit

The Experiment is called "Light and Sound".

 

It has you walk through setting up some Transistors to make an LED blink.  Then you swap out some resistors and add a capacitor to make the LED fade out.

 

Then it says:

 

Remove the LED, the 470-ohm resistors, and the 220µF capacitor, and substitute a little loudspeaker, a 100µF coupling capacitor, and a 1K resistor.

 

First, there is no explanation of what a 'coupling' capacitor is compared to a regular capacitor.  I bought a kit so I'm not sure if I'm using the wrong capacitor or not.  There all little cans except for these tiny orange and a blue one which are kind of square and the regular round ceramic capacitors.

 

I get absolutely no sound.  Just a click and a pop sound and only when add power quickly.

 

I thought maybe if I went further with the instructions I'd get something so I completed the build further down where you basically repeat the build above with additional resistors and adding the speaker.  Still no sound!

 

No clue what I'm doing wrong.  I verified the speaker works by testing it with my set of "Snap Circuits".

Parents

  • For your experiments you can actually do away with the "Coupling" capacitor.

    The only thing it really does is to prevent you leaving the speaker permanently on allowing only pops/clicks! to be passed through.

    You can graduate later to adding the coupling capacitor when it is fully explained that it is acting as a low frequency filter (which is a device to attenuate (turn the volume down on) low frequency signals - like leaving the speaker permanently on.).

     

    To make sound what you need to do is to turn off and on the output pin driving the speaker at the frequency you want.

     

    Here's a bit of pseudo code to help you.

     

    Turn off bit     // Ensure output bit is ready to pop the speaker

    loop:

      Turn on bit     //pop speaker

      wait

      Turn off bit     //reset output bit ready to pop the speaker again

      wait

    goto loop

     

    Have a look at posts on the element14 community for more information.

     

    The challenge after getting the sound to work is to have the sound working whilst simultaneously doing something else.

  • in reply to COMPACT

    Thank you for the part about doing away with the coupling capacitor.  That is how I was able to get my first sounds.

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