Hi,I want to build an audible tone generator with knobs or buttons for selecting the frequency, and perhaps a display to show the current frequency.I have some brief experience with arduino and amtels so I know some of what I will need but could use some advice in a few areas. I've basically broken it down into the following pieces:1) tone generation. It looks like there is a sample program that can output tones rather easily, so I think I'm ok on this part. I was looking at the toneMelody example and it looks like I can output a given frequency pretty easily2) The speaker. the toneMelody specifies an 8 ohm speaker. Can I get one of these at radio shack? I want to be able to produce tones as low as 20Hz. Would that be an issue?RS sells many 8 ohm speakers but few will reproduce down to 20Hz faithfully, and even if a few could not without a proper designed speaker enclosure. More important any 8 ohm speaker no matter how small will damage an arduino output pin if connected directly, you need a series resistor of maybe 150 ohms or higher to protect the pin which in turn will consume most of the sound signal. You need to add audio amplification to drive a 8 ohm speaker properly.3) Amplification. Later, I want to drive something bigger. Can I just plugin into an 'line in' where my 8 ohm speaker was and use a stereo? In general, how do I control speaker volume in the case where I am not outputting to my stereo?You would need to wire the signal through a series audio coupling capacitor to eliminate the DC voltage of the arduino output pin and then utilize proper signal amplification or attenuation to the level your sound equipment requires, i.e. headphone level, speaker level, pre-amp line level input, etc. 4) control + display I could go several routes with this one. If I have analog control, like a knob, I want to be able to display the actual frequency on an LCD. OR, I could have digital buttons to control frequency and display the number on an LCD. Any advice here? a button for up and a button for down connected to the lcd, and then just read out that value for input into the tone generator? Is radio shack a good place for getting little knobs?Controlling and displaying the tone generator should be pretty straight forward and you have pretty much a lot of freedom to choose what kind of user interface you want to present for controlling and displaying the tone library.Radio Shack is not a good place to buy standard parts as their selection is pretty limited and their prices are pretty high compared to what you can buy on-line:http://www.taydaelectronics.com/potentiometer-variable-resistors/knobs-16.htmlLeftyAnything I am missing?Thanks in advance,Cliff
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