Code Practice Oscillators

From BrauhausWiki

For the 2006 Arlington County Fair, I built a pair of Morse Code sounders to be used as a demo. I found the circuit online. It has been published in various forms over the years - the version I worked off of was from the ARRL publication Now You're Talking .

This circuit employs a 555 Monostable Multivibrator chip to make a square wave oscillator. I made a couple changes to the ARRL version - specifically changing the "tone control" potentiometer to just a pair of resistors, and added an RC lowpass filter to make the square wave into something a bit closer to a sine. This prevented the tone from being quite as harsh. After the addition of the filter, the volume was somewhat lower. Since this was to be used in a public area at the Fair, which was likely to be generally fairly noisy, I considered adding an op-amp to buffer and or boost the output.

(too be continued...)