    
Starface
Senior Member
Username: Starface
Post Number: 2917
Registered: 1-2005
| | Posted on Thursday, October 07, 2010 - 12:21 pm: | 
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So you want to sharpen those rusty Morse code skills. Short of humming dits and dahs you might want to generate some sounds using a key. We all remember those buzzers we used as kids. They were basically door bells with the hammer removed, and didn't produce a very realistic sound. Today, by replacing the old door buzzer with a piezo buzzer we can utilize the same simple series circuit to produce a much more pleasant tone. Piezo buzzers are found in things like microwave ovens that signal when you coffee is warm, and can be purchased for as little as a dollar. If you have a HF radio, and don't mind being tied down to it, most of these allow you to send code to your speaker only, and make good code practice oscillators. Or, you might want to build a code oscillator utilizing one of the oldest, and still very popular integrated circuits the 555 timer.
It is certainly a more complicated approach than an electro magnet or piezo buzzer in series with a key and battery, but if you are interested in learning more about the 555 timer, and dusting off those soldering skills the extra effort is justified.
Here is the parts list:
1, 9 volt battery connector
2. Resistor, 689 ohm
3, Resistor 1 K
4. Resistor 10 K 5, pot
5. 25 K (pitch control)
6. pot 500 ohm (volume control)
7. Condenser 0.22 Mfd
8. Condenser 10 Mfd
9. Speaker 8 ohm
10 IC chip 555 timer
11 8 pin dip socket
12 Key jack
13 Substrate of some sort to mount the above equipment
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