Morse Code Practice Oscillator
by Tony van Roon
R1 = 3K3 IC1 = 555 Timer IC
R2 = 15K S1 = Morse Keyer
P1 = 500 ohm
C1 = 0.047uf (47nF)
C2 = 0.01uF (10nF)
C3 = 4.7uF/16v
speaker (LS) can be any 8-ohm type up to 2-watts. C1 and C2 are ceramic
capacitors. C3 is an electrolytic type.
IC1 is a CMOS MC1455P or
equivalent. The cmos type consumes a lot less current when used with the 9-volt
battery, but if you don't want to spent the money then the LM555, NE555, etc.
are fine too and are pin-for-pin compatible with each other.
S1 is your Morse-keyer. To get a more precise duty-cycle replace the components
within the shaded gray area from Fig. 1 with the ones in Fig. 2. The diode can
be 1N4148 or equivalent. The zenerdiode is between 5.2 and 5.8 volt. Ra and Rb
are experimental to suit your personal taste. C is about the same.
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Copyright © Tony van Roon,