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morse code oscillator schematic

Portable Morse Code Practice Oscillator

Little circuit of a Morse Code Oscillator is presented here. Excellent for learning and teaching Morse code, this code practice oscillator – ideal solution to practice sending the code and improve your speed – is a light-weight portable unit powered by one AA cell (1.5V/1.2V) and is based on the well known ‘Joule-Thief’ concept. There is little to say about the actual working of this project, which is well within the scope of the beginner and is ideal as a novice experiment.

Schematic of the Morse Code Generator Circuit

morse code oscillator schematic

Parts
BAT: 1.5V/1.2V AA cell – 1
S1: SPST Switch – 1
R1: 1K ¼ w – 1
C1: 100µF/25V – 1
T1: 2N2222A – 1
D1: 1N5819 – 1
BZ1: Piezo-Buzzer (3-24VDC) – 1
J1: Ear-Phone (EP) socket – 1
X1 (L1 & L2): 15+15 turns of 36 SWG wire on a torroid core having 13.5 mm outer dia x 10mm inner dia x 6.5 mm height (refer similar circuits published earlier)

The circuit is best built on a small piece of veroboard as shown here. Since this is a ‘JouleThief Engine’, the component values are not very critical, hence you can do your own experiments by following near-similar circuits published elsewhere in this website. After construction,the unit (including the AA cell holder, Power Swich, Buzzer and the EP socket) should be fitted in a compact plastic case. Use any suitable cable for connecting the Morse Key to the KEY IN socket of the Oscillator.

Features

  • Single cell operation
  • Truly Portable
  • Rich Sound Output
  • Simple & Economical

morse code oscillator prototype

Lab Note

In the prototype, maximum voltage available across C1 is 15 VDC with the 1.2V cell. This voltage falls to near 5VDC when keying is ON, and revert to 15VDC when keying is OFF. So at the start of every keying, around 15VDC is pumped to the buzzer to make it happy, and the result is a good sound output. Tested with one commonly available ‘Bump Switch’ as the Morse Key!

7 Comments

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  • T.K.Hareendran

    @Quiet: I prefer the traditional Morse key , if you’re preparing for the ham test. For machine recognition of hand-sent Morse codes, here is a good project to try:
    https://sites.google.com/site/lofturj/cwreceive

  • T.K.Hareendran

    @Quiet: Here, the same mono jack (J1) is used to connect the paddle/Morse key. No problem, you can connect any tactile (or similar push button) switch to start keying. See, it’s tested with a bump switch!

    • Quiet

      Thanks for the info. I am looking to build a CW Keyer using Arduino to practise for the jam test. Wanted to know if I can use the bottom switches before buying a paddle.

  • Quiet

    Hi. What is the function of the oscillator? Does this generate perfectly timed dits (like a watered down version of a CW Keyer)? Or is it just to provide enough voltage to properly power the buzzer?

    tl;dr How is this different from a simple circuit of a switch(maybe even a straight key), a buzzer and a battery all connected in series?

    • Quiet

      @TKH thanks for the clarification. Also on a somewhat related topic, most Keyer or oscillator schematics just provide a mono Jack to connect a paddle or a key i.e., a well engineered contraption of metal that completed the circuit with metal contacts. Can a simple 2-terminal push button (closes circuit only when kept depressed) work instead of metal contacts? Maybe add handles for comfortable operation.
      Or is that not really suitable for this application?

    • T.K.Hareendran

      @Quite: Actually this is an “unorthodox” design, but closely following the basic concept (a simple buzzer-switch circuit) of the morse code practice oscillator. Here, main difference is in the buzzer driver circuitry; just a 1.2V to 1.5V (even weak) single-cell can drive the standard buzzer for a very long time!

  • AdamJWong

    I found samples of these components at biscoind.com , but I couldn’t find the rest. Are there any low-cost online sources?
    T1: 2N2222A – 1 https://www.biscoind.com/CentralSemiconductor/2N2222A
    D1: 1N5819 – 1 https://www.biscoind.com/Miscellaneous/1N5819M-13

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