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.
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.
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!