The diagram presented below shows a simple circuit of a bird sound generator. All the parts are very common and the transformer is an ordinary type as found in small transistor radios at the output stage
Circuit Operation
The circuit is basically a feedback oscillator circuit that is configured around a small output transformer. The transistor forms the main active components here.
When mains power os applied to the circuit, the 4K7 resistor resists the voltage and drops it to lower levels suitable for operating the DC electronic circuit.
The diode rectified the low level AC to DC while the capacitor filters and smoothens the rectified DC.
Initially the voltage reaches the base of the transistor which instantly conducts and pulls the one half winding of the transformer to ground, forcing a strong induced current across the secondary winding.
However the moment this happens, the entire voltage is shorted to ground via the transformer winding and this eliminates any biasing voltage at the the base of the transistor and it fails to support the conduction.
The transistor releases the transformer activation which reverts a strong back emf to the secondary winding.
However the moment the transistor stops conducting, the voltage at it's base is restored and the cycle repeats again.
This repeated pulsation of the transformer induces a strong back emf oscillation at the secondary of the transformer, which is amplified over the connected loudspeaker.
The associated components, the 10 resistor and the 0.1 capacitor performs the feedback function for keeping the transistor active with a certain foxed frequency range.
The frequency of the circuit may be adjusted through the 4k7 pot and the 0.1uF capacitor so that any desired tone can be achieved at the output over the speaker.
The above adjustments helps to refine the tone of a particular bird to any form and helps to replicate the results as closely as possible.
Dear Swagatham
I have assembled this type of circuit before 20years. The bird chirping sound is very pleasing.
Bot, now a days the output transformer is difficult to get in our local area. (I am sure, it is available in Online.)
So, cian you please re design the circuit using a 3V-0-3V or 6V-0-6V/500mA secodary, 220V primary transformer instead of the audio output transformer.
Thanks in advance.
Dear Anil, you can use a step down transformer without any changes to the circuit. We just have to make sure that the transformer primary specs and the circuit supply specs are matching, meaning if the circuit is designed work with 9V then use a 9-0-9 transformer and so on.
In this design since a 4k7 resistor is used for dropping the current, any low voltage transformer should work…a 3-0-3 or a 6-0-6V all should work with minor difference in the output volume
Dear Swagatham,
No, no…no. You may not understand my question well. I am just asking about the tranformer that connected the speaker in your circuit.
Can a 3V-0-3V or 6V-0-6V/220V stepdown transformer use in place of the OUTPUT TRNSFORMER with minor or major modifications in the circuit….?
Dear Anil, yes you can do it without any changes to the circuit. The size and weight of the transformer will be the only issue here.