Hi

From: http://www.zen22142.zen.co.uk/Circuits/Music/canary.htm

Q1) How do I know that my audio transformer is 1K : 8R? Is it by simply measure the DC resistance?


Q2) If I wanted to use a ferrite core, how much should the number of turns for the primary and secondary coils, and will this core be simply a rod or one removed from a computer power supply?


Q3) How the above circuit operates? I know that the transformer is for impedance matching between the transistor high impedance and the low one of the 8 ohm speaker. Also I know that the transistor operates as an oscillator and I understand that the 47K resistor biasing the base of the transistor to start oscillating. Finally I know that the R1+C1 have a close relation to the tone frequency,,,, But what I don't know is the function of the two small caps 10n and 22n and why they have a very small capacitance related to the other two 100u caps.

Thank you very much

 

Hi

From: http://www.zen22142.zen.co.uk/Circuits/Music/canary.htMl



Q1) How do I know that my audio transformer is 1K : 8R? Is it by simply measure the DC resistance?

You should buy this transformer, not make it. They are commonly available

Q2) If I wanted to use a ferrite core, how much should the number of turns for the primary and secondary coils, and will this core be simply a rod or one removed from a computer power supply?

See answer to Q1 above

Q3) How the above circuit operates? I know that the transformer is for impedance matching between the transistor high impedance and the low one of the 8 ohm speaker. Also I know that the transistor operates as an oscillator and I understand that the 47K resistor biasing the base of the transistor to start oscillating. Finally I know that the R1+C1 have a close relation to the tone frequency,,,, But what I don't know is the function of the two small caps 10n and 22n and why they have a very small capacitance related to the other two 100u caps.

What did the guy at zen.co.uk say? He posted the circuit, so he should be your first source of information.

 

Its a modified Hartley oscillator, the inclusion of R1 C1 ensure the oscillator shuts off fast, and C1 discharges through Q1, producing the chirping sound.

 

You should buy this transformer, not make it. They are commonly available
See answer to Q1 above

What did the guy at zen.co.uk say? He posted the circuit, so he should be your first source of information.

NO No No

Oh dear, I do not want to buy this transformer even if the price was one cent
I'm here to discuss scientific issues and is not going to receive tips out of context
When you do not have an answer to the question: it is better to not answer
I know and read what the author said about his circuit
thank you

 

Hi

From: http://www.zen22142.zen.co.uk/Circuits/Music/canary.htm

Q1) How do I know that my audio transformer is 1K : 8R? Is it by simply measure the DC resistance?


Q2) If I wanted to use a ferrite core, how much should the number of turns for the primary and secondary coils, and will this core be simply a rod or one removed from a computer power supply?


Q3) How the above circuit operates? I know that the transformer is for impedance matching between the transistor high impedance and the low one of the 8 ohm speaker. Also I know that the transistor operates as an oscillator and I understand that the 47K resistor biasing the base of the transistor to start oscillating. Finally I know that the R1+C1 have a close relation to the tone frequency,,,, But what I don't know is the function of the two small caps 10n and 22n and why they have a very small capacitance related to the other two 100u caps.

Thank you very much

Please do let us know how satisfactorily this circuit works.

 

1k:8 ohm transformers are usually advertised as such. It's a selling point for use in audio outputs.

 

Your questions about the design of the transformers are open questions -there are many other variables than the number of turns, though the number of turns is a key parameter. You might learn a lot by visiting the websites of some of the transformer core manufacturers such as Magnetics, Inc., Fair-Rite, TDK, Ferroxocube, Metglas Inc., NLMK (pdf file), ATI Grain-Oriented Electrical Steel, plus there are many more that you can find easily.

Maybe the two design resources below will be of some help.

Audio Transformer Design Manual

How To Wind Your Own Audio Transformers

 

Q1) How do I know that my audio transformer is 1K : 8R? Is it by simply measure the DC resistance?

The transformer turns ratio is the answer.

N = Np/Ns = turns ratio

N- the turns ratio
Ns - is the number of turns on the transformer’s secondary winding
Np - is the number of turns on the transformer’s primary winding

So the relationship to the resistance can be calculated as:

Zp/Zs = (Np/Ns)^2

So for your case
1kΩ/8Ω = 125 ---> N = √125 = 11

Q2) If I wanted to use a ferrite core, how much should the number of turns for the primary and secondary coils, and will this core be simply a rod or one removed from a computer power supply?

No, you cannot use it. The ferrite cores without air gap want work here, also the losses in the core will be quit big for such a low frequency. Because the ferrite cores are optimize for high frequency circuit.

Q3) How the above circuit operates? I know that the transformer is for impedance matching between the transistor high impedance and the low one of the 8 ohm speaker. Also I know that the transistor operates as an oscillator and I understand that the 47K resistor biasing the base of the transistor to start oscillating. Finally I know that the R1+C1 have a close relation to the tone frequency,,,, But what I don't know is the function of the two small caps 10n and 22n and why they have a very small capacitance related to the other two 100u caps.

C1 - gives only this "chirp" sound.
10nF and 22nF set the "high" frequency tone.
http://mmcircuit.com/understand-rcc-smps/

 

Thanks to DickCappels and Jony130

 

hello Jony130,
what is this chart for?

 

hello Jony130,
what is this chart for?

To create a Sound of Chirping Canary
it works as a house ringer

 

To create a Sound of Chirping Canary
it works as a house ringer

I don't understand the chart code?

 

To create a Sound of Chirping Canary
it works as a house ringer

Does it sound much like a canary?

 

It's not bad, especially considering the parts count. There is an audio file on the website.

ak