Very simple circuit help..

[funkkube]

Hi
I have a problem that requires a tone to be genereated in one channel of stereo and the other channel will have a mic input.
It has to be powered by battery - 9v? and low powered.
Ideally i should be able to adjust the volume of the tone.
I was thinking of using a 555 chip?
Any ideas/advice would be helpful!
I have an A Level in Electronics but that was 20 years ago so I am very rusty!!
Cheers in advance
Mat

 

[transistor495]

Cheers!

It is so easy to implement at least by 555 chip metronome circuit as you already mentioned. Pass the audio output to the one channel of stereo amplifier for eg, a TDA2822 chip, and the other channel is provided the amplified mic output. Use a stereo volume control if you want to keep same level of volume control for both or use separate control. You've to search for a decent mic amplifier circuit. 9V battery is enough.

 

[funkkube]

Thanks for the swift reply!
Sorry I missed out some information.
The stereo output will be going into a MIC stereo input on a device so the volume of the tone has to be controlled.
cheers..

 

[transistor495]

Are you sure that the MIC input socket is stereo? Maybe one channel is not used or it may be a mono input. If it's stereo MIC amp. then feed the one channel to the tone generator through potentiomenter and other channel directly to MIC.

I'm not sure whether the MIC input(dynamic?) of a device will accept the normal volume level of the 555 tone generator. Use potentiometers to decrease it damn down.

 

[funkkube]

Hi
Its definitely stereo!
I will try it out..
Thanks!

 

[Hero999]

To avoid over-driving the input too much you'll need a potential divider to deduce the voltage.

The mic input will be very sensitive and will only need 20mV or so signal, if the potentiometer is 1k, connect a 100k resistor in series with it to divide the voltage by about 100.