I'm trying to create a circuit to blink lights at the precise frequency for a mind machine. The lights need to be in sync with audio.
Audio channel 1 300 hz Audio channel 2 310 hz
The led needs to blink at 310-300 = 10 hz And it should be in sync with the audio I.e. It should peak when both audio channels peak
I tried using a computer to generate the frequencies and a lm358 opamp . I am getting confused whether this is the right opamp I should use and what kind of external circuitry I should use.
The audio frequencies may be changed to 300 to 350 hz to get desired effect.
Edit : more details: The input frequencies are generated by a computer or an MP3 player. I don't know what voltages they are.
The brightness of the led can be changed.. I think this is easily controllable by using a potentiometer. I want to experiment with different LEDs of different power and brightness (upto 1w). But for now I'm testing normal 5mm red LEDs .
The whole thing needs to be powered by a 5v battery ( so no negative voltages available)Switching between different output waves is desirable, if it's easy to achieve, or only sine wave is fine.
I have an Arduino uno and pro mini if that's useful. I do not have an oscilloscope, so using an Arduino to count output frequency.
heres a video of what I achieved so far. It's a lm358 with almost no external circuitry. Showing result for sin and square wave. http://youtu.be/Aj5mE7mWrZA
In future I also need frequency filters to filter out interesting frequencies from audio. E.g. When nature sounds are mixed with the 300 and 305 hz audio channels to give relaxing effect, 300 and 305 hz signal needs to be filtered and fed to this opamp circuit. Frequencies of interest lie between 300 and 360 hz.