LDR to pass audio.

[makaze]

Hi.

I would like to build a circuit that uses LDR's or other devices to pass or block an audio signal.

Simply I would like to pan an audio signal left to right in response to one or more LED's blinking.

Thanks for any input.

Tom.

 

[ronsimpson]

About 40 years ago I used Light Dependent Resistors to adjust gain in audio. The LDR responded a little slower than I liked but it did work.

I put a LDR and light bulb (LED in your case) in a heat shrink tube to keep room light out.

 

[ChrisP58]

Hi.

I would like to build a circuit that uses LDR's or other devices to pass or block an audio signal.

Simply I would like to pan an audio signal left to right in response to one or more LED's blinking.

Thanks for any input.

Tom.

How many dB of range do you need? What are you controlling the action from?

There are a few ways to control audio, with different trade-offs of functionality. Which is best will depend on what the rest of your needs are.

 

[Nigel Goodwin]

As already mentioned, LDR's are fairly slow - and in Ron's case bulbs greatly more so - which was an advantage, a bulb/LDR combination gave pretty good attack/decay for AGC etc.

 

[schmitt trigger]

I also built an LDR/lamp attenuator using the concepts described above. Boy, that was years ago!

The most difficult part, if I remember correctly, was to match the input voltage vs attenuation in the two channels across the control voltage range. LDRs have a wide, wide tolerance.

 

[fernando_g]

Also, if I remember properly, LDRs wavelength response is fairly similar to the human eye, meaning that for best performance use green LEDs.