optocoupler 6N138 as a switch

Using Arduino General Electronics
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hi there!

I aim to build an audio switch controled by a pulse out from arduino, and i was wondering if it was possible to use an optocoupler for this porpouse.
Since i have some 6N138 this would be the ideal option.
Is this possible with good results?
If anyone knows of a good schematic for this, let me know.

I don't want to use cd4066 cmos chips since they will put to much "pop" noise when switching states.

thanks in advance

2

Hi,

How fast does this "switch" need to be?

I have used optocouplers that drive a Photoresistor rather than a semiconductor. They can have audio distortion much less than 1%. Clare was one manufacturer a few years ago.

I have also built successful audio switches and volume controls by mounting red LEDs to photo-resistors with clear epoxy and either dipping in black paint or putting in heat-shrink tubing. These were in Broadcast equipment and worked well.

If you are just doing On-Off then no problem. If you need VERY high attenuation you may need to use two optocouplers in an 'L' network configuration.

OPtocouplers with semiconductor outputs are nonlinear and will add distortion. A dual optocoupler with the output photo-transistors back-to-back will at least be symmetrical.

Tell us a little more about what you want to accomplish...

3

i want to build a very simple tremolo/paner for my guitar and your idea with a dual optocoupler is great.
i want to use 2 optocouplers and one of them ill have a voltage inverter on the switching voltage so i can get a left/right effect

i didn't want to go with a vactrol (led +ldr) because e want the switching to be "choppy" or "square like"

my main question now is, how to use the transistor that is inside the opto as a switch. i can't find a schematic with this configuration.
would something like this work? ImageShack - Best place for all of your image hosting and image sharing needs hummm... i don't think so...
any idea?

4

manatee:
i want to build a very simple tremolo/paner for my guitar and your idea with a dual optocoupler is great.
i want to use 2 optocouplers and one of them ill have a voltage inverter on the switching voltage so i can get a left/right effect

i didn't want to go with a vactrol (led +ldr) because e want the switching to be "choppy" or "square like"

my main question now is, how to use the transistor that is inside the opto as a switch. i can't find a schematic with this configuration.
would something like this work? ImageShack - Best place for all of your image hosting and image sharing needs hummm... i don't think so...
any idea?

Wow, that looks weird to me?? I supposed the base-collector junction of a turned-on transistor is lowish impedance. But what voltage swing on the audio is workable. If it's not DC coupled up between 0 and 5 V th distortion would be 'high'..

The idea with the TWO optocouplers was that the transistors would be turned on or off, and the back-to-back configuration would mean that the audio could swing + and - and have a forward-direction transistor conducting OK..

So the outputs of the optocoupler are tied together back-to-back and it's a two-terminal device used as a switch in your audio circuit... I think..

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