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uclaros

DOUT->Optocoupler

3 posts in this topic

Hi all!

After quite an absence from the forum I came back to start posting again, and all I can say is that I missed uCapps!

My question is:

I have an amp that uses a few H11F2 optocouplers for channel switching.

Wanting to midify the channel switching, I thought of building a MIDIO128 and use ULN chip to control relais, and the relais would control the optocouplers!

After I finished the MIDIO128 core I thought : "maybe I could power the optocouplers directly from the DOUT and skip all the relais and stuff."

The my optocouplers' datasheet says that their minimum resistance (on position) is when there is applied a I(current) of 16mA. The amp uses 12V over a 470 resistor, so it's about 25mA.

I know that 25mA would be ok for the DOUT module (5V over 220 ohms) but the thing that bothers me is that since the DOUTs are multiplexed, I am afraid it may affect the sound (by turning each switch on-off-on-off-on....)

The datasheet says also: Turn on time:25uSec, Turn off time:25uSec max.

What do you think? Will I have a problem? Maybe I should use a capacitor on each out? But hten again, I need it to switch pretty fast when I change the DOUT state.

Any thoughts are welcome!

Hi again,

uclaros

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Hi uclaros,

It's worth a try. I don't see the point that the sound could be affected, because the output values are latched with the RCLK pin, which means: during the time the values are shifted through the chain, the output stage will stay stable. With the RCLK signal, all outputs will get their new value at the same moment

Best Regards, Thorsten.

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Hi TK!

I'm gonna test it on the weekend and post my results!

Maybe i'll post a few pics too, plus my modified Core pcb (it's a compact no-lcd,no-ain,no-bankstick,yes-din,yes-dout,yes-midi-through core board)

Thanks for your fast reply! (as always!)

C'ya!

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