Alternate protection circuit for this digital envelope generator?

Happy new year, friends!

On to the next, I would like to build this digital envelope generator which is based on the ADSRduino. I know that the original ADSRduino has a few things that could be improved upon but this one looks like it nets good results.

I’m stuck on the protection circuit though (correct me if that’s the wrong terminology). He uses two schottky diodes, which I don’t have. I’m wondering if there’s another protection circuit that I can use, or if I can use something instead of the schottky diodes. Worse case scenario, I have a 40106 if that works? Any help is appreciated, thanks!

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I don’t see any schematic at the site you linked.

That’s the other problem. Sorry to turn up empty handed. The files on the user’s github don’t appear to have any schematics in a form I can view. The Kicad file won’t open and I’m not even sure if that’s a schematic. Left a comment for the creator, I hope they respond! If they do, I’ll report back.

Haven’t gotten a response yet, but Emilie gives a good argument as to why Schottky diodes are necessary to protect against high and negative voltages.

Use Schottky diodes, it’s important! Normal diodes have a 0.7V drop, so they will clamp between -0.7V and +5.7V, and this is already too much for the MCU. Check in the diode datasheet, that they have a low voltage drop, below 0.3V.

Drats, I’m just gonna have to nab some of those then.

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You can also use a single 5.1 V Zener diode to ground. The drawback to that is it will distort the voltage as it approaches 5.1 V whereas Schottkys will not, so a Zener is fine for gates and triggers but Schottkys are better for control voltages. Either way you also need a series resistor between the diode(s) and jack, to protect the protection diode.


Very good to know. Gonna grab some Schottkys to err on the side of caution as I will inevitably plug something crazy in by accident. :sweat_smile:

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