ESP8266 Community Forum

- Wed Jan 17, 2018 11:59 am #73222

Few comments

MOSFET seems to be upside down. Drain is shown connected to 0V. I suspect you are trying for an open drain output.

There is nothing limiting input current to opto. If you are assuming external resistor or a current source that's ok but I would put in at least a limiting series resistor to avoid blowing the opto.

The output would follow the input when used in input mode. That may be OK.

If the GPIO is output and the input turns the opto on then there is a serious conflict. You should have a series resistor from the emitter to limit this. A value of say 2.2K will still allow a good high to be developed on input but limit the current if the opto turns on and GPIO is output low.

Schematic attached for your review, thanks and greetings

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It is never too late to learn

- Wed Jan 17, 2018 2:28 pm #73228

Few comments

MOSFET seems to be upside down. Drain is shown connected to 0V. I suspect you are trying for an open drain output.

There is nothing limiting input current to opto. If you are assuming external resistor or a current source that's ok but I would put in at least a limiting series resistor to avoid blowing the opto.

The output would follow the input when used in input mode. That may be OK.

If the GPIO is output and the input turns the opto on then there is a serious conflict. You should have a series resistor from the emitter to limit this. A value of say 2.2K will still allow a good high to be developed on input but limit the current if the opto turns on and GPIO is output low.

Schematic attached for your review, thanks and greetings

And here are the gerber files in case you want to fabricate it.

You do not have the required permissions to view the files attached to this post.

It is never too late to learn

- Wed Jan 17, 2018 4:25 pm #73237 That looks better.