I want to use arduino board as remote "button pusher" on my PC so I can remotely start/stop/reset it. The ATX spec says the power button signal is 5v that needs to be driven low.
Can I do this using logic shifter? I have TXS0108E in the spare parts box.
My understanding is that I'd use pin in open drain mode to do that if it was 3v3, but with 5v it has to be something extra. Relay or transistor is obvious.
Why would you need to? Assuming the Arduino is 5v, and the ATX can be controlled with 5v, what do you need to shift?
not all arduinos have 5v logic. mine is 3v logic.
Might have been a good idea to mention that in your original post ?
Ehh, there are a few of them, different.... Which Arduino?
What is that? Any datasheet?
Use a 5 volt logics Arduino and You might drop the level shifter. How much current does that power button signal use? 20 mA is the design max for an output.
Yes, that should work ok, provided that the Arduino and the pc share common ground. If not, an opto-isolator could be used.
If using a transistor, almost any ordinary npn would be fine. Don't forget a current limiting resistor on the base on the npn.
So you have something like this?
Should do what you need. A single logic level MOSFET will also work.
Thanks. Figured out the resistor and the common ground, but the "open drain" term still confuses me. I understand you drive the input to the ground essentially and wasn't sure if the level shifter is gonna handle that without unwanted side effects.
If using an npn transistor, you would make the Arduino output high for a fraction of a second. This would cause a small current to flow out of the Arduino pin, through the series resistor and into the npn base, out of the emitter to ground. This would switch the transistor on, causing it to conduct current from its collector to it's emitter. That would pull the power button pin to ground.
It's the npn which is "open drain" here, or strictly speaking, "open collector".
I wired the shifter as stupid relay and it works as one. Amazing, given it's auto-sensing bi-directional and I'm not sure how it guesses the direction correctly.
The tech spec says it's designed for open drain use cases, so I lucked out.
Seems like a waste. You could save the level shifter for another project where it would be better used. A single transistor is all that is needed for this project.
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