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I have the Arduino Yun. The goal is to control a remote control by emulating the button press. The button switches GND. I will use the 5 V of the USB that powers the Yun to power the remote (over a 3V regulator of course) and use the GND to switch the buttons on using a transistor or MOSFET.

The MOSFET I tried was not able to be triggered by the Yun (BS170).

So I found some NPN Transistors I could hopefully use:
S8050
S9013
S9014
S9018
2N3904
2N5551
A42
C1815
C945

What do you think?


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Look for logic level MOSFETs if you want to use them.  Either way, you are assuming an open-collector (or Open-drain) circuit.  If that is the case, great!  If not, then you'll need to revisit your plans.

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So my transistors wouldn't work?

I am not sure about the circuit. The buttons simply shortcut GND to the board. Therefore I assumed to do this with a transistor.
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A transistor should work just fine.  The only one I recognize off the top of my head is the 2n3904, and it should suffice for what you want.  Just remember that while a MOSFET is voltage driven, a transistor is current driven, so you need the appropriate resistor in series with the base to supply the correct base current.

I am also assuming you will be using an open collector circuit.
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So my transistors wouldn't work?

I am not sure about the circuit. The buttons simply shortcut GND to the board. Therefore I assumed to do this with a transistor.

They might work!  What you need to check is how the rest of the circuit connects to the button.  Most likely you will be able to replace it with a transistor.  I'd recommend the standard 2n3904 or 2n7000, though the BS170 should work as well.  Make sure you have it hooked up right.
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The C945 (2SC945) that you have is a nice choice as it is a very high gain (Beta) GP NPN Silicon transistor... Any of them are more than suitable but you already have the C945 transistor..

Doc
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First you need to find out the max current draw of your remote - then decide on a
transistor, since it needs to be able to handle that current level.  If the current
draw is small it will make the choice easier of course.
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Thanks, the draw is very minimal. I took a B675A - oversized but works. smiley-wink
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