user10392: I have a little personal project involving an Arduino Uno and an amp board from Sure Electronics. The amp has contacts for a mute function that involves shorting the contact to ground. I would like to control this muting with the Arduino which I was planning to do with a relay. However I think I might be complicating things and I thought it might be possible to do it directly with the pins.
Can I use the Arduino to directly short a circuit to ground? Or would I need something more complicated to be safe?

user10394: I can't see how much current the amp board will sink into the Arduino so like FuaZe I would recommend using your Arduino to drive an external component that you know can take the current.  This isn't really complicating the design too much, use an NPN transistor, with the P connected to the Arduino and just write High to the pin when you want to apply the mute.  If you blow the transistor then its going to cost you a few pence for a new one, if you blow your Arduino you are down £20!

user2881: Depends on the voltage that is on that mute pin. If it's below 5 volt, you could use the arduino pin. You can measure the voltage using a multimeter.
If it's more than 5v you can use a NPN transistor and resistor combination. 
Current isn't a problem with these kinds of "settings" pins, as there is just a pull-up resistor that by default (unconnected) sets the pin to HIGH. By connecting the pin to ground you set the pin to LOW.

10392: <p>I have a little personal project involving an Arduino Uno and an amp board from <a href="http://store.sure-electronics.com/audio/audio-amplifier-board/low-power-100w/aa-ab31521" rel="nofollow" title="Sure Electronics">Sure Electronics</a>. The amp has contacts for a mute function that involves shorting the contact to ground. I would like to control this muting with the Arduino which I was planning to do with a relay. However I think I might be complicating things and I thought it might be possible to do it directly with the pins.</p>

<p>Can I use the Arduino to directly short a circuit to ground? Or would I need something more complicated to be safe?</p>
 10394: <p>I can't see how much current the amp board will sink into the Arduino so like FuaZe I would recommend using your Arduino to drive an external component that you know can take the current.  This isn't really complicating the design too much, use an NPN transistor, with the P connected to the Arduino and just write High to the pin when you want to apply the mute.  If you blow the transistor then its going to cost you a few pence for a new one, if you blow your Arduino you are down £20!</p>
 2881: <p>Depends on the voltage that is on that mute pin. If it's below 5 volt, you could use the arduino pin. You can measure the voltage using a multimeter.</p>

<p>If it's more than 5v you can use a NPN transistor and resistor combination. <img src="https://i.stack.imgur.com/19QUa.png" alt="enter image description here"></p>

<p>Current isn't a problem with these kinds of "settings" pins, as there is just a pull-up resistor that by default (unconnected) sets the pin to HIGH. By connecting the pin to ground you set the pin to LOW.</p>
