Bridging a very low voltage connection?

Hey everyone, I have what would appear to be a very basic question. I have hacked a USB keyboard circuit so that by touching the two protruding wires together, it registers as an "enter" keypress.

The only problem that I have is: how do I make the Arduino bridge those wires when I push a button? I already have the wiring and programming hooked up for the button press (right now, it just lights the LED on the board for 1 sec), but I wasn't sure how to connect the two leads from the keyboard to the Arduino.

As far as I can tell, all it requires is completing the circuit. But the voltage is super low (my meter read something in the ballpark of 0.06v), so trying to use a 5v pin to trigger it would probably end up blowing something up. I considered using a relay to physically bridge the gap, but that seems like overkill (I know relays are usually used to trigger higher voltage circuits, not lower). The only other option I can think of is a transistor, but I have no idea how to find the right one to use.

Any suggestions are appreciated!

Use an optocoupler / optoisolator

Why can't you just use a button to control it? Feed one end to one side of the button, and the second end to the other side..

Or would that be too resistive?

@MikMo: I didn't think of that...I've heard of optocouplers before but never considered their possible application here. I'll have to check it out.

@TchnclFl: Oh, I think I just killed a few brain cells with that epic facepalm. The button I'm using is a 2-lead in, 2-lead out and only one of the leads each is being used for the Arduino. It should be as simple as plugging the wires into the remaining open ports.

I was so hung up on the Arduino triggering the keypress (because that and the button operation must be simultaneous) that I completely missed the simplest option...must remember Occam's Razor!

Since it's a standard PC-type keyboard, there's a 99.9% chance that the key is part ofa scanned matrix of switches (I'm pretty sure there are some examples in the Playground area of what this means. If not, google should turn up dozens of them).

If you were going to make hundreds or thousands of these, you could figure out how the scanning matrix is laid out, so you could determine how to close the circuit using a transistor to save money. But, since you're probably doing only one, the simplest approach is to spend the extra dollar, and connect the contacts of an inexpensive relay to those wires. Pretty much any relay will do (if you don't have access to a cheap parts source, you can get a suitable one at Radio Schlock), and you can definitely find examples in the Playground of how to turn it on and off.