Interface integration - 5 VDC pull down with arduino

Hello, So I'm hoping this is an easy one. Not to used to electronics yet, so not sure the best way to approach this.

I have a control panel that uses a button. The unpressed button is 5 VDC, when pressed, the signal is sent to ground causing a low and a Samsung IC chip reads the low and does an action.

I need to connect to the 5 VDC and make it low.

What I'm not sure is how to go about making it low. Can I use pinMode(INPUT_PULLUP) to use the internal resisters of the arduino? I'm using a Uno so it should be at least 20K. My concern with that is the current. Way to measure and make sure it's safe? But, is it even going to work?

I've Googled and searched a bit on the forums, I'm sure the answer is out there, but not knowing the proper keywords, it's hard to find.

Thanks in advance.

I was able to figure it out.

I connected the Arduino directly to the controls. When the Arduino control isn't being used, I have pinMode(INPUT), this allows for manual and remote (Finger button press and IR remote) control. When controlling it programmatically, I use pinMode(OUTPUT),digitalWrite(pin,LOW).

Now I'm figuring out how to sense a LED. Not connecting a phototransistor type device to it, no room. The voltage difference is 60mV when the LED is high, but analogRead isn't picking it up, might have a different GND then currently plugged into.

Are you trying to see if the LED is on or off? How is it wired and where are you sensing? Dwight

You could put a resistor in parallel to the LED so that when off it would be closer to ground. It only needs to shut about .5 ma. A 3.9K would be enough. Dwight