Using a transistor to control a pull-down switch

Question

^{simulate this circuit – Schematic created using CircuitLab}

I have a Runcam 2 video camera. It uses a temporary switch to turn on/off and start/stop recording. I would like to control these functions with an arduino. Once side of the switch is 3V the other is ground. Pushing the switch pulls the 3V to ground. I've soldered two wires to the switch and can operate the camera by shorting the two wires. I would like to use an NPN transistor with the base controlled by an arduino pin or other suitable method to operate the camera. I've searched the archives and the closest I found was using a transistor to pull a pin low. It did not help. I am limited in my electronics knowledge and would appreciate any help.

Answer 1

You have Q1's emitter and collector swapped. It might work in that configuration but it's not the right or most reliable way.

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. NPN transistor ORed with internal switch.

I've redrawn the circuit in a more conventional fashion. Positive voltages are to the top, grounds at the bottom and logical control flow from left to right.

The camera will have a pull-up resistor on the input and SW1 pulls it to ground. Your Q1 will do the same thing.