Turn a switch off with the correct voltage

Question

I have an old mouse side switch which seems to produce a constant 3.28 volts which acts as the off state. Then when I push the button the voltage drops to 0. What is the easiest way to inverse these actions? I am wanting to apply 3.28 volts in order for the button state to be perceived as on but I am not sure how that could be done.

This is needed because I am running a program that takes in a mouse button as the action so instead of clicking the button I need to be able to apply a voltage across the pins in order to simulate a click. I could use a different device instead of a mouse to do this but I am trying to complete my project without buying anything new.

Answer 1

... I am wanting to apply 3.28 volts in order for the button state to be perceived as on ...

It means I want to wire the button up to something so that when a voltage is applied the computer will think I was pressing that button. So really I am not clicking it but I am simulating a click by applying voltage.

Applying a voltage is not the way to do it. The switch is "ACTIVE LOW". You want to apply a short-circuit to pull the line low in the same way the switch does to simulate a button press.

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. Two options.

If your control circuit shares a common ground with the mouse and computer then you can use the circuit of Figure 1a. When the μC (microcontroller) output goes high Q1 will switch on and pull the OUT line low in the same way the button does.

If your control circuit cannot share a common ground then the opto-isolator circuit shown in Figure 1b does the same job while maintaining isolation between the two circuits.

Answer 2

First off, switches don't produce voltage, what you are most likely seeing is that you are measuring a voltage potential across the switch. The switch is in an 'open' state, and that voltage would be there whether the switch was there or not.

When you press the button, you are closing the switch and grounding the two points across it, thus the voltage goes to zero.

The safest thing to do, to avoid destroying your mouse, is to wire these two points to the N.O. contacts of a relay. If you use a relay board made for a microcontroller such as an arduino or raspberry pi, then you can control the state of the relay programatically.