Replacing microswitch with arduino

Hi all.

The question is about controlling the projector screen using the projector remote control.

Using arduino, I read the remote control codes that interest me and wrote a control program.
I do not want to create a new circut to control the screen but I would like to use the one that is factory in this screen. It is a system based on wireless communication. The factory circut also has the ability to control microswitches on the controller housing and I would like to plug in there with arduino.

The question is, can I somehow simulate the action of such a button in arduino? so to pass the signal between two pins?

Each button has a voltage of 5V, 5.2V, 4.7V, the second button contact leads to a common point for the three buttons. It looks like depending of the voltage the appropriate relay was activated.
The factory relays are on 12V, so I can't control them directly with arduino. The easiest way would be to simply push the button, but how can I do it without adding a relay instead of a button?

Maybe plug transistors before relays, and arduino will control transistor which open and let flow 12v to relay? What is the easiest way?

"The question is, can I somehow simulate the action of such a button in arduino? so to pass the signal between two pins"?

You need to know exactly what function the micro switches perform and how they perform it. The voltages you mention mean nothing because nobody knows exactly where the measurements were taken and under what conditions?

A Micro-Switch normally has 3 terminals, a Common and a Normally Open and a Normally closed. Using a transistor to bypass a switch can be easy enough but you need to know how the switch is used in circuit, a schematic of the product would help.

Ron

Microswitch are normally open, because they have two pins, on each one is voltage and on the second one isn’t. When push the button voltage appearing on the second pin and then relay is switching.

Just connect two pins is the easiest solution without decoding all circuit. But question is how easy it is to reach with arduino.

Each button has a voltage of 5V, 5.2V, 4.7V, the second button contact leads to a common point for the three buttons.

You have not indicated polarity, which pin is your RED voltmeter probe on?
Does the meter show a negative sign ( - )?

I marked +

Those are not micro switches, they are tactile button switches.Getting naming conventions correct helps.

So, back to what I asked, how do they work in circuit with respect to the electronics?

Ron

I don't have schematic diagram, so I can't answer to your question.
Only one what I can do is connect two pins of button to get intended effect

You have a meter right? Frequently button switches like that use a pullup and go to common (ground). The idea is to see how the switch is configured in the circuit.

Here is an example:

The 10 pullup holds Vout high. A button press makes Vout low.

You measure each side of the switch to common (ground) if one side is zero and the other 5 V (or some level) and pushing the switch takes it to ground then you know what the switch is doing.

That or as mentioned just put a set of relay contacts across it and be done.

Ron

You oftentimes can replace a momentary switch with an optocoupler. Whether this works depends on the actual circuit of the device. Mind the polarity (or use an AC out optocoupler).

You always can replace a momentary switch with a relay. That's basically just an electronically operated switch.

In both cases wire your optocoupler or relay in parallel to the existing switch.

I think I'll try with optocoupler, is small and can be controlled directly from arduino. Only to check if current and voltage is in range of this optocoupler.

Thanks for help

Ron_Blain:
Those are not micro switches, they are tactile button switches.Getting naming conventions correct helps.

This is a microswitch: https://uk.rs-online.com/web/p/microswitches/6822660
They are used to interface moving parts of machinery to the control electronics and have lots of accessory parts available for various ways to actuate them. They are usually SPDT momentary action.

This is a tactile switch: https://uk.rs-online.com/web/p/tactile-switches/1034414/ - these are SPST NO momentary action design to be pushed by fingernails or via push rods connected to buttons on a front panel.

System is assembled and working fine. Optocoupler connected directly to arduino and is ok.