Using Arduino to simulate a SPST switch

Projects General Guidance
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My apologies for asking what could be considered a very basic question... but my knowledge of Arduino is very fundamental...

I need to simulate an SPST switch with an Arduino just open and close a circuit to "ground".

Here is the scenario: I already have a setup where based on analog data received from a Yo-yo potentiometer an LED is lit depending on the value received. Currently, I have a physical switch that just closes a circuit to "ground" so an instrument can detect that the switch has closed. I'd like to replace that switch (SPST) with an Arduino function.

I haven't found any examples but those that use Arduino to close a circuit to send power to LEDs and others.. on those there are recommendations for the usage of relays... I guess I could do something similar but I wondered if there is a simpler solution...

Your help and input will be greatly appreciated

Thanks
Enrique

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If the arduino and the instrument can share the same ground AND the input on the instrument is not connected to anything above 5V, then you can do this with a digital output. If one or both of these is not true, then an optoisolator is probably the simplest option.

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simplier as relay is a FET.

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You can get a relay module rated at 10A 250V for under a buck from some china suppliers. They are designed to work with the Arduino and have an onboard transistor to drive the relay. Try this link: Arduino - Relay | Arduino Tutorial

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What is the voltage across the switch when it is OFF? How much current flows through the switch when it is ON?

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@emertins

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Please explain why they are the same. To to me a relay is a mechanical device that does not care if it is AC or DC being controlled. A FET is an electronic device that only does DC. If you check the link the transistor/fet driver for the relay is on the module which was designed for logic level inputs.

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you can't simply connect relay to arduino, you need current amplifier and not forget a flyback diode, so i mean if a transistor is anyway there, then it is simplier to use this one transistor

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Thanks everybody for all your ideas. I spent time measuring voltages everywhere in my circuit and it is so low that my meter couldn't tell. However, to stay on the safe side, I relatively small relay board ($9 from Amazon) and that did the trick.

Again I want to thank all of you for your invaluable input!
Very best regards
Enrique

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I think that for a lesson, led13 could indicate the switch state.
Then, every Arduino with a led13 would be enough.
A kit of sensor 'switches' and electronic switches could make many lessons.

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There are reed relays with 5V coils (500Ω) - and with the diode built in.
The relay contact ratings are typically modest.

media (littelfuse.com)

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