Optocouplers - Interfacing with an existing circuit. (Button)

Ok, super green here, and I need to setup an Arduino Nano to do 2 things.

  1. To Press a button on another circuit.
  2. To Read the pressing of that button from the other circuit.

This is what i know about the device I need to push the button on...

  • Its signal voltage for that button is .42v
  • Its a Normally open single pole switch.
  • When you apply an LED across the 2 poles of the switch, it lights up, and goes off when the switch is pressed. The Switch itself responds normally when the LED is connected in this manner.

I have Selenium photocells of several sizes, shrink tubing, and LEDs.
I also have some 817c optocouplers. (x4) but they are on a x4 relay Sainsmart board and I'd like to avoid de-soldering them, and use the Selenium photocells and LEDs. If Possible.

Can Anyone Assist me in how to do this?

If I can get to the point of being able to read the switch and press the switch from an The Arduino IDE, Then I just need to tell it to press the switch every 86400000 milliseconds, with some kind of de-bounce so its acting consistently.

After it presses it 3x, I need it to press the button 2x fast to reset the cycle.

Please, how do I go about using the optocoupler to interface with this button?
(Or can I make one from the photocell and the LEDs?)

Please help! I'm Arduino dumb, but I can learn... :slight_smile:

Simplest way first, if possible, replace the single pole switch with a double pole version so one pole can be dedicated direct to the Nanos input pins?

I really need the 2 circuits to bee completely isolated from each other.

So I got brave and tried a few things…

I tried connecting an LED to the switch, and that works. It lights up but does not effect the switch’s operation. It goes “OFF” when you press the switch manually.

At the same time, I can connect a selenium photo-resistor to the button, and it also does not effect the switch, until you bathe it in light. then it presses the switch :wink:


Does that mean that I can just whip up x2 Red LED photo isolators with some black shrink tubing?

One to read the switch as input on the Arduino, and the other to act as an LED based trigger for the button?

It certainly looks that way…

DPST momentary tactile switches seem to be few and far between.

The only issue I have now is that the photo-resistor does push the button, but it also shuts off the LED.

So it would go into a loop I do believe, If I tried to use it to read the button state.

Is there any way around this ?