Programmatically shunt pins

Other Hardware Device Hacking
1

I'm looking for a way to do the following WITHOUT a relay.
I have a contact switch with 2 wires that's normally open. I want to connect these 2 wires to 2 Arduino pins (I'm using an ESP8266) and programmatically close the switch, then after a short delay, turn the contact off so that the switch is back to being open. Is this even possible without a relay and if someone has an idea, a snippet of code would be appreciated.
Mike

2

Why do you want to do this ?

If you are looking for a way to operate a switch on another device using an ESP8266 then start by determining what the switch actually does. For instance, it would be common for a switch to take one of the contacts to VCC or GND when operated,

3

Depends on how the switch is wired. If it's part of a matrix you will need something like an analog switch (CD4066, 74HC4066, MAX4066).

If the switch has a pull-up on one side and Ground on the other:

  // Initialize pin to pulled-up side
  pinMode(SwitchPin, INPUT);

  // Close switch
  pinMode(SwitchPin, OUTPUT);

  // Open switch
  pinMode(SwitchPin, INPUT);
4

I have device that needs to be powered off and on remotely. A timer switch will handle that easily. The problem is that when it's powered up, a button needs to be pressed for 10 seconds or so to complete the start up process and since I'm remote I can't do that. So my plan is to open up the device, find the 2 contacts that are crossed when the button is pressed and temporarily close them with the arduino that will power up using the same timer switch.

5

Thanks, this is promising, I'll look into it

6

Why the objection to using a relay ?

7

Just looking for a simpler way. I thought there might be a way to make two pins act as a shunt. It's not a big deal.

8

Do you even need an Arduino to do this ?

9

I don't know. I need to close a circuit for about 15 seconds and then open it. It needs to happen about every 3 days. To me it seemed like a $5.00 Arduino would be a cheap easy way to do it but I'm open to suggestion.

10

Hi, @Mike505
A very important question?
When the contacts are open, what voltage do you measure across it.

Is the button multiplexed?
Is the button part of a potential divider?

If there is a DC voltage across the contacts, then just connecting a microcontroller output to it will not work.
Look up optocouplers they would be a better solution, and not need a driver transistor like a relay would.
https://www.jameco.com/Jameco/workshop/Howitworks/what-is-an-optocoupler-and-how-it-works.html#:~:text=An%20optocoupler%20

Tom... :grinning: :+1: :coffee: :australia:

11

555 chips are even cheaper

12

Thanks to all who responded. This gives me enough to contemplate for now.