Using GPIO to trigger external button

Other Hardware General Electronics
1

I have a ESP8266 Wifi board. The board has a couple of GPIO's mapped to a header.

I have a GBS-8100 VGA-CGA board with some buttons. These buttons have 3.3v across the contacts when open.

How would I wire a circuit to trigger a button with a GPIO?

Alternatively if anyone knows how I might use a resistor or something else to lower the default brightness on the GBS-8100 might also be an option. Or any other way of configuring this board to a different set of defaults (like firmware) to survive power down.

2

This sounds like an XY problem.

Tiggering a button makes no sense.

What are wanting to do in the big picture?

3

you can build a robotic arm that will press the button for you when gpio is triggered.

4

Sounds to me like you want a relay across the button contacts, so you then have a new switch in parallel with the existing button. Then use the ESP's IO pin to energise the relay?

Why can't you just press the button?

5

So all I needed to do was hook a HIGH GPIO to the 3.3v side of the button. when I toggle the GPIO LOW/HIGH it activates the button logic.

6

You will also have to share grounds, otherwise nothing will work.

A relay will work. Or use an optocoupler in parallel with the manual switch.

7

wvmarle:
You will also have to share grounds, otherwise nothing will work.

A relay will work. Or use an optocoupler in parallel with the manual switch.

Why wouldn't I just use the GPIO HIGH LOW levels to make it work?

It works as I have said. The closet shared ground is as far back as the mains. I don't need a relay or an optocoupler.

8

If it works already, why asking how to do it?

9

For circuits to work, they need to be, well, circuity... without the ground I can't picture where you're getting a circuit. (But it might be a similar case to those beloved Jdd-Vcc relay modules, where there's a circuit but it's not through the ground.)

A schematic might help puzzled readers understand what you wanted and what you did.

10

If that works, then you do have a shared ground somehow - possibly a sneak path (do you have more than one button connected this way? That would indirectly achieve the same thing... I was going to say this was a bad way to do it, but on reflection, it's actually not so bad, because it makes the configuration safe for the ESP8266 if it is not powered but the other board is).

Also worth noting for others reading this, if you'd used a 5v board, connecting as you described would have trashed the GBS-8100. These sort of tricks also only work because the buttons are wired in the normal way for single buttons, ie, they are connected to an I/O pin on some controller on the GBS-8100, pulled up to supply voltage (3.3v) and grounded when the button is pressed. A better approach here is to use an opto-isolator - this would prevent the ESP8266 from damaging the GBS-8100 if it tries to "press" a button while the GBS-8100 is not connected to power.

The relay method will always work, even if you don't know how the switch you're controlling is wired.