Replace a pushbutton with arduino.

Wazzup guys! I have an RC remote witch has 4 push buttons for controlling the car itself.
I was wondering if i could desolder these buttons and connect arduino, and then the arduino can be programmed via S4A, with scratch, so I can use my keyboard arrows to control the rc car. Have a nice day :slight_smile:

I was wondering if i could desolder these buttons and connect arduino,

Only if you know what the button is doing and make the Arduino do the same thing. It might be shorting the switch to ground, or 5V or some other value.

So you need to know the circuit in the remote or to probe the remote with a meter or oscilloscope to see what technique you need to use.

One simple way might be to put an opti isolator across the button and and drive the LED in the opto from an Arduino pin / resistor.

But what if, one if the pin of the push buton is connected to ground, and the other to a digital pin, so this way I can just select "digital pin 13 on or off"

The first step is to measure the two terminals of each button to see if one side of each button is Ground (which is a fairly common configuration). If so, you can connect the OTHER side of the button to an Arduino pin and use:

void press(byte pin) {
    digitalWrite(pin, LOW);
    pinMode(pin, OUTPUT);
}

void release(byte pin) {
    pinMode(pin, INPUT);
}

Note: The Arduino's Ground has to be connected to the transmitter's Ground.

Kinorter:
But what if, one if the pin of the push buton is connected to ground, and the other to a digital pin, so this way I can just select "digital pin 13 on or off"

If you are lucky and the remote works off 5V and you connect the ground then maybe.
But the chances that the remote is battery powered so the 5V signal from the Arduino might be too much or too little and if so it could damage the Arduino or remote. That is why I advise you to use an opto isolator.

Before going too far you should find out whether the switches are wired to separate inputs or, if they're wired as a voltage divider and thus only use one controller input.