Simulating a button press on a rc transmitter

Hi, I got myself an RC car which uses simple buttons in the transmitter to make it go forward, back, left right. Now I want to control the car using the arduino..

I saw this post http://www.jonasolson.se/content/arduino_tutorial/, but was wondering if there was a different way to do it.. Also, the pictures look to show the soldering on the back of the buttons, but the back of my circuit board doesn't look anything like that..

A long time ago I did something similar with an IR remote (below). I used an NPN transistor, but the optical isolator might be a cleaner choise. You may need to solder the button connections at the chip (top or bottom) and not at the button site, depending on the board construction.

http://web.comporium.net/~shb/irmods.htm

Thanks for the replies. I've decided I am going to use the opto-isolator to control the car, and agree that soldering the connections to the pins of the chip is probably the easiest way to do it. My question is: how do I know which pin to solder which wire to?

In the image below you can see the whole circuit board, where the 14 parallel dots of solder are is the chip.

IMAG0010 by Y.P.F.L, on Flickr

Here's the wiring so far:

Assuming the round silver things are the button points, here is my guess:

One side of the buttons are all connected to a common ground. Bottom right chip pin goes to the far right button. Third pin from bottom right is a common ground. Fourth pin from bottom right goes to the far left bottom button. Fifth pin from bottom right goes to the far left top button.

You can check this out with a meter. If this looks good, and you can power the transmitter up opened as pictured, you can try carefully touching the appropriate chip pins to see if the RC car responds. For touching small points, I put a somewhat straightned safety pin on the ends of a jumper lead.

I just did this as my first arduino project. I did not run from the IC. If you want to run from the IC, hold each button down on the remote and probe the IC chip pins until you see which one goes HIGH (+5v) for each button.

My car had to many surface mount components, so i went from the ANALOG motor leads. Here is a link to my thread (with much useful information from guys in the know like Richard Crowley and Grumpy Mike. Also on page 2 my Code is posted.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1289693288/0

One side of the buttons are all connected to a common ground. Bottom right chip pin goes to the far right button. Third pin from bottom right is a common ground. Fourth pin from bottom right goes to the far left bottom button. Fifth pin from bottom right goes to the far left top button.

It looks to be that you are right :) I tested each pin with a meter and the voltage went up I pressed the correct buttons. I don't entirely understand the left/right buttons though.. They appear to be sharing the same pins, but changing voltage?

Okay, so it turns out that the pictures on Jonas Olson's website didn't show the back of the circuit board: the buttons are just metal contacts and all I had to do was peel them off to reveal the contact points!

So, I went and got my four opto-isolators today, and am connecting everything now.

Here is my test code, feel free to check it!

/* Control An RC Car
* 
*Code to control a car remote control using 4 opto-isolators
*
* 
* @author: Toby Makins 
* @date: 21/11/10 
* 
*/ 


void setup() 
{ 
pinMode(8, OUTPUT); //Right 
pinMode(9, OUTPUT); //Left 
pinMode(10, OUTPUT); //Forward
pinMode(11, OUTPUT); //Back
} 

void loop() 
{ 
digitalWrite(8, HIGH); //Turn Right For 1 Second 
delay(1000); 
digitalWrite(8, LOW); 

digitalWrite(9, HIGH); //Turn Left For 1 Second 
delay(1000); 
digitalWrite(9, LOW); 

digitalWrite(10, HIGH); //Accelerate Forward For 3 Second 
delay(3000); 
digitalWrite(10, LOW); 

digitalWrite(11, HIGH); //Reverse For 3 Second 
delay(3000); 
digitalWrite(11, LOW); 
}