With this project you can modify any rc car you want. You just need a speaker, LED, breadboard, rc car, wires, computer and of course an Arduino. You can pragramm any sound you want to the Arduino and then te speaker plays it.
Step 1: Connect a Speaker and One (or Two) LED's to Your Arduino
First you connect your Arduino to your computer. Then you connect your Arduino and your Speaker to a breadboard: You put a wire in the 5V connection of the arduino and you lead it to the breadborad to connect it with the speaker (now programm any sound you want into the arduino programm on your computer and the speaker plays it). The next step is connecting the LED: put a wire into the 3,3V connection of the arduino and lead it to the breaboard to connect it with the LED and then you lead a wire back to GND connection of the arduino.
Step 2: Attaching Everything to Your Rc Car
Now you've already done the biggest part of this modification you can take the top of your rc car and place the Arduino, breaboard, speaker and the LED and attach it to your rc car. Also drill a hole in the roof of your rc car to put the LED trough.
Step 3: Put Everything Back Together
Now you've attached everything to your rc car you can put the rc car back together and take the LED trough the roof of your rc car to make it look like a siren. Make sure you don't block the USB connection of your Arduino otherwise you cant connect a powerbank to it.
Now you're done, you connect a powerbank to the USB connection of your arduino and the LED lights up, and the speaker will play the sound you've programmed in the Arduino programm on your computer.
Step 4: The Result
Here the result of the modification.