Buzzer

The buzzer is the smallest part on the car and the first one children go for. It sits on digital pin 2 and does three jobs in the sketch: a horn, a reversing beep, and Happy Birthday.

Buy the passive one

Two different parts are both sold as "Arduino buzzer", and they are not interchangeable.

• Active — there is an oscillator inside it. Give it a DC voltage and it makes one fixed tone, usually around 2 kHz. It cannot make any other note.
• Passive — no oscillator. It makes whatever frequency you feed it, which is exactly what the Arduino tone() function produces.

The car sketch calls tone(buzzerpin, melodyHappy[i], noteDuration) to play a tune, so it needs the passive one. On an active buzzer, Happy Birthday comes out as a single flat note held for the length of the song.

Wiring

The module has three pins.

• I/O or S → Arduino digital pin 2
• VCC → Arduino 5V
• GND → Arduino GND

A bare two-pin buzzer works too: one leg to pin 2, the other to GND. If one leg is marked +, that is the one that goes to pin 2.

How much current it pulls

A small buzzer draws roughly 30 mA. An Arduino output pin is rated at 40 mA absolute maximum, and 20 mA is the figure Atmel actually recommends designing to. So a bare buzzer straight off pin 2 is inside the limit, but not by much. That is a good reason to prefer the three-pin module, which usually puts a small transistor between the pin and the buzzer and lets the 5V rail do the work.

One thing tone() quietly breaks

On an Uno, tone() takes over Timer2, so analogWrite() stops working on pins 3 and 11 for as long as a tone is playing. The car is safe from this by accident and by design: its speed pins are 5 and 6, which are on Timer0. The wheels hold their speed while the horn sounds.

Testing it on its own

Before you wire the rest of the car, put this in an empty sketch's setup() and upload it. One second of a 1 kHz tone means the buzzer, the pin and the wiring are all good.

void setup() {
  tone(2, 1000, 1000);
}

void loop() {
}

Get the car sketches

Every part of the car