In this electronics project, you use two 555 timer chips to build an audible beeper, with both timers configured in astable mode. Each time controls a different audible tone on the beeper.

One timer generates an audible square-wave tone of approximately 500 Hz; the output of this 555 is sent to a speaker so the tone can be heard. The other has a much lower frequency of about 1.5 Hz. You connect its output to the reset of the 500 Hz timer to turn the tone on and off, which creates the beeping effect.

Before you start, have a look for a moment at the project’s schematic diagram. For the first timer chip — designated 555 (1) in the schematic — the RC network uses resistors of 1 kΩ and 470 kΩ along with a 1 μF capacitor to produce the 1.5Hz output.

The second timer — 555 (2) — uses two 100 kΩ resistors and a 0.01 μF capacitor to create the 500 Hz output. The output of the first timer is sent to the reset of the second timer, and the output of the second timer is sent through a 22 μF capacitor to an 8 Ω speaker.

Note: You could easily build this circuit using a single 556 dual-timer chip. You’d have to adjust the pin designations on the schematic accordingly.

The speaker used in this circuit can be any 8 Ω speaker. If you have an old unamplified computer speaker, you can use it. Solder 2–3″ lengths of 20-gauge solid wire to the speaker terminals so you can easily connect the speaker to the breadboard.


Here are some extra-credit assignments for this project, in case you want to experiment with the circuit a bit:

  • Try building the circuit with a single 556 chip instead of two, 555 chips.

  • Replace the 100 kΩ R3 with a 1 kΩ resistor, and then add a 1 MΩ potentiometer in series with the resistor. As you turn the potentiometer, the tone changes.

  • Add a 1 MΩ potentiometer in series with R1. Then, as you turn the potentiometer, the beeping rate changes.

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