The oscillation continues …

So, we’re back with something really cool : an automatic 2-tone generator 😉

For this, we use the oscillator circuit of above and we add an astable multivibrator !

Now, the 2 tones are produced automatically. The potentiometer sets the depth of the 2 tones.

Our Lectron start and expansion kit has all the parts needed and has even more parts to do some experiments as will published here.

But let’s first build the 2-tone generator. Here’s the diagram :

Auto 2-tone

Now, let’s add some PWM (Pulse Width Modulation). With an extra potentiometer and a small modification to the circuit, we will add the possibility to change the length a pulse occurs. This control does not affect the speed of the astable multivibrator. Of course, we can use this kind of circuit to control the brightness of a light bulb. I will certainly publish this circuit later. In the meantime, can anyone  post a schematic here ?

But first, let’s build the PWM for our tone generator. Here’s the diagram :

tone PWM


Some experimental tips :

  • change the two 10uF capacitors into one 0,1uF and the other one into a 0,47uF capacitor.
  • Replace the 0,1uF capacitor in the tone generator into 47nF.
  • Fiddle around with both potentiometers to find the “perfect” police siren.

Tomorrow, we will be back with another cool circuit around this generator.

Till then