Hello Michael,

    Well, I’m using Splan from Abacom software.  Here’s the link

    It’s a very easy but yet powerful tool for drawing schematics. Just pick your symbol and place it on a grid. It will snap to it’s position then.

    This time, I’ve changed the background of the images to light grey to resemble the original circuits. Do you like it, or do you prefer the cool white ?

    I have a (almost) full set of symbols for the Lectron system and I’m willing to share the library.

    But let’s continue today with some new cool circuitry : a siren and a super siren !

    These are build upon the principle of our VCO of above with some new circuitry.

    Here’s the diagram of the siren. After building it, do not connect the ground block to the 100µF capacitor yet.

    Now, press the switch. Do you hear the tonal quality of our oscillator ? It has a resonant filter circuit consisting of the speaker coil in parallel with a 0,47µF capacitor (can you spot it in the diagram ?) This produces a warm sound. The combination of R and is responsible for the frequency. Don’t forget to fiddle the potentiometer to find the perfect rise and fall of the siren.

    Now, connect the ground block and press and release the switch …


    But wait, there’s more ! Let’s build a super siren !

    This siren works fully automatic and by fiddling the 3 potentiometers, you can create a lot of sound effects 😛

    The circuit consists of the PWM astable multivibrator coupled to the siren circuit of above. The potentiometer at the right adjusts the influence of the 0,47µF capacitor to the circuit. It has also an effect on the AC current flowing through the transistors, thus also on the sound itself.

    Super Siren

    Lectron is a real cool tool, isn’t it ?

    Have fun with the siren 🙂