User manual

purpose there are two buffer amplifiers and the electrolytic
capacitor energised by operating voltage.
Mission: Warm up two capacitors simultaneously, so that the
oscillators always have the same rising frequency. This requires a
little practice and much skill, as you must detect by sound, when
one of the oscillators tends to escape the coupling: 3 points.
23 Organ for two hands
The second 10 nF (103) capacitor is behind the door number 23. It is meant to be used to make a two-tune organ. The tones will be changed by finger pressure on
the sensor wires. Two fully independent tones can only be achieved if both sensors are touched by two persons who are well insulated from one another. By
touching hands each tone affects the other one.
Info: the circuit hardly differs from the beat oscillator from the
previous day. However, since the skin resistance is essentially
higher than the installed 10 k

, the capacitors must be downsized.
Mission: Replace one of the two capacitors by one of 100 nF and the
respective sensor wires - by a 33 k

resistor. Thereby, an organ will
receive a permanent second tune with steady tone, similarly as
with a bagpipe. You can now play melodious duo-tones. However,
only a real music genius will manage playing a double-tune
Christmas carol. You get 10 points if you make it convincing, and
respectively less, if the result is less satisfactory.
24 Sparkling stars
Until now, only relatively high-ohmic resistors were used to conserve the battery so that it possibly last until Christmas. But behind the last door, you will find only
1 k

resistor (brown, black, red). On Christmas Eve no weird sounds should spoil the atmosphere, therefore the piezo panel will be used not as a loudspeaker but
as an acoustic sensor. When the family sings the Christmas carol with enough effort, gentle flickering of the three LEDs starts, which after some time gets weaker
and then stops. This festive light can be placed on the Christmas tree. And if no one wants to sing any more, a twig of the Christmas tree can be tapped to make the
sensor trigger the light again.
Info: the sensor itself is the knock sensor known from day 13 with slowly declining output voltage. Via a 1 k

series
resistor, it powers three LEDs, which are additionally steered by three op-amps. What is actually new about this
experiment is the three-stage phase shifting oscillator. The LEDs are switched on in a row and with smooth