User manual

output frequency drops both at higher and at a lower input voltage. Since the bi-polar op-amp does not operate
across the entire voltage range, deep and less deep phases can be found.
Mission: in addition, integrate an LED with a suitable series resistor so that the signal sequence of the slower
oscillator can be seen: 3 points.
21 Light alarm
You will find a 3.3 M

resistor (orange, orange, green) behind the door number 21. It will be used in a slow oscillator. In addition, there is a light sensor switching
on the tone. This alarm system can be used to protect the Christmas gifts from premature detection. If anyone enters the prohibited area and switches on the light,
an intermittent warning signal is generated. Without alarm, alternately flashing red and green LEDs can be seen, which can be used as a readiness indicator.
Info: components of the circuit are also known already. This time, there are two diodes, which can stop the
oscillator. The tone is triggered only when red and green LEDs are locked.
Mission: Use also the remaining resistors and capacitors to change the tone, pitch or repetition frequency: 2 points.
22 Beat tones
Behind the door number 22, there is a 100 nF (104) capacitor, using which two oscillators with the same frequency can be made. Both tones reach the loudspeaker.
Change the frequency of one oscillator by warming up the capacitor with the finger. This will result in beat tones. With cooling, the frequencies reach comparable
levels, the beat slows down until disappearing.
Info: if two tone pitches are very close together, ascending and
descending volume is perceived in tune with the tone difference. If
the frequency difference is very small, the two oscillators snap
into the same frequency. However, they still can be through
different phases changing volume and sound. The challenge
consists in uncoupling the two oscillators as profoundly as pos-
sible to make small frequency differences also possible. For this