This is a sound effect generator circuit using small electronic components to generate since birds up to siren. With two IC-CMOS are main.
This circuit can many loud sound in one. It is valuable for very educational, since the counter circuit, to convert digital signals to analog signals. Features of controlling frequency of Oscillator circuit using two CMOS Gate, All studies have a small budget.
The operation of circuit.
To see and understand the work even more as the circuit diagram in Figure 1. A signal from a frequency generator, before is send to a speaker driver circuit, they will be fed back to a 2^8 counter circuit to become as binary signals.
The binary digit set will be send to next step to a converter circuit into a level voltage as the value of that binary signal. And this voltage is used to control the frequency generator again, which it need to increase or reduce frequency as the controlled voltage is higher or lower.
Figure 1 The schematic of the circuit
As working in this way, the result was that frequency signal of the frequency generator will be high or low at all time. If the signal is high frequencies. The counter circuit will count a lot. The voltage controller of the frequency generator will rise very fast.
The oscillation of sound, it will be fast, such as birds singing loud that “jip..”. In the opposite, if is low frequency signal, the oscillation of sound will slow down became the siren go out. After the idea to create the circuit already. Let’s see how to build this circuit to come up with anything better.
From circuit in Figure 2 , We will start at the 2^8 counter circuit before, is CMOS-IC number of CD4040, get frequencies signal in to pin 10, then the counting will show as binary digit on form of voltage signal. Which if from 9-volts become to 0-volts actually CD4040 count up to 2^12, but we will use just 2^8 only.
Resistors-R1 to R9 are used to change the binary signal that show out of pin 13, 4, 2, 3, 5, 6, 7 and 9 sequence number 8 characters from left to right to single voltage signal. By control current which out of several lead rises as numbers increased.
This current is base current of transistor-Q1, to control amount of current that flow to collector lead to emitter lead next.
IC2/1, IC2/2, R10, R11 and D1 to D4 are combined as the square wave generator circuit, which is controlled frequency by quantity current that can flow through Q1. The frequencies output can change by the current discharge flow through C1.
But since current charge and discharge to C1 on two way only. Which transistor-Q2 only one can not work on two ways. So add diode-D1 to D4 are connected as a bridge to cause current backward through Q1 one way all times.
The rest is IC2 / 3 to IC2 / 6 use as the speaker driver circuit that must to use all four ICs connects to parallel together, since each ICs will can provide low current.
The building and application
Start from make the PCB copper foil track layout(Actual-size) as Figure 3 before, then solder the components as Figure 4. The caution; IC pins,and lead of transistors, electrolytic capacitors carefully before to use. The switch-S1 is normally open pushbutton characteristics on any types. A sized-speaker of 8 ohms, 0.25 watts so reasonable.
The adding resistances-R10 to adjust a using in proper rage.
But sometimes has some problem is the frequency generators circuit does not work. Because value of R10 and R11 distorted, cause press switch-S1, then no loud sound and IC2 may be also hot. We must release the Switch-S1 before, then adjust R11 again, and press S1; Try listening again. Until you get the sound you want, if completed, the circuit is installed in the box and connect the power cables completely.
Parts list you will need.
C1_____0.1uF 50V____the mylar capacitor types____= 1 pcs.
C2_____100uF 16V____Electrolytic Capacitors_______= 1 pcs.
D1-D4__1N4148 ____75V 150mA Diodes____________= 4 pcs.
IC1____CD4049 __Hex Inverter Gate IC___________ = 1 pcs.
Q1____BC547 or BC549 __45V 100mA NPN Transistor = 1 pcs.
R1____5.6K___¼W +5% ___Resistors________________ = 1 pcs.
R2____12K ¼W +5% ___Resistors___________________ = 1 pcs.
R3____22K ¼W +5% ___Resistors___________________ = 1 pcs.
R4____47K ¼W +5% ___Resistors___________________ = 1 pcs.
R5____100K ¼W +5% ___Resistors___________________ = 1 pcs.
R6____220K ¼W +5% ___Resistors___________________ = 1 pcs.
R7____470K ¼W +5% ___Resistors___________________ = 1 pcs.
R8, R9____820K ¼W +5% ___Resistors________________ = 1 pcs.
R10____1K ¼W +5% ___Resistors_____________________ = 1 pcs.
S1________Switch of normally open pushbutton
9-volts battery and Snap connector
Loudspeaker of 8 ohms, 0.25 watts.
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