This ticking Clock Sound Effect Circuit was built just with transistors and resistors and capacitors that without any IC component. It is ideal for you to learn the fundamental circuit knowledge by this practical and simple circuit.
The necessary materials:
1 x 8Ω 0.25W Speaker
1 x 100K Resistor
1 x 1M Resistor
1 x 100μF Electrolytic Capacitor
1 x 10μF Electrolytic Capacitor
3 x 9013 NPN Transistors
1 x 9012 PNP Transistor
1 x Button Switch
1 x LED
2 x Jumper Wires
2 x Pin Header
Step 1: Solder the Resistors to the PCB
There are just two resistors deployed in this circuit. One is 100KΩ and the other is 1MΩ. Image 1 is showing the 1M resistor inserted in the position of R1 and image 2 is showing the 100K resistor inserted in the position of R2. How do we know the value of each resistor?
There are two approaches to figure it out. One is to use a multimeter to measure it out and the other is to read the resistance value from the color bands printed on its body. For example, in image 5, the resistance value of resistor A is 1MΩ while the resistor B is 100kΩ. For resistor A, the first color band is brown which represents digit number 1 and the second color band and third color band are black which represent digit number 0; the fourth color band represents the multiplier, it is yellow, the corresponding digit number is 10k. The fifth color band represent the tolerance and the color is brown, the corresponding digit number is±1%. Let us put them together we get 100 x 10k = 100 x 10000k = 1MΩ, the tolerance is ±1%. Likewise, the color bands from first to the fifth of resistor B are brown, black,black,orange and brown, we can get its resistance by 100 x 1k = 100kΩ, and its tolerance is ±1%. For more details of reading resistance value from color band please go to mondaykids.com by right clicking your mouse to open a new tab on your browser.
Step 2: Solder the Electrolytic Capacitors to the PCB
The electrolytic capacitors have polarity, the long leg is anode while the other is cathode. Follow image 6 to image 10 to solder the electrolytic capacitors into the PCB. You can read the capacitance of the electrolytic capacitor from its body and insert it to the corresponding position where there is the same value printed on the PCB. The long leg should be inserted into the hole near the ‘+’ symbol.
Step 3: Solder the NPN and PNP Transistors to the PCB
Please note that the flat surface of transistor should be at the same side of semicircle printed on the PCB. For 9013 NPN transistor there is a model number, S9013, carved on the flat surface of the transistor, and the 9012 PNP transistor do likewise. 9013 NPN and 9012 PNP transistors should be inserted into area that have 9013 and 9012 respectively printed on the PCB.
Step 4: Solder the LED to the PCB
The LED light have polarity, the long leg should be inserted into the hole near the symbol ‘+’ on the PCB. Please follow image 14 to image 17 to accomplish this step.
Step 5: Solder the Pin Header to the PCB
The short part of the header pin should be soldered to the PCB and leave the long part for the outer connection. When soldering you need to use a stuff such as solder wire roll to raise it up before you solder.
Step 6: Solder the Jumper Wire to the Speaker
Please follow image 21 to image 24 to accomplish this step. Before we solder the jumber wires to the speaker we should melt some solder wire to the exposed part of the jumper wire and connection part of the speaker.
Step 7: Analysis
Actually this is a low frequency oscillation circuit that the frequency is about 1Hz. That means it oscillates one time per second. When press down the button switch, the electrolytic capacitor,C1 is charging, and V1 is conducted and then V2 is conducted and then V3 is conducted, and then V4 is conducted finally. However, the conducted state of V4 won’t last long, actually it is instant. Because when V4 is conducted, the voltage of the anode side of C2 is dropping down to about 0V rapidly that causes the voltage of the other side of C2 falls down to about 0V rapidly, the NPN transistor, V3 is cut-off. But in the meantime, the side of C2 connected to the base of V3 starts charging and for about 1 second the accumulated voltage reaches the bias voltage of the transistor, the V3 conducts again. These processes repeat again and again that generating the 1Hz signal to drive the speaker to make a Ticking Clock Sound Effect Circuit.
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