DIY a NE555 Circuit to Generate Sine Wave

This tutorial teaches you about how to DIY a NE555 circuit to generate sine wave. This affordable DIY kits is very helpful for you to understand the how can the capacitors work with resistors to control the charging and discharging time that to generate a sine wave.If you are a newbie in electronics please refer to Resistor Knowledge and Capacitor Knowledge to learn more.

The necessary materials:

3 x 1k ohm resistors

2 x 100k ohm resistors

1 x 15k ohm resistor

3 x 10k ohm resistors

1 x 1M ohm resistor

1 x 4.7k ohm resistor

1 x IN4007 diode

2 x NPN transistors

1 x Potentiometer

2 x 4.7μF electrolytic capacitors

4 x 104 ceramic capacitors

6 x header pins

1 x NE555 IC

Insert the related resistors into the printed

circuit board(PCB) respectively. Pleas kindly note that the corresponding resistance value is printed on the PCB like 10k in a rectangle. You must check and verify the resistance before you do this step. There are two common approaches to check the resistance of a resistor, one is read the color codes from its body, the other is much straiforward that utilize a multimeter to directly measure it out. However, reading the color codes is not a troublesome thing, for example, the resistance value of the resistor in the picture above is 10k ohms. How to know that? As we can see that, the 1st color band is brown which represents the digit number 1, the 2nd and the 3rd color bands are black which represents 0, and the 4th band is red which represents 100, let us connect them together and we get 100 x 100 = 10000ohms = 10k ohms. The 5th color band means the tolerance of the resistor that is brown represents ±1%. So, the big takeaway we can get from the color codes are resistance value and tolerance. In this case the resistance of the resistor is 10k ohms, the tolerance is ±1%. For more details of reading color codes from resistor please go to Read Color Codes.

Insert the resistors into the PCB one by one as shown in the picture above.After soldering them with the soldering iron station, cut off the superfluous part of the pins.

Insert the diode and capacitors into the PCB and solder them.

This step is a little bit hard to fulfil as when you are trying to solder the pins of IC on the back side of the PCB the IC can be loose and drop down to the surface of desk. Until you raise the PCB with a small thick thing such as a foam pad as shown below you will get it ready to solder successfully.Please beware of the semicircle symbols on both of the PCB and IC surrounded by red circles that they should be in the same direction.

The flat side of the NPN transistor should be on the same side of the diameter of the semicircle printed on the PCB.

Pleas note that electrolytic capacitors have polarity. DO NOT connect inversely or the capacitors will end up bombing. The long leg of electrolytic capacitor is anode while the short leg is cathode. If someone has trimmed the legs, try finding the white color band on the capacitor’s body. The pin nearest the white color band will be the negative, cathode pin.

So far the main part has been well built. Next step is to connect a voltage source of 5V to 9V with the circuit board. By connecting the cap to the corresponding header pin, you will be able to obtain a square wave, sawtooth wave, triangle wave and sine wave respectively.

In fact, the original wave go out from the NE555 circuit is square wave. How to turn the square wave to the different shapes of waves? This is where the resistors and capacitors come into play. Resistors have the ability to limit the current flow through, while capacitors have the ability to store energy. Capacitors can be cooperative with resistors to control the charging and discharging rates of the capacitors that to trim the waves to different shapes.

The below image is the RC circuits connected in series to generate the waves. When the square wave goes across R5 and C7, from this article, we can see that the discharging curve for a RC discharging circuit is exponential, so the RC circuit composed of R5 and C7 convert the square wave to sawtooth wave. Likewise, the R6 and C8 convert the sawtooth wave to triangle wave, the R7, R9 and C9 convert the triangle wave to sine wave.

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