In this tutorial, I will explain how to design a sine wave inverter made with a solar panel, and I simulate it in Proteus design suite. The inverter will be designed with the 555 timer IC as the oscillator. Basically, we know that the 555 timer IC is used to generate a square wave oscillation, but in this tutorial, I will show you how you can use the 555 timer IC circuit to obtain a sine wave oscillation, which you can in turn use with a step-up transformer to obtain a sine wave inverter.

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## What is a solar inverter?

A solar inverter is a device that converts a direct current to an alternating current which can be used to power devices that work with alternating current. In this design, the direct current used for the circuit is the direct current generated from the solar panel.

## Parts of the sine wave inverter

**The oscillator circuit.****The voltage transformation circuit**

The aim of designing an inverter, is to obtain an alternating voltage that can be sinusoidal or square wave. Most times, a sinusoidal wave or sine wave inverter is preferable to the square wave inverter due to the effects both has on the device they are used with.

It is easy to design a square wave inverter than a sine wave inverter, because the core parts needed to design a square wave inverter are cheap and readily available than those used for a sine wave inverter. However, there are clever ways to electronically convert a square wave signal to a sine wave signal, once that is done, one can utilize this output to make a sine wave inverter. This was what I did in this design.

A square wave oscillator was converted to a sine wave oscillator, this sine wave oscillator was in turn used to design the sine wave inverter that was simulated in Proteus circuit simulator. If you do not have Proteus already installed on your computer, you can download Proteus with the Proteus download button below.

The 555 timer IC is a powerful IC that is used for making a monostable and astable multivibrator. Check my tutorial on what is a 555 timer and how to use it .

In this tutorial, I used the astable multivibrator mode of the 555 timer IC to produce a perfect square wave oscillation with 50% duty cycle and 50Hz frequency in the Proteus simulation. To realize this, we used the circuit diagram and calculation below.

The circuit above can be used to generate a 50% duty cycle with a 555 timer IC. *Note that in the inverter circuit, the battery was replaced with the solar panel.*

When we say duty cycle, what we mean is that the time the output voltage from the IC stays ON is equal to the time the output stays OFF. See image below:

Looking at the 555 timer circuit diagram, here is what happens; to have a 50% duty cycle, we would want the capacitor C2, to be charged at the same rate it is discharged. And this capacitor can be charged through resistor R1 and R2, and can be discharged through resistor R2. But, to make sure that it is charging only through resistor R1, and is discharging through only resistor R2, we connected the diode D1 and D2. Diode D2 will ensure that the capacitor does not charge through resistor R2, and diode D1 will ensure that the capacitor discharges only through R2. This will ensure a 50% duty cycle for the oscillation.

To obtain 50Hz frequency using this very design, you can use the formula below, with this formula, you will assume some component values, and use the formula to obtain the appropriate values for the remaining components.

ON time (ton) = 0.694(R1)C in seconds(s) [because capacitor is charging just through R1]

OFF time (toff) = 0.694R2C in seconds (s) [because capacitor is discharging just through R2]

Vibration cycle time (T) = ton + toff in seconds(s) [total time of the oscillation]

=0.694(R1)C+0.694R2C =0.694C(R1 +R2)

= 0.694C(R1 + R2) = 0.694(R1 + R2)C

= 0.694(R1 + R2)C

Frequency (f): 1/T in hertz (Hz) [frequency of the oscillation]

Frequency = 1/0.694(R1+R2)C

So, in your calculation, you will take Frequency to be 50Hz, you then assume any values for any two of R1, R2 and C, then, you can use the formula to obtain the value for the third parameter.

Once you have obtained the values for the various components you will use for the design and simulation, you will then open your Proteus circuit simulation software to carry out the simulation. If you do not have Proteus on your computer, use the “**Download Proteus**” button below to download Proteus V8.11 on your computer.

After installing Proteus on your computer, go ahead and draw the circuit in Proteus as shown below:

The solar panel Proteus library used in this simulation was downloaded from the engineering projects website: https://www.theengineeringprojects.com/

The various components you need for the simulation and their values are given below.

- 555 timer X 1
- 10nF capacitor X 1
- 20uF capacitor X1
- 144uF capacitor X 1
- 1n4001 diode X 2
- LED X 1
- 100Ω resistor X 3
- 80Ω resistor X 1
- Solar panel X 1
- Tip41 transistor X 1
- Tip42 transistor X 1
- 12 to 220V step-up transformer

## Sine wave inverter circuit explanation

If you made the connections exactly as shown in the circuit diagram above, you will obtain a perfect square wave at pin 3 of the 555 timer IC. This square wave oscillation is sent to a switching pair of Tip41 NPN and Tip42 PNP bipolar junction power transistors through a 20uF capacitor; the exponential charging and discharging of the capacitor C2 reshapes the square wave to a sine wave.

Now, as the pair of transistors switch, they drive the direct current from the solar panel power supply to produce a sine wave alternating current at the primary side of the transformer. This sine wave voltage is induced to the secondary side of the transformer to produce a 220V sine wave inverter that can be used to power domestic appliances in the house.

Also, note that this is a simulation, hence, electronic components like the transformer need to have there parameters adjusted to give the expected result. If you want to learn how to use a step-down transformer and a step-up transformer in Proteus, see the tutorials below.

The waveforms of the simulation are shown below. This includes the square wave and the sine wave.

The square wave in yellow is the output waveform from the 555 timer IC, and the sine wave in blue is the sine wave inverter output voltage wave form. This shows how we can convert a square wave from a 555 timer IC to a sine wave that can be used to produce a sine wave inverter.

For the power output of the inverter, we use the transformer formula to calculate that.

Vs x Is = Vp x Ip

We have

Vs = 220V

Vp = 12V

Ip = The current of the solar inverter

So, if we assume the solar panel current is 50A, then we can calculate the output power of the inverter.

Is =?

Is = Vp x Ip

Vs

12 x 50/220 = 600/220 = 2.72A

Therefore, the output power of the inverter will be

Power = Vs x Is = 220 x 2.72 = 598.4W

If you have any question concerning the simulation, do not hesitate to post it in the comment section.

you can checkout other Proteus simulation videos I’ve made in the past:

How to simulate an astable multivibrator with a 555 timer

How to simulate a step-down transformer in Proteus

How to simulate a scrolling text display in Proteus

Battery level indicator simulation in Proteus

How to simulate dark activated light/street light in Proteus

How to simulate Arduino in Proteus