12v Led Battery Level Indicator Circuit (Led Bar Graph)

Most often, I come across many situations where I needed a lead acid battery voltage level monitoring circuit. Here is an example; I use lead acid battery for my inverter and so it requires constant voltage charging. But inverter provides current charging only, so I use a self-made battery charger circuit which provides a constant 14 volt charging. Charger output should be maintained at 14 volt; else it will reduce the battery life.

This made me think of building a battery voltage monitor circuit one for myself, and here is my circuit design. It can indicate voltages using Led’s in levels of 8 with variable sensitivity. You can use this led level indicator for monitoring battery voltage.

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Op amp 741 Non Inverting Amplifier Circuit with Simulated Waveform

Non-inverting amplifier is one of the most popular op amp circuits similar to op amp inverting amplifier circuit. It provides a gain to the input signal without any change in the polarity. If a sine wave is fed to the input of this op amp non inverting amplifier, the output will be an amplified sine wave with zero phase shift. Here the input is applied to the non inverting terminal of the op amp. The non inverting amplifier gain is given by the expression A=1+Rf/Ri where Rf is the feedback resistance and Ri is the input resistance. The input impedance of non inverting amplifier is extremely large, typically 100MΩ.

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Zero Crossing Detector (ZCD): Comparator circuit using 741 op amp

Zero crossing detector(ZCD) is a voltage comparator that switches the output between +Vsat and –Vsat (Vsat: Saturation voltage almost equal to 14V) when the input crosses zero reference voltage. Then what is a comparator? In simple words comparators are basic operational amplifier circuits that compare two voltages simultaneously and switches the output according to the comparison. We can say zero crossing detection circuit is a comparator example. We will discuss in detail about comparator in our upcoming articles. Inverting zero cross detector circuit schematic using op amp 741 IC is shown below along with working, input output wave forms.

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Wein Bridge Oscillator using ic 741 op amp

Wien bridge oscillator is an audio frequency sine wave oscillator of high stability and simplicity. Before that let us see what is oscillator? An oscillator is a circuit that produces periodic electric signals such as  sine wave or square wave. The application of oscillator includes sine wave generator, local oscillator for synchronous receivers etc.

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Summing amplifier/ Inverting adder circuit using op amp 741

Summing amplifier or an adder is used to sum two signal voltages. Voltage adder circuit is a simple circuit  that enables you to add several signals together. It has wide variety of applications in electronic circuits. For example, on a precision amplifier, you may need to add a small voltage to cancel the offset error of the op amp itself. An audio mixer is another good example of adding waveforms (sounds) together from different channels (vocals, instruments) before sending the combined signal to a recorder.

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Binary Phase Shift Keying (BPSK) modulation using CD4016 with Simulated output waveform

In binary phase shift keying (BPSK) modulation scheme, the phase of a carrier is changed in accordance with the digital pulse signals. BPSK modulator is basically a phase modulator. Here the transmitted signal is a sinusoid of fixed amplitude. It has one fixed phase when the data is at one level and when the data is at the other level, phase is shifted by 180 degree. Binary phase shift keying method has variety of applications in digital communications systems such as the wireless LAN standard, IEEE 802.11, digital modems, wireless telephone networks etc.

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Digital to analog converter using R 2R ladder network and 741 op amp with simulated output waveform

What is DAC? Digital to analog converter (DAC) is used to get analog voltage corresponding to an input digital data. Data in binary digital form can be converted to corresponding analog form by using a R-2R ladder (binary weighted resistor) network and a summing amplifier. It is more common and practical. Below is the circuit and output simulated waveform of R-2R ladder network DAC. This circuit also uses an op amp (741) summing amplifier circuit.

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Triangular wave generator using Op Amp 741, circuit working and simulated output waveform

Operational amplifier based triangular wave form generator is simple circuit that is widely used in function generators. Here is the circuit for Triangular wave generator using 741 op amp. We know that the integrator output waveform will be triangular if the input to it is a square wave. It means that a triangular wave generator can be formed by simply cascading an integrator and a square wave generator, as illustrated in figure.

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Op Amp 741 Inverting Amplifier Circuit, Simulation with output wave form and working

Inverting amplifier is one of the most popular Operational Amplifier circuits. The output changes in such a way that tries to avoid saturation and counteract the change caused by the input. This makes the amplifier stable. The amplifier tries to resist change and so avoid saturation. As the open loop DC gain of an operational amplifier is extremely high,

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RC Phase shift Oscillator using 741 op amp- Design and output waveform simulation

RC phase shift oscillator is a sinusoidal oscillator used to produce sustained well shaped sine wave oscillations. It is used for different applications such as local oscillator for synchronous receivers, musical instruments, study purposes etc. The main part of an RC phase shift oscillator is an op amp inverting amplifier with its output fed back into its input using a regenerative feedback RC filter network, hence the name RC phase shift oscillator.

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