Low battery indicator using op-amp amplifier
This ultra-short blog post describes my attempt at a generic low-battery indicator that could hopefully be reused for many projects. This circuit alerts the user when the battery needs changing or charging. A couple of circuits are described here. One of them lights up a warning LED whenever the voltage drops below a certain value. The other circuit can be used to replace the typical power-on LED.
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Considerations In Designing Single Supply, Low-Power Systems Part II: Battery Powered Systems
I Description of LM II Design of the System. IV Test Results of the System. The LM series are general-purpose operational amplifiers. It is intended for a wide range of analogue applications. The high gain and wide range of operating voltage provide superior performance in integrator, summing amplifier, and general feedback applications.
LM has both inverting inputs and non-inverting inputs. The output of the operational amplifier is the product of gain and input voltage. The low battery alarm system is mainly composed of reference power supply circuit, sampling circuit, voltage comparator circuit and output circuit.
The reference power supply circuit consists of a voltage regulator and a current limiting resistor, which is added to the inverting input of the voltage comparator and provides a reference voltage for it. The sampling circuit is composed of two resistors in series to form a series voltage divider, which is used as the input signal of the whole circuit, and a part of the battery voltage is compared with the reference voltage.
The voltage comparator circuit judges whether the output is high level or low level by comparing the voltage of the reference power supply circuit and the voltage of the sampling circuit. The output circuit judges whether the light-emitting diode is in the conducting state by the received output voltage from voltage comparator, thereby giving an alarm signal to indicate the battery power is too low.
Figure 1. Structure of the System. The hardware circuit of low battery alarm system is shown in Figure 2. Figure 2. Hardware Circuit. The reference power supply circuit consists of current limiting resistor R2 and voltage regulator VDZ. This system takes the stable voltage of the regulator as the reference voltage of the comparator LM, and connects it to the inverting input of the LM The stable voltage is 5V. R1 and R3 are connected in series to form a sampling circuit, which is connected to the in-phase input terminal of LM The intermediate point is the sampling voltage, that is, taking part of the battery voltage as the detection voltage, i.
The output circuit consists of R4 and LED. According to the voltage value at the output of the voltage comparator to determined whether the LED is on or off.
It can be seen from Figure 4 that the potential of pin 6 is higher than the potential of pin 7. LED do not emit light because of the reverse voltage. This indicates that the battery voltage is normal and the alarm function is not activated.
At this time, the potential of pin 7 is higher than the potential of pin 6, the LED is turned on due to the forward voltage. And the light indicates that the battery power is too low. The alarm function is activated.
Figure 3 shows the wiring structure of low battery alarm system. The automobile battery is connected to the voltage comparison device through the car key switch, and provides power for the automobile circuit load lighting system, instrument system, etc. When the battery voltage is normal, the load voltage is normal. And the vehicle can start normally. The instrument system can display and work normally. When the battery voltage is too low, the voltage comparison device will send out a light alarm signal.
At the same time, if the power supply voltage can not reach the required voltage level of the system, the corresponding lighting, instrument and other systems will not operate. Figure 3. Wiring Diagram of the System. It can be seen from table 1 that when the battery voltage is lower than 10V, the alarm indicator is on; when the battery voltage is higher than 10V, the alarm indicator is off. Therefore, the circuit can give an alarm when the battery voltage is lower than 10V, and stop when the battery is recharged to above 10V again.
The alarm system does not work when the output voltage of the battery is above 10V. It fully shows that the design scheme of the circuit is correct and feasible. Test Results of the System.
Battery voltage status. Alarm indicator status. An LM operational amplifier is a DC-coupled high gain electronic voltage amplifier. It has only one op-amp inside.
An operational amplifier IC is used as a comparator which compares the two signal, the inverting and non-inverting signal. It was first manufactured by Fairchild semiconductors in the year The number indicates that this operational amplifier IC has 7 functional pins, 4 pins capable of taking input and 1 output pin.
The most common Op-Amp is the and it is used in many circuits. Its main purpose is to amplify increase a weak signal - a little like a Darlington Pair. Operational amplifiers have two power supply rails because they usually need to swing bipolar - output voltages that go either positive or negative in response to the normal range of input signals. Without the dual supplies the output signal would clip at the ground potential.
Testing a IC The circuit is commonly called as voltage follower. A voltage is applied to pin3 of the op-amp through the variable resistor 10K. All we need to do is to verify whether the voltages V1 and V2 are exactly same or not.
Check them using a multi-meter. An op amp is a complex electronic device, which consists of resistors, capacitors, transistors and diodes. It is commercially available in integrated circuit form.
Most commonly available and used op amp IC is IC The IC is a small chip. It comprises eight pins. Gain-Bandwidth Product: For an Op-Amp the gain, G is defined as the gain when a signal is fed differentially into the op-amp and no feedback loop is present. Short circuit and overload protection provided. In theory, the dc output voltage will be zero if both the inputs of the IC are connected to the ground. Large common mode rejection ratio CMRR and differential voltage ranges.
No external frequency compensation is required. Um, the LM is an audio power amplifier with a KHz bandwidth. The LM is an operational amplifier with a typical unity gain bandwidth of 1 MHz.
In other words, they are entirely different sorts of things and not at all interchangeable. Neither is very good at higher frequencies. Much better part in almost every dimension than the LM It will likely perform slightly better too as it has a slightly better specification frequency, slew rate, etc , plus you get four identical op amps in a single 14 pin package.
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Irene 2 Sep Alliance Semiconductor Co Ametherm Amphenol Aerospace Operat Author: Irene. Date: 13 Oct Introduction In recent years, with the continuous development of new technologies, storage batteries as a power source not only play an important role in transportation railroad, subway, ship , power generation, communications, aerospace, chemical, traditional automobiles and other industries.
In addition , batteries have also begun to be used in the fields of electric vehicles EV and hybrid electric vehicles HEV as power sources or power auxiliary power sources. Do you know what are 2 features of batteries compared with disposable rechargeable batteries? That is multiple recycling and high efficiency and energy saving. When the car is not started, it must rely on the battery to supply power to the starter until it drives the engine to rotate.
When the battery voltage is insufficient or the battery is damaged , it is difficult to provide sufficient power, thus causing the engine to fail to run. Therefore , this blog proposes the design of a low-battery alarm system for car batteries based on LM In general, when the battery voltage drops to a certain limit, it will send out a reminder. The principle of the reminder is that the circuit judges whether the battery is working normally by installing a sound and light signal alarm system.
Low Battery Level Monitor Using Op-Amp 741
In this tutorial, we are making a Battery High Low monitor. Various batteries ranging from 6 to 12V can be monitored through this circuit. The main component of this circuit is a low-cost LM operational amplifier IC. It contains two separate high gain op-amps in one chip.
Operational Amplifiers (Op Amps)
Parts Used:. R1 — 1M. R2 — K. R4 — E. D2 — IN L1 — LED any color. U1 — Op-Amp BT1 — 12V. Circuit Description:. A op-amp is employed as a voltage comparator.
Battery High Low Monitor using LM358
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Battery Level Indicator for any Battery
For adjusting the circuit you have to use an adjustable power supply and set its voltage on Now again change the power supply voltage to 12V and adjust the 10K variable resistor connected with pin 2 of the IC until the red LED goes off. After making these settings make a final test with the circuit and again increase the power supply voltage to After these adjustments your circuit will be ready to use with your 12V batteries. Now on fully charged battery or on When the battery voltage falls on
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The proposed circuit was requested by one of the avid readers of my blog. It is a low battery warning indicator circuit using opamp IC and can be used for monitoring a particular low battery voltage threshold. The above circuit can be modified by adding a relay stage for controlling a particular stage which may be relevant to the low battery cut of actions. The above low battery indicator circuit can be even further improved in the following manner for controlling both lower and the upper charging thresholds:. Apply a Confirm by flipping the preset as above. Ignore the lower relay as it will switch ON as soon as the input supply is switched ON, so its operation is obvious. That's it, the low battery warning circuit is all set now and will accurately respond to the above settings or any different setting that may be preferred and implemented by the particular user.
The circuit shows three state of battery voltage i. The circuit of battery voltage state indicator is build around very popular and low costs op-amp IC This circuit uses two op-amps in comparator mode, which compare the battery voltage with references voltage.
Part I of this two-part series Designs using ac line power appeared in the last issue of Analog Dialogue In it, we discussed the implications and performance tradeoffs in converting to a single-supply system using conventional i. We continue here with the considerations involved in design for low-power operation, particularly for portable and remote applications with batteries. In a battery-powered system, time is the critical parameter. Unlike ac-powered systems, where supply voltage varies within a specified range and the availability of rated current is unlimited in duration, a battery can only supply power for a finite length of time before it requires recharging or replacement.
I Description of LM II Design of the System. IV Test Results of the System. The LM series are general-purpose operational amplifiers. It is intended for a wide range of analogue applications. The high gain and wide range of operating voltage provide superior performance in integrator, summing amplifier, and general feedback applications.
Amplifiers and Comparators Minimize menu. Please log in to show your saved searches. ST's operational amplifier portfolio provides a unique choice of high performance, low power, precision op amps and tiny packages. It addresses voltages from 1.
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