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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Simple Continuity Tester Circuit Using 555 Timer

Normally we use continuity testing to check if a circuit, PCB or cable is continuous or not. It also helps us to check if a bulb is burnt out or not. Simply we can do the test by using a battery and a led or buzzer, but they are not precise or accurate.

Usually we use a continuity test multimeter which is little bit costly and bulky too. Also these give a positive indication even when there is 100 ohms of resistance between the probes.

So how to make a continuity tester which has no such kind of drawbacks. This circuit is built around a common 555 chip wired in astable mode. The continuity test circuit can precisely judge continuity as that low 6 to 8 ohms(which can be set by using the preset). Speaker is used to indicate the continuity.

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12v Battery Charger Circuit with Auto Cut off

This is a simple DIY charge controller schematic posted in response to a request by one of our readers on our facebook page. The main component of this auto battery charger circuit is a 555 timer which compares the voltage in the battery. It turns ON the charger if the battery voltage is below the variable preset voltage (12 volt chosen here) and turns OFF the charger if the voltage reaches 13.8 volt. The battery charging voltage of the charger can be varied by adjusting the variable resistor and maximum charging is limited by a 13.8V zener diode on the fifth terminal of 555 IC.

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How to Build a Digital Voltmeter of your Own?

How to build a voltmeter for DC voltage measurements without using multimeter testing? This is a simple digital voltmeter circuit that can measure voltages from 0V to 9V.The main part of this circuit is a dot bar display driver IC LM3914. Input voltage applied to this IC generates an output which is converted into a binary value by the priority encoder IC 74147. It is then displayed on the seven segment display by the help of a common anode seven segment display driver IC 7447.However the voltmeter accuracy of this digital voltmeter schematic is limited to a sensitivity of 1V.

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LED dot display based Battery charge level indicator circuit diagram

At many situations we need to display the amount of battery charge through some kind of indication methods like LED dot display or LED bar display. Here CG comes with a battery charge indicator circuit using LED dot display. This battery power level indicator circuit is build around LM3914 IC. It is able to sense voltage levels and is capable to drive a display of 10 LEDs in dot mode or bar mode.

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Simple LM35 Electronic Temperature Sensor Indicator Circuit

This is a simple temperature sensor circuit diagram using LM335 temperature sensor and LM3914 IC. Here the complete temperature range becomes observable through an array of LEDs. The LM35 is an integrated circuit temperature sensor for sensing temperature in degree Celsius scale. The LM3914 is an efficient display driver cum milli volt measuring IC and it is very easy to apply as an analog meter circuit.

In this temperature monitoring system the milli volt output from the LM35 is converted to digital temperature indicator by means of LM3914 IC. The LEDs in this circuit shows the temperature levels digitally via 20 steps. This temperature indicator circuit is absolutely the simplest to build, as it is based on a single stand alone IC LM3914 by Texas Instruments, which executes the entire process of indicating the temperature range.

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Simple fire alarm- thermistor circuit diagram

Here i-St@r comes with a simple and automatic fire alarm and detection system. This fire detection alarm circuit is based on thermistor. What is a thermistor? A thermistor is nothing but a variable resistor whose resistance increases as temperature decreases. Fire detection is simply possible via this low-cost alarm circuit.A simple potential divider arrangement using thermistor is capable of sensing the temperature (presence of fire) and alerting us with a warning signal. This is suitable for your home security systems. Also school students can do this fire detector circuit as their high school science fair projects. Here I will explain in detail about fire alarm circuit wiring with animation/ simulation of fire alarm.

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Low water level indicator alarm circuit for Water tank

Most of the time we wish to have a water low level alarm (liquid level alarm) circuit to know if the amount of water inside the tank has decreased in order to switch ON the water pump set. Don’t worry about that, we can implement a simple water low level indicator sensor alarm circuit for your home or office with the help of liquid level probes. Our water level sensor alarm detects the fluid level using a transistor switching circuit. We have already discussed about different types of fluid level alarms and water tank level indicators, they are mainly to detect overflow from the water tank. But this one indicates that the tank is near to be emptied.

(This circuit is posted as per the request from one of our reader MR. Ramz)

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Water quality checker project simple circuit diagram

How to measure water purity? How to test water quality using a simple electronics project? You can perform water purity measurement and water quality analysis using this water purity checker circuit. This circuit is built around a simple LDR (Light Depended Resistor) and some discrete components. The most attractive feature of our water purity tester is that it gives a beep sound when the water purity level goes below a threshold value. You can implement this simple electronic project in your domestic water tank for water quality monitoring and testing.

The detailed circuit diagram and constructional details of water quality testing device are given in this article. Also you can integrate this with our previous circuit of water tank level controller, the resulting circuit will be an advanced engineering project. When the amount of mud in the water reservoir exceeds a threshold value, our water quality testing equipment starts producing a beep sound to alert us that the quantity of mud in the water has increased and needs a cleaning.

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Water tank overflow liquid level sensor alarm circuit

Water tank overflow liquid level sensor alarm circuit is a simple electronics project for school students. In the previous articles we had discussed about numeric water level indicator and water level controller circuit ,but those circuits are much complex and are advanced projects for engineering students. The circuit schematic for water tank over flow alarm is shown below. It produces a beep sound when the water tank  is completely filled by water.

The advantage of this project circuit is that it saves water from accidental over flow. The circuit simply consists of a liquid (water) level sensor or water level detector with BC547 transistors. Any electronics hobbyist can implement this circuit at your home or work places at a cheap rate ($0.5). The heart of this water over flow circuit is  the transistor switching part. So this circuit always prevents the wastage of water when you forget to switch OFF the motor pump set after switch ON.

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Mobile cell phone detector (sniffer) circuit diagram: engineering and diploma project

Here is a simple engineering project circuit of handy mobile cell phone detector (sniffer). This pocket-sized mobile communication detector or sniffer can sense the existence of a mobile device. So it can be used to avoid the use of mobile phones in private rooms, examination halls, etc. It is also useful for detecting the use of mobile phone for spying and other related activities. The circuit can detect incoming and outgoing calls, SMS, MMS, GPRS usage and video transmission even when the mobile phone is set aside in silent mode. The instant bug detects RF (Radio Frequency) transmission signal from a mobile phone, it produces a beep sound alarm.

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Simple battery charger circuit and battery level indicator with low battery recharge alarm

This is a simple 12V rechargeable smart battery charger circuit. You can use this best battery charger circuit as car battery chargers, Inverter battery charger, Emergency light battery charger etc. An automatic indicator alarm circuit also comes along with this battery charger schematic. The main advantage of this indicator is that a buzzer informs us when the battery needs recharge. This circuit schematic definitely helps for your daily life battery charging applications.

Also Read:

•  12v Battery Charger Circuit with Auto Cut off
•  LED dot display based Battery charge level indicator circuit diagram

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Numeric water level indicator- liquid level sensor circuit diagram with 7 segment display - Engineering project

Water level indicator circuit or liquid level sensor displays the current level of water in any water tank reservoir. Here we use a simple real time encoding circuit with 7 segment display. It can also be used as a water level meter or water level detector. Combining this project with our previous post ‘Automatic water tank level controller’ will give a complete automated control system for home and industries. This water level sensor consist of 8 to 3 encoder (74148- 8 line to 3 line priority encoder) with some water sensor arrangement. The encoded level is displayed on a 7 segment digital display. This circuit uses one 'Hex display', it does't require driver IC to encode. It makes the implementation simple. You can use '7 segment display' with appropriate driver IC 7447.

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