12V Battery Level Monitor

LM3914 IC is the IC used in this circuit. This IC is also called as dot display driver or bar display driver. It has the ability to sense the magnitude of input analogue signals and able to drives up to 10 LEDs at a time. There are two modes of displays we can choose; dot or bar, depends upon the purpose. Pin 9 is connected with power supply and it tends to get a graph output else IC gives dot display.

lm3914 circuit

We can use LM3914 IC to monitor 12V battery level. The power supply needed for this circuit will get from the input battery itself. LED D1 to D10 will show the level of battery. By using very simple components, we can easily monitor the battery level with this IC.

1.IC LM39141
3.Resistor 56KΩ
Resistor 18KΩ
Resistor 4.7KΩ
4.Variable Resistor 10 KΩ1

LED Emergency light

The portable LED lamp circuit with simple components are so easy to make. Here we are using high luminescent LEDs for making the lamp. The circuit needs 6V rechargeable lead acid as power supply.

Circuit diagram


The circuit will get AC 230V as input voltage, this supply collected by the step-down transformer that will regulate AC into fluctuated DC. The fluctuation is overcome by using bridge rectifier connected along with the transformer. The capacitor C1 stabilizes the DC supply on the circuit.
The 5V two channel relay used here to switch the power action ON/OFF when the power gets into the regulator IC 7805. There is a 6V DC battery used in the circuit in connection with the relay, in between the relay circuit the diode 1N4007 is used to direct the voltage path. The output pins from regulator IC 7805 and negative pole of the 6V DC battery are connected with the seven LEDs serially along with each resistor in one side.

Components List

1.Transformer Stepdown 
(230V to 9V)500mA
2.Diode 1N40078
3.Relay 9Volt1
6.IC 78051
7.Capacitor 100uF & 0.1uF1
8.Resistor 220 Ω7
9.LED white7