LM3914 12V Battery Level Indicator

The affection of this circuit is the LM3914 from civic semiconductors. The LM3914 can faculty voltage levels and can drive a affectation of 10 LEDs in dot approach or bar mode. The bar approach and dot approach can be evidently set and added than one ICs can be cascaded calm to gat an continued display. The IC can accomplish from a advanced accumulation voltage (3V to 25V DC). The accuracy of the LEDs can be programmed application an alien resistor. The LED outputs of LM3914 are TTL and CMOS compatible. 

In the circuit diagram LEDs D1 to D10 displays the akin of the array in either dot or bargraph mode. Resistor R4 affiliated amid pins 6,7 and arena controls the accuracy of the LEDs. Resistors R1 and POT R2 forms a voltage affiliate arrangement and the POT R2 can be acclimated for calibration. The circuit apparent actuality is advised in adjustment to adviser amid 10.5V to 15V DC. The arrangement of the circuit can be done as follows. After ambience up the circuit affix a 12V DC antecedent to the input.

Now acclimatize the 10K POT to get the LED10 afterglow (in dot mode) or LEDs up to 10 afterglow (in bar mode). Now abatement the voltage in accomplish and at 10.5 volts abandoned LED1 will glow. About-face S1 can be acclimated to baddest amid dot approach and bar blueprint mode. When S1 is closed, pin9 of the IC gets affiliated to the absolute accumulation and bar blueprint approach gets enabled. When about-face S1 is accessible pin9 of the IC gets broken to the absolute accumulation and the affectation goes to the dot mode. 

With little modification the circuit can be acclimated to adviser added voltage ranges. For this just abolish the resistor R3 and affix the top akin voltage to the input. Now acclimatize the POT R2 until LED 10 glows (in dot mode). Abolish the top voltage akin and affix the lower akin to the input. Now affix a top amount POT (say 500K) in the abode of R3 and acclimatize it until LED1 abandoned glows. Now abolish the POT, admeasurement the accepted attrition beyond it and affix a resistor of the aforementioned amount in the abode of R3. The akin adviser is ready.

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Solar Charger Circuit by LM317

Here is a solar charger circuit is used to charge lead acid batteries or Ni-Cd with solar power. Circuit harvests solar energy to charge a 6 volt battery 4.5 Ah battery for various applications. The charger has voltage and current regulation and voltage cut-off facilities.

The circuit uses a 12 volt panel solar energy and a variable voltage regulator IC LM 317. The solar panel consists of solar cells each rated at 1.2 volts. 12 volt DC is available from the panel to charge the battery. Load current flows through D1 to the voltage regulator IC LM 317. By adjusting the adjustment pin, voltage and output current can be regulated.

VR is placed between the adjustment pin and ground to provide an output voltage of 9 volt battery. Restrict resistance R3 load current and the diode D2 prevents the discharge of the battery current. Transistor T1 and zener diode ZD act as a cutoff switch when the battery is full. Usually T1 is off and the battery current load.

When the voltage at the terminals of the battery rises above 6.8 volts, Zener conducts and provides the current basis of T1. Then land becomes the output of the LM 317 to stop charging.

via : electroschematics.com

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2 Volt Battery Monitor by IC LM3914

This 2 Volt Battery Monitor by IC LM3914 circuit makes it possible to monitor the charging process to a higher level. Adjustsments end are simple and all you need is a digital voltmeter for the necessary precision. Connect an input voltage of 12.65 volt between the positive and negative poles and adjust the 10K potentiometer until the LED 10 lights up. Reduce tension and the sequence of all other LED lights. Control has been an enlightening about 11.89 volts.

At 12.65 volt and higher the battery is fully charged, and 11.89 is considered "empty". This circuit, with the components shown, uses less than 10 mA. Of course you can adapt this circuit for their own needs, making small modifications. The previous circuit is set to "point" mode, which means only one LED at a time goes on. To use the mode of "bar", then connect pin 9 to the positive supply rail, but obviously with increased current consumption. The brightness of the LEDs can be adjusted up or down by choosing a different value for the 4K7 resistor connected to pin 6 / 7.

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