12V battery level indicator circuit (LED bargraph)
12V battery level indicator circuit with LED bar /dot display LM3914. The heart of this circuit is the LM3914 from national semiconductors. The LM3914 can sense voltage levels and can drive a display of 10 LEDs in dot mode or bar mode. The bar mode and dot mode can be externally set and more than one ICs can be cascaded together to gat an extended display. The IC can operate from a wide supply voltage (3V to 25V DC). The brightness of the LEDs can be programmed using an external resistor. The LED outputs of LM3914 are TTL and…
Read More24V lead acid battery charger circuit
Description. This lead acid battery charger circuit is designed in response to a request from Mr.Devdas .C. His requirement was a circuit to charge two 12V/7AH lead acid batteries in series.Anyway he did not mentioned the no of cells per each 12V battery. The no of cells/battery is also an important parameter and here I designed the circuit assuming each 12V battery containing 6 cells. When two batteries are connected in series, the voltage will add up and the current capacity remains same. So two 12V/7AH batteries connected in series can be considered as a 24V/7AH battery. The circuit given…
Read MoreAutomatic changeover circuit
Description. The circuit diagram shown here is of a automatic changeover switch using IC LTC4412 from Linear Technologies. This circuit can be used for the automatic switchover of a load between a battery and a wall adapter.LTC4412 controls an external P-channel MOSFET to create a near ideal diode function for power switch over and load sharing. This makes the LT4412 an ideal replacement for power supply ORing diodes. A wide range of MOSFETs can be driven using the IC and this gives much flexibility in terms of load current. The LT4412 also has a bunch of good features like reverse…
Read MoreBattery eliminator circuit
Description. Here is the circuit diagram of a battery eliminator circuit that can be used as a replacement for 9V PP3 batteries. The circuit given here can be used to power any device that operates from a 9V battery. The transformer T1 steps down the mains voltage and bridge D1 performs the job of rectification. Capacitor C1 is a filter. IC LM317T is the regulator here. The value of R1, R2 and R3 are so selected that the output voltage of IC1 will be steady 9 volts. Circuit diagram. Notes. Assemble the circuit on a good quality PCB. Transformer T1…
Read MoreNi-MH battery charger using LT4060
Description. This is the circuit diagram of a very powerful and efficient Ni-MH battery charger using IC LT4060 from Linear Technologies. In addition to Ni-MH batteries Ni-Cd batteries can be also charged by slightly modifying the circuit.For charging Ni-Cd batteries connect the CHEM pin (pin12) of the IC to +Vcc.Here the circuit is configured to charge 2 cells connected in series. By altering the connections of SEL0 and SEL1 pins, upto 4 batteries in series can be charged using this circuit. For charging a single cell, connect SEL0 and SEL1 pins to GND. For charging two cells, connect SEL1 to…
Read MoreNi-Cd battery charger circuit
Description. This circuit can be primarily used for charging 12V Ni-Cd battery packs. Any way 6V and 9V battery packs can be also charged by using this circuit a little compromise on power efficiency. The built in automatic current regulator regulates the charging current to somewhat 4 amperes. When the charging current reaches 4A, the voltage across resistor R1 becomes 0.7V and switches the transistor Q1 ON. The transistor Q2 which is now in ON state will shorts the base of Q3 to ground and inhibits the biasing of Q4 through which the charging is done. That is how the…
Read MoreCar battery charger
Description. Given below, is a very simple circuit that can be used for charging car batteries. In this circuit there is facility for monitoring the charging current and voltage. The circuit is based on the IC MC78T12ABT from Freescale.The IC is nothing but a 7812 in TO-3 package with 3A capacity. The transformer T1 steps down the mains voltage and diodes D1&D2 does the job of rectification. Capacitor C1 does the filtering and C2 acts as a decoupling capacitor. The ground terminal of IC1 is lifted to 2.1V using the diodes D3 , D4 and D5 . So the output…
Read MoreBattery charging indicator circuit
Description. This simple circuit can be used to monitor whether a battery is charging or not. The voltage comparator IC LM393 is the heart of this circuit. The LED D1 will remain ON whenever there is at least 25 milli ampere current flowing to the battery. This particular circuit is designed for a 12V battery with charging current less than 1A.By slightly modifying the component values, the charging current and voltage can be modified. Circuit diagram with Parts list. Notes. Assemble the circuit on a good quality PCB. The IC1 must be mounted on a holder. Do not use this…
Read MoreFlashing battery monitor
Description. Here is a simple circuit in which an LED will continue flashing as long as the voltage of the battery to be monitored is above the set level.The transistors Q1 and Q2 are wired as a complementary astable multivibrator.The circuit can operate from a voltage range from 6V to 12V. The voltage level at which LED has to stop flashing can be set by adjusting the preset R4.When the battery voltage reaches the threshold the flashing frequency decreases and when the voltage goes below the threshold the LED becomes OFF.The diode D1 is used to compensate the changes in…
Read MoreBattery operated mini night lamp
Description. This is the circuit of a low power LED night lamp that will automatically switch OFF at day time. The CMOS timer IC TS555CN is wired as a square wave generator operating at around 5Hz.The output voltage from the IC1 is doubled using the combination of capacitor C2 and diode D2 in order to drive the LED. The LED can be a bright white LED. At day time the resistance of LDR drops to few K Ohms and inhibits the IC from producing oscillations. Circuit diagram with Parts list. Notes. Assemble the circuit on a general purpose PCB. The…
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