Battery Backup Supply | Electronic Project Circuits

Posts Tagged ‘Battery Backup Supply’

DC Adapter with Battery Backup

With just a low cost DC adapter and the circuit described here it is possible to build a low cost stabilised, uninterruptible 9 V supply. On the grounds of safety and economy, a simple unstabilised 12 V D.C. adapter is used as the power source, a universal adapter with its output set to 12 V will do equally well. The output voltage of an adapter under low load conditions (up to approximately 1/3 of the rated output current) is over 15 V, even at the rated output current, there will be sufficient voltage to supply a 9 V voltage regulator.

Regulator 6V 3W for a Hub Dynamo bicycle

This is a regulator for a 6V/3W bicycle hub generator system. The purpose is to manage the powering of bicycle lights from the hub generator and from rechargeable batteries, to charge the batteries using excess power from the generator, and to provide intelligent charging of the batteries from an AC adapter, when needed.

The switch has three positions: charge-off-light. In the charge position, the bicycle dynamo charges five AA NiMH batteries if those are drained. If the batteries are reasonably full, then the circuit draws virtually no power. In the light position, if the dynamo’s average voltage is below some threshold value, then the bicycle lamps are fed by the batteries aided by the rectified dynamo If the dynamo voltage is high, the lamps are fed directly by AC from the dynamo and the dynamo excess power is used to recharge batteries. The direct use of AC maximizes efficiency. Additional circuitry is provided for an intelligent charging of the batteries from an outlet using a 12V AC or DC adapter. Practice shows that that additional circuitry may be redundant. A flickering green LED indicates the activity of the dynamo in the charge mode and the fact that the light is fed by AC in the charge mode. A red LED indicates the fast charge state when the charging is done from an outlet.

Source: http://www.nscl.msu.edu/~daniel/sreg.htm

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Categories: Automotive, Power supply Tags: Battery Backup Supply, bicycle dynamo circuit

Battery Backup Supply with IC 7812 and 7805

Here is circuit 9V power supply regulator with battery 12V backup system.
Use IC 7812 and 7805 control voltage output by R3 1K output 9V 1A max.

This is a 9V power supply which will work even on power failure. It uses a rechargeable battery and regulators. A transformer with 15-0-15 AC volts output is required. In the first regulator U1 the output is lifted up by 1.4V and in the second regulator U2 by a resistor divider. In the second regulator the voltage across resistor R3 is 5V, so the current is 5V / 1K = 5mA this adds to the quiescent current of 5mA from the regulators ground terminal and flows into the resistors R1 and R2 in parallel which form 404 ohms, 10mA thru 404 ohms is 4V. So the output will be 5 + 4 = 9V. Note that the charge and discharge paths of the battery are separated with diodes.

Source:http://schematics.blogspot.com/2004/10/battery-backup-supply.html
Thank you.