auto switch over

Discussion in 'General Electronics Chat' started by krishnanhemanth, Nov 15, 2010.

  1. krishnanhemanth

    Thread Starter New Member

    Feb 5, 2010
    hi every body
    i have a circuit that works on 6v dc with 1amp. the circuit has a dc jack input.
    the circuit can be powerd by batteries and also can be powerd by external power supply through the 6v dc power jack.
    present situation:
    a) power the unit using batteries and the system works
    b) power the unit using external power supply,then the battery power disconnects and the system works through external power source.
    c) remove the external power supply, the system still works because the battery is available.

    the problem
    The system fails to power up if the external power supply is switched off.
    Meaning if the external power supply is input through the dc jack and if there is any external power loss, the system fails to draw power from the battery because the pin is still in the dc jack.
    solution required
    what am i to do to see that the circuit draws power from the battery if there is an external power supply loss while the pin is still plugged in to the dc jack

    plz help

  2. eblc1388

    Senior Member

    Nov 28, 2008
    Make sure the external power voltage is slightly higher than the 6V battery voltage.