5volts battery back-up

[nenayd]

in my project i remove the battery of my cellphone and connected it directly to 7805. But then realized when a power interruption has been occured...my pic system booted up but the cellphone remains off...it requires to press the "on" button of the unit.

my problem is what can i do to the cellphone to be able to boot up automatically when the power comes back...

my idea is to put a battery back up on it...but i dont know how...can anyone show me a simple circuit for this...thanks a lot.

 

[Nigel Goodwin]

in my project i remove the battery of my cellphone and connected it directly to 7805. But then realized when a power interruption has been occured...my pic system booted up but the cellphone remains off...it requires to press the "on" button of the unit.

my problem is what can i do to the cellphone to be able to boot up automatically when the power comes back...

my idea is to put a battery back up on it...but i dont know how...can anyone show me a simple circuit for this...thanks a lot.

Easiest way would be to leave the battery connected, and trickle charge ti from the external power - that way it will stay on for the life of the battery is the power disappears.

Or you could add a timer circuit, using a couple of 555's (or anything you wanted) to short out the power switch briefly a preset time after the power comes on (you need to wait a while, for it to power up).

 

[nenayd]

if i let the battery connected and it's charger as its main power source...there could be a possibility of damage to the battery.

 

[Nigel Goodwin]

if i let the battery connected and it's charger as its main power source...there could be a possibility of damage to the battery.

That's why I said 'trickle charge', you can leave the battery on 'trickle charge' permanently. Or you could build a decent quality charger, one which drops to 'trickle charge' when it's fully charged - but for your purposes a crude trickle charger should be good enough.