build backup supply for pic

[potetojb]

hello..

i want build buckup supply for my pic. can some one help me.

i use adapter for supply my pic,but if the supply my pic if off and the data is lost.
so i want build backup supply for supply my pic if the adapter supply off.

i realy need help.

or some one have circuit for rechargeable batteries.

or some know how to save the data in PIC

 

[Tohu]

Hi,
you have a several way. First, you can put battery, regular or accu, wih diode OR you will switch battery and adapter to the voltage regulator. Second way is to use a only capacitor, and put the proccessor in sleep mode, the wake up evvent will be adaptr switching on. The hird, and may be best way, is to forgot about power supply backup and use EEPROM to stor data, or external NVARM or MRAM.

 

[potetojb]

thank

now i know how to write and read data to eeprom.

now i success buld backup supply. but the problem is i want use rechargeable batteries in buckup supply circuit. i dont know how can i charge the batteries.

can some one share the circuit for rechargeable batteries..

 

[spdchk]

I designed this circuit to charge a 9V re-chargable battey to keep my PIC real-time
clock running in case of power failure.

R1, the 1k POT can be tuned to the desirable voltage level for the battery.
The battery MUST be higher than 7.5 volt, so you can use any battery up to 12V.

Remember to alway set the charge voltage at about 15% above normal battery
voltage, eg. a 12 battery usually charges at 13.8V

The 5V out goes towards the PIC circuitry, and the 12V output was used as the
power supply for solenoids and other higer voltage equipments/devices

 

[nikhilele]

if we are using 12V battery then we have to keep 13.8 and converting 13.8V to 5V heats up the 7805 regulator