[moved] How can I add a backup battery to keep my pic microcontroller project working

[moved]how can i add a backup battery to keep my pic microcontroller project working

Hi All,


i need to add a backup battery to keep my pic microcontroller working when the main source goes down .
how can i do that ?

Regards :wink:

Re: [moved]how can i add a backup battery to keep my pic microcontroller project work

It depends on what the voltage and current demands of your design are. Do you need to keep power ONLY on the PIC or does it rely on other devices attached to it being powered up at the same time?

Brian.

Re: [moved]how can i add a backup battery to keep my pic microcontroller project work

Hi,

sounds like a simple question...but there are a lot of details to be considered.

the simplest way is to OR the two supplies with a pair of schottky diodes.
* for reduced voltage drop you could use a "ideal diode circuit"
* or you could use a superevisory circuit like MAX795 (that´s the one I have the number in mind, but there are many others...maybe better fit your needs)

Additionally it depends
* supply current and estimated battery backup time
* periferals you want or don´t want to shut down during backup time
* supply voltage range of your microcontroller
* supply voltage and expected supply voltage accuracy during normal operation and during backup
* your software running at the microcontroller during backup
* you battery chemistry and battery health requirements
* your complete circuit
* and a lot of other things.

Klaus

Re: [moved]how can i add a backup battery to keep my pic microcontroller project work

thank you

I'm using pic16f877a with dht22,ds1307 module,ugn3013 hall effect switch and esp8266 ^,^

i want to keep all the circuit working if the main source goes down .

i'm using 9-12v ac-dc adapter .



regards

Re: [moved]how can i add a backup battery to keep my pic microcontroller project work

Hi,

I must guess: you have a 12V/100Ah car battery --> use two diodes at the 9V/12V node.

Klaus

Re: [moved]how can i add a backup battery to keep my pic microcontroller project work

no i dont have car battery ^^

i dont know how to determine the batery type for my system ^^

and how to charge the battery and how to protect the battery from any thing may damage it ^^

Re: [moved]how can i add a backup battery to keep my pic microcontroller project work

Hi,

but you need to know essential informations like:
how much current your system draws
... and how long it should operate from the battery..
... and your schematic..

If you dont know this ... we can´t know this either.

Klaus

Re: [moved]how can i add a backup battery to keep my pic microcontroller project work

KlausST said:

Hi,

but you need to know essential informations like:
how much current your system draws
about 150 mA
... and how long it should operate from the battery..
12 hours
... and your schematic..

If you dont know this ... we can´t know this either.

Klaus

Click to expand...

thank you

Re: [moved]how can i add a backup battery to keep my pic microcontroller project work

You did not mention the maximum voltage intended to use, is it 9v ? Or you use a regulator to reduce that voltage from 9-12v adapter you mentioned ? There are a myriad of battery kind options, each one requiring a particular type of charger. As for current capacity, the first approximation, disregarding losses, derating, temperature, etc ...


Obviously, a choice with a good margin would be adequate, and in those cases I would consider selecting one battery (or a bank) with twice of that capacity.

Re: [moved]how can i add a backup battery to keep my pic microcontroller project work

i will use dc to dc converter to obtain 5v