I would like a circuit which would run off a 9v supply from a mains adaptor. It also needs a 9v battery backup that will kick in when the mains supply is unavailable. Has anyone got any ideas on how this is done?
Make sure that the adapters output is slightly higher then the battery voltage, then just connect them toghether with 2 diodes.
The battery will automatically take over when the adapter stops working.
Yes, Since the main power (9.5V) is higher then the battery (9V) there will be no drain of the battery during normal operation. If the main power fails the battery will take over.
Yes, Since the main power (9.5V) is higher then the battery (9V) there will be no drain of the battery during normal operation. If the main power fails the battery will take over.