Battery back-up

[HANIFF]

I need some ideas on a battery back-up circuit that will work once a particular circuit is activated. The main power supply will be functional, but the back up ckt. will work only when the activated signal is received and the main power supply is interrupted. If the ckt. is not activated and the main power supply is interrrupted, the back-up is deactivated.

Thanks

Han

[ante]

HANIFF,

Welcome to the community.
I need to know some more details. What is the

[Kevin Weddle]

That sounds like a simple switch, but I won't ask why you need to distinguish between the two supplies. You can activate and deactive a circuit using a semiconductor if the voltages allow. I would correct the voltage in order to use a simple semiconductor rather than use a relay.

[HANIFF]

Thanks for the responses.
I am designing an alarm using AC input and 5VDC output from the power supply. The alarm will be activated by a non-contact input/signal. When activated, if shaken or AC removed an alarm will sound. In the deactivated mode the alarm does not sound.
I need to design a battery back-up that will allow the alarm to sound once the AC is interrupted in the activated state. I have designed a ckt. using gates, relays and transistor but I need to see other ideas of how to do a batt. back-up for the ckt.
Thanks. I hope I provided enough info.

Thanks again
Han

[ante]

HAN,

What kind of battery do you have 12V or 6V and what

[HANIFF]

Thanks again for the response.
I am looking at a DC range of 3-6 V

Han

[ante]

Han,

This is the easiest way I can think of, but maybe you had something different in mind?

Ante ::)

[HANIFF]

Thank you very much.
Its different from what I have but I will test it.
Once again, thank you.

Han