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firealarmfreak
09-21-2008, 04:43 AM
hey i have the board of education and i am making a fire alarm control panel. I was wondering if there was a way of making power supervision.

This means that when the power goes out, the board of education immiditaly switches to battery power and the basic stamp goes to my trouble section of code to indicate its running on backup, so the alarm system is still active even though the powers out.

Thanks,

Chris.

Post Edited (firealarmfreak) : 9/20/2008 9:03:12 PM GMT

Mike Green
09-21-2008, 04:52 AM
1) Please edit your original message to include a meaningful subject.

2) Look at Tracy Allen's website for some discussion of voltage monitoring with a Stamp, particularly for monitoring battery voltage.
(www.emesystems.com (http://www.emesystems.com)).

3) Both the input supply and the battery would be connected through diodes (like Shottky power diodes) to the BOE so that the highest voltage supply would provide current for the BOE. When the input supply voltage drops below the battery voltage, the BOE would automatically be powered by the battery. The Stamp could monitor both the input supply voltage and the battery voltage to warn when the input supply is gone and to warn when the backup battery voltage drops below some threshold.

firealarmfreak
09-21-2008, 05:05 AM
do i need an uninterrupted power supplie for this? or can i use a normal 9 volt battery for the boe? also can you make a diagram, i looked at the site you gave me and it confused me, I would like a diagram as simple as possible.

thanks.

chris.

Bruce Bates
09-21-2008, 05:19 AM
firealarmfreak -

There are all sorts of supervisory IC's depending on exactly what you want them to do. Here are are a few from Maxim:
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2649/t/al

http://www.maxim-ic.com/products/supervisors/battery_backup/

Most voltage monitors expect to see 5 VDC which means checking the voltage regulator output, and not directly at the battery. Certainly both can be done but by two different means.

Regards,

Bruce Bates

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When all else fails, try inserting a new battery.

Post Edited (Bruce Bates) : 9/20/2008 9:39:20 PM GMT

Mike Green
09-21-2008, 05:55 AM
Here's one simple example using a 6V battery of some kind. Note that the BOE requires an input voltage above 5.5V to properly regulate. With a 6V battery and silicon diodes (like the 1N4001), this isn't quite enough although it'll work. You'd be better off with a Shottky diode which has a lower voltage drop. You could also use a 7.2V rechargable battery pack for backup or a 5 cell alkaline or lithium AA battery pack.