Electronic Alarms and Home Security Devices - help needed! with design of alarm system

I hope someone can help me with the design of an elaborate water alarm system. I am putting in an apartment in the basement and want to know if any water is getting in (thunderstorms/hurricanes). I have waterproofed, but want to take no chances.

I want each of the 16 problem areas to have its own led and toggle switch. That way, if one area is wet, I can toggle it off and remove it from the system, but keep the rest of the areas covered.

I want the alarm to sound in 2 locations (one with an auto-dialer).

My problem is that I don't know enough to figure out what amount of power it will need -- or how to calculate the resistors, etc.

The longest single round trip of wire will be 120 ft. The total wire needed will be 1300 ft. , since each problem area will have its own loop. It will be a normally-open loop since the water will close it.

Does that mean a 9v battery would be enough? I have the worst 5 areas temporarily covered by a 9v and 22 gauge wire and it seems to work ok, but I need something permanent before the walls are finished.

Can anyone tell me if a 9v would still work and what gauge wire to use (I have a lot of 22)? Or am I missing something I should know first?

thanks

It sounds like you have found a basic "roll your own" system that will do what you want.

The 9v battery will hit a wall if you expand to the scale you are describing. Get yourself an inexpensive power supply such as:

Altronix: a leading manufacturer of electronics and high technology components (http://www.altronix.com/index.php?pid=2&model_num=SMP3)

Or

ELK-P624 Power Supply (http://www.elkproducts.com/products/elk-p624.htm)

Give the thing a small backup battery, (you don't need a lot of amp hours for this), and you should be good to go.

Thanks for your quick response. I have never used a power supply before -- this will get power from a transformer and then pass that power to the system?

Can't I just replace the battery with a transformer? If a 9v battery is too small, would 12v transformer be enough? or 16v?

And would 1 amp be okay? or should it be higher/lower?

You can tell I am a novice -- so thanks for your help -- I need it!

Yes, you use a transformer to supply power to the power supply board.

Since it sounds like you have already worked this thing out to work on DC voltage, thus the power supply. Basically the only thing that changes is the size of the inline resistor or the type of LED you choose.

I am not sure I understand. Doesn't the transformer change it to DC power? Why the power supply?

No, the transformer provides 16vAC. The power supply does the AC to DC conversion. You _can_ find wall transformers that provide DC output, but they are harder to come by. If you can find one that provides the current you need, go that route.

As I said, I'm a novice-- I guess that's obvious. Thanks for your help.