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Hi Everyone , i have this simple setup of mine and i want to know how can i compute the total loading of this setup:

the siren is rated 12V 15W and i connected it with a 12V 1A Adapter and it works just fine .

i know that P=IV then I=P/V

but im confused if the siren is really consuming 15W knowing that the adapter is only generating 12V x 1A =12Watts, right ?

and from the rating given, 12V 15W, so here the current must be 15/12 = 1.25A , but the adapter is giving only 1A,

how can i compute for the correct wattage and current consumed by the siren when connected with a 12v 1A adapter? tnx!

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If the speaker part is 8 ohms and the siren circuit gives it a squarewave of plus and minus 5.5V over and over then the power in the speaker is (11V squared)/8 ohms= 15.1W for half the time which is an average power of only 7.5W.

Maybe the siren's power rating is its (fake) peak power of 15.1W.

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