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Inaudible alarm

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kwame

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Hi folks
I have bought a 12VDC car horn for an alarm system.I have used a 12VDC transformer +full wave rectifier to reduce/convert the 220VAC to 12VDC.
When i turn the system on,the alarm is almost inaudible.The 60db horn cannot be heard 2 meters away .But when i flick the - ,+ wires gently at their contacts,it blares loudly.But when i solder the same -and+wires firmly in place it is almost inaudible.
Why?
 
Not enough info to tell.

What is the amp rating of the transformer output (I assume it's 12VAC not 12VDC)? Is that sufficient to power the horn?

Do you have a filter capacitor on the bridge output?
 
Hi the amps of the car horn is not stated.The output of the transformer is 2000mA.Output is DC not AC.I have a filter capacitor which is working.
I am using what is popularily called flexible cabble in local palance.Could that be a cause?Or i should try a much thinner wire?
 
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If I remember correctly a car horn will draw approx. 10 to 12 amps. Sounds like your transformer doesn't have enough current to make the horn work.
 
I'm quite sure gerty is correct. When you momentarily make a connection by flicking the wire, the horn sounds loudly since the capacitor is supplying the high current the horn requires but can only supply it for a short time before it is discharged.

If you don't know how much current the horn requires, hook it up to a car battery with a multimeter in series set to measure current.
 
Hi,

Does the alarm tone need to be a steady one? If not just use a piezo siren, which can be very loud indeed. some are over 110dB at 12v and only 100mA or so, well within spec of your transformer.

They are also small, tough and reliable.

Al
 
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