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Asnieres sur Seine - France
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I'm playing around with a networked sensor alarm. I've got the sensors (smoke, gas, temperature and humidity).

I want this to replace our smoke alarms by lighting up (LEDs), sending messages (Twitter, EMail, SMS, ...) and making lots of noise.

I know how to light things up and send messages.

But I need to make a lot more noise than I know how to at the moment. I have a KPEG110 piezo buzzer and a COM-11089 PCB mount speaker and I can make tones on these. But this is nowhere near the sort of volume I need for an alarm.

What can I use that I can easily hook up to my Arduino and will fit in a nice tiny form factor?

Thank you in advance for any advice and suggestions.
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Manchester (England England)
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Try this one:-
http://www.maplin.co.uk/two-tone-mini-siren-3224
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the land of sun+snow
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Yeah, it's probably easier to buy a loud buzzer with built-in drive cktry than build one.
G_M's buzzer is a monster, 90mA and 110 dB!

OTOH, if you're building one yourself, the secret is use a largish drive voltage, and
pulse it at the resonant frequency specified for the device. I have a CEM-1203, 42-ohm
magnetic [not piezo] transducer that I tested recently.

I drove it with a 2N3904 NPN inverter and tried 3.3V, 5V, and 9V. Its resonant frequency
is about 2 Khz, and when driven well off that frequency, the loudness was way down.
Also, at 3.3V the sound was weak, at 5V the volume it was good, but at 9V and 2 Khz,
it was so loud and obnoxious, it drove me out of the room.

So, you just need to choose the design parameters properly. Also, in this case, the currents
were somewhat higher than the Arduino I/O pins can output, so the volume will never be
very high without using the inverter driver ckt. It's all a matter of the right ckt.
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Asnieres sur Seine - France
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If I go for G_M's mini-siren what do I need to put between my Arduino and it?

I assume I have to put something between the 5v out on the Arduino and the Mini-Siren to "boost" the output?

Do I put this magical piece of kit between the line and the Arduino or between the ground and the Arduino?

I'm more used to going the other way and putting resistors between the Arduino and the "weaker" object (LEDs, buzzers, ...).

Maplin will ship to France so I will order a few of these things. But I want to make sure I have everything (hardware) to make this work.

Many thanks all!
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Manchester (England England)
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Just use a simple transistor, like the first circuit on this page:-
http://www.thebox.myzen.co.uk/Workshop/Motors_1.html
Replace the motor and diode with you siren.
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Asnieres sur Seine - France
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I am a software guy who is (re)learning about the hardware side of electronics slowly but surely.

I haven't worked with transistors or relays yet.

Would this sort of thing do the trick?

http://snootlab.com/lang-en/tinker-it/229-t000200-thermistor-module.html

How and where would I connect this to the Arduino and the siren? In other words between which pins and +/ground?

Many thanks
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Manchester (England England)
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Quote
I haven't worked with transistors or relays yet.
Good time to start.

Quote
How and where would I connect this to the Arduino and the siren?
+5V to siren, other end of siren to NO of relay, COM of relay to ground.

Arduino
+5V to arduino 5V, Gnd to arduino ground. Input to any output on the arduino, say pin 2.
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