We are working on a project where we want to sound an alarm if somebody is messing around with our Robot (e.g., the Robot is being shaken abruptly or the cameras/LIDARs are blocked). I am using "loud speakers" (4.1 x 3 inch 10 Watts 8 ohm speakers), but they are not loud enough.

Are there any small speakers or alarm systems small enough, but loud enough (closed to a car alarm) that you would recommend? Ideally something that I can just plug into the robots computer, or interface with through a microcontroller. Either one would be fine.

  • $\begingroup$ The answer to this will depend on size, power supply and required volume. Presumably you can't just add an audio amplifier between your existing alarm generator and the speaker? $\endgroup$
    – Andrew
    Sep 3, 2014 at 18:44
  • $\begingroup$ Currently I have a Boss audio amplifier for the speakers. I have 4 speakers (with the specs mentioned about) and they are getting full power at 12V. We are using an overspeced 26V battery that supplies more than enough power for all devices. I want something can be heard 100-300 meters away or scare/throw someone on the ground because of the noise, yet something that I can send signals to with a computer and/or MCU. Thanks for you help. $\endgroup$
    – Pototo
    Sep 4, 2014 at 1:07
  • $\begingroup$ Can you explain why simply using a car alarm siren would not work for you? $\endgroup$
    – Ian
    Sep 4, 2014 at 2:36
  • $\begingroup$ A car alarm siren would definitely work. Any that you recommend? $\endgroup$
    – Pototo
    Sep 4, 2014 at 4:42
  • $\begingroup$ If you just want to make really load noise, there are signal horns usually used in football stadiums with something around 135dB powered by 12V This systems use a compressor and are not speakers anymore.... for example this one here on ebay: here on ebay $\endgroup$
    – TobiasK
    Sep 4, 2014 at 13:56

1 Answer 1


If you don't mind a hacky solution then opening one of these might be the best way to go. Just replace the button with a FET (or standard transistor) and be on your way. If you wan't a more traditional/better looking solution, then the best thing I can recommend is getting a larger speaker/amplifier. It looks like one can buy car horns, but that would probably take more wiring than necessary. If I were in your position, I would go with the electronic whistle.


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