Saturday, January 16, 2016

One of my current projects: Arduino police siren w/simple, custom transistor amplifier/speaker driver circuit

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By Gabriel Staples Written: 16 Jan 2016
Last Updated: 16 Jan 2016

A Few Other Articles:
So, a few days ago I got a car horn *and* a car audio speaker to play a siren sound!

In these two videos, I do a quick desktop demo of playing a siren sound through first a "fixed frequency" car horn, and then through a standard car audio speaker, rated at 120W peak, 60W RMS, and 4 Ohms. Using an Arduino, a relatively simple, custom transistor-based amplifier circuit, and the Arduino core tone() function in my code, I drive the horn and speaker to play a siren sound by sinusoidally varying the driving frequency.  I also show the signal to the devices on an oscilloscope, and briefly discuss and hook up a Schottky diode in a "snubber diode" configuration to knock down the inductance-induced voltage spikes created each time the square wave has a falling edge.

First, watch the "fixed frequency" type car horn play a varying-frequency siren sound:




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Next, watch the car audio speaker get driven by the same Arduino, code, amplifier circuit, and 3S LiPo battery. It is *much* louder!


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7 comments:

  1. I watched your video very successful, I want to do the melody work in the car horn (I tried to run the horn on different frequencies but the volume is low) How can I increase the horn decibel? I am very pleased if you can help me very importantly.

    ReplyDelete
  2. I watched your video very successful, I want to do the melody work in the car horn (I tried to run the horn on different frequencies but the volume is low) How can I increase the horn decibel? I am very pleased if you can help me very importantly.

    ReplyDelete
    Replies
    1. Try driving the speaker through a high-power H-bridge designed for driving DC motors. To power it, use a LiPo battery of the correct voltage for the speaker. Also consider placing a high-capacitance (ex: 4700uF or larger) AC-coupling capacitor in series between the speaker and the H-bridge to help remove any DC bias.

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    2. Also use the Arduino ToneAC library to drive the H-bridge/speaker so that you can dual-drive the speaker, thereby getting less DC bias and double the volume that you'd normally get from the basic "tone" library.

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    3. WARNING: for the AC-coupling capacitor, it *must* be bipolar, meaning it is electrolytic but NOT polarized. If you use a polarized capacitor and then dual-drive it, you'll blow the capacitor. It is possible to make an electrolytic bipolar capacitor from two electrolytic polarized capacitors back-to-back, with a couple of high-speed diodes too, but I'll have to explain that one more later. Try googling it or just buy a bipolar (non-polarized) electrolytic capacitor to start.

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  3. Could add from my facebook address.https: //m.facebook.com/devotedster? Ref = bookmarks

    ReplyDelete

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~Sincerely, Gabriel Staples.

P.S. Yo hablo español también. Je parle français aussi. (I speak Spanish & French too).