Connect with us

Hardware to play loud MP3 in traffic?

Discussion in 'Audio' started by Winfried, Sep 9, 2014.

  1. Winfried

    Winfried

    17
    0
    Dec 11, 2013
    Hello

    I don't know much about electronics, but I'd like to build an MP3 player for use on my bicycle and play a loud car horn in case of emergency.

    I thought about using car horns, but they draw a lot of current so require a beefy battery as well.

    Before I investigate further, I'd like some feedback from experienced users about how feasible it'd be.

    I guess I just need this:
    • Compact MP3 player
    • Waterproof loudspeaker
    • Battery (li-po, li-fe-po?)
    • Switch
    • Cables
    Thanks for any help.
     
  2. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Many Lithium batteries use in RC cars/planes/helicopters can pack quite a punch and provide a lot of current. The question here will be if you plan to charge it every night, or if you plan to put a dyno on your bike.
     
    Last edited: Sep 9, 2014
  3. Winfried

    Winfried

    17
    0
    Dec 11, 2013
    I probably won't need to charge it that often, since it's only to be used instead of a loud car horn and only in case of emergency.

    I was more worried about how 1) big the speaker has to be and 2) much energy the amp will use.
     
  4. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Unfortunately, I am not enough of an audio guy to quote you a decent size speaker or amp. Anything I provide in that regard would be a guess, but I'd guess you should aim at the 20Watt mark for an amp and use a couple 4" speakers, or a 4x6" car speaker.

    The amp will be variable, but a 20W amp will draw up to 2Amps from a 12V battery.
     
  5. Winfried

    Winfried

    17
    0
    Dec 11, 2013
    Thanks much for the feedback. 2A isn't bad but thankfully, I won't need to use it often so I guess a small li-fe-po battery could do to power the amp + two speakers.
     
  6. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    I just want to confirm that theses speakers are for music, and you will be using an alternative for a 'horn'?
    Those may not be loud enough to be heard from within car unless you are pretty close and they don't have excessive external noise dampening. I still think a horn or siren is desired for emergency use.
     
  7. Winfried

    Winfried

    17
    0
    Dec 11, 2013
    The speakers will only be used to play the horn. I don't listen to music while I ride.

    Hand horns work OK, but in an emergency, it's just not as safe as just pushing a button:
    [​IMG]
     
  8. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    I thought you were trying to do both. MP3 music normally, and a horn for emergencies.
    I'd use a motorcycle horn and a couple RC Lithium batteries then.
    Some RC cars draw more amperage through the motors than 5 Amps. All you'd need is the horn, batteries, a relay and button. (Optional resistor)
     
  9. Winfried

    Winfried

    17
    0
    Dec 11, 2013
    I thought the MP3 + amp + speaker solution would use less power and be lighter, but car horns + battery is fine. Thanks for the info.
     
  10. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    You're right, but if you want the volume, you'll need to draw more power. You also won't get a louder horn with audio equipment unless you specifically build it to produce a horn sound.

    The motorbike horn draws less current, and the circuit will draw nothing unless you push the button. Just make sure the battery has at least a peak discharge of 5A and you're golden. You just wont be able to lay on the horn all day or use it for weddings ;)

    (Less components, and easier wiring)
     
  11. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    I agree with Gryd3 here. An audio amplifier and speaker are not the answer. Speakers are designed to reproduce a (reasonably) wide range of frequencies fairly accurately, and are not very efficient (modern speakers are 5% or less, usually). A horn will be a lot more efficient in terms of power consumption, but especially in terms of size, because it uses a resonant chamber (at least, car horns do) and a tapered vent.

    You'll probably end up using a battery powered electric horn. The battery doesn't need to have a lot of capacity but it needs a high short-term current capability. Lead-acid would be good, apart from the weight. Lithium ion might be best.

    If you just want to make a lot of noise, a motorbike horn may be best. If you want to sound like a car, get a car horn! You may be able to adjust it internally to reduce the power consumption at the expense of a slight reduction in volume.
     
  12. Winfried

    Winfried

    17
    0
    Dec 11, 2013
    Thanks for the infos.

    I actually already got those 12V car horns that come with a 30A relay.

    As for the battery, I read that lead-acid can be a bit heavy for use on a bicycle, so should look at li-po or li-fe-po instead with a high C (discharge rate in Coulomb?).
     
  13. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
  14. Winfried

    Winfried

    17
    0
    Dec 11, 2013
    So li-po or li-fe-po it is. Apparently, li-fe-po batteries are less prone to explosion in an accident so should be a safer choice for use on a bicycle.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-