[MOVED] Hardware to play loud MP3 in traffic?

[JamsheedKianoush]

Hello

I don't know much about electronics, but I'd like to build an MP3 player 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.

 

[BradtheRad]

A technical consideration or two...

To play a sound loudly, you need to move a lot of air. This requires power. Your speaker must either move a small cross-section of air a long distance, or a large cross-section of air a short distance. Which is to say, you'll need a special speaker construction.

A few D batteries could power an automobile horn. Maybe 8 or 9V. You would not necessarily need 12 V.

However...

I don't recommend you use anything but an old-fashioned jingle bell.
It can be heard amidst traffic, its sound is friendly, and anyone hearing it will identify it as a bicycle.

A bicyclist is often close to pedestrians. So, if I were standing at a curb, and I heard an automobile horn next to me, I'd jump out of my skin. My first thought would be 'Get out of the way, a car is coming at you.' It's the sort of thing that can give people a heart attack.

Furthermore if equipment on your bicycle looks valuable, you can expect it to disappear when you're not around.

 

[JamsheedKianoush]

Thanks for the infos.

I do intend to either keep a regular bike bell for pedestrians or play an MP3 that sounds the same, in terms of pattern and volume. The car horn would be used in heavy traffic or when a truck is operating (like the one that backed up and almost ran me over a few weeks ago).

 

[Audioguru]

A loudspeaker is designed to play a wide range of frequencies so it is not efficient. It uses lots of power (needs a huge and heavy battery) to be loud.
A car horn is designed to play only one frequency efficiently. It uses low power (needs a small lightweight battery) to be loud.

Today a ****** woman (it looked something like a woman) nearly ran over me (I had the green light and she had the red light) because her braking foot got stuck in her gown or mask. Her mask blocked the view of me on my bicycle and the red light.
I stopped her expensive SUV with my glare. I swore loudly.

 

[JamsheedKianoush]

Thanks for the info.

So car horns are the way to go. I got those 12V horns and the **broken link removed** that came with them.

To save weight, it looks like li-po or li-fe-po battries are lighter than lead-acid. However, I read it's very important to keep the battery at least 20% charged, so there should be a way to show the user how much energy is left.

 

[Audioguru]

A Li-Po cell is 3.2V when the load should be disconnected and is 4.2V when fully charged. It should be stored at 3.7V.
A proper balanced Li-Po charger circuit should be used to avoid an explosion or fire.

A 3-cells Li-Po battery is 12.6V when fully charged, is 11.1V when half charged and is 9.6V when the load should be disconnected.