Electronics, Lighting, & Gadgets - Battery-powered horn that sounds like car horn (pattern, dB)?

Hello

I know about the AirZound, the (Mini)Megahorn, and the Thunder Horn, but I'd rather a horn that sounds like a car horn and plays at the same volume.

The Wolo Twin Power 200 / 118 Decibels-520/630 HZ (http://www.wolo-mfg.com/elec.htm) is just what I'm looking for, but it runs on a 12v battery.

Ideally, it should be easy to remove from the bike so I can take it with me when I need to park it outside.

Is there really no company that makes a bicycle horn that runs on regular batteries (AA or 9V) and plays a sound similar in pattern/dB to a car horn?

Thank you.

I mean, something that sounds just like this, without the huge box + cables:

http://www.youtube.com/watch?v=_6APeUHUOcA

Probably not going to find it. Car horns draw several amps at 12 volts. That's a lot of power. Sound is logarithmic; getting a little more sound takes a lot more energy.

The bottom line is that to provide that kind of sound levels, a standard single car horn draws 6 amps at 12 volts, which is 72 watts. You aren't going to be able to get the same level of sound with less power input than that. Lower voltage, more amps. 6 amps is already very challenging for most batteries that are fairly light.

Add to that, cars actually have TWO horns, so double that.

What you really need is a source of a big whack of power for a short period of time. It would be neat to figure out a way to have a brake that made noise on demand, since brakes are dissipating a heck of a lot of energy quickly.

You might consider using a 12v battery from a cordless drill for the power source and then work on a quick release mount for the horn.

Probably not going to find it. Car horns draw several amps at 12 volts. That's a lot of power. Sound is logarithmic; getting a little more sound takes a lot more energy.

The bottom line is that to provide that kind of sound levels, a standard single car horn draws 6 amps at 12 volts, which is 72 watts. You aren't going to be able to get the same level of sound with less power input than that. Lower voltage, more amps. 6 amps is already very challenging for most batteries that are fairly light.

Add to that, cars actually have TWO horns, so double that.

What you really need is a source of a big whack of power for a short period of time. It would be neat to figure out a way to have a brake that made noise on demand, since brakes are dissipating a heck of a lot of energy quickly.

Could you somehow charge a capacitor with your brakes then use that for a power surge?

Could you somehow charge a capacitor with your brakes then use that for a power surge?

Sure. First, you need a big enough generator to act as a brake and to be able to generate 100 watts at 12 volts (typical generator hub is 6 watts at 6 volts I think). That'll probably weigh about 5 pounds.

You need 6 amps for 1 second? That's 6 coulombs of energy you need to store. At 12 volts, that's half a farad of capacitance. Since the horn will actually stop working when it gets down to 9 volts or so, and the voltage on a capacitor is proportional to the remaining charge, you need 4x as much as that, or 2 farads.

2 farads of capacitors that are fast enough to be capable of delivering 12 volts at 6 amps will be about the size of a lunchbox and will weigh another 4 or 5 pounds.

So yeah, you could do it. It would be very complex and would weigh probably about twice what a lead acid cell would, and would add a lot to the spinning mass.

EDIT: actually after doing some research I think this would be about 10x heavier and at least 20x more size to give you a 1 second burst, versus a lead acid cell which would give you 20 minutes of horn sounding per charge and take up a fraction of the space.


I was thinking more along the lines of a mechanical horn. You've already got a lot of mechanical energy, and you want to produce mechanical energy. Converting to electrical energy along the way is inefficient and a lot of junk to carry around the other 99.9% of the time.

Something like a horn diaphragm that could be linked directly to a corrugated disc on the wheel.

In the end any such thing would be ridiculously complicated and I doubt would be much (if any) lighter than a small 12V gel cell and a car horn.

Here's a battery that would be more than enough:
http://www.batteryspace.com/sealedleadacidbattery12v23ahs1.aspx
It weighs 2 pounds and would fit nicely on top of a rack. Combined with the car horn, maybe 3 pounds. It has enough power to honk a horn for about 20 minutes continuously per charge. $25 for the whole deal, very simple. A cordless drill battery would also be a good option, and might be a little lighter.

Thanks everyone for the education + ideas. Unfortunately, I don't the skills to build my own solution on either a drill battery or a lead battery.

Maybe I'm wrong, but I think there's a business opportunity here :-)

Actually, it struck me while riding my bike yesterday: If the MegaHorn/ThunderHorn can blast 105dB with a 9v battery, why can't the same kind of horn play something that sounds more like a car horn instead?

The reason I prefer that sound is that car/truck drivers are used to it, while the MegaHorn (http://www.youtube.com/watch?v=V5Rz6i_Okw0) and the ThunderHorn (http://www.youtube.com/watch?v=TLRpMNRC_VY) play tones that sound like nothing they're used to (and I don't like the AirZound because it's too bulky to carry with me.)

I used to be into R/c helicopters and the Lipo batteries they use are super powerful. 2.2 amp hours at 12.6v fully charged. They also have a discharge capacity of 45c+ and thus can put out 60-80amps if needed. Very light, much lighter than a lead acid battery. You do need to ensure they don't go below 20% charge so one with a low voltage cutoff like they use in transmitters would work well.

I know next to nothing about audio, but I think lower frequencies require more power to produce the same sound pressure level. If so that is why all the high decibel horns that run on small batteries are really high pitched.

There is an issue, from my own experience, that seems to eat into the original premise of Winfried, which may tie with what ItsJustMe is mentioning. To radiate effectively within the frequencies that are characteristic for car horns, the radiator needs to be attached rigidly to a stiff mount. Possibly even the resonance frequencies of that mount need to be tweaked. This does not mesh with the desire to be able to take the device off the bike and carry away. Of course you can go with something ineffective but then the power source needs to be even bigger.

I used to be into R/c helicopters and the Lipo batteries they use are super powerful.

Thanks for the tip. I'll throw that idea to people who are into that sort of thing and see what they think. Looks like a nice week-end project :-)


To radiate effectively within the frequencies that are characteristic for car horns, the radiator needs to be attached rigidly to a stiff mount. Possibly even the resonance frequencies of that mount need to be tweaked. This does not mesh with the desire to be able to take the device off the bike and carry away.

Good to know. That would explain why I failed finding a compact, loud bike horn that sounds closer to a car horn.

Alternatively, as seen in Paris this very afternoon...
243313

It probably takes a bit getting used to not to sound the horn without meaning to by sitting too hard on the mattress pump that now stands at the base of the seat.

I have a moped horn on my bike, powered from 5 NiMH AAs, but it is attached permanently to the bike's rack. In my surroundings, it has worked very well reducing, multiple times, the chance of an accident and enhancing my stature in road negotiations.

If you look up car horns on wikipedia, you'll find an explanation of how the horn part of it is critical to really conducting the audio energy to the air. The vibrating surface by itself is not very efficient in this regard, the horn is required to really get a large volume of air moving, rather than just super-compressing air in a small volume and turning a lot of the energy into waste heat. Sometimes there's just no substitute for something that's large and substantial.

I have a moped horn on my bike, powered from 5 NiMH AAs, but it is attached permanently to the bike's rack.

I'll add this to the list of ideas.


The vibrating surface by itself is not very efficient in this regard, the horn is required to really get a large volume of air moving, rather than just super-compressing air in a small volume and turning a lot of the energy into waste heat.

That explains why the AirZound sounds loud but not at all like a car horn.

Seems like a simple handpump is enough to power a couple of loud horns:

"Painfully loud bike horn w/ hand pump"
http://www.youtube.com/watch?v=VFcFs6qQY1Q

Has anyone tried it?

Seems like a simple handpump is enough to power a couple of loud horns

There is the Dealextreme Horn (http://www.dealextreme.com/p/ultra-loud-bicycle-air-horn-truck-siren-sound-120db-23681). I even got it, but have not got around yet to mount it, so cannot tell about the experience.

I think anything you have to actually pump is an immediate failure. Even when just pressing the button on the AirZound, I don't always have time to hit the button. At least when it's just a button I can still keep my hands on the bars while pressing. If I had to take a hand off to pump something I would never use it.

I think anything you have to actually pump is an immediate failure. Even when just pressing the button on the AirZound, I don't always have time to hit the button. At least when it's just a button I can still keep my hands on the bars while pressing. If I had to take a hand off to pump something I would never use it.

True, but there is room on a bike for more than one signal. E.g. I thought about installing the particularly loud signal for encounters with trucks. Also, one can be innovative. I was thinking about mounting the DX horn in such a way that I could stomp onto the pump with my foot.

I was thinking about mounting the DX horn in such a way that I could stomp onto the pump with my foot.

Good idea :-) Anybody's feeling like building a prototype?

In the meantime, I ordered the Megahorn (http://www.chainreactioncycles.com/Models.aspx?ModelID=21720). I'll report back about its effectiveness as compared to the AirZound.

I would like a better solution then the air zound aswell. It's good on paper but alittle jinky out in the field.

Just got back from Amsterdam: The ding-dong is pretty effective with pedestrians :-)

I don't have the tech skills to tell, but I'm surprised there's no battery-powered horn that can play two tones, at two different volumes: One regular volume ding-dong to warn pedestrians, and one 100dB for cars (if it can't play car horns, I'll settle for the annoying Megahorn tune).

And it should be compact and easy to remove from the bike: The AirZound is a bit big to fit in a backgpack, not to mention there's no lock to prevent pushing the button while it's in the bag ;-)

There's an opportunity right there for an engineer.

Could you somehow charge a capacitor with your brakes then use that for a power surge?

This is a Darwin Award waiting to happen.

This is a Darwin Award waiting to happen.

In what way, because it's likely not to work when you need the horn, or the brakes are not likely to be as effective when trying to regenerate power rather than just dumping energy as heat as normal brakes do?

I can see either of these being a good argument against the idea.

Good idea :-) Anybody's feeling like building a prototype?

In the meantime, I ordered the Megahorn (http://www.chainreactioncycles.com/Models.aspx?ModelID=21720). I'll report back about its effectiveness as compared to the AirZound.

This type of horn is already in use and was designed and made by TrafficDroid of London, his youtube and twitter alias is Sonofthewind. His current model, I believe is the DroidHorn 3.0 however 4.0 may be in the manufacturing stage!

Search for Droid Horn and you will find him.

2 farads of capacitors that are fast enough to be capable of delivering 12 volts at 6 amps will be about the size of a lunchbox and will weigh another 4 or 5 pounds.

So yeah, you could do it. It would be very complex and would weigh probably about twice what a lead acid cell would, and would add a lot to the spinning mass.



This is also very dangerous without some kind of protection mechanisms. I was hanging out at my friend's car stereo place where they have big capacitors like 1 or 2 farads. While working on a 1 farad cap, one guy inadvertently bridged the terminals. A flash of light later, the screwdriver fused to the cap terminals and melted such that it formed an arc as if it were made of melted cheese hanging between the terminals.

Personally, I'd just suggest an actual car horn -- go down to Autozone and pick one that sounds like you want it to sound. Perhaps something with a low pitch so you don't sound like a compact car. :)

For power, get a R/C LiPo pack, 3 or 4 cells. A fully charged 3s pack puts out 12.6 volts, and a fully charged 4s pack puts out 16.8 volts. A car with the engine running is usually right around 13.8 volts, and I imagine that the exact voltage probably doesn't matter much to the horn -- I'll bet they work reasonably well from 11 volts to 17 volts, but the higher voltages might be somewhat louder and higher pitched.

A 1000 mAh pack is probably more than big enough -- I think most car horns take around six amps, and a 1000 mAh battery can deliver that for a full ten minutes before dying. You just need to make sure you have a pretty good sized switch, big enough to support six amps. (You could go with a relay, but that complicates things.) Autozone probably sells an appropriate switch button as well.

Considering how small your battery would need to be, I wouldn't even think of messing with a generator or bank of capacitors. (Though if you already have the generator to power your lights, and you're the kind of guy who can make a charger to keep your LiPo battery fully charged from that (it'll probably need to boost the voltage and make sure it doesn't exceed 4.2 v/cell), that might be a neat project.)

Thanks much for the infos. I don't have the skills to build this myself, but I might meet someone who can.

Why the need to sound specifically like a car horn? Car horns have many different sounds among all the makes and models - from the lower-pitched American car horns, to the dinky "beep beep" sound of most Japanese and other Asian cars, to the high-pitched air horn sound from a Ferrari:


http://www.youtube.com/watch?v=Y4E8loO1LPk

I say as long as the horn is loud enough, it really doesn't matter what it sounds like. It WILL get motorists' attention if it's in the 110+ dB range.

I think anything you have to actually pump is an immediate failure. Even when just pressing the button on the AirZound, I don't always have time to hit the button. At least when it's just a button I can still keep my hands on the bars while pressing. If I had to take a hand off to pump something I would never use it.

What you need is a small air tank you can pump up before riding, and an electronic valve for push-button action.

I just use a real car horn, a very small 12V lead-acid gel cell and a horn relay, both of which are smaller than fist sized together, and a button. Didn't take long to hook up.

I'd be interested in any picture/infos about how to build this myself, provided it's doable by someone who has zero knowledge of electricity.

why not try 2 9v batteries? it just might work depending on how often you expect to use it you might only get a few or maybe a dozen little squirts out of the batteries but it will be small and light.

why not try 2 9v batteries? it just might work depending on how often you expect to use it you might only get a few or maybe a dozen little squirts out of the batteries but it will be small and light.9v batteries (the little ones used in smoke alarms) won't put out anywhere near the amperage needed to power a car horn. Not even once. Not even with two in parallel.

8-10 AA batteries might, however -- especially if they're NiCd or NiMH.

Hmm I am not so sure of that. I will have to try it when time allows. Horns don't cross me as "high amp" devices considering the dinky wires they use to wire them up. maybe we are thinking different kinds of horns? I think thinking the little shell shaped thing bolted in front of the radio of most every car on the road.

not the "air horns" on the roofs of trucks and rv's

I have run quite a few of the 12v car neon lights on pairs of 9v batteries with no issues (runs about 20 minutes) including 2 3ft green neon tubes. they are not "high power" but they are not led's either :-)

The guy who leads a local "social" group ride every month hauls this behind him, powered by 8 AA batteries, that runs for upwards of 3 hours sometimes. Surely the same could power a car horn for a *very* long time.

https://sphotos-b.xx.fbcdn.net/hphotos-ash3/s720x720/554387_10150826073088363_730120523_n.jpg

The guy who leads a local "social" group ride every month hauls this behind him, powered by 8 AA batteries, that runs for upwards of 3 hours sometimes. Surely the same could power a car horn for a *very* long time.Well, remember that 8 AA batteries has much more energy than a 9v battery -- but even more important, it has a much lower internal resistance. 9v batteries are not made for high drain devices.

According to wikipedia (http://en.wikipedia.org/wiki/Vehicle_horn#Automobile) vehicle horns draw about 5-6 amps. AA's can't really provide that much power very effectively (but maybe if you did 10 or 12 it might work), and 9v batteries certainly can not.

And really, if he's going to haul a speaker that large he might as well give it more power, or if he doesn't need it he should go for a smaller speaker. 8 AA's divided by three hours works out to an average of about six watts. The large speaker can make six watts sound decent, but he could go a lot smaller.

I've got a bike stereo that's 1/4th the size of that, powered by a 7 Ah gel cell (I didn't have a larger LiPo at the time I put it together) that does about 25 watts and it'll go for three hours as well. It's probably a good deal louder than this as well, mounts to my rack rather than needing a trailer. (Though if I put the amplifier and battery to this speaker, it would probably work significantly better than the small enclosure I've made.)


Hmm I am not so sure of that. I will have to try it when time allows. Horns don't cross me as "high amp" devices considering the dinky wires they use to wire them up. maybe we are thinking different kinds of horns? I think thinking the little shell shaped thing bolted in front of the radio of most every car on the road.I'm not sure what you're talking about then. Speakers?

Oh, you meant radiator, not radio. Yes, that's what I'm talking about. They take around sixty watts, which must be at least ten times what your friend with the bike stereo is using.


not the "air horns" on the roofs of trucks and rv'sI'm not the OP so I'm not sure exactly what he's referring to, but I think those are closer to what he was after -- either that, or horns like this (http://en.wikipedia.org/wiki/File:Caterham_Roadsport_building_-_028_-_Horns_-_Flickr_-_exfordy.jpg). (That would be the sort that takes 5-6 amps, probably each.) And really, the air horns on the roofs of trucks and rvs might be just perfect for what he wants. Certainly, they're small enough to mount on a bike.

If you want a "horn" that's not much louder than a bike bell, here's an option (http://www.dealextreme.com/p/6-alarm-sound-bicycle-horn-with-mount-black-1-6f22-9v-100db-52764) -- and it runs on a 9v battery. If you want something that sounds like a car horn, it's hard to beat an actual car horn -- but that will require something beefier. 8 AA's might be able to do it (especially if rechargeable or the high discharge rate alkalines, as they can handle higher currents than the standard alkalines) but it would be marginal.

He meant "shell shaped thing bolted in front of the radiator". Radio was a typo, probably mobile device auto correct. Damnyouautocorrect.com hahaha

yeah I have NO clue where "radio" came from :-) hehehe

yep one of these buggers your typical on 99% of the cars out their horn

http://carphotos.cardomain.com/ride_images/3/403/2201/26006100099_large.jpg

I could be flat out wrong but I think a pair of 9v in series would run that just fine in short little blasts.

http://carphotos.cardomain.com/ride_images/3/403/2201/26006100099_large.jpg

I could be flat out wrong but I think a pair of 9v in series would run that just fine in short little blasts.

Well, let's do the math.

According to this page (http://home.earthlink.net/~schultdw/rdas/output/9v.html) the internal resistance he measured from an alkaline 9v battery is 1.5 ohms (and that is pretty close to my guess, so I have no reason to doubt it.)

The maximum power that can be extracted from a battery when the external resistance is equal to the internal resistance (which gives you 50% efficiency, by the way) -- so that's 1.5 ohms externally, 3.0 ohms total. 9 volts / 3 ohms = 3 amps, and since half the resistance is internal to the battery, our load only sees 4.5 volts * 3 amps, or 13.5 watts. Considering that these horns require about 60 watts, and that 13.5 watts/battery is an absolute maximum under ideal conditions ... no. Your horn might make a noise, but it would sound sick at best.

Maybe if you had four 9v batteries -- two in series, two in parallel -- you could get close to 60 watts, assuming that your batteries are fully charged. (If the horn uses 6 A at 12 V, then it has about 2 ohms, so it's pretty close to right for this, by the way.) Six 9v batteries, 3 in parallel, two in series, would probably do it.

AA batteries aren't really designed for this level of discharge either, but they'll work far better, especially NiMH or NiCd cells (which have lower internal resistances than the alkaline cells.) Ten of them would probably work acceptably well for short blasts.

Really, I'd suggest a R/C LiPo battery. They *are* designed for this level of discharge (and a lot more) -- a 20C 2000 mAh 3s pack is pretty typical and yet cheap, and the 20C means it's rated for a continuous discharge rate of 40 amps -- so six amps (or 12 amps if you use two of them like many cars do) would be no sweat.

Like I said I could be flat out wrong here but I just can't see that horn taking 60watts. that is the power a halogen headlight takes. More.

when I turn on a headlight There is a audible drop in engine RPM as the alternator loads down to power the headlight (yes one was running a relay test)

when I use the horn under the same conditions there is zero audible change in engine rpm.

again maybe it does take 60watts but I find that hard to believe. that is a crap ton of power for such a little horn.

I guess I am just going to have to try it and see what happens :-)

Here you go, Hella supertone or universal disc horns - they all need 5.5 amps at 12 volts:

http://cat.hella.com/hella-nafta/upload/USAData/2009_Horns_information_flyer_mounting_instructions.pdf

man thats a ton of power. guess my metro horn is a really wussy horn cause it does NOT take no 5-6 amps of power :-)

I will have to see what my oooga horn takes.

Thanks for the infos. So it looks like to an electric alternative to the AirZound could use about 3 amps and be powered with a 2000mAh 3s R/C LiPo battery (www.rchelicopterfun.com/rc-lipo-batteries.html)?

Thanks for the infos. So it looks like to an electric alternative to the AirZound could use about 3 amps and be powered with a 2000mAh 3s R/C LiPo battery (www.rchelicopterfun.com/rc-lipo-batteries.html (http://www.rchelicopterfun.com/rc-lipo-batteries.html))?If you use an actual car horn, you're looking at six amps rather than three, but that battery would handle it just fine, and would probably give you 20 minutes or so of blasting (so about 20x what the AirZound would give you.)

If you're using something else, then you'll have to see how much current it draws, but as long as it draws less than 40 amps a 2000 mAh LiPo battery will probably be fine (especially in small bursts.)

Although I haven't ever tried this before because my wife says it is a stupid idea, I would love to see my Thunderpower megaphone (http://www.thunderpowermegaphones.com/) become my horn. It would definitely cause a riot on the road. Hmmm... Can this be truly possible? Just an idea worth exploring. :)

Found this one:

278464

This project looks good...

http://www.orpland.com/

... although I'd rather something louder and sounds more like a car horn instead, even if it means having to hook up a bigger battery.

wow that orp looks pretty nice. I like the friendly tone option too for when you want to alert but not annoy :-)

a 12V motorcycle Gel cell, battery and the actual horn out of a car in the bone yard?

Here there is an older guy mounted a big air-compressor and tank in the back of his pickup truck
and mounted 2 horns off the exhaust stack of a couple ocean going Ships,
to sound "for emergencies"..