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Electronics, Lighting, & Gadgets HRM, GPS, MP3, HID. Whether it's got an acronym or not, here's where you'll find discussions on all sorts of tools, toys and gadgets.

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Old 07-05-07, 12:39 PM   #1
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My Bike "Horn" project

I could just get a tacky bell but hell no. I got this 120db portable alarm on a keychain gizmo from the source (Radio Shack).

This thing is really loud. And I know the pedestrians are going to hear this one when I come up on them.

The idea is to rip apart a Bullet type LED headlight. I already have the 5 LED Raleigh headlight which works very good for $9.99. I plan on getting another one and converting it into the horn.

I'll be ripping out the guts of the LED light, the guts from the portable alarm and swapping them. The idea is that where the 5 LEDs are at the front of light is where I'll place the piezo buzzer instead. At the back a wire will be sticking out that will go to a pushbutton switch which will be mounted on the left grip right next to the Shimano pushbutton shifter.

So my handlebar will look like it has two identical LED headlights but one of them will actually be a 120DB "horn". The left one is the horn, the right one is an actual headlight.

I'll post pics of the completed project as well as a "How-to" for anyone who's interested in building one for themselves.
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Old 07-05-07, 06:04 PM   #2
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sounds mean, and delightful.
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Old 07-05-07, 06:07 PM   #3
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and the reason you need an airhorn?
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Old 07-06-07, 09:44 AM   #4
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Because pedestrians on the Multi-use paths or bike trails block the trail entirely. So I have to warn them that a fast moving bike is coming.

It wouldn't be much of a problem with the two moms with double wide baby pushers weren't walking side by side using up the whole path width.

It seems my bell is inadequate because I can ring it only 5 ft behind the pedestrians and they don't react at all. They just keep using up the whole path. I figure a 120DB "siren" triggered from about 50ft away will give them plenty of warning without startling them.

The other reason is to get the attention of cars that simply don't bother seeing me and they just can't hear my bell at all. With a 120DB "siren" they should hear it just fine and they'll see me crossing the street. I just want to make sure they know I'm there. The louder the better!
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Old 07-06-07, 02:24 PM   #5
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Please include the Radio Shack stock number when you post more detail.
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Old 07-07-07, 11:05 PM   #6
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The Alarm is a Nexxtech personal alarm at the source. Part No 4900428 at the Source. Sorry... I can't find the equivalent on RadioShack's website.

Part 1 : The parts we need

Here's the handlebar 5 LED light we'll use. I already have 2 of them. One will be used as a light and the other will be the horn. That way it looks nice on the bike and it'll be nice and compact... and loud.

Lets open it up and take a look inside. We have the cap, the battery holder, the outter casing and the mount.

Now lets really tear it apart. These are all the bits and pieces from the front to the rear.

Now we'll discard the pieces we don't need. I just put them in my parts bin for future projects. Those 5 ultra bright LEDs may come in handy in the future. The only piece that we'll need from the LED light are these:

The next part which will actually be our Horn is this gadget:

It uses an A23 12V battery and has a 140db ear piercing siren. You simply pull the keychain ring out, much like a handgrenade pin, and the blue part will scream its head off until the pin is put back in.

Lets take a look of its internal parts.

Next I discard the parts I don't need to my parts bin. What remains is what we really need.

So here is the final parts we'll need for this project.

The pushbutton switch was a spare I had laying around in my parts bin. The goal is to remove the pin holder on the alarm and replace it with the pushbutton. The wire will be sticking out of the back of the casing. All those alarm parts in the middle will be crammed into the light's battery holder (the black thing at the top middle). The lens on the top left will have a hole drilled right through the middle to let the sound go out forwards.

The next step will be drilling, cutting, soldering and so on. I'll probably introduce a few odd bits here and there to complete the project though. We'll see as it goes along.
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Old 07-08-07, 06:00 PM   #7
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That looks nice! I have the same LED blinkie tho mine keeps falling off from time to time so I have to dummycord it when I take the bumps. Also it is PITA that it takes 4xAAA tho the trade off is a bright light. Please post step by step images (hire a buddy as the camera man with a 6pack of beer as a reward? ) of the soldering as some of use can work a soldering iron but need detailed step by step images.

Also can you see if that unit will give phantom mileage to the bike computer? Thanks.
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Old 07-08-07, 08:43 PM   #8
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I'll glady use 4 AAA when compared to the brightness. My Cateye is just not bright enough for midnight runs in poorly lit wooded areas. The Raleigh cost less and is better for the handlebar. The only advantage the Cateye one has is its ability to easily strap onto my helmet.

Anyway, before I can really post a step by step, I have to figure this stuff out first. So far I have my plan and I've figured out which parts I need but now I have to figure out how to make it happen.

It'll probably be mostly trial and error at first.

Phantom mileage to the bike computer? I guess it depends on the computer right? I don't use a conventional computer anyway.
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Old 08-06-07, 05:05 PM   #9
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I hope you find add a way of channelling the sound otherwise it'll be only you who gets the full benefit. What's wrong with whistling at pedestrians, it's focused and the doppler effect means that people can actually locate you and instantly judge your speed - you'll be surprised how fast people react to it. It's better than my airzorn which I save for coaches and trucks who accidentally try to take my road space - and for the taxis who deserve it.
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Old 08-09-07, 12:14 AM   #10
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I have an AirZorn (sp?) and use it only on knuckle heads in vehicles that are
a danger to those on 2 wheels & dogs trying to chew my foot off...
Bells or a loud voice are more appropriate trail behavior.

Please don't use such a loud device just to reduce your incovenience.
There are other people out there that don't need the additional noise pollution.
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