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Novice question about wiring AA batteries to 12V Big Rig Horn

Novice question about wiring AA batteries to 12V Big Rig Horn

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  #1  
Old 05-03-13, 04:40 PM
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Novice question about wiring AA batteries to 12V Big Rig Horn

Hello,

First off I'm hoping this is in the right forum section, and secondly please be merciful to me because I'm just messing around as an inexperienced person playing with what I think is a funny idea..

I'm going to build a little "do not disturb" box that has a red light on top of it so that if people see the light turned on, they'll leave me alone while I work at my desk. More of a novelty than anything. Anyway, what I've done so far that does work:

Lined up 8x AA batteries, 1.5V each, and contained them in some battery boxes I took out of some dollar store flashlights. The two battery boxes are connected in series fashion.

I improved the wiring gauge by removing the original wires and adding some I stripped from an old CRT monitor power cable. I'll include a picture of what I mean at the bottom.

Anyway, I've been able to touch the ends of these wires to a red "clearance light" that runs on 12V and the light shines consistently etc. I then wanted to try to connect these wires to power a 12V 'Big Rig Freeway Blaster' car/truck horn so that if people ignored the red light I could startle them (I am aware that this is 130 DB and I will probably have to muffle the horn to prevent damaging people's hearing)

When I connect the wires to the terminals on the horn, there are sparks and the horn clicks, but there is no tone coming from it.

I have next to no electrical knowledge at all, so all I thought was that if I could get 8 AA batteries to add up to 12V I'd be in business, but something isn't working. Does anyone know what it might be?

Thank you!

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  #2  
Old 05-03-13, 05:08 PM
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Horns take a lot more juice (current) than most people think. I'll bet if you tried it on your car battery it would work.

Might want to look at Radio Shack for a piezo electric buzzer that doesn't require any electronics...just a DC voltage.

Oh...and apparently that horn has a hi and low tone...make sure you are going to just one terminal and ground.
 
  #3  
Old 05-03-13, 05:14 PM
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Thank you for the reply. To further diagnose the horn in particular, just so I know what's going on, I'd like to add this:

the documentation that comes with the horn shows that the left terminal would take the positive wire, and the terminal on the right says "negative or ground wire". Since this is a portable device running on batteries, I would think that I couldn't ground it (again I'm novice with this stuff) and that I'd be wanting to use the negative line that completes the circuit.

I'd like if someone could confirm if that logic is correct.

Also, besides meeting the 12v criterion that I thought was all that was needed, what other factors could be making it not work right? Are the batteries unable to produce the right amperage, or something? I'm unfamiliar with the science of these terms though.
 
  #4  
Old 05-03-13, 05:26 PM
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I used the term ground...as thats the way it's normally referred to on a vehicle. Negative is the same in a DC circuit...normally.

And yes, I don't think the batteries you have can produce enough amps. Think of it this way...could you light the light with a car battery...sure. Could you start the car with your battery pack....nope...probably wouldn't even get a click.

Not sure how much a horn normally requires...but I think mine is protected by a 10 amp fuse inn the car...and no way your battery pack can supply that.
 
  #5  
Old 05-03-13, 05:35 PM
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I would think that I couldn't ground it (again I'm novice with this stuff) and that I'd be wanting to use the negative line that completes the circuit.
Yes, with modern automotive devices ground and negative are one in the same.

Are the batteries unable to produce the right amperage, or some
Almost right. More correctly can't provide enough amperage. The batteries you are using are rated in milliamps. One milliamp being one one thousandth of an amp. I have tried testing auto horns on a 6 amp battery charger and it pegged the amp meter. Six amps just wasn't enough and six amps is six thousand milliamps. As Vic said you need to use an audio device consistent with available current (amperage) or use a much bigger battery.

Just an example of something that would work: Amazon.com: Megalert Mega Horn Electronic Bicycle Horn 105 db: Sports & Outdoors
 
  #6  
Old 05-03-13, 05:51 PM
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Ok, I see what you mean now. Thank you for helping to clear all that up! I'll either go with the buzzer that you talked about or maybe investigate plugging this device into a wall outlet.. but then I'd probably have to have something convert it from 120V AC to 12v DC at the same time as keeping an eye on amperage, if I understand this correctly, and that will be a new learning process too.

I've found out that this freeway blaster draws 4.5 amps, so while people are still looking at this thread, if I were to use a 12V DC adapter from a wall outlet, that ran 5 amps, would that work for both the horn and the clearance light, or would the clearance light get burned by the current? Or would it only draw what it needed and things be fine? Thanks so much for all the help so far.

*Edit: And Ray2047, thank you for the suggestion for the other horn device

**Edit 2: it appears from looking it up that the amperage isn't a forced flow, so each device (light, horn) would draw what it needed -- therefore I expect that getting a 12v DC 5 or 6 amp adapter would meet the needs of both the horn and light and be the solution I'm looking for as far as I can tell.
 
  #7  
Old 05-03-13, 06:20 PM
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I'm not sure of your work environment, but I can tell you if you set off a 130 dB horn in my presence, you wouldn't need the batteries any more. You may not even be able to find them, if you know what I mean. I would use a more innocuous method of attention getting like the buzzer mentioned. You really don't want to endanger anyone's hearing, which 130 dB will do in only a few seconds.
 
  #8  
Old 05-03-13, 08:49 PM
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I wouldn't use that horn indoors if I were you.:NO NO NO:

Anyway, a 10A 13.8V power supply should power everything great.
 
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Old 05-03-13, 08:54 PM
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Power supplies are funny things. Most have short circuit detection built in to them and to most power supplies a car horn would appear as a dead short. Make sure whatever supply you get you can return if it doesn't work.

And Justin is right..... more than likely a 10 amp supply will be needed.
 
  #10  
Old 05-05-13, 09:45 AM
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Thanks everyone for helping out! I think I have everything I need now.

And yes, if I still go ahead with this horn idea, I plan to have it both muffled and contained inside a thick wooden box. And even still I'm going to do careful testing first because I want to make sure it's safe for people, but if possible, still carrying the novel sentiment of "wow he just blasted us with a truck horn" even if I have to severely nerf the sound level.
 
  #11  
Old 05-05-13, 10:13 AM
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If you have to quieten it down, why use it? You are making a statement. Use something more run of the mill, like a motorcycle horn.
 
  #12  
Old 05-05-13, 10:24 AM
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Instead of an actual horn why not a recording of a horn? Look for cheap recording devices such as those in a greeting card or toy where you leave your own message. (Strip the recorder from the card or device.) Lots of sources for sound effects on the internet you could record onto it.

Example from a quick search: Amazon.com: RE-Recordable PUSH BUTTON Sound Module/Chip (104 seconds): Everything Else

Amazon.com: 300 Second (5 Minute) digital voice recorder Recordable Sound Chip for Make Your Own Stuffed Animals: Toys & Games
 
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