The On-Line Magazine of Rideable Model Railroading
  NUMBER 117

WWW.DISCOVERLIVESTEAM.COM 

© October 05, 2008   

©Roy Stevens (ridetrains.net) and Discover Live Steam. This material may not be published, rewritten, or redistributed without written permission.

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Build a Good Sounding Horn for Cheap
 

 

Written by Roy Stevens
 

There has long been a need in this hobby for a good horn somewhere between an expensive Phoenix Sound system and the stand-in auto or scooter horn.  This has been the subject of many internet discussions with no resolution Ė until now.  This simple and effective horn system can be built for less than $20 and can replicate any horn you like, from a Nathan K3 to a Southern 5-chime steam whistle, so long as you can produce a recording or have access to the real thing.  Itís built with two components: powered computer speakers and the guts of a recordable greeting card.  Just about any powered speakers should work, but the ones I use work nicely with common 12vdc and most should work fine with some basic electrical knowledge.  I purchased the OG-691 speakers (above) at a local computer store but they are available through Newegg.com, item #N82E16836131004.

Editors note:  Newegg.com is sold out.  I suggest you do a Google search for that stock number.  Hopefully you can still find some on close-out.  If not, other speakers of similar design will work just as well.

The other item is the greeting card sound module (right), available from Electronics123.com at this writing the item was directly on the front page or click this link.

The first thing to do is record your favorite horn sound to the sound module.  I recommend this web site for some good samples.  Some experimentation will be needed to get a good recording that can be Ďplayedí by using the power tab to get short or long bursts.

Editors note:  Pick the sound module that works for your application.  The card in this story reproduces a 20 second sound, not repeatable without resetting the "power tab".

Before disassembling the speakers, for your safety I recommend cutting off and disposing of the 120v plug.  Then take apart the one with the controls by removing the four screws in the back.

Note the voltages marked on this transformer (right). If you are using different speakers this is the best way to find your input voltage. The 10v is voltage at full load, under normal conditions this transformer will provide up to 14v, so our input voltage of 12v from the battery is perfect. I used the same connection points before the bridge rectifier so battery polarity is not an issue. If this is Swahili to you, donít worry, just follow the instructions and it will work fine.


click to enlarge

The bottom of the powered speakers circuit board.  The thicker blue wires are where you will connect the power from the battery and the red, white, and blue wires are where you will connect the output from the sound module, i.e. the wires that you will unsolder from the speaker on the sound module. Begin by unsoldering the blue wires (see right photo) and removing the transformer and power cord. Solder on two wires that will connect to the battery, I used the power cord with the plug cut off. Then unsolder the three wires from the sound plug and unsolder the white wires to the speaker on the sound board. I didnít have any extra small wire and the white wires to the sound module speaker were a little short, so I borrowed some wire from the connection to the other speaker. I wasnít planning on putting it very far away inside my loco anyway. The finished connections are shown in this photo.


click to enlarge

Shown is the completed connections to the speaker board (right). Note the small white jumper between where the red and white wires connected. This allows the use of both speakers thereby doubling the volume.


click to enlarge

Note that I have bent the power tab up to expose two pads on which to solder the wires to an activation button, it must be a normally open momentary pushbutton.  Iíve put the button in a hole drilled in the top of the speaker for demonstration purposes (right), but longer wires to your normal horn button on the control pendant or panel would be much more useful.  Also note that Iíve used a small screw to secure the sound module to the hole vacated by the transformer.  The red wires appear to go to the activation button, but they are still attached to the record switch which is out of sight.

Connect the new power wires to a 12vdc source and enjoy the sounds of real railroading.

Of course if this all seems too complicated, completed systems will be available on my website.


click to enlarge

The above article is ©discoverlivesteam.com and Roy Stevens (ridetrains.net).
You may use the ideas presented here for your own use. Producing the above described product for resale (or using in products that are sold) is prohibited without permission of the author, Roy Stevens.

Written by Roy Stevens

©Discover Live Steam and Roy Stevens (ridetrains.net) . This material may not be published, rewritten, or redistributed without written permission.

Would you like to discuss the ideas in this article? 
Post a comment or question here.

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