DIY Train Horn from DEWALT Drill: Step-by-Step Guide

This guide walks you through a proven method for building a powerful handheld train air horn using a standard impact tool housing.

In this article, I’ll show you which parts are required to build an Impact Train Air Horn, and how much it actually costs. I’ll also include links to all the components I use.

I have personally hand-built hundreds of handheld train horn units since 2022, right after I arrived in the United States from Ukraine with my family. Back home, I wasn’t a professional mechanic, but I always loved tinkering with tools. When I came to America, those skills became my lifeline. I originally started building these horns as a side job just to support my family.

The early stages involved extensive testing and refinement to arrive at a reliable, repeatable configuration.

That’s exactly why I documented this guide — to outline a finalized method that avoids common pitfalls and is now consistently used in real builds.
Let’s get to work!



Before you start:
I’ve put together a hands-on video showing the entire process step by step.
Below the video, you’ll also find a detailed written guide with photos.
Feel free to use either format, but I recommend watching the video first and then following along with the illustrated instructions.

Video demo
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What I Use for This Build

Below, I have listed all the necessary parts you will need, along with their estimated costs based on current Amazon prices at the time of writing. For your convenience, I have also included direct links to all the materials used in this project so you can find exactly what you need.

1,2)Quad Train Horn Kit- $39.99
3) Trigger Switch - $8.39
4,6)Remote Control & Receiver - $9.99
5) Automotive Relay - $5.99
7) Impact Driver / Drill - $77.88

So, in summary, the parts to build your own Impact Train Air Horn will cost $64.36 if you already have a drill, or $142.24 if you don't have one and need to buy it.

In addition to the main hardware, I use a few consumables.

1) Hex-head fasteners with ~ 3/4" length.
2) Electrical Crimp Connectors - $6.99
3) Vinyl Tubing(1/4" ID) - $32.56
4) Electrical Wires - $11.98
5) Door Seal Strip - $12.99
6) Heat Shrink Tubing - $11.88

All these supplies on Amazon cost an additional $76.40


You might already have some of these items in your garage, meaning you won’t need to buy everything on this list.

However, if you are starting from scratch and want to save money, I recommend grabbing the Complete DIY Kit on my website. It costs roughly the same as buying just the main parts on Amazon, but it includes the exact amount of supplies you need—so you instantly save at least $76 compared to buying bulk packs separately.

DIY Kits & Pre-Assembled Options

Choose a DIY kit or a fully pre-assembled option to save time and money.

Full DIY Kit with Remote Control (Black)

Full DIY Kit with Remote Control (Black)

$64.00
Full DIY Kit with Remote Control (Chrome)

Full DIY Kit with Remote Control (Chrome)

$74.00
Prewired Full DIY Kit with Remote Control (Black)

Prewired Full DIY Kit with Remote Control (Black)

$84.00
Prewired Full DIY Kit with Remote Control (Chrome)

Prewired Full DIY Kit with Remote Control (Chrome)

$94.00
Full DIY Kit with Remote Control (Black)

Full DIY Kit with Remote Control (Black)

$64.00
Full DIY Kit with Remote Control (Chrome)

Full DIY Kit with Remote Control (Chrome)

$74.00
Prewired Full DIY Kit with Remote Control (Black)

Prewired Full DIY Kit with Remote Control (Black)

$84.00
Prewired Full DIY Kit with Remote Control (Chrome)

Prewired Full DIY Kit with Remote Control (Chrome)

$94.00

THE BUILD PROCESS

SAFETY FIRST:

Eye Protection: Always wear safety glasses when drilling or cutting plastic.

Hearing Protection: Never test the horn indoors or without ear protection. It is extremely loud!

Battery Safety: Always disconnect the battery before working on the wiring.

STEP 1: Disassembly

A) First, I remove the eight screws securing the impact driver housing and separate the two halves.

B) Using wire cutters, I disconnect the Contact Plate located at the bottom of the housing by cutting all three wires that connect it to the internal components.

C) Once free, I remove the motor, gears, and the original trigger switch—I won't need these parts anymore. The only part I keep is the Contact Plate. I also plan to replace the original trigger with a new button later on.

STEP 2: Drilling the Housing

A) Next, I temporarily screw the housing halves back together using a few screws. I need the shell to be assembled so I can accurately drill the two mounting holes for the horn base.

B) I aim to position these holes dead center, both horizontally and vertically on the flat side of the housing. This placement is crucial to ensure the horns attach in the correct spot and don't interfere with other components later.

Note: I take my time with this step because it is the most sensitive part of the build—there is no room for error here. I highly recommend double-checking that your drill bit size perfectly matches the diameter of the fasteners before you commit to drilling.

STEP 3: Wiring the Electronics

A) First, I prepare the wires to the following specific dimensions: four black wires for connections, each 4 inches long, and one piece of red wire, 9 inches long.

B) The Negative Connection: First, I solder a black wire to the negative contact on the Connector Plate. I solder the other end of this wire to the bottom contact of the trigger switch

C) Relay Power Input: Next, I take a second black wire and solder it to that same bottom contact on the trigger. I run the other end to one of the power pins on the relay. Crucially, at this same spot on the relay, I also solder the black wire coming from the receiver.

D) Relay Output: I solder the third black wire to the other power pin on the relay. Later, I will attach a crimp connector to the loose end of this wire—this is what will power the compressor.

E) The Control Circuit: Now for the signal. I connect the fourth black wire from the top contact of the trigger switch to one of the control pins on the relay. To this same control pin, I also attach the white wire from the receiver.

F) Completing the Loop: On the remaining control pin of the relay, I solder the blue wire from the receiver.

G) The Positive Line: Finally, I take my long red wire and solder one end to the positive terminal on the Connector Plate. I twist the other end together with the red wire from the receiver and secure them both into a single crimp connector.

H) The Final Touch. To finish up the wiring harness, I attach a crimp connector to the loose black wire coming from the relay. This connector is what I will eventually plug into the compressor to power it.

That completes the electrical assembly. Now, I always test the connections with a multimeter before moving on.

STEP 4: Pairing the Remote

Now that the electronics are soldered, I pair the remote control to the board before putting everything into the housing.

I find the small black button on the receiver board and press it once. The LED lights up, signaling it is ready to learn. While the light is on, I press the button on my remote. The receiver light flashes to confirm it has memorized the code.

A Crucial Warning:
I am very careful never to press the receiver button twice during this step. If you do, it enters "Latch Mode," meaning the horn will blast continuously until you click the remote again—you definitely don't want that for a train horn.

If I ever accidentally activate this mode, I reset the receiver to factory settings by pressing the small button 8 times in a row to wipe the memory.

STEP 5: Internal Assembly

A) Placing the Electronics
I usually position the receiver right next to a vent or an existing hole in the case. I make sure the pairing button is accessible from the outside—that way, if I ever need to pair a new remote later, I won't have to tear the whole tool apart again. I secure the receiver board firmly using a hot glue gun.

I also use hot glue for the trigger switch. Since this is a universal switch and not custom-molded for this specific drill housing, it needs that glue to stay solid and not wiggle.

B) Routing the Antenna
I pay close attention to the white antenna wire. I try to route it so it is stretched out as much as possible inside the case. From my testing, this maximizes the signal range.

C) Installing the Compressor
Before dropping the compressor in, I remove the two little tabs on its sides. If I don't, they will get in the way, and the case won't close properly.

Since the compressor is slightly smaller than the original motor space, I use some foam weather stripping tape to wrap it. This fills the gap and keeps it snug so it doesn't rattle.

D) Closing Up. Finally, I connect the crimp connectors to the compressor terminals—Red wire to Positive (+) and Black wire to Negative (-).

E) Once connected, I neatly tuck all components into the housing and screw the case back together.

STEP 6: Final Assembly

A) Mounting the Base. I screw the horn base securely onto the housing using the mounting holes I drilled earlier.

B) Connecting the Air Line.
I connect the vinyl air tubing from the compressor output to the horn base. I always measure and cut the tubing to the exact length I need so it looks clean and doesn't kink.

C) Attaching the Trumpets
Finally, I screw the four trumpets onto the base. Now the train horn is fully built and ready to blast!

⚠️ DISCLAIMER

Safety & Liability:
This guide is for educational purposes only. The author and Honkup.com assume no liability for personal injury, property damage, or voiding of warranties resulting from this project. Working with power tools and electrical components carries inherent risks. Always follow standard safety protocols.

Legal Compliance:
The train horns featured in this guide are extremely loud. Do not use this device in close proximity to people or animals. It is the sole responsibility of the user to ensure that the use of this device complies with all local, state, and federal noise regulations and laws.