Introduction: Build Your Own Countdown Regatta Box

An countdown "box" is a box with horns. When a regatta starts the box sounds the horns at predetermined intervals: 5 minutes before the start, 4 minutes before the start, 1 minute before the start and at the instant of the start. There are two types of sequences: 3 minute and 5 minute. In this instructable me and Chris LaBorde will show you how to build one by yourself. Because marine salt and water environment of boats, the box must be at least splash proof. Using the box will release two volunteers.

Step 1: Components Needed

This photo shows an LCD shield and one realy module.

Arduino UNO from dfrobot

One LCD Shield from (see photo)

Two relay modules from

One YUASA deep cycle 12 V 7A battery

One charger for the Battery of 8A

One piezo buzzer

Three push connect only switches

One toggle switch

One on/off interrupter

One splash proof box

A set of two horns and a compressor with the air tubes.

One Tupperware small

Cables, shrink tubes, solder (optional)

Step 2: How to Charge

1. Open the box to charge the battery when needed.

When battery charging push the red toggle switch to charge mode. When not charging push back to 'normal'

Step 3: How to Use

The big green button starts the countdown.

The small button sounds the horn manually (override in case of emergency)

The yellow button inside the box toggles the sequence type between: three minute countdown or five minute countdown.

Step 4: How to Wire

1. Stack the lcd shield on the arduino board.

2. Connect the relays inputs to pins D11 and D2, connect relay D11 to piezo and D2 to the compressor.

3. Connect the big green button to the lcd push buton 'LEFT' (solder cables to the switch pins in the LCD board, the push button will override the lcd 'LEFT' button)

4. Connect the yellow push button the the lcd push button 'SELECT' (same as 3)

5. Connect the small green button between compressor + and battery + poles (to sound it manually)

6. Connect battery to charger via the red switch and baterry to compressor and arduino power input via the 'normal' position of the red switch.

Step 5: The Splash Proof Box

Find a splash proof box with rim seal. Use foam at the bottom so nothing is loose. Once the wiring is done put the Arduino and relay modules inside a Tupperware for added waterproofing. Make holes for the tubes that power the horns. And fix the horns as in the picture.

Step 6: Programming the Arduino

To program the Arduino: Download the Arduino IDE to your laptop. Upload the code to the Arduino with a usb cable. Source is here: the time units is 100ths of second and the time resolution < 10ms approx.


tomatoskins made it!(author)2015-03-02

This is cool! When I watched your video, the horns starteled me. Great design!

harriken made it!(author)2015-03-02

The layout is Chris design. Now we are working on a leaner version with no battery. We shoudl attach a sticker that says "sounds hazard - wear protection" LOL

NeilB95 made it!(author)2017-05-08

This is great but our club uses a combination of lights and horn. I wonder if I could modify this to do our start sequence?

Advance Notice - Two lights flashing and repeated hornApprox 1 minute before warning signal (short duration)

Warning- One light, single horn and flag 5 minutes before start

Preparatory - Two Lights, single horn 4 minutes before start

One Minute - One light, single horn 1 minute before start

Start - No lights, single hornAt start

Pcplod made it!(author)2017-05-10

Hi I am also wanting to build start regatta system to include lights and horn, very similar to your start sequence New to electronics and will be buying first UNO

if you move forward with your project let me know :-)

DavidW69 made it!(author)2015-09-01

Works flawlessly! Great project. Having little to no experience with building electronics, it took me a while to figure out exactly what components to purchase and how to wire them together. However, it's a very do-able project and the end result is a fully automatic start box that works really well - at about 1/3 the cost of buying one.

nalsalam made it!(author)2017-01-09

Congratulations! Nice box. I ordered your parts list and am midway through building one myself. The relays are back-ordered and so I dug deeper into datasheets to look for another. During that process I found that the relays you used are rated for 10A (15A maximum) but the compressor on the Wolo horns I bought says could draw 18A. Have you had any issue with the DFRobot relays being beefy enough? Also, I wondered if you found the buzzer to be loud enough. I worry that being inside the box, it may be hard to hear on a windy day. Also, it does not appear that the buzzer needs a relay, right?

harriken made it!(author)2016-04-13

your box is great!

harriken made it!(author)2016-04-13

wow glad it worked for you :)

DavidW69 made it!(author)2015-08-05

Thanks so much for posting this. Going to make one for our J/22 class and if successful one or two more for our junior program. Im pretty good with mechanical things but have no experience with electronics. I've tried to source all the things on your list - but there are a lot of options for each item. Would you mind proofing my shopping list to be sure Im buying the right components? Here is a link to the list I've assembled with SKU's on each item (you can comment on the document)

Also I couldn't find the "on/off interrupter" for the toggle switch -there are many options - could you give me the details on the toggle switch?

Thanks again


harriken made it!(author)2016-04-13

DavidW69 has a picture of it in its photos

DavidW69 made it!(author)2015-08-05

that should say "or the toggle switch"

harriken made it!(author)2016-04-13


RyanS29 made it!(author)2015-07-27

Love this and would like to make one for my club. I'm good with the wiring, but not code writing. Your code for the 3 minute start seems to be different than what we use. We use 3 long blast at 3 mins, 2 at two mins, 1 long 3 short at 1:30, 1 at 1 min, 3 short at 30 secs, 2 at 20 secs, 1 at ten secs, and count down from 5 secs to start. Could you lead me through changing the code to achieve this. Thanks for any help

harriken made it!(author)2016-04-13

modify the vector

unsignedlong sch_3[] <-- indicates horn or buzz time in 10x ms units

h_or_b3[] <-- code: buzz = 0, short horn (sh) = 1, long horn (lh) =2 extralong horn 3

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