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 dfrobot.com (see photo)

Two relay modules from dfrobot.com

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: https://github.com/orioli/ollie/blob/master/produc... the time units is 100ths of second and the time resolution < 10ms approx.