Alarming Tennis Ball

Introduction: Alarming Tennis Ball

About: I am MacGyver McDaniel, yes just like the tv show. Instructables is an awesome website to where I plan on sharing more great instructables.Technology has always been fascinating and I love to learn how machine…

A tennis ball that when activated will sound an alarm. A simple magnet and the remote is used to arm and disarm the device. Once armed only time and the remote can disarm the device. Its great as a way to break the silence. Use it around others to be even more exciting.

Step 1: Materials

1 - Doberman Security Toolbox Alarm ($15  Home Depot)
1 - Tennis Ball

--- I found a cheap window alarm for $1 at the dollar store, simply removed the batteries and housing from the casing.----
3 -  LR44 Button cell batteries
1 - Casing for 3 LR44 batteries 

-- Stand --
2 - Plastic or paper cups

Soldering Iron
Solder - for electronics
Exacto knife or razor knife
general purpose super glue (Picked up at dollar store for $1)
Clamps or device to hold in place while using the saw
saw, preferably one for cutting plastic. 

Step 2: Shrink the Electronic Components

The Doberman Security Toolbox Alarm is a small rectangular shape that in no way could fit in the small dimensions of a tennis ball. We must take away the plastic housing and rearrange the parts to be in a compact shape. Be careful as to not break any of the soldered joints or you will have to use the soldering iron to re solder. 

Remove plastic cap on back. It makes cutting easier.
Using the saw cut around the edge of the housing until the housing is split into two halves. 
Remove the housing.
Cut the plastic edges of the electronics to make the size smaller. 
Cut the battery compartment from electronics
Cut the speaker housing from electronics
Trim speaker housing until the shape is circular rather than the square shape. 

After removing the existing AAA compartment by de soldering the wire leads, attach the LR44 Batteries and compartment. It is important to swap the AAA housing for the button cell housing as AAA takes too much room inside the tennis ball. As long as you have batteries that output the same voltage as before you should be ok. Removing three 1.5v AAA batteries results in needing three 1.5v button cell batteries. Use the remote to check that the device works.

Carefully bend the antenna into a smaller square shape the size of the electronic parts shape. 

Step 3: Concealing Electronics Into Tennis Ball

Using an exacto knife or razor knife cut along the tennis ball's line. Only cut half of the tennis ball line allowing the ball to retains its circular shape. Use the picture to get a better idea of the cut pattern.

Rearrange the electronic parts until the most compact shape is achieved. You may need to tape the back of the speaker and electronic board as to keep the wires from touching causing a short. 

Place the electronics into the ball through the cut out. Then fold back the tennis flap until the original sphere shape is achieved. Place the black magnetic reed switch in position that the arrow is pointing outwards towards the outer wall. Try to place the switch that once concealed will be located directly under the outside label. This helps in identifying where the magnet has to be positioned to arm device. 

Step 4: Making a Stand/case

The cup stand has a compartment for the remote and magnet while the ball rests on the top. To make the stand use a plastic or paper cup, a knife, and some clear tape.

Cut the cup in the middle.
Lay the top half of the cup upside down, wide part down.
Insert the bottom half of the cup inside the top half, bottom of cup should be with the top of the top side cup.
Tape the middle of each half together.

Insert remote and magnet inside the holder. Place the ball on top. That's it!

Step 5: In Action

Arm the device by placing a strong magnet near the magnetic reed switch, located inside the ball. Using remote press the "Arm" button once. If you hear one beep then the device is armed. Keep the magnet by the ball until you throw the ball. After 5 seconds of the ball being away from the magnet the alarm will activate. Once activated the only way to deactivate is with the remote control. Press the "Disarm" button on remote to disarm and turn off the alarm. 

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    10 years ago on Introduction

    How far away will the disarm/arm button work? also if I threw the ball would it break?


    Reply 10 years ago on Introduction

    The Remote uses radio frequency to arm and disarm the device. I would say about 5 feet it will work. I have tried it at ten feet and it has worked too. Sound wise I have noticed that the alarm sound is significantly less when inside the tennis ball. If you drill minute holes or cuts in the tennis ball the sound will not be as significant.

    I would try finding a car alarm kit or some remote activated alarm instead. The device I used has to be activated by a magnet and when the magnet is removed it will sound the alarm. Unfortunately in sense of secrecy it results in the person having to physically remove the magnet and throwing the ball before the alarm sounds. It makes more sense to instead put a remote activated alarm in place of the electronics i chose. You would then be able to sound the alarm remotely as well as stop it without any magnets just the remote.


    Reply 10 years ago on Introduction

    The sound must be activated when the person throws the ball so that is what I needed. Will it break when thrown? and 20 feet should be enough for my pourpose.


    Reply 10 years ago on Introduction

    If you use a good glue the tennis ball itself should not break on impact. I have thrown the ball many times and it has not broken. The one thing I did find was that the magnetic switch inside the tennis ball would sometimes move from its original position. I would pack tissue paper around the electronic parts to make the fit more snug. It appears that the tennis ball shell absorbs most of the impact and not the electronic parts on the inside. You should be fine throwing it.