Everything Is OK! Alarm - Mechanical Joule Thief

One of Homer Simpson's greatest inventions was the 'Everything is OK' alarm (session 10) which sounds to let everyone know it's OK. This project is along a similar vain.

It will transmit to a nearby radio and has a red LED light so the hard of hearing will also know everything is OK.

It was inspired after making 'The beer can jewel thief' which increases voltage to momentarily light a LED - would the LED, light constantly if the circuit was rapidly turned on and off? As this buzzer is basically a rapid switch - combine the two so the LED appears to light constantly. Hence, I present to you the 'Everything is OK' alarm.

Step 1: Make an Electromagnet

An electromagnet is at the heart of this project. It is made by wrapping about 200 turns of .3 mm of copper wire around a big nail in the same direction. A battery powered drill can help to do this faster.

The diagram shows the circuit the electromagnet is added to.

Step 2: Make the Stand

The buzzer's stand follows this design. Make it from a suitable piece of wood. A tomato plant stake can be used to give a rustic look. This look is enhanced by not taking any measurements, just judge lengths by eye. A switch is made from the top on a tin can and a smaller nail. Use some suitably length screws to assemble the wood as shown in the photos. Sand paper the part of the tin can lid which will be in contact with the smaller nail. Drill a hole in the upper support and slide in the electromagnet previously made. Screw on the tin lid, connect a 1.5 volt battery and check that electromagnet will attract the tin lid when turned on.

Step 3: Test the Buzzer

Add another support and drill a hole for the smaller nail. Insert the nail so it will touch the tin can lid where sanded. Connect one lead of a 1.5 volt battery to one end of the electromagnet circuit and connect the other end to the smaller nail. Connect the other end of the electric battery to the tin lid. Position the two nails so the electromagnet is close to the lid when the smaller nail makes contact. The idea is the nail touching the tin lid creates an electrical circuit which energies the electric magnetic which in turn pulls the tin away from the smaller nail contact, which shuts down the electromagnet, the tin lid goes back to touching the smaller nail, this energises the magnetic field which once again pulls the lid from touching the nail and so the process continues as the magnetic field is created and then collapsed. This results in a buzzing sound and the creation of localised radio waves.

Step 4: Make a Battery Holder

A battery holder can be made from the top section of a beverage can and sanding the inside to make a good connection as shown in the photos. Or just buy a battery holder or attach the wires to the battery with some Sellotape.

Step 5: Testing the Light - Joule Thief

Having created an oscillating electromagnetic circuit, a joule thief circuit is made by connecting a 1.8v LED across the negative and positive wires. The longer leg of the LED is connected to the positive side of the battery. By creating and collapsing the magnetic field a reverse voltage is created in the wire, when this is added to the voltage already being applied to the LED it turns on each time the magnetic field collapses. This is kinda cool as you have created a circuit which makes more voltage than the battery provides. The 1.8v LED will light up from the 1.5v battery and appear to remain constantly on, or flicker a bit.

Step 6: Testing Transmitter

If a small am radio is held nearby it will pick up the radio transmission created by the oscillating electromagnetic circuit. If you turn the volume of the radio up, even more people can be assured that 'Everything is OK'