Joule Thief From a Beer Can

This is one of the simplest joule thief's you are likely to come across. It is made from a couple of beer cans, some Sellotape, a LED and a battery. It incorporates a manual magnetic pulse trigger to power a 1.8volt LED from a 1.5 volt battery.

So how does the Joule Thief circuit work? Here's an explanation: in this past instructable:
https://www.instructables.com/Joule-Thief-Circuits...

Paraphrasing the authors explanation: When the striker is held briefly against the LED wire attached to the battery, current flows through the coil and creates a magnetic field around the coil.
But when it is is released the magnetic field suddenly collapses and creates a 1.4 volt voltage with a reverse polarity for a moment. It is as if the coil has become like a temporary battery connected in series with the actual battery, presenting 2.8 volts to the LED. The LED reacts to this by flashing on for a moment. Touching with the striker again repeats this cycle. If you could do this rapidly enough, the LED would appear to be solidly ON.

1.8V LED (Light Emitting Diode)

1.5V AA Battery

Couple of Beer Cans

Sellotape

180 grit sandpaper

Make some aluminium wire from one of the beer cans as described in this instructable.
https://www.instructables.com/Repurposing-Beverage-Cans-for-Low-Voltage-Electric/

Wrap the wire with Sellotape to make it insulated.
Wrap six turns of wire around a beverage can.
Sellotape a 1.5 Volt Battery to the base of the can Attach one end of the wires to the positive terminal. All connections should be rubbed with sandpaper first.

Attach the shorter of the two LED leads (negative) to the negative terminal of the battery using Sellotape. The other LED lead is attached to the free wire about 7 centimetres from the end. Attach the tab from the can to the end of the wire. This will be the "striker".

The LED won't lite up because it requires 1.8 volts. Here's where the striker at the end comes into play.

Touch the striker against the LED lead, this completes the circuit and creates a magnetic field in the wire. When the striker is removed, the magnetic field just created collapses, inducing a current into the wire and this, added to the current feeding the LED is enough to make it glow momentarily. Strike the LED lead again for another flicker. If this was done multiple times a second our eyes would perceive it to be a steady light.

I attached the striker around the LED lead as I figured this way it could strike the lead multiple times in a second. Another way is to make a rapid switch as shown below.

The light only turns on for a moment when the the electromagnet circuit collapses (turns off), if this can be switched on and off rapidly the light will flash.

A rapid switch can be made with a strip of aluminium cut from a can. Sand the strip and then make ridges along it by crimping it over a matchstick a number of times. Place some Sellotape to cover part of the drink tab. Connect the strip to a battery lead then run the tab along the ridges. The LED light will flash as the circuit is rapidly turned on and off.

A pair of tweezers with ridges along the handle also works well.

If you are interested in similar electronic projects, check out:

Rechargeable Tin Can

Tin Foil Battery

Variable Resistor from a Pencil

Everything is OK! - Mechanical Joule Thief