MAKE: Blog: HOW TO - Make a rusty nail LED night light

HOW TO - Make a rusty nail LED night light

Rustynail
Dick shows you how to make your own rusty nail LED night light!

These blocking oscillator type power supplies work best with ferrite cores, and sometimes they can be hard to locate. Some readers have expressed anxiety over making inductors, and that is understandable since to many, inductors have an aura of mystery about them.
Just to prove that these inductors aren't magic, or even that critical for that matter, I wound one on a rusty nail that I noticed laying beside the road one day while waiting for a tow truck. It is a 2-1/2 inch (6.5 cm) long flooring nail, which serves as the inductor's core.

The wire is a twisted pair of #24 solid copper wire that I pulled from a length of CAT-5 (ethernet) cable, which is similar to the wire used to connect telephones inside buildings. I wound 60 turns of the twisted pair in about three layers around the flooring nail, then I connected the start end of one conductor to the finish end of the other conductor and that made it into a 120 turn center tapped inductor.

I connected it to a 2N2222, a 1K resistor, a 1.5 volt penlight cell, and a white LED. Nothing happened. Then, I put a .0027 uf capacitor across the 1 K resistor (it happened to be on the work bench) and the LED came on. Sometimes you need .001 uf or so. The LED glows nicely and the circuit draws 20 milliamps from the AA cell. The waveform on the oscilloscope looks terrible, but the point is that the circuit oscillated with even this rusty nail, and it boosted the output of the 1.5 volt AA cell to over 3 volts peak to drive the LED.

Those who are familiar with some aspects of coil core selection would quickly point out that the eddy currents would be huge since iron has a low resistance compared to ferrite, or air for that matter, and that there would also likely be other types of large losses. The point here is not that you should run out and buy some flooring nails to make LED lamps, but that this circuit was not "designed", but was thrown together and worked quite readily. If a rusty nail and some telephone wire is enough to light up a white LED, then the inductor is not so critical. So, relax, go buy a ferrite core and get started on your project.

Rusty Nail LED Night Light - [via] - Link.

Comments

Oldest comments listed first.

Posted by: Windell_Oskay on March 27, 2007 at 7:36 PM

Although the link doesn't point it out, this is another example of a Joule Thief (as previously featured here), simply one of the coolest circuits there is.

Posted by: Myself248 on March 27, 2007 at 7:39 PM

Hehehe, Windell you beat me to it! The layout looked suspiciously familiar...

I like Big Clive's compact construction, personally. Not that there's anything wrong with big iron-core inductors, but ferrite wastes less energy.

Posted by: paulsw on March 28, 2007 at 3:36 AM

This is a great kick in the butt to get started on that joule thief I was going to make. I keep coming across the ferrite cores I bought and thinking "I really must make that"

Posted by: Big Clive. on December 8, 2007 at 8:20 PM

Another useful source of nice little ferrite toroids is dead compact fluorescent lamps. Just take care when opening them to avoid getting a fist-full of glass. The two parts of most CFL cases pop apart with gentle (or carefully destructive) application of a thin screwdriver tip.

Subscribe to MAKE Magazine!

Subscribe today, save 42% and get web access to MAKE free. MAKE Digital Edition is available only to subscribers.

$34.95 / 1 year
(4 Quarterly Issues)

Subscribe now

Void your warranty, violate a user agreement, fry a circuit, blow a fuse, poke an eye out... Welcome to the Make Blog!

Features and more @ MAKE!

Get MAKE 14 - Subscribe or on newsstands!

Add MAKE to iGoogle - GoogleGoogle.
Add MAKE to your RSS reader - Real simple.

Why advertise on MAKE?
Read what folks are saying about us!

Click here to advertise on MAKE!

Phillip Torrone
Senior Editor
Tel: 707-827-7311

Gareth Branwyn
Robot Maker

Kip Kay
Video Maker

Jonah Brucker-Cohen
Artist / Researcher

Suggest a Site!

Natalie Zee Drieu
Senior Editor
CRAFT

Becky Stern
Culture jammer

Collin Cunningham
Sound Maker

Marc de Vinck
CNC Maker

Current Podcast

Maker's Notebook Pocket - CRAFT Video Podcast Download the MP4 Video or HD Version | Subscribe to CRAFT in iTunes Love your Maker's Notebook, but wish it had a pocket? Well, in this video I'll show you how easy it is to add your own. This... More...

Get the Make blog sent via email

Enter your email to receive the Make blog each day:

WOW! Thanks to everyone involved with Maker Faire Bay Area: attendees, makers, exhibitors, sponsors, volunteers, and crew...it was AMAZING! Over 400 Makers and 60,000+ attendees! Be sure to check out the photos @ Flickr, and our Maker Faire posts for all the action! The next scheduled Maker Faire is Austin: Oct. 18th & 19th, 2008 - Travis County Expo Center!