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using a coil and magnet to power an LED

M

Mike Pinch

Hi,

I am interested in using a coil and a moving magnet to briefly light up an
LED. I have only a basic understanding of electronics.

Does anyone have any advice on what parts or circuit I would use to
accomplish this?

Thanks,

Mike
Seattle
 
D

DaveM

Mike Pinch said:
Hi,

I am interested in using a coil and a moving magnet to briefly light up an
LED. I have only a basic understanding of electronics.

Does anyone have any advice on what parts or circuit I would use to accomplish
this?

Thanks,

Mike
Seattle
Click to expand...

Ummm Err... Ahhhh Is this a trick question???
Really, the LED, coil and moving magnet are the only things you need, if the
magnet is strong enough and the coil is large enough and the movement is fast
enough. Can you elaborate a bit more on the specifics of your project, or is it
classified?

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!
 
F

Frank Bemelman

Mike Pinch said:
Hi,

I am interested in using a coil and a moving magnet to briefly light up an
LED. I have only a basic understanding of electronics.

Does anyone have any advice on what parts or circuit I would use to
accomplish this?
Click to expand...

I would try a coil and a moving magnet.
 
A

amdx

Mike Pinch said:
Hi,

I am interested in using a coil and a moving magnet to briefly light up an
LED. I have only a basic understanding of electronics.

Does anyone have any advice on what parts or circuit I would use to
accomplish this?

Thanks,

Mike
Seattle
Click to expand...
Hi Mike,
I'm sure you have seen the flashlights that you shake back and forth,
causing
a magnet to slide inside of a coil. These flashlights store the charge in a
capacitor
while your not shaking it. Is this the idea your after?
Would a rotating coil and a stationary magnet work for you? Go to Radio
Shack
and get a small DC motor, connect the LED to the motor with the correct
polarity
and then spin the motor, the LED should glow.
Give us a better idea of what your after.
Mike
 
J

John Larkin

Hi,

I am interested in using a coil and a moving magnet to briefly light up an
LED. I have only a basic understanding of electronics.

Does anyone have any advice on what parts or circuit I would use to
accomplish this?

Thanks,

Mike
Seattle
Click to expand...

Wind a couple/few hundred turns of small-gauge wire around maybe a
toilet-paper cardboard core. Use maybe #30 enameled magnet wire.
Connect it to the led or preferably to a pair of leds connected
anti-parallel.

Drop a super-magnet, like one of the rare-earth things from an old
hard drive, through the hole, the faster the better. The led's should
flash.

More fun: drop a supermagnet straight down inside a long hunk of 3/4
inch copper water pipe. Release it and quickly look down the pipe as
it drops.

I recently tried dropping a quarter down the bore of a megabuck
superconductive magnet, expecting the eddy currents to slow its fall.
It never came out the bottom, not because of the field but because it
jammed in a flange halfway down. Very embarassing.

John
 
M

martin griffith

Yabbut, the OP is not interested in that.


I bet ;)
Click to expand...
You win,I lied. I couldn't find a symbol for a hand waving a coil (or
magnet)


martin
 
F

Fred Bartoli

martin griffith said:
You win,I lied. I couldn't find a symbol for a hand waving a coil (or
magnet)
Click to expand...

Did you put that nice zero threshold bridge, so that it lights whatever the
direction you move the magnet.

And with a transformer, if you suffer from Parkinson's disease you could
make yourself a powerless christmas tree.
 
M

Matt

Another cute experiment is to create a "motor-generator" from a couple
of DC "muffin fans" like those used to cool computers. You connect the
leads of the first fan to an LED/series resistor combination (keeping
the polarity correct), and then you connect the leads of the second fan
to its proper power source. The second fan will start spinning. Now,
place the first fan close to the second one so that its airflow turns
the blades of the second fan. As the second fan turns, it generates
electricity to light the LED.

Anyone remember those old 28 VDC motor generator sets used to power
portable World War II electronic field gear?
 
P

Paul Hovnanian P.E.

martin said:
You win,I lied. I couldn't find a symbol for a hand waving a coil (or
magnet)
Click to expand...

No. You just model the coil and magnet in spice and then pick up the PC
and shake in back and forth, just like one of those flashlights.
 
M

Mike Pinch

I just got back. Thanks for the feedback.

The application isn't really classified in the sense that I'm not planning
on putting LEDs into a stronglink or anything but there are some geometrical
constraints which will mostly impact the coil. Any standard LED will fit
into the space I have. The intent is to have the LED flash briefly but
intensely. The coil needs to fit in a fairly narrow space so it needs to be
"flat" (as in probably occupying less than 1/4 inch thickness) . The coil
can be long. Let's say we had a long thin coil with lots of windings.

If there is a long slender coil (say 4 inches long wrapped around an 1/8"
diameter mandrel) with the proper number of turns, does the influence of the
magnet (which is let's say 1/4" diameter x 1/10" thick) become
time-dependent? Will the induced current gradually build up as this magnet
traverses along the coil? Are additional components needed in this case?
Remember, I am looking for a briefly flashing LED -- no constant output
required.

Also, I am messing around with various coils, chokes and wal-warts. Some of
these devices seem to have a metal mandrel, some don't. How do I know what
kind of mandrel (core) to use?

Regards,

Mike



Paul Hovnanian P.E. said:
John_H said:
[snip]

Take the guts out of this:

http://www.sharperimage.com/us/en/catalog/productdetails/sku__DK013ZZZ

and you have what you need. Moving magnet, coil, LED, let there be -
shake shake shake - light!
Click to expand...

Don't forget the bridge rectifier and the supercap.

--
Paul Hovnanian mailto:p[email protected]
------------------------------------------------------------------
Disclaimer - These opiini^H^H damn! ^H^H ^Q ^[ .... :w :q :wq :wq! ^d
exit X Q ^C ^? :quitbye CtrlAltDel ~~q :~q logout save/quit :!QUIT
^[zz ^[ZZZZZZ ^H man vi ^@ ^L ^[c ^# ^E ^X ^I ^T ? help helpquit ^D
man quit ^C ^c ?Quit ?q CtrlShftDel "Hey, what does this button d..."
Click to expand...
 
C

Christopher

Hello Michael,

Just when I thought I had it you changed rules.

Actually one method is using three small button type batteries and a
super bright LED. Make certain the LED forward voltage is under 4
volts. Kids tennis shoes use this method. Look around in the toy
section Walmart, I found packs of three 1" plastic marbles for $3 with
a built in flashing IC chip, circuit board, four colors super brite
LED's and the three batteries. That's for each marble!

This triggers from a small spring switch that senses a mild impact.


Trying to achieve 4 volts off of a very small coil and magnet seems a
bit challenging.

I don't think you mentioned what triggers your LED, physical motion?


If there is a long slender coil (say 4 inches long wrapped around an 1/8"
diameter mandrel) with the proper number of turns, does the influence of the
magnet (which is let's say 1/4" diameter x 1/10" thick) become
time-dependent? Will the induced current gradually build up as this magnet
traverses along the coil? Are additional components needed in this case?
Remember, I am looking for a briefly flashing LED -- no constant output
required.
Click to expand...


* * *
Christopher

Temecula CA.USA
http://www.oldtemecula.com
 
M

Mike Pinch

Christopher,

Excellent feedback; thanks.

I didn't want to use batteries in this application. The application is such
that human intervention to change batteries is undesirable.

Here's a question -- does a coil necessarily need to be wound in a circular
fashion (cross section) or could a coil be wrapped around say a flat piece
of something (like a popsicle stick)?

Mike
 
L

Lukas Louw

Hi,
I am interested in using a coil and a moving magnet to briefly light up an
LED. I have only a basic understanding of electronics.

Does anyone have any advice on what parts or circuit I would use to
accomplish this?

Thanks,

Mike
Seattle
Click to expand...

Our 20 month old has sneakers with a couple of LEDs on them that flash when
she walks. I assume there is a coil with a loose fitting magnet in the
shoes. Let me see if the wife kept the older too small ones, and I'll cut
them open to see what's inside...

Lukas
 
F

Fred Bloggs

Lukas said:
Our 20 month old has sneakers with a couple of LEDs on them that flash when
she walks. I assume there is a coil with a loose fitting magnet in the
shoes. Let me see if the wife kept the older too small ones, and I'll cut
them open to see what's inside...

Lukas
Click to expand...

A battery...
 
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