Ridiculously low power LED flasher for science day

[engie]

Hi,
I'm designing an experiment for an electricity themed science day*.
We're going to build super simple motors by coiling some enamled wire,
taking the ends of the coil wire and filing off one side of each end
and sitting this in two stirrups that are connected to a small battery,
with a magnet underneath the coil - you've probably seen the idea
before. These work nicely as motors, and can spin at a fair clip if you
get a nice coil.

I would also like to show that this design works as a (horribly
inefficient low power) generator. As the current generated by this
design is going to be incredibly small, are there any simple, low
component count circuits that could be implemented to store up charge
and discharge it through an LED when there's enough to light it up?

Thanks,

Stephen English

*At SciTech - http://www.scitech.co.uk

 

[Luhan]

Hi,
I'm designing an experiment for an electricity themed science day*.
We're going to build super simple motors by coiling some enamled wire,
taking the ends of the coil wire and filing off one side of each end
and sitting this in two stirrups that are connected to a small battery,
with a magnet underneath the coil - you've probably seen the idea
before. These work nicely as motors, and can spin at a fair clip if you
get a nice coil.

I would also like to show that this design works as a (horribly
inefficient low power) generator. As the current generated by this
design is going to be incredibly small, are there any simple, low
component count circuits that could be implemented to store up charge
and discharge it through an LED when there's enough to light it up?

Get an el-cheapo (tm) volt-ohm meter from Radio Shack. Put on the
lowest DC volts range, you should get some action from the needle when
you run the 'generator'.

Luhan

 

[John Larkin]

Hi,
I'm designing an experiment for an electricity themed science day*.
We're going to build super simple motors by coiling some enamled wire,
taking the ends of the coil wire and filing off one side of each end
and sitting this in two stirrups that are connected to a small battery,
with a magnet underneath the coil - you've probably seen the idea
before. These work nicely as motors, and can spin at a fair clip if you
get a nice coil.

I would also like to show that this design works as a (horribly
inefficient low power) generator. As the current generated by this
design is going to be incredibly small, are there any simple, low
component count circuits that could be implemented to store up charge
and discharge it through an LED when there's enough to light it up?

Thanks,

Stephen English

*At SciTech - http://www.scitech.co.uk

Any idea what the open-circuit voltage will be like? I'd expect the
source impedance to be low, so there may be lots of current available
but maybe not enough voltage to drive an led directly.

If you wind a reasonable coil and drop a super-magnet through it, it
will flash an led directly, pretty bright. Also fun: drop a magnet
down the bore of a copper water pipe.

John

 

[Joerg]

Hello Stephen,

I would also like to show that this design works as a (horribly
inefficient low power) generator. As the current generated by this
design is going to be incredibly small, are there any simple, low
component count circuits that could be implemented to store up charge
and discharge it through an LED when there's enough to light it up?

Supercaps or gold caps. Get one that is rated for high currents (not for
mamory backup). Around $2-3 a pop at the mail order places. However, you
might have to boost your voltage a bit.

For flashing you can use a simple 74HC14 oscillator. Add a resistor in
series with a diode over the feedback for asymmetrical duty cycle, to
allow short flashes. I just had to do that and found that the human eye,
my eyes at least, can discern 5-10msec flashes at 1/2 sec intervals
quite well.

 

[ian field]

Hi,
I'm designing an experiment for an electricity themed science day*.
We're going to build super simple motors by coiling some enamled wire,
taking the ends of the coil wire and filing off one side of each end
and sitting this in two stirrups that are connected to a small battery,
with a magnet underneath the coil - you've probably seen the idea
before. These work nicely as motors, and can spin at a fair clip if you
get a nice coil.

I would also like to show that this design works as a (horribly
inefficient low power) generator. As the current generated by this
design is going to be incredibly small, are there any simple, low
component count circuits that could be implemented to store up charge
and discharge it through an LED when there's enough to light it up?

Thanks,

Stephen English

*At SciTech - http://www.scitech.co.uk

Google "Thomas Scarborough" - he's published loads of stuff on this sort of
theme.

 

[Humphrey B. Bear]

Hi,
I'm designing an experiment for an electricity themed science day*.
We're going to build super simple motors by coiling some enamled wire,
taking the ends of the coil wire and filing off one side of each end
and sitting this in two stirrups that are connected to a small battery,
with a magnet underneath the coil - you've probably seen the idea
before. These work nicely as motors, and can spin at a fair clip if you
get a nice coil.

I would also like to show that this design works as a (horribly
inefficient low power) generator. As the current generated by this
design is going to be incredibly small, are there any simple, low
component count circuits that could be implemented to store up charge
and discharge it through an LED when there's enough to light it up?

Thanks,
Stephen English
*At SciTech - http://www.scitech.co.uk

If you can find one, (in Australia, I think that Jaycar sell them), an
LM3909 LED flasher IC may be what you need. It will brightly flash a LED
regularly from a 1.5V or slightly lower supply, by using an internal
charge-pump voltage
doubler. A Google search will turn up heaps of results, including the
datasheet at:-

http://www1.jaycar.com.au/images_uploaded/LM3909.PDF

.... Humphrey

 

[Humphrey B. Bear]

If you can find one, (in Australia, I think that Jaycar sell them), an
LM3909 LED flasher IC may be what you need. It will brightly flash a LED
regularly from a 1.5V or slightly lower supply, by using an internal
charge-pump voltage
doubler. A Google search will turn up heaps of results, including the
datasheet at:-

http://www1.jaycar.com.au/images_uploaded/LM3909.PDF

... Humphrey

As an afterthought, if I were you I would first build one of these
generators, then measure it's output into a small load, to check the
viability of the idea. If the output is too low, you might not be able to
power any kind of LED flasher without spinning the coil fairly fast.
.... Humphrey

 

[Bill Beaty]

Supercaps or gold caps. Get one that is rated for high currents (not for
mamory backup). Around $2-3 a pop at the mail order places. However, you
might have to boost your voltage a bit.

I gave up on that type of generator and made this one instead.
It's VERY simple, yet it directly produces enough output to light
an incandescent bulb.

ULTRA-SIMPLE GENERATOR
http://amasci.com/amateur/coilgen.html

Any flasher circuit will involve charging a capacitor. So first see if
your "generator" can produce enough voltage for success: hook a
1000uF capacitor and a meter across the generator, spin it, and
see what voltage you get. If it's below a volt, flasher circuits
won't work.

I wonder if a step-up transformer, a diode, and a capacitor would
get you enough voltage?

((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
[email protected] UW Chem Dept, Bagley Hall RM74
[email protected] Box 351700, Seattle, WA 98195-1700
ph425-222-5066 http//staff.washington.edu/wbeaty/

 

[Si Ballenger]

Hi,
I'm designing an experiment for an electricity themed science day*.
We're going to build super simple motors by coiling some enamled wire,
taking the ends of the coil wire and filing off one side of each end
and sitting this in two stirrups that are connected to a small battery,
with a magnet underneath the coil - you've probably seen the idea
before. These work nicely as motors, and can spin at a fair clip if you
get a nice coil.

I would also like to show that this design works as a (horribly
inefficient low power) generator. As the current generated by this
design is going to be incredibly small, are there any simple, low
component count circuits that could be implemented to store up charge
and discharge it through an LED when there's enough to light it up?

I don't know if something similar exist in the UK, but you might
want to check the "dollar stores" (where every thing is a dollar
or less) for electronic gizmos to work with. I've found clear
balls with flashing LEDs inside that would provide a cheap and
quick LED setup. They also have toys and gizmos that have small
electric motors that can also be used as generators. They have
LCD watches that can be powered by a "potato battery" and toy
cell phones that have speech chips in them.

 

[ian field]

I don't know if something similar exist in the UK, but you might
want to check the "dollar stores" (where every thing is a dollar
or less) for electronic gizmos to work with. I've found clear
balls with flashing LEDs inside that would provide a cheap and
quick LED setup. They also have toys and gizmos that have small
electric motors that can also be used as generators. They have
LCD watches that can be powered by a "potato battery" and toy
cell phones that have speech chips in them.

In the UK, the QD chain of stores have LED keychains. They started at £1.99p
then dropped to 99p - last time I looked they were charging the lower price
as well as offering buy one get one free!

 

[Joerg]

Hello Bill,

I gave up on that type of generator and made this one instead.
It's VERY simple, yet it directly produces enough output to light
an incandescent bulb.

ULTRA-SIMPLE GENERATOR
http://amasci.com/amateur/coilgen.html

What if someone cranks it too hard and the cardboard catches fire?

))

Any flasher circuit will involve charging a capacitor. So first see if
your "generator" can produce enough voltage for success: hook a
1000uF capacitor and a meter across the generator, spin it, and
see what voltage you get. If it's below a volt, flasher circuits
won't work.

Careful with that if the circuit is not loaded. As a kid I blew up more
than one electrolytic with an old phone crank because the voltage kept
running up.

You can get stuff going below 1V. That's why I kept lots of Ge transistors.