Forever Flasher (& flashlight)

I built the flasher circuit from Dave Johnson's website, See URL
http://www.discovercircuits.com/PDF-FILES/3vledfs1.pdf
But it just went full on, wouldn't flash. So I had to put a 2.2k from
Q2 base to emitter to get it to flash. I also used two 0.1 uf ceramic
caps instead of rhe 0.68 uF, and the flash rate is right around 1 Hz.
The peak current is 17 mA, and average current is about 100 micromps
at 3V.

I then connected it to a 3V photovoltaic cell and a 1N4148 to prevent
the current from going back into the photocell, and a 6800 uF
capacitor to store the current generated by the light. I put the
photocell directly under a light bulb, and it works fine, and it keeps
working for less than a minute when the light is turned off. So now I
need a lot bigger capacitor, something that will run it for a coupla
hours.

I'm thinking that it would work good using a pair of 1 F, 2.0V
supercaps in series, charged by the photocell.

I bought a Forever Flashlight, the one that has a single white LED,
with a magnet and coil in the barrel that charges up a supercap when
it is shaken. It works, but I'm disappointed in the light output.
The instructions say to shake it for 90 seconds, but even longer than
that gives the LED only a few mA, not a really decent amount. It has
a lens to concentrate the LED's light, so it's better than just the
bare LED alone. Obviously it's meant to be used for situations where
a regular flashlight might not be working, like in an
emergency/earthquake preparedness kit. The body of the flashlight is
clear plastic so I can see the parts inside, and there's a supercap in
there, but the plastic is too thick to see the value, which is
blurred.

So I'm wondering if I should order a couple of these supercaps. The
solar cell is rated for 3V at 40 mA, see the SPL-60 on All Electronics
website, http://www.allelectronics.com/cgi-
bin/category.cgi?category=565&item=SPL-60&type=store
It puts out an honest 4V in bright sunlight, so I would think that it
will charge two 1 F supercaps in series in a few minutes. 3 TCs at 40
mA would be 38 seconds, roughly. Maybe I should try for a couple
farads to keep it running all night long. Has anyone done this
before? Do these supercaps have low enough leakage to stay charged up
for a half a day? After seeing their performance in the 'Forever'
Flashlight, I'm not so sure.

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it looks like you could use a peak at Elna's catalog,

Their 100F capacitor (I'm picking the biggest one because I can) rated
at 2.5V
charts out to run for about 200 seconds at 50mA (I'm taking this at a
1.5V cutoff,
use a switching (buckboost) led controller and get more. especially if
you are useing
more than one with a supply of 4V. I dont know what elna's 100F
capacitor costs. I imagine
its not cheap.

CATALOGS! I must have more catalogs! HA, HAHAHAHAHA!

Dan

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See if you can find one of those "wind up" flashlights. Similar to the
Freeplay radios. That seems to be better technology in terms of time
spent winding vs illumination time. I've seen one with a selectable
xenon mode (runs charge down fast) or 3 white LEDs (less light for much
more time).

If a while LED uses 20 mA, then a 40 mA PV cell will give you 2 minutes
of run time for each minute of charge time (ignoring losses and lots of
other things). If you fully charge the supercaps in 38 seconds, you'll
only get about twice that running time. Add super caps (and $$) to get
more time.

You might be better off looking for some DC-DC converters, NiMH charging
controllers, etc. and using as many mAh of battery capacity as you need
for your design illumination time requirements dictate.

 

Er, the flasher takes about 100 microamps. That means that it should
run maybe 400 times longer than the charging time, something less than
4 hours. I guess I could parallel a second pair of 1 Fs to give a
total of 1 F at 5VDC. That should give a flash time of several more
hours. I can't say because I don't know what the cutoff voltage is
for the flasher.

Batteries go bad, I want to have a forever flasher, not a 5 year
flasher. That's why the 1 F supercaps.


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Don't be ripped off by the big book dealers. Go to the URL
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Just when you thought you had all this figured out, the gov't
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As a coincidence, you should take a look at the DutchForce forum...
http://www.dutchforce.com/~eforum/index.php
The specific thread is:
http://www.dutchforce.com/~eforum/index.php?board=10;action=display;threadid
=452

Tim (Sc3mat1c)

 

Lithium D cells are $20 (US) or so, and have a capacity of around 20Ah.
This would run the flasher for around 200000 hours, or around 22 years.
Add a light sensitive switch, and you can probably extend this a bit.
And you can leave off the solar cell too.

A couple of NiCd AA cells would probably run it for around 6 months, after
a full charge.

(this is probably around the right draw, they'll self-discharge in around a
year in most climates anyway)

 

Here's the URL for one of the schematics of the inverter. This one
says it works down to .4V, there are others on his website.
http://www.belza.cz/ledlight/m2d.htm

I was thinking of putting the circuit and solar cell in a clear epoxy
block. I've done it before by pouring a thin layer, and arranging the
working circuit, then pouring another thicker layer over that. Trick
is to get rid of the bubbles. So using a 5 year rechargeable battery
is not an option. I would consider using rechargeable cells if it was
in a package with a battery holder. But I've already got one of
those. ;-)

I checked out the eBay URL, but it's not clear to me how many LEDs are
in the package. It says 100 pcs but in the pic looks like it's a lot
less. And the 'buy it now' price is a bit on the low side for that
quantity. So I'm not sure if I'd buy them. Another factor that
bothers me is that any time one buys LEDs at cut-rate prices, there is
a very high likelihood that they're seconds or rejects. I've
purchased low priced LEDs that have flaws in the lens, or that are not
centered properly in the epoxy package, etc. I've done very well by
buying from Nichia or from Wilcoxson's www.whitelightled.com. Also,
you can buy Yoldal LEDs that are similar from
http://www.8000mcd.com/catalog.html but I haven't bought any from
there, so I can't vouch for the quality.

So, has anyone purchased some of those eBay LEDs?

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Just when you thought you had all this figured out, the gov't
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Forever isn't 6 months, nor 5 years, nor 22 years. Thanks, but I'd
really like to get the info I asked for on the 1 F supercaps.

BTW, I have a 1 LED flasher that runs off four AA 2000 mAh Ni-MHs, and
it lasts for about a month, maybe a little more. I don't know what
the peak current thru the blue LED is, but it's very bright. Maybe
two flashes per second. I've noticed the Ni-MHs lose some of their
capacity sitting around for a month or three. But that's just a
guesstimate.

If I pot a clear epoxy case of the LED in clear eopxy, what does it do
to the beam pattern? Suddenly the index of refraction is the same as
the lens, so it isn't a lens any more. POOF! The beam goes wide
angle, I would guess. Maybe I'll have to dunk a couple LEDs in a
glass of water to see what happens!

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Just when you thought you had all this figured out, the gov't
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I would not be very certain that the supercap would still be working
after 20 years.

Why do you want 'forever'?

Ni-MH have a very bad self-discharge rate, especailly in high temps.
You may well find NiCd better.

Pretty much.

 

Relevant circuits on my page at http://members.shaw.ca/novotill/
1) LED flasher
2) Solar Engine

....Stepan

 

Leave

Leave an air space in front of the LED lens to reduce that problem.

 

Good idea! Probably ought to try to keep the epoxy with co-planar
surfaces also.

Or, better yet, pot with the LED lens sticking clear thru the
encapsulation.

...Jim Thompson
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For proper E-mail replies SWAP "-" and "_"

Why is it that Democrats can't debate politely?
And are only rude and interruptive.
Lack of mental capacity?

 

Sorry about that. I thought you were trying to apply the supercaps to
the flashlightapplication, not the flasher.

 

Yeah, wacky is the right word. I checked the flickering LED circuit
and it looks like the values for the caps and Rs in the oscs aren't
right. But you _have_ to resave that gawdawfully huge delayed off
switch .PNG to 1024 by 768 size. The 6600 pixels wide is ridiculous!

The solar engine doesn't seem to do anything other than store up and
release the charge in the capacitor. I'm not sure how this would help
my situation.

The LED flasher is a V boost circuit. We've already been thru a few
of those here in ABSE and the other sci.electronics ngs. I checked
that ferrite bead on both Digi-Key's and Mouser's website and it's
just a tiny thing. I can't figure how you could pass that many turns
of even fine wire thru the center hole. The only way I can see how
you'd do it is to wind the wire around the outside like a regular
bobbin. Even then the thing is going to be tiny, with really fine
wires. And I don't believe this has 120 uH inductance (nor 120 mH, as
it says in the text).

Anyhoo, this circuit is kewl for 1.5V stuf, but I've already got 3 or
4V from my solar cell, so no problem. It runs the flasher okay. It's
just a matter of pulling in enough charge from a few minutes in direct
sunlight, where the LED can't be seen, and then once the cap is
charged, bring it inside where it can flash for hours. Or it could be
set near a window to charge up and as the sun sets, it continues to
flash for hours. That's why I need the 1F or so supercap and some
info on how they work in this kind of circuit.

I bought some already wound inductors from Mouser, and they work good
for the inverters I made. It would be easy to just wind a few turns
of #28 or finer wire around the outside of the bobbin of this inductor
to give a feedback tickler coil like the one you made. I like already
assembled coils because of repeatability factors and just plain time
savings.


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Don't be ripped off by the big book dealers. Go to the URL
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http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
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If I pot a clear epoxy case of the LED in clear eopxy, what does it do

If you stick that solar cell in clear epoxy it will fail after short time
because of different thermal expansion. (done that, that's why I say that)
Rather take some silicon based potting and glue the cells on top only. Then
use a frame with a plastic or glass inlet to protect the cheap cells from
humidity.

ciao Ban

 

Silicon is a hard substance that is used to make solar cells.

Silicone is a polymer that's used to make everything from flexible tubing
to sex toys.

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---------------------------+-------------------------+--------------------------
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Now you've _really_ ruined my day! Y'see, the solar cells _already_
come from the factory mounted in clear epoxy! Now what am I gonna do?
Are they going to fail when I put them in the sunlight? :-(

But since they are already coated with epoxy, I can assume that
potting them in an epoxy block will not do any more harm. Am I right?

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Don't be ripped off by the big book dealers. Go to the URL
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http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
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Are you sure that this is epoxy and not some other more flexible stuff? I
tell you I had some(33) Siemens 6" monocrystalline cells. They were coated
with some whitish epoxy-like material on the back. to combine them i poured
some epoxy mixed with these small glassballs and the hardener only on the
back, the front was a special glass. The assembly worked for one year, but
when left in the hot sun for some time, there were cracks all over the
individual cells, I had to throw everything. :-((
I then inquired and found out about my mistake. The Siemens guy told me that
this coating is really the most difficult part of the game.
I do not know about polycristalline or amorph cells, but the monocrystalline
cells are utterly brittle and damaged easily.
removed irrelevant x-posts
ciao Ban

 

Are you another self appointed apostrophe inquisitor or what? There is
already one in this group. But maybe in holydays.

thanks for the correction Ban

 

Sorry, it's just a pet hate.