'LED Flasher Competition' from 1998

  • Thread starter Watson A.Name - 'Watt Sun
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Watson A.Name - 'Watt Sun

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I was googling groups and I came across this post from 1998. It also
talked about the Forever Flasher, AKA Infini-Flasher that we talked
about here a week or so ago.

He claimed that the Infini-Flasher was efficient and the only circuit
that would run for 24 hours off .3 farad.

I built the circuit at the following URL and talked about it in the
SED, etc. newsgroups. It says runs 6 months off a 150 mAh battery.
http://www.discovercircuits.com/PDF-FILES/3vledfs1.pdf

The first one I built used about 100 mixroamps average at 3VDC and
would run for 90 or so seconds off a 6800 uF cap. I built another
one, and changed some parts values, and lowered the 4700 ohm resistor
to 2200, which gave it a shorter pulse width, and that reduced the
average current. Now it draws an average of 44 microamps and runs for
over 5 minutes off the 6800 uF cap. It's getting really boring timing
this with a stopwatch.

I figured that it would take 288 of the 6800 uF caps in parallel to
run this circuit for 24 hours, or a total of about 2 farads. That's
about 6 times as much capacitance as the Infini-Flasher. Which seems
to indicate that the Infini-Flasher is drawing only 7 or 8 microamps.

I reduced the average current substantially by changing some values,
so I believe it's possible to further reduce the average current. I'm
going to build another of the same circuit, but I'll use a higher
value resistor for the 47 ohm LED current limiting resistor. Also,
slowing the flash rate down to less than once a second will also
reduce the average current.

Here's a part of the original post.
----------------

This is called the "Forever Flasher" because, given an adequite
supply of sunlight once a day it will flash forever (*even*
during night-time and low light conditions).

As you said it would be pretty trivial to make an LED flasher
that ran on solar cells. This one is special because it will
run for about 24 hours or so in complete darkness with only .3F
worth of caps. I did indeed try an LM3909 for this and it only
lasted about 20 minutes on the same caps!

This is the only circuit idea I know of that will run for about
24 hours in complete darkness flashing an LED off of .3F worth
of caps. Can someone come up with another circuit that's more
effecient? "The sci.electronics.design LED Flasher
Competition!" :)
------------------

--
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@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
That's not a bad design.

Here's some suggestions for making a more efficient flasher:

#1: Use a FET in a blocking-oscillator setup. The FET will have much lower
voltage drop than the transistor in the original design.

#2: Use a small toroidal transformer to couple the FET to the LED, about a
1.5:1 stepdown ratio. Remove the 47 ohm current-limiting resistor.
 
George R. Gonzalez wrote:
That's not a bad design.

Here's some suggestions for making a more efficient flasher:

#1: Use a FET in a blocking-oscillator setup. The FET will have much lower
voltage drop than the transistor in the original design.
Click to expand...
For a 2N4401 at a few dozen milliamps, the V drop will be less than a
tenth of a volt. That's no worse than a FET. For a BC337, it's even
less. Besides, you need a few volts to turn the Enh mode FET on fully,
and there may not be a few volts available.

#2: Use a small toroidal transformer to couple the FET to the LED, about a
1.5:1 stepdown ratio. Remove the 47 ohm current-limiting resistor.
Click to expand...
Too expensive and too much hassle. The toroid has to be hand wound, and
that's a big pain, too. I bought some Amidon toroids, a buck apiece!
That's more expensive than all the rest of the parts combined.


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"Lizard Blizzard" <NOSPAM@rsccd.org> wrote in message
news:bhu9op$3pj95$1@hades.csu.net...
George R. Gonzalez wrote:
That's not a bad design.

Here's some suggestions for making a more efficient flasher:

#1: Use a FET in a blocking-oscillator setup. The FET will have much
lower
voltage drop than the transistor in the original design.

For a 2N4401 at a few dozen milliamps, the V drop will be less than a
tenth of a volt. That's no worse than a FET.
Click to expand...
I respectfully disagree. FET's can have much less than an ohm of on
resistance.


For a BC337, it's even
less. Besides, you need a few volts to turn the Enh mode FET on fully,
and there may not be a few volts available.
Click to expand...
That's the beauty of a blocking oscillator-- all you need is a bit of
forward bias and the oscillator coil does the rest. No high voltage needed!


#2: Use a small toroidal transformer to couple the FET to the LED,
about a
1.5:1 stepdown ratio. Remove the 47 ohm current-limiting resistor.

Too expensive and too much hassle. The toroid has to be hand wound, and
that's a big pain, too. I bought some Amidon toroids, a buck apiece!
That's more expensive than all the rest of the parts combined.
Click to expand...
I thought we were optimizing for best efficiency, which is often not the
same as least cost!
 
In article <bi0bq9$1rf$1@lenny.tc.umn.edu>, grg@umn.edu mentioned...
"Lizard Blizzard" <NOSPAM@rsccd.org> wrote in message
news:bhu9op$3pj95$1@hades.csu.net...
George R. Gonzalez wrote:
That's not a bad design.

Here's some suggestions for making a more efficient flasher:

#1: Use a FET in a blocking-oscillator setup. The FET will have much
lower
voltage drop than the transistor in the original design.

For a 2N4401 at a few dozen milliamps, the V drop will be less than a
tenth of a volt. That's no worse than a FET.

I respectfully disagree. FET's can have much less than an ohm of on
resistance.
Click to expand...
A BJT can have less than an ohm, too. But then you don't need to use
a 2N3055 for a few dozen milliamps. A 2N7000 is a typical enhancement
mode FET that could be used for a single LED. It has 5 ohms
resistance.

For a BC337, it's even
less. Besides, you need a few volts to turn the Enh mode FET on fully,
and there may not be a few volts available.

That's the beauty of a blocking oscillator-- all you need is a bit of
forward bias and the oscillator coil does the rest. No high voltage needed!
Click to expand...
That's the problem, too. It requires an oscillator coil.

#2: Use a small toroidal transformer to couple the FET to the LED,
about a
1.5:1 stepdown ratio. Remove the 47 ohm current-limiting resistor.

Too expensive and too much hassle. The toroid has to be hand wound, and
that's a big pain, too. I bought some Amidon toroids, a buck apiece!
That's more expensive than all the rest of the parts combined.

I thought we were optimizing for best efficiency, which is often not the
same as least cost!
Click to expand...

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
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
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
In article <bi0bq9$1rf$1@lenny.tc.umn.edu>, grg@umn.edu mentioned...
"Lizard Blizzard" <NOSPAM@rsccd.org> wrote in message
news:bhu9op$3pj95$1@hades.csu.net...
George R. Gonzalez wrote:
That's not a bad design.

Here's some suggestions for making a more efficient flasher:

#1: Use a FET in a blocking-oscillator setup. The FET will have much
lower
voltage drop than the transistor in the original design.

For a 2N4401 at a few dozen milliamps, the V drop will be less than a
tenth of a volt. That's no worse than a FET.

I respectfully disagree. FET's can have much less than an ohm of on
resistance.
Click to expand...
A BJT can have less than an ohm, too. But then you don't need to use
a 2N3055 for a few dozen milliamps. A 2N7000 is a typical enhancement
mode FET that could be used for a single LED. It has 5 ohms
resistance.

For a BC337, it's even
less. Besides, you need a few volts to turn the Enh mode FET on fully,
and there may not be a few volts available.

That's the beauty of a blocking oscillator-- all you need is a bit of
forward bias and the oscillator coil does the rest. No high voltage needed!
Click to expand...
That's the problem, too. It requires an oscillator coil.

#2: Use a small toroidal transformer to couple the FET to the LED,
about a
1.5:1 stepdown ratio. Remove the 47 ohm current-limiting resistor.

Too expensive and too much hassle. The toroid has to be hand wound, and
that's a big pain, too. I bought some Amidon toroids, a buck apiece!
That's more expensive than all the rest of the parts combined.

I thought we were optimizing for best efficiency, which is often not the
same as least cost!
Click to expand...
I thought we were making a flasher, not a piece of test equipment.
:) But I don't see anything wrong with using a toroid, or an
inductor. It's just that a toroid isn't as easy to wind as a ferrite
bobbin. I'm thinking it should be on the level of the average
person's skill. And an average person doesn't have toroid building
skills.

I also wouldn't expect that a 5 or 10 amp power FET would be used in
this circuit, which needs only a hundred or so mA peak to drive the
LED. A 2N7000 costs a dime, a high power FET can cost several
dollars. A high current, low Vce(sat) transistor such as the 2SD965
in the TO-92 package might cost only a quarter.

I've recently built some blocking oscillators using a toroid, fine
wire, and a single transistor. This is for a V boost circuit to
convert a single 1.5V cell into 3.6V for the white LED.

The trend is for these circuits to use a Maxim or similar chip,
surface mount it with other parts such a schottky diode and transistor
to make a nickel-sized circuit board. SSome chips have a shutdown
pin, which could be gated to give the LED flash capability.

Some of these circuits have an efficiency of close to 90 percent. But
because the chip runs at 2 MHz and has high currents, it's like
designing an RF power amp, so you might as well buy the evaluation PC
board. And the board has to act as a heat sink for those tiny parts.

I'm just looking for a circuit that is optimized for inexpensive and
readily available parts, simple enough for the average hobbyist to
build. I'm not against change. A year or two ago I saw a number of
projects that used the BS170 or 2N7000 enh mode FETs for low power
switching, and I thought that these were too unusual and hard to find
for the average hobbyist. But I bought a bag of the 2N7000s, and I've
now seen how they can be used for projects to take advantage of the
FET's unique characteristics. But I still can't see using a power FET
with .05 ohms and costing two dollars or more to drive a single LED.

Oh, one other thing about a blocking osc. I've worked on tube
equipment that used the transformers for blocking oscillators. But
these worked at hundreds of kHz, not 1 flash a second. I would think
that to get one to oscillate at 1 Hz, the transformer would have to be
very big.

I'd like to see a circuit that uses both V boost and a flasher. That
way, a blue or white LED could flash off a 3V supply.

--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
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
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
In sci.electronics.misc Watson A.Name - 'Watt Sun' <alondra101@hotmail.com> wrote:
<snip>
I'd like to see a circuit that uses both V boost and a flasher. That
way, a blue or white LED could flash off a 3V supply.
Click to expand...
I've done this, though admittedly using 5 transistors.
Two two transistor astables, one power transistor.

The fast astable has the base resistors commoned and run from the output
of the slow one.
Starts up at ~0.498V to run a 3.6V LED.

In this case, the variable output power is a feature to indicate battery state.

Efficiancy is quite good, as the fast astable (with the low value resistors)
has only leakage current flowing when the power is off, and the slow astable
has very high value resistors.

However, I've been disssapointed in my (very brief) search for high value
SMD resistors, ideally in the smaller packages, the ranges seem to stop
at 1M.
25M would be nice, 100M would be lovely.

--
http://inquisitor.i.am/ | mailto:inquisitor@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
"The theory of everything falls out trivially." -- Etherman, sci.physics kook.
 
In article <bi50m2$j9e$1$8300dec7@news.demon.co.uk>,
root@mauve.demon.co.uk mentioned...
In sci.electronics.misc Watson A.Name - 'Watt Sun' <alondra101@hotmail.com> wrote:
snip
I'd like to see a circuit that uses both V boost and a flasher. That
way, a blue or white LED could flash off a 3V supply.

I've done this, though admittedly using 5 transistors.
Two two transistor astables, one power transistor.
Click to expand...
Astable meaning astable multivibrators? The ratio of a mvb assuming
equal parts is 50%, but for a flasher, it might be better at 10% on
and 90% off. Easy to do with the right choice of caps and res. But
it mioght be easier to use a flasher circuit. I've built some flasher
circuits that draw only a few mA, used as yours did to drive the base
resistor of a CW RF beacon.

If you ever want to see some odd astables, visit Torrens' 4QD website
and check those out. http://www.4qdtec.com/mvibs.html



The fast astable has the base resistors commoned and run from the output
of the slow one.
Starts up at ~0.498V to run a 3.6V LED.

In this case, the variable output power is a feature to indicate battery state.

Efficiancy is quite good, as the fast astable (with the low value resistors)
has only leakage current flowing when the power is off, and the slow astable
has very high value resistors.

However, I've been disssapointed in my (very brief) search for high value
SMD resistors, ideally in the smaller packages, the ranges seem to stop
at 1M.
25M would be nice, 100M would be lovely.
Click to expand...
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
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
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
In sci.electronics.misc Watson A.Name - 'Watt Sun' <alondra101@hotmail.com> wrote:
In article <bi50m2$j9e$1$8300dec7@news.demon.co.uk>,
root@mauve.demon.co.uk mentioned...
In sci.electronics.misc Watson A.Name - 'Watt Sun' <alondra101@hotmail.com> wrote:
snip
I'd like to see a circuit that uses both V boost and a flasher. That
way, a blue or white LED could flash off a 3V supply.

I've done this, though admittedly using 5 transistors.
Two two transistor astables, one power transistor.

Astable meaning astable multivibrators? The ratio of a mvb assuming
equal parts is 50%, but for a flasher, it might be better at 10% on
and 90% off. Easy to do with the right choice of caps and res. But
it mioght be easier to use a flasher circuit. I've built some flasher
circuits that draw only a few mA, used as yours did to drive the base
resistor of a CW RF beacon.
Click to expand...
Current was a couple of uA at 1.2V, using rather high value resistors,
and very unequal capacitors. (1n and 680n)

It doesn't quite work like a 'proper' astable, the 680n capacitor doesn't
charge anywhere near all the way.
IIRC, it was around 60:1.

If you ever want to see some odd astables, visit Torrens' 4QD website
and check those out. http://www.4qdtec.com/mvibs.html
Click to expand...
Will have a look.

--
http://inquisitor.i.am/ | mailto:inquisitor@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
<Squawk> Pieces of eight!
<Squawk> Pieces of eight!
<Squawk> Pieces of eight!
<Squawk> Pieces of eight!
<Squawk> Pieces of eight!
<Squawk> Pieces of nine!
<SYSTEM HALTED: parroty error!>
 
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