U.S. Pat 6,366,028 LED Flashlight Circuit

june 2002, LED torch

That works well on one AA battery with white LEDS, you can pretty much get it to drive whatever you want from whatever source you want and I think it does the job as well as any I've seen.

I get "No such Patent Number found, please check the number and try again" at

when searching on 6366028

: > I built the circuit in the above patent

that CMG uses : > in their Infinity flashlight. Essentially it's an asymmetrical : > astable multivibrator F-F, with one collector load being an inductor. : > I used a 100 uH instead of the 220 uH that the schem calls for. The : > transistors weren't given, so I used BC337-25 for both. : >

: > My problem is that it starts to oscillate a .65V, and if I go over : > 1.14VDC, it quits. The freq is 822(!) kHz, very high for these : > circuits, but the patent says it's supposed to be about 500 kHz. I'm : > gonna try a larger inductance to see what happens. I'm using the : > values for the two caps of 1000 pF and 330 pF. : >

: > Right now, I can't even get it to work on a single AA Ni-MH cell, : > because the voltage is too high. :-( I'm gonna increase some of the : > resistor values to see if it helps and slows it down to below the AM : > BCB. It comes in loud and clear on the radio. : : I get "No such Patent Number found, please check the number : and try again" at

when searching on 6366028

I found it easily. You need to put in the commas. 6,366,028, use Patent Number Search.

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In article , snipped-for-privacy@hotmail.com mentioned...

Thanks for the idea. But by their own admission in the article, the total current drawn from the single cell is 20 mA, multiplied by 1.5V, gives 30 mW total. When accounting for the efficiency, this gives less than 1/4 the light output the LED is capable of. The BC547 transistors do not have a low enough Vce(sat) at higher currents, so they can't drive the LED to full brightness. The mini choke should be checked to make sure it has low enough resistance to allow the required current. A single LED needs at least 120 mW for full brightness, that's 80 mA at 1.5VDC. But if the circuit is only 67% efficient, then the total battery current should be about 120 mA.

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In article , snipped-for-privacy@bellatlantic.net mentioned...

Well, I'm holding the original printout and that's the right number. Did you do the right things, like including the commas?

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On Sun, 30 Nov 2003 20:28:54 -0800, Watson A.Name - "Watt Sun, Dark Remover" Gave us:

I found it on the first search I did on the site, and the commas are NOT required.

in

I found the patent but I can't display the drawings, any chance of putting it somewhere or sending it by email to me so I can read it please. dknpower at ntlworld.com

in

get

it

I did some messing with the a circuit very similar to the one in the above link. I didn't use BC547 transistors :)

results, Y axis = resistance of LDR (ohms) and X axis = power (mW)

With the LED mounted next to an LDR and never moved I used a current source (blue diamonds), voltage source and resistor (orange squares) and the purple square and yellow triangle were using the oscillator circuit.

I figured that current source was the most efficient, voltage source least efficient and the nearer I could get to the current source graph then the more efficient my torch was. I thought the result was pretty good.

In article , snipped-for-privacy@hotmail.com mentioned...

I don't have it at home, I d/l'd and printed it at work because it's a big file, probably too big to email.

I downloaded the plug-in to allow viewing of the .TIF files. It's free. I think it's AlternaTIFF.

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in

wrote

uses

inductor.

The

I'm

the

AM

putting

dknpower

Got it sorted and can look now. It's essentially the same circuit really its just a matter of dumping the inductor into the LED and messing about with the components until you get it to run off whatever voltage you need it to run off. When I was messing I couldn't find any concrete effect from altering the frequency in terms of efficiency, I did sort of half believe that the slower it went the more efficient it was but the improvement wasn't really enough to be sure and if you went too slow the LED visibly flashed, most annoying..

Oddly enough, the big blue LEDs I have seem to have lots of capacitance. Thus, if you put a diode in series with the LED, the efficiency seems to go way up.

Here is the circuit I'm using; I built it, and its working quite well... According to simulations, the efficiency is better than 50%, and the current spikes reach about 100mA...

Should I patent it? I mean, the part about using the extra diode? :)

The original circuit abuses the transistors as well by generating large negative spikes. This one does somewhat better. Maybe it was the capacitance of the LED, although I don't really understand the effect.

Regards, Bob Monsen

: > "Watson A.Name - Watt Sun, Dark Remover" wrote in : > message news: snipped-for-privacy@news.dslextreme.com... : > > I built the circuit in the above patent

that CMG uses : > > in their Infinity flashlight. Essentially it's an asymmetrical : > > astable multivibrator F-F, with one collector load being an inductor. : > > I used a 100 uH instead of the 220 uH that the schem calls for. The : > > transistors weren't given, so I used BC337-25 for both. : > >

: > > My problem is that it starts to oscillate a .65V, and if I go over : > > 1.14VDC, it quits. The freq is 822(!) kHz, very high for these : > > circuits, but the patent says it's supposed to be about 500 kHz. I'm : > > gonna try a larger inductance to see what happens. I'm using the : > > values for the two caps of 1000 pF and 330 pF. : > >

: > > Right now, I can't even get it to work on a single AA Ni-MH cell, : > > because the voltage is too high. :-( I'm gonna increase some of the : > > resistor values to see if it helps and slows it down to below the AM : > > BCB. It comes in loud and clear on the radio. : >

: >

: >

: >

: > june 2002, LED torch : >

: > That works well on one AA battery with white LEDS, you can pretty much get : > it to drive whatever you want from whatever source you want and I think it : > does the job as well as any I've seen. : : Oddly enough, the big blue LEDs I have seem to have lots of capacitance. : Thus, if you put a diode in series with the LED, the efficiency seems to go : way up. : : Here is the circuit I'm using; I built it, and its working quite well... : According to simulations, the efficiency is better than 50%, and the current : spikes reach about 100mA... : :

Forgive me if I seem less than knowledgeable, but is uH the same as uF?

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µF is microfarad, a unit of capacitance µH is microhenry, a unit of inductance

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: > : > "Watson A.Name - Watt Sun, Dark Remover" : > wrote in : > : > message news: snipped-for-privacy@news.dslextreme.com... : > : > > I built the circuit in the above patent

: > that CMG uses : > : > > in their Infinity flashlight. Essentially it's an

< snip >

: > below the AM : > : > > BCB. It comes in loud and clear on the radio. : > : >

: > : >

: > : >

: > : >

: > : > june 2002, LED torch : > : >

: > : > That works well on one AA battery with white LEDS, you can : > pretty much get : > : > it to drive whatever you want from whatever source you want : > and I think it : > : > does the job as well as any I've seen. : > : : > : Oddly enough, the big blue LEDs I have seem to have lots of : > capacitance. : > : Thus, if you put a diode in series with the LED, the efficiency : > seems to go : > : way up. : > : : > : Here is the circuit I'm using; I built it, and its working : > quite well... : > : According to simulations, the efficiency is better than

50%, : > and the current : > : spikes reach about 100mA... : > : : > : : >

: > Forgive me if I seem less than knowledgeable, : > but is uH the same as uF? : >

: > Bill : : µF is microfarad, a unit of capacitance : : µH is microhenry, a unit of inductance

Are there certain types of device that produce inductance? Sorry if I am asking so many questions, I've only ever done repairs to electronic devices by advisement of technical personnel.

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No problem.

Yes, they are called inductors. You can buy inductors (chokes, coils, they have lots of names) at radioshack, or various other electronics suppliers.

You can also make them by making a coil of wire. The idea is to reinforce the magnetic field that gets generated when current flows through a wire. Inductors basically build up a magnetic field, the value of which is related to the current flowing through the coil.

The 'formula' for making them depends on their radius, length, number of turns, and 'core material'.

L = mu(r) * (N^2 * A / l) * 1.26e-6

where mu(r) is the relative permeability of the core material, which is simply 1 for air; N is the number of turns of the coil; A is the area of a loop of the coil in sq meters; and, l is the length of the coil in meters. (The 1.26e-6 term is the permeability of air in SI units, called mu nought. Its a fudge factor for using SI units. The real formula is permeability of the core times turns squared times area over length.)

So, to get 33uH on an air coil, you need about 82 turns of wire on a 1cm diameter coil of 2cm length. If you use an iron or steel core, you'll need considerably fewer turns.

Regards, Bob Monsen

Thank you Bob. I did discover that they were chokes/coils, as I had suspected, but your explanation of their construction and how they are formulated made it very clear. I now know what to call them and how to find out what their ratings are when I reverse-engineer a circuit. Incidentally, is there an easy method for taking a reading on them to find out their value?

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Yes, you can buy inductance meters. I've heard a rumor that this is a good one:

If you have access to a signal generator, you can test them directly by observing the resonance frequency of a circuit with an inductor and a capacitor of known value, using the equation

L = 1/((2*PI*f)^2 * C)

There are also markings on them to tell you what their inductance value is. They use the same color scheme as resistors, except that the value depicted is in micro-henries (uH) rather than ohms. So, a 33uH inductor will be orange orange black, and then a color band for precision. There are other schemes for marking as well, see a book such as "Practical Electronics for Inventors" by Sherz at your library for more details on inductor markings. There are also websites that have this information.

Regards, Bob Monsen

: > Thank you Bob. I did discover that they were chokes/coils, : > as I had suspected, but your explanation of their construction : > and how they are formulated made it very clear. I now know : > what to call them and how to find out what their ratings are : > when I reverse-engineer a circuit. Incidentally, is there an easy : > method for taking a reading on them to find out their value? : : Yes, you can buy inductance meters. I've heard a rumor that this is a good : one: : :

: : If you have access to a signal generator, you can test them directly by : observing the resonance frequency of a circuit with an inductor and a : capacitor of known value, using the equation : : L = 1/((2*PI*f)^2 * C) : : There are also markings on them to tell you what their inductance value is. : They use the same color scheme as resistors, except that the value depicted : is in micro-henries (uH) rather than ohms. So, a 33uH inductor will be : orange orange black, and then a color band for precision. There are other : schemes for marking as well, see a book such as "Practical Electronics for : Inventors" by Sherz at your library for more details on inductor markings. : There are also websites that have this information. : : Regards, : Bob Monsen

Thanks Bob, I will look for some sites. I've never seen ones marked before, but then again, I wasn't sure what they were either. Thanks again.

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In article , snipped-for-privacy@hotmail.com mentioned...

First I changed the inductor to 220 uH. That slowed it down from 820 to 780 kHz. I then added a 1.7k trimpot to the 560 ohm to reduce the base bias to the output transistor. It made the freq decrease a lot, from 780 kHz to below 500 kHz. But the current decreases dramatically, and of course the LED dims dramatically too. So I have to change the bias on the other transistor at the same time, too. I'm considering doubling the cap values, too to reduce the freq.

Anyway, the idea isn't to slow it down, it's to get it to work up to

1.5 or so VDC. Right now, it quits at 1.18 VDC.

Warm up the soldering iron, it's back to experimenting.

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