1.5v to 3.3v LED circuit

Looking to drive a white superbright led (1-4) from 1.5v to 2.5v
battery, led requires 3.3v @ 20ma, is there a suitable small circuit, or
single chip device

TIA

 

http://tinyurl.com/5843f

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.

 

An NPN, a 1.5V AA battery, two resistors, a capacitor, a diode and a simple,
hand-wound threaded toroidal. D2 can be a diode-connected 2N3904, a 1N4148, or
a Schottky like a 1N5817-1N5819.

V+ V+ V+
| | |
| | |
| )|. .|( (about 50" of
| )| |( magnet wire
| )| T1 |( for both
| + )| |( windings)
--- | |
- B1 | | D2 R2
--- \ +---|>|---+---/\/\---,
- / R1 | | 220 |
| \ 2200 | | |
| / | | |
| | |/c Q1 | --- ~
| '------| 2N3904 --- C1 \ / ~
| |>e --- 100uF --- LED
| (B1 > 1V) | | |
| | | |
gnd gnd gnd gnd

It will drain a AA battery fairly completely, before quitting.

Jon

 

Jon...

I have a hell of a time with ASCII schematics. Could you possibly post a
"real" schematic to alt.binaries.schematics.electronic?

Jim

 

copy into notepad and then format -> font -> "fixedsys"

 

You should be able to set your newsreader for a fixed font. I use
Courier.

Cheers!
Rich

 

I have Courier as my default font and I still have a hell of a time reading
an ASCII schematic. Sorry.

Jim

 

Is it an inability to recognize the symbols?

I guess I'm asking this because it took me exactly zero time to see and
understand an ASCII schematic the first time I saw one and I've had very little
trouble ever after, so I'm honestly curious about what makes this difficult for
some -- I completely lack the personal experience to understand the trouble, so
I'd appreciate any clues about what you perceive and don't perceive.

Meanwhile, I'll try and load over a schematic in some format you can see. I
have a few other things to take care of before I struggle with that, though.

Jon

 

http://www.qsl.net/yo5ofh/hobby circuits/led_circuits.htm
http://users.cableaz.com/~cappels/dproj/ledpage/leddrv.htm
http://www.discovercircuits.com/PDF-FILES/ac14fls.pdf
http://repairfaq.ece.drexel.edu/sam/bledl1.gif

Just some google results. There are much more of them.

petrus bitbyter

 

I'll have to throw in with petrus here, then. What's the hard part?

Do your ASCII schematics not look like this one?:
http://www.neodruid.net/images/ASCII_Art.jpg

Good Luck!
Rich

 

No, they don't. The link you sent was quite readable. The schematic in
this newsreader was highly compressed in the x dimension and absolutely
unreadable. However, as I sit here and look, the fact that I've got my
settings to Courier doesn't seem to make a difference. Just looking at this
font I can tell it is a variant of Helvetica, or Arial, or whatever other
san-serif font you want to call it.

I need to do some more investigation as to why it looks like this. Or
perhaps only the OUTGOING messages look like this...

Thanks,

Jim

 

Lordy, Outlook Express makes you change the font in no less than THREE
places in order to force messages to Courier. THe default fixed width, the
default proportional width, and the little checkbox on the "advanced" tab to
default all incoming messages to the default settings.

Windoze does it again.

Thanks for the help, Rich...

Jim

 

If you use OE and the font is not set to default to a fixed width font, you
can
select 'view' then move down to 'text size' then move to 'fixed' to see it
on the
ASCII art on the fly.

 

GMAB
Why bother to explain, He's a top poster, his inability to
understand anything is clear. He thinks upside down! >)

 

I really despise those who suggest that the 2N3904 is capable of doing
this job adequately. With that wimpy transistor, you will be lucky to
get enough current to power the LED at 8mA. Use a 2N4401 or the BC337.
Or if you want to get a lot more current, try the 2SD965 or NTE11. If
you can get some disposable flash cameras from your neighborhood
drugstore or photo shop, the flash inverter uses this kind of
transistor, and makes a great source for free transistors.

The above circuit is okay, but since the LED _is_ a diode, you don't
need the D2 and C2 filter cap, just connect the LED across the emitter
and collector. And R1 will have to be lower, probably 1k, if you use
something better than the 2N3904. The 2N3904 won't cut it with even a
470, it'll just get hot and poof. And whatthe hell is R2 there for?
That's just wasting power and ruining the efficiency!

 

I'm actually using one and it's pretty decent on a white LED. If you have to
despise me for it, I guess I can only hope to make it up some time later on.
(I'm just a modest hobbyist, so I take corrections from just about anyone.)

Fair enough.

Actually, that's what I did before. In fact, I had no R2, as well. I just
added those for tinkering, at some point, to smooth the pulses through the LED.

Yes, I started out just as you say. Works just fine. This is what I'd started
with:

V+ V+ V+
| | |
| | |
| )|. .|( (about 50" of
| )| |( magnet wire
| )| T1 |( for both
| + )| |( windings)
--- | |
- B1 | |
--- \ +---------,
- / R1 | |
| \ | |
| / | |
| | |/c Q1 --- ~
| '------| NPN \ / ~
| |>e --- LED
| (B1 > 1V) | |
| | |
gnd gnd gnd
(can be connected to V+, as well)

Threading up the transformer on a tiny toroid is dead easy, too. By the way,
I've picked up some small packages of them from a local electronics supply
house, but I've not found a good web site that has them. Do you know of a good
source for various ferrite toroids?

Jon

 

Excellent tip.

If the reason we use ASCII Schematics is because of the text based
USENET. Then why do some websites still use ASCII Schematics?

 

Leftover source material from the days of telnet perhaps...

 

Because if it works, don't fix it!

Cheers!
Rich

 

Italians with groups like this on their local ones
like it.hobby.elettronica
use interesting program to draw & see schematics for posting
in text only usenet IMHO much bettter than ASCII ...

its FidoCAD (maybe someone could write to the author to make an
English interface & help file for it). Can be found here: less than
1Mb installed:
http://www.enetsystems.com/~lorenzo/fidocad_win.asp

you draw a standard schematic, export it as text & paste it into a
message like this (pasted code) interesting oscillator:

[FIDOCAD]
MC 85 45 0 0 580
MC 70 45 1 0 170
MC 50 55 0 0 170
MC 50 45 0 0 120
LI 85 45 60 45
LI 60 55 85 55
LI 50 45 45 45
LI 45 45 45 55
LI 45 55 50 55
MC 45 65 0 0 045
LI 45 65 45 55
LI 100 45 100 25
LI 100 55 100 75
MC 100 25 3 0 010
MC 100 75 1 0 020
TY 105 15 5 3 0 0 0 * +6V
TY 105 80 5 3 0 0 0 * -6V
MC 105 30 0 0 170
MC 105 65 0 0 170
MC 120 30 0 0 045
MC 120 65 0 0 045
LI 105 30 100 30
LI 120 30 115 30
LI 105 65 100 65
LI 120 65 115 65
LI 110 50 135 50
MC 140 50 0 0 075
MC 145 50 0 1 075
TY 60 60 5 3 0 0 0 * 2x 47nF
TY 45 35 5 3 0 0 0 * 1mH
TY 115 60 5 3 0 0 0 * 100n
TY 115 25 5 3 0 0 0 * 100n
TY 155 45 5 3 0 0 0 * 34kHz
TY 75 35 5 3 0 0 0 * LM6181

You to see it with that installed program, just copy that upper
complete code, open the program, from menu open:
modifica/incolla/come nuovo documento .... & so you see the
schematics like usuall one; IMHO not a bad trick ... & easier than
ASCII pics schematics ...

Try it 4 fun ...