audio recording on IC -help wanted

"booth multiplier" <boothmultipler@hotmail.com> schreef in bericht
news:24160f43.0412010351.84cbc6d@posting.google.com...
Dear All,
I'd like to built a driver circuitry for 8 Luxeon leds in series.
Each of them has a forward voltage at 3.5 V at 350 mA. 8 in series
makes 28V. I have applied the 28 volt works fine, but if I want to
make them flash it's not working, they simply don't flash. The ON
OFF sequence is like this: 1 sec OFF, 0.4sec ON, 0.1 sec OFF,0.4sec
ON, 0.1 sec OFF AND SO ON. Do I need a higher voltage for flashing?
Thanks
Click to expand...
You treated the LEDs like resistors which they are not. According to the
manufacturers information you always has to use a series resistor to limit
the current through the LEDs. Look at:
http://www.lumileds.com/pdfs/AB11.PDF
for instance.
As LEDs are current driven devices you'd better look for a current source.
See simple schematic below. The 350mA you mentioned is the maximum current
the LED can handle without being damaged. With a lower current the light
production will slightly decrease but the life expectance of the LED will be
much better. Another important thing is temperature and heat production. Too
high a temperature will also decrease life expectance of the LED or may even
damage it. The example below has only two LEDs but you can add more if you
increase the supply voltage accordingly. T2 and R3 make up the on/off
switch. A 5V on R3 removes the base current from T1 so its collectorcurrent
vanishes and the LEDs go off.

+------+ 9V
| |
.-. V
| |R2 - LED
| | |
'-'1k5 |
| V
| - LED
| |
| |
| |
| |
+-----------+ |/ T1
| +----| BC635
| | |>
| Si V |
R3 | - |
___ |/ T2 | .-.
-|___|--| BC546 | | |R1
4k7 |> Si V | |2.2 Ohm
| - '-'
| | -
---------+-----------+------+ GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de


petrus bitbyter


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"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:Zanrd.48182$lN.15705@amsnews05.chello.com...
"booth multiplier" <boothmultipler@hotmail.com> schreef in bericht
news:24160f43.0412010351.84cbc6d@posting.google.com...
Dear All,
I'd like to built a driver circuitry for 8 Luxeon leds in series.
Each of them has a forward voltage at 3.5 V at 350 mA. 8 in series
makes 28V. I have applied the 28 volt works fine, but if I want to
make them flash it's not working, they simply don't flash. The ON
OFF sequence is like this: 1 sec OFF, 0.4sec ON, 0.1 sec OFF,0.4sec
ON, 0.1 sec OFF AND SO ON. Do I need a higher voltage for flashing?
Thanks

You treated the LEDs like resistors which they are not. According to
the
manufacturers information you always has to use a series resistor to
limit
the current through the LEDs. Look at:
http://www.lumileds.com/pdfs/AB11.PDF
for instance.
As LEDs are current driven devices you'd better look for a current
source.
See simple schematic below. The 350mA you mentioned is the maximum
current
the LED can handle without being damaged. With a lower current the
light
production will slightly decrease but the life expectance of the LED
will be
much better. Another important thing is temperature and heat
production. Too
high a temperature will also decrease life expectance of the LED or
may even
damage it. The example below has only two LEDs but you can add more if
you
increase the supply voltage accordingly. T2 and R3 make up the on/off
switch. A 5V on R3 removes the base current from T1 so its
collectorcurrent
vanishes and the LEDs go off.

+------+ 9V
| |
.-. V
| |R2 - LED
| | |
'-'1k5 |
| V
| - LED
| |
| |
| |
| |
+-----------+ |/ T1
| +----| BC635
| | |
| Si V |
R3 | - |
___ |/ T2 | .-.
-|___|--| BC546 | | |R1
4k7 |> Si V | |2.2 Ohm
| - '-'
| | -
---------+-----------+------+ GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de


petrus bitbyter
Click to expand...
First off, he said 8 LSes in series, yours shows only 2 and 9V supply.
For more than 28V at more than 1/3 amp, I would say that the BC635 will
quickly butn up. You need a TO-220 type transistor like the TIP31 on a
heatsink. The two diodes should be 1N4002 or better. Remember these
Luxeon Stars are $15 or so apiece! If you give him the wrong advice and
they burn up, that's well over a hundred dollars!!

> ---
 
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com>
schreef in bericht news:10qtra7hl853k9f@corp.supernews.com...
"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:Zanrd.48182$lN.15705@amsnews05.chello.com...

"booth multiplier" <boothmultipler@hotmail.com> schreef in bericht
news:24160f43.0412010351.84cbc6d@posting.google.com...
Dear All,
I'd like to built a driver circuitry for 8 Luxeon leds in series.
Each of them has a forward voltage at 3.5 V at 350 mA. 8 in series
makes 28V. I have applied the 28 volt works fine, but if I want to
make them flash it's not working, they simply don't flash. The ON
OFF sequence is like this: 1 sec OFF, 0.4sec ON, 0.1 sec OFF,0.4sec
ON, 0.1 sec OFF AND SO ON. Do I need a higher voltage for flashing?
Thanks

You treated the LEDs like resistors which they are not. According to
the
manufacturers information you always has to use a series resistor to
limit
the current through the LEDs. Look at:
http://www.lumileds.com/pdfs/AB11.PDF
for instance.
As LEDs are current driven devices you'd better look for a current
source.
See simple schematic below. The 350mA you mentioned is the maximum
current
the LED can handle without being damaged. With a lower current the
light
production will slightly decrease but the life expectance of the LED
will be
much better. Another important thing is temperature and heat
production. Too
high a temperature will also decrease life expectance of the LED or
may even
damage it. The example below has only two LEDs but you can add more if
you
increase the supply voltage accordingly. T2 and R3 make up the on/off
switch. A 5V on R3 removes the base current from T1 so its
collectorcurrent
vanishes and the LEDs go off.

+------+ 9V
| |
.-. V
| |R2 - LED
| | |
'-'1k5 |
| V
| - LED
| |
| |
| |
| |
+-----------+ |/ T1
| +----| BC635
| | |
| Si V |
R3 | - |
___ |/ T2 | .-.
-|___|--| BC546 | | |R1
4k7 |> Si V | |2.2 Ohm
| - '-'
| | -
---------+-----------+------+ GND
created by Andy4s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de


petrus bitbyter

First off, he said 8 LSes in series, yours shows only 2 and 9V supply.
For more than 28V at more than 1/3 amp, I would say that the BC635 will
quickly butn up. You need a TO-220 type transistor like the TIP31 on a
heatsink. The two diodes should be 1N4002 or better. Remember these
Luxeon Stars are $15 or so apiece! If you give him the wrong advice and
they burn up, that's well over a hundred dollars!!

---
Click to expand...
You're really quick with your comment but did you read what I wrote? I gave
an example, not a full fledged design. The components in the example are
used within the specs. If you really think I'am wrong, prove it.
Nevertheless, if you want to stay on the safe side a power transistor may
have its use, but a heatsink for less then 0.5W seems a little bit
exaggerated to me. Both power transistor and heatsink are only required if
you want to increase the power voltage wihout adding LEDs in the collector
chain. I also wonder what special properties requires the 1N4002 or better.
Why should a 1N4148 (for instance) not be good enough?

petrus bitbyter


---
Outgoing mail is certified Virus Free.
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On Thu, 02 Dec 2004 19:11:38 +0000, petrus bitbyter wrote:
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message

"booth multiplier" <boothmultipler@hotmail.com> schreef in bericht
news:24160f43.0412010351.84cbc6d@posting.google.com...
Dear All,
I'd like to built a driver circuitry for 8 Luxeon leds in series.
Each of them has a forward voltage at 3.5 V at 350 mA. 8 in series
makes 28V. I have applied the 28 volt works fine, but if I want to
make them flash it's not working, they simply don't flash. The ON
OFF sequence is like this: 1 sec OFF, 0.4sec ON, 0.1 sec OFF,0.4sec
ON, 0.1 sec OFF AND SO ON. Do I need a higher voltage for flashing?
Thanks

First off, he said 8 LSes in series, yours shows only 2 and 9V supply.
For more than 28V at more than 1/3 amp, I would say that the BC635 will
quickly butn up. You need a TO-220 type transistor like the TIP31 on a
heatsink. The two diodes should be 1N4002 or better. Remember these
Luxeon Stars are $15 or so apiece! If you give him the wrong advice and
they burn up, that's well over a hundred dollars!!

You're really quick with your comment but did you read what I wrote? I
gave an example, not a full fledged design. The components in the example
are used within the specs. If you really think I'am wrong, prove it.
Nevertheless, if you want to stay on the safe side a power transistor may
have its use, but a heatsink for less then 0.5W seems a little bit
exaggerated to me. Both power transistor and heatsink are only required if
you want to increase the power voltage wihout adding LEDs in the collector
chain. I also wonder what special properties requires the 1N4002 or
better. Why should a 1N4148 (for instance) not be good enough?
Click to expand...
It's because Watson's afraid of anything over 24V. ;=)

Actually, I'm pretty much afraid to use LEDs that cost fifteen bucks! =:-O

Cheers!
Rich
 
On 1 Dec 2004 03:51:05 -0800, boothmultipler@hotmail.com (booth
multiplier) wrote:

Dear All,
I'd like to built a driver circuitry for 8 Luxeon leds in series.
Each of them has a forward voltage at 3.5 V at 350 mA. 8 in series
makes 28V. I have applied the 28 volt works fine, but if I want to
make them flash it's not working, they simply don't flash. The ON
OFF sequence is like this: 1 sec OFF, 0.4sec ON, 0.1 sec OFF,0.4sec
ON, 0.1 sec OFF AND SO ON. Do I need a higher voltage for flashing?
Thanks
Click to expand...
The only efficient way of running 8 x 1W luxeon led's in series is to
use a switch mode, current regulated, power supply. I haven't tried
these devices in series and I don't know their failure modes. If one
fails short circuit then a non-current regulated supply will cause ALL
other series leds to fail catastrophically. To run 8 in series
luxeon's (1W) requires a PSU of around 15W (max rated) running at a
safe 50% of maximum load.

Lumileds publish a list of devices for use in luxeon flash
applications http://www.lumileds.com/pdfs/AB28.pdf and at least one
electronics hobbyist publication has produced a design for a psu for
running 1 x 5W or 2 x 1W (or 3W)luxeon's in series.

Commercially available drivers for series luxeon's are available
http://www.theledlight.com/luxeonaccessories.html but the flash
function would have to be supplied by an additional piece of circuitry
with your required duty cycle.
 
"Rich Grise" <rich@example.net> wrote in message
news:pan.2004.12.02.22.05.24.42442@example.net...
On Thu, 02 Dec 2004 19:11:38 +0000, petrus bitbyter wrote:
"Watson A.Name - "Watt Sun, the Dark Remover""
NOSPAM@dslextreme.com
"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message

"booth multiplier" <boothmultipler@hotmail.com> schreef in bericht
news:24160f43.0412010351.84cbc6d@posting.google.com...
Dear All,
I'd like to built a driver circuitry for 8 Luxeon leds in
series.
Each of them has a forward voltage at 3.5 V at 350 mA. 8 in
series
makes 28V. I have applied the 28 volt works fine, but if I want
to
make them flash it's not working, they simply don't flash. The
ON
OFF sequence is like this: 1 sec OFF, 0.4sec ON, 0.1 sec
OFF,0.4sec
ON, 0.1 sec OFF AND SO ON. Do I need a higher voltage for
flashing?
Thanks

First off, he said 8 LSes in series, yours shows only 2 and 9V
supply.
For more than 28V at more than 1/3 amp, I would say that the BC635
will
quickly butn up. You need a TO-220 type transistor like the TIP31
on a
heatsink. The two diodes should be 1N4002 or better. Remember
these
Luxeon Stars are $15 or so apiece! If you give him the wrong
advice and
they burn up, that's well over a hundred dollars!!

You're really quick with your comment but did you read what I wrote?
I
gave an example, not a full fledged design. The components in the
example
are used within the specs. If you really think I'am wrong, prove it.
Nevertheless, if you want to stay on the safe side a power
transistor may
have its use, but a heatsink for less then 0.5W seems a little bit
exaggerated to me. Both power transistor and heatsink are only
required if
you want to increase the power voltage wihout adding LEDs in the
collector
chain. I also wonder what special properties requires the 1N4002 or
better. Why should a 1N4148 (for instance) not be good enough?
Click to expand...
This circuit doesn't have very good current stability to start with.
The LED current depends on the forward voltage drop across those two
diodes; this Vf changes with temperature. Using heftier diodes with
greater dissipation will give some improvement in stability.

It's because Watson's afraid of anything over 24V. ;=)
Click to expand...
Nope. I've been installing a PBX all day today, Neg 48V (more
like -56VDC) all over the place. Ten gauge wiring, etc. Each phone
line has enough current, maybe 150mA, to make a nice blue spark when you
short it. Scares the hell out of some of the contractor's techs. I get
a kick out of seeing them go "WHOA! What was that?" when that happens!

Actually, I'm pretty much afraid to use LEDs that cost fifteen bucks!
=:-O
Click to expand...

I was using four 1N4002s and maybe a 1N5818 schottky in series for a
dummy while I was experimenting with my LSes. Better safe than sorry at
that price.

Cheers!
Rich
Click to expand...

+------+ 9V
| |
.-. V
| |R2 - LED
| | |
'-'1k5 |
| V
| - LED
| |
| |
| |
| |
+-----------+ |/ T1
| +----| BC635
| | |
| Si V |
R3 | - |
___ |/ T2 | .-.
-|___|--| BC546 | | |R1
4k7 |> Si V | |2.2 Ohm
| - '-'
| | -
---------+-----------+------+ GND
Click to expand...
 
"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com>
schreef in bericht news:10r06101ne9pua1@corp.supernews.com...
"Rich Grise" <rich@example.net> wrote in message
news:pan.2004.12.02.22.05.24.42442@example.net...
On Thu, 02 Dec 2004 19:11:38 +0000, petrus bitbyter wrote:
"Watson A.Name - "Watt Sun, the Dark Remover""
NOSPAM@dslextreme.com
"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message

"booth multiplier" <boothmultipler@hotmail.com> schreef in bericht
news:24160f43.0412010351.84cbc6d@posting.google.com...
Dear All,
I'd like to built a driver circuitry for 8 Luxeon leds in
series.
Each of them has a forward voltage at 3.5 V at 350 mA. 8 in
series
makes 28V. I have applied the 28 volt works fine, but if I want
to
make them flash it's not working, they simply don't flash. The
ON
OFF sequence is like this: 1 sec OFF, 0.4sec ON, 0.1 sec
OFF,0.4sec
ON, 0.1 sec OFF AND SO ON. Do I need a higher voltage for
flashing?
Thanks

First off, he said 8 LSes in series, yours shows only 2 and 9V
supply.
For more than 28V at more than 1/3 amp, I would say that the BC635
will
quickly butn up. You need a TO-220 type transistor like the TIP31
on a
heatsink. The two diodes should be 1N4002 or better. Remember
these
Luxeon Stars are $15 or so apiece! If you give him the wrong
advice and
they burn up, that's well over a hundred dollars!!

You're really quick with your comment but did you read what I wrote?
I
gave an example, not a full fledged design. The components in the
example
are used within the specs. If you really think I'am wrong, prove it.
Nevertheless, if you want to stay on the safe side a power
transistor may
have its use, but a heatsink for less then 0.5W seems a little bit
exaggerated to me. Both power transistor and heatsink are only
required if
you want to increase the power voltage wihout adding LEDs in the
collector
chain. I also wonder what special properties requires the 1N4002 or
better. Why should a 1N4148 (for instance) not be good enough?

This circuit doesn't have very good current stability to start with.
The LED current depends on the forward voltage drop across those two
diodes; this Vf changes with temperature. Using heftier diodes with
greater dissipation will give some improvement in stability.

It's because Watson's afraid of anything over 24V. ;=)

Nope. I've been installing a PBX all day today, Neg 48V (more
like -56VDC) all over the place. Ten gauge wiring, etc. Each phone
line has enough current, maybe 150mA, to make a nice blue spark when you
short it. Scares the hell out of some of the contractor's techs. I get
a kick out of seeing them go "WHOA! What was that?" when that happens!

Actually, I'm pretty much afraid to use LEDs that cost fifteen bucks!
=:-O

I was using four 1N4002s and maybe a 1N5818 schottky in series for a
dummy while I was experimenting with my LSes. Better safe than sorry at
that price.

Cheers!
Rich



+------+ 9V
| |
.-. V
| |R2 - LED
| | |
'-'1k5 |
| V
| - LED
| |
| |
| |
| |
+-----------+ |/ T1
| +----| BC635
| | |
| Si V |
R3 | - |
___ |/ T2 | .-.
-|___|--| BC546 | | |R1
4k7 |> Si V | |2.2 Ohm
| - '-'
| | -
---------+-----------+------+ GND
Click to expand...
This circuit does not have a very good stability. But IMHO it's much better
then connecting the LEDS in series to a battery (or other power supply)
without any current limiting at all. If you want to improve it's stability a
little bit you'd better first increase the current through the diodes by
lowering R2 then use beefier diodes. But why make things difficult? I'm sure
you can calculate and measure the variations in the LED current due to
temperature changes but I doubt if you will *see* that as variations in the
light with the naked eye. If you nevertheless want more control you'll have
to make a different design. Maybe you have a proposal?

petrus bitbyter



---
Outgoing mail is certified Virus Free.
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"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:CWWrd.56069$lN.11068@amsnews05.chello.com...

[snip]

+------+ 9V
| |
.-. V
| |R2 - LED
| | |
'-'1k5 |
| V
| - LED
| |
| |
| |
| |
+-----------+ |/ T1
| +----| BC635
| | |
| Si V |
R3 | - |
___ |/ T2 | .-.
-|___|--| BC546 | | |R1
4k7 |> Si V | |2.2 Ohm
| - '-'
| | -
---------+-----------+------+ GND



This circuit does not have a very good stability. But IMHO it's much
better
then connecting the LEDS in series to a battery (or other power
supply)
without any current limiting at all. If you want to improve it's
stability a
little bit you'd better first increase the current through the diodes
by
lowering R2 then use beefier diodes. But why make things difficult?
I'm sure
you can calculate and measure the variations in the LED current due to
temperature changes but I doubt if you will *see* that as variations
in the
light with the naked eye. If you nevertheless want more control you'll
have
to make a different design. Maybe you have a proposal?

petrus bitbyter
---
Click to expand...
Yeah, the following commonly seen circuit, posted here many times by
myself and others, is used more often than the above because it's more
stable, but still not very good. As with your circuit, it has to be
scaled up in current and power to meet the 350 mA needed for the Luxeon
Star. Use a BD135 or TIP31 for Q1, on a heatsink if it gets too hot to
touch. And the 10k to 47k needs to be lower also. With the 33 ohms
changed to 2 ohms, it should give about 300 mA.

You can also use the LM317 as a current limiter, see the circuit in the
datasheet.


+--------------------+------- Positive
| | Supply V.
| |
| --- LED
10k \ \ / =====>
to 47k / ===
ohms \ |
/ |
| / Q1
| | / Gen'l
| | Purp NPN
+----------------| 2N3904 or
| | 2N2222A
| | \ E
Q2 \ \
Gen'l \ | |
Purp NPN | 470 ohms |
2N3904 or |------/\/\/\----+
2N2222A | |
E / | |
/ \
| 33 ohms /
| for \
| 18ma /
| |
| |
| |
+---------------------+-------
Negative Supply V.
 
On 3 Dec 2004 07:35:20 -0800, veryfree123@hotmail.com (Watson A.Name)
wrote:

IIRC, with the LSTTL chips, the schottky TTLs use a schottky diode
between base and collector to prevent the collector from going below a
certain voltage into saturation, thus speeding up the turn-on. I've
never seen a discrete circuit using this, but is it a workable
solution to put a 1N5711 schottky signal diode between the base and
collector of a 2N2369A or 2N3904 for example, to prevent it from
saturating, and help speed up its switching? I was thinking of
driving an IR LED with a signal that's fairly quick, and I don't think
that an open collector TTL chip would have enough current. But then
maybe parallel open collectors? Or what?
Click to expand...
(1) How "quick" does ANY circuit need to be when flashing an LED?

(2) A 2N2369A is gold-doped, thus does not need to be
Schottky-clamped to prevent charge storage.

(3) The 1N5711 data sheet shows only 2pF of capacitance, so it should
be OK.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
In article <18ebe27.0412030735.60f39e82@posting.google.com>,
Watson A.Name <veryfree123@hotmail.com> wrote:
IIRC, with the LSTTL chips, the schottky TTLs use a schottky diode
between base and collector to prevent the collector from going below a
certain voltage into saturation, thus speeding up the turn-on. I've
never seen a discrete circuit using this, but is it a workable
solution to put a 1N5711 schottky signal diode between the base and
collector of a 2N2369A or 2N3904 for example, to prevent it from
saturating, and help speed up its switching? I was thinking of
driving an IR LED with a signal that's fairly quick, and I don't think
that an open collector TTL chip would have enough current. But then
maybe parallel open collectors? Or what?
Click to expand...
In discrete land, the voltage swing is often too large for just a
schottky. In those cases a "Baker clamp"[1] is used. I have used the
schottky clamp method at 10V and had it work.


[1] Baker clamp is like this


Simple version:



D1
-------+------->!--------+----
! !
! D2 !/
------->!------!
!\ e
!

It takes away base drive when the collector gets down to one diode drop.
D2 is often the E-B junction of another transistor. This circuit works ok
but the speed and capacitance of D1 is an issue during turn off.



All that said, you want to use a MOSFET to drive the IR LED. They switch
quite fast with no extra work. The Supertex TN0604 driven by HC logic
like this:

+12V
+-------+
! !
\ \
/R1 /R2
! \
V !
--- !
! !
!!----+-------
-----!!
!!--
!
GND

R1 sets the diodes current.

R2 speeds up the discharging of capacitances during turn off. It needs to
be about 100-1K depending on how fast you need.

--
--
kensmith@rahul.net forging knowledge
 
Hi Larry,

If speed mattered, I would use a small MOSFET. They are
inexpensive and good for interface to logic.
Click to expand...
That depends. If the control signal originates from 3.3V logic or even
lower levels a FET becomes rather sluggish without some major level
shifting or toroid transformers. I have been in that pickle more than
once and reverted to bipolar. Besides the good old 2N2369 there are some
other fine RF transistors such as the BFS17A.

Regards, Joerg

http://www.analogconsultants.com
 
On Fri, 3 Dec 2004 11:02:14 -0800, "Larry Brasfield"
<donotspam_larry_brasfield@hotmail.com> wrote:

"Jim Thompson" <thegreatone@example.com> wrote in message
news:m241r09bp2ub2iv5st4j8uvlg6c4dfjrq2@4ax.com...
...
(1) How "quick" does ANY circuit need to be when flashing an LED?

Maybe it is signaling to something not a person?

(2) A 2N2369A is gold-doped, thus does not need to be
Schottky-clamped to prevent charge storage.

Gold doped BJTs still exhibit charge storage. That doping
reduces carrier lifetime, so such transistors can switch off
in a few 10's of nS, but preventing saturation will still speed
up the turn-off.

If speed mattered, I would use a small MOSFET. They are
inexpensive and good for interface to logic.
Click to expand...
The 2N2369 at 10mA load turns off in 30ns. With the 1N5711's CJO=2pF
I doubt that you will get much improvement... might even be worse.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
In message <KNJrd.52392$lN.24565@amsnews05.chello.com>, petrus bitbyter
<p.kralt@reducespamforchello.nl> writes
You're really quick with your comment but did you read what I wrote? I
gave an example, not a full fledged design. The components in the
example are used within the specs. If you really think I'am wrong,
prove it. Nevertheless, if you want to stay on the safe side a power
transistor may have its use, but a heatsink for less then 0.5W seems a
little bit exaggerated to me. Both power transistor and heatsink are
only required if you want to increase the power voltage wihout adding
LEDs in the collector chain. I also wonder what special properties
requires the 1N4002 or better. Why should a 1N4148 (for instance) not
be good enough?
Click to expand...
I built a mains power supply for a Luxeon star as follows:-

Live / hot --------------
|
|
O 40 watt light bulb.
|
|--------------------|
V luxeon A 1N4007 diode
|--------------------|
|
|
Neutral / return -----

It lights, but doesn't flash like Luxeons are meant to. At least it's
not flashing slowly. It appears to be flashing very quickly at a speed
that only registers with peripheral vision.

Have Luxeon had a bad batch of their LEDs or do I need to use a
different light bulb? A friend says that Luxeons don't flash, but I've
seen them do it in cheap disco lights so he's just talking complete
rubbish.


--
Dick Endaway.

Pro electronic services for disco's done cheap.
 
Clive Mitchell wrote:
In message <KNJrd.52392$lN.24565@amsnews05.chello.com>, petrus bitbyter
p.kralt@reducespamforchello.nl> writes

You're really quick with your comment but did you read what I wrote? I
gave an example, not a full fledged design. The components in the
example are used within the specs. If you really think I'am wrong,
prove it. Nevertheless, if you want to stay on the safe side a power
transistor may have its use, but a heatsink for less then 0.5W seems a
little bit exaggerated to me. Both power transistor and heatsink are
only required if you want to increase the power voltage wihout adding
LEDs in the collector chain. I also wonder what special properties
requires the 1N4002 or better. Why should a 1N4148 (for instance) not
be good enough?


I built a mains power supply for a Luxeon star as follows:-

Live / hot --------------
|
|
O 40 watt light bulb.
|
|--------------------|
V luxeon A 1N4007 diode
|--------------------|
|
|
Neutral / return -----

It lights, but doesn't flash like Luxeons are meant to. At least it's
not flashing slowly. It appears to be flashing very quickly at a speed
that only registers with peripheral vision.

Have Luxeon had a bad batch of their LEDs or do I need to use a
different light bulb? A friend says that Luxeons don't flash, but I've
seen them do it in cheap disco lights so he's just talking complete
rubbish.
Click to expand...
Are you talking about these? I believe they are meant to flash at a high
rate...

http://www.luxeon.com/products/line.cfm?lineId=17

Now, your bulb thingy will work, but the initial current will be
painful. Light bulbs start out with a very low resistance, which quickly
increases as the bulb heats up. See

http://members.misty.com/don/bulb1.html#sur

Thus, your luxeon is being subjected to hideous currents when you flip
on the light. I just measured the resistance through an 'off' 100W light
bulb (USA). The resistance was 10.3 ohms. Now, if you put 120V across
10.3 ohms, the current will be

120/10.3 = 11.65A

Once it heats up, the resistance will go up to 120^2/100 = 144 ohms.
That is more than a 10x increase in resistance.

You might be able to snub the initial rush of current using a soft-start
device, as outlined in Don Klipstein's tutorial given above. However, I
guess it would be easier and safer just to use a 5V wall wart.

--
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.
 
On Sat, 4 Dec 2004 00:45:20 +0000, Clive Mitchell
<clive1@emanator.demon.co.uk> wrote:

In message <KNJrd.52392$lN.24565@amsnews05.chello.com>, petrus bitbyter
p.kralt@reducespamforchello.nl> writes
You're really quick with your comment but did you read what I wrote? I
gave an example, not a full fledged design. The components in the
example are used within the specs. If you really think I'am wrong,
prove it. Nevertheless, if you want to stay on the safe side a power
transistor may have its use, but a heatsink for less then 0.5W seems a
little bit exaggerated to me. Both power transistor and heatsink are
only required if you want to increase the power voltage wihout adding
LEDs in the collector chain. I also wonder what special properties
requires the 1N4002 or better. Why should a 1N4148 (for instance) not
be good enough?

I built a mains power supply for a Luxeon star as follows:-

Live / hot --------------
|
|
O 40 watt light bulb.
|
|--------------------|
V luxeon A 1N4007 diode
|--------------------|
|
|
Neutral / return -----

It lights, but doesn't flash like Luxeons are meant to. At least it's
not flashing slowly. It appears to be flashing very quickly at a speed
that only registers with peripheral vision.
Click to expand...
Why should it flash slowly? Using your circuit the LED will be on for
one half cycle and off for the other. So, in Europe it will flash 50
times a second, in NA 60 times a second.

Have Luxeon had a bad batch of their LEDs or do I need to use a
different light bulb? A friend says that Luxeons don't flash, but I've
seen them do it in cheap disco lights so he's just talking complete
rubbish.
Click to expand...
Any LED will flash if used on a "flashing" power supply.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.
 
Jim Thompson wrote:
On 3 Dec 2004 07:35:20 -0800, veryfree123@hotmail.com (Watson A.Name)
wrote:

IIRC, with the LSTTL chips, the schottky TTLs use a schottky diode
between base and collector to prevent the collector from going below a
certain voltage into saturation, thus speeding up the turn-on. I've
never seen a discrete circuit using this, but is it a workable
solution to put a 1N5711 schottky signal diode between the base and
collector of a 2N2369A or 2N3904 for example, to prevent it from
saturating, and help speed up its switching? I was thinking of
driving an IR LED with a signal that's fairly quick, and I don't think
that an open collector TTL chip would have enough current. But then
maybe parallel open collectors? Or what?

(1) How "quick" does ANY circuit need to be when flashing an LED?

(2) A 2N2369A is gold-doped, thus does not need to be
Schottky-clamped to prevent charge storage.

(3) The 1N5711 data sheet shows only 2pF of capacitance, so it should
be OK.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
Click to expand...
I thought that the 2N2369A was fast because it was bribed with gold...
 
Jim Thompson wrote...
The 2N2369 at 10mA load turns off in 30ns.
Click to expand...
One can actually do far better than that with a 2n2369.

I assume you get the 30ns number from the datasheet's MAX specs,
which are 13ns storage time and 18ns turn-off switching time at
Ic=10mA and Ib_on = 3mA (wow, way to high) and Ib_off = -1.5mA
(wow, way too low). Even under these less-than ideal conditions
a real transistor would be faster than the MAX specs. Moreover,
we'd be making a discrete circuit with our 2n2369, so we would
have capacitors available, which we'd use to increase the base
drive during transitions. This allows us to reduce steady ON
base drive, reducing OFF storage time, and to increase turn-off
base drive, speeding up switch-off time. In this fashion I have
been able to push 2n2369 style parts down to the 5ns territory.

With the 1N5711's CJO=2pF I doubt that you will get much
improvement... might even be worse.
Click to expand...
2pF is the MAX value, for most of the swing the capacitance is
closer to 0.8pF (and smaller Schottky diodes are available for
super-fast switching). But even a 2pF 1n5711 would not be much
of a problem, 10mA applied to 2pF will slew 5 volts in just 1ns.
A Schottky diode is often worth its small extra capacitance.


--
Thanks,
- Win
 
Ken Smith wrote:

In discrete land, the voltage swing is often too large for just a
schottky. In those cases a "Baker clamp"[1] is used. I have used the
schottky clamp method at 10V and had it work.


[1] Baker clamp is like this


Simple version:



D1
-------+------->!--------+----
! !
! D2 !/
------->!------!
!\ e
!

It takes away base drive when the collector gets down to one diode drop.
D2 is often the E-B junction of another transistor. This circuit works ok
but the speed and capacitance of D1 is an issue during turn off.



All that said, you want to use a MOSFET to drive the IR LED. They switch
quite fast with no extra work. The Supertex TN0604 driven by HC logic
like this:

+12V
+-------+
! !
\ \
/R1 /R2
! \
V !
--- !
! !
!!----+-------
-----!!
!!--
!
GND

R1 sets the diodes current.

R2 speeds up the discharging of capacitances during turn off. It needs to
be about 100-1K depending on how fast you need.
Click to expand...
There are plenty of drivers that avoid saturation and charge recovery
delays.
View in a fixed-width font such as Courier.


.
.
.
. V
. dd
. |
. +-------+
. | |
. | c
. |\ |/ Voh-Vbe,on-Vled(I)
. ----| >----| I~ ------------------
. |/ |\ Re
. CMOS e
. buffer |
. / saturation not possible
. Re
. /
. \
. |
. ---
. \ /
. ---
. |
. gnd
.
.
.
.
.
.
.
. V+
. |
. ---
. \ /
. V ---
. dd |
. | c
. |\ |/ Voh-Vbe,on
. ----| >----| I~ ----------
. |/ |\ Re
. CMOS e
. buffer |
. / V+> Vo,h + Vled(I) + 0.7V
. Re
. /
. \
. | saturation not possible
. gnd
.
.
 
On 4 Dec 2004 04:06:27 -0800, Winfield Hill
<hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

Jim Thompson wrote...

The 2N2369 at 10mA load turns off in 30ns.

One can actually do far better than that with a 2n2369.

I assume you get the 30ns number from the datasheet's MAX specs,
which are 13ns storage time and 18ns turn-off switching time at
Ic=10mA and Ib_on = 3mA (wow, way to high) and Ib_off = -1.5mA
(wow, way too low). Even under these less-than ideal conditions
a real transistor would be faster than the MAX specs. Moreover,
we'd be making a discrete circuit with our 2n2369, so we would
have capacitors available, which we'd use to increase the base
drive during transitions. This allows us to reduce steady ON
base drive, reducing OFF storage time, and to increase turn-off
base drive, speeding up switch-off time. In this fashion I have
been able to push 2n2369 style parts down to the 5ns territory.

With the 1N5711's CJO=2pF I doubt that you will get much
improvement... might even be worse.

2pF is the MAX value, for most of the swing the capacitance is
closer to 0.8pF (and smaller Schottky diodes are available for
super-fast switching). But even a 2pF 1n5711 would not be much
of a problem, 10mA applied to 2pF will slew 5 volts in just 1ns.
A Schottky diode is often worth its small extra capacitance.
Click to expand...
But that's a requirement of 10mA of DRIVE current.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Jim Thompson wrote...
Winfield Hill wrote:

Jim Thompson wrote...

The 2N2369 at 10mA load turns off in 30ns.

One can actually do far better than that with a 2n2369.

I assume you get the 30ns number from the datasheet's MAX specs,
which are 13ns storage time and 18ns turn-off switching time at
Ic=10mA and Ib_on = 3mA (wow, way to high) and Ib_off = -1.5mA
(wow, way too low). Even under these less-than ideal conditions
a real transistor would be faster than the MAX specs. Moreover,
we'd be making a discrete circuit with our 2n2369, so we would
have capacitors available, which we'd use to increase the base
drive during transitions. This allows us to reduce steady ON
base drive, reducing OFF storage time, and to increase turn-off
base drive, speeding up switch-off time. In this fashion I have
been able to push 2n2369 style parts down to the 5ns territory.

With the 1N5711's CJO=2pF I doubt that you will get much
improvement... might even be worse.

2pF is the MAX value, for most of the swing the capacitance is
closer to 0.8pF (and smaller Schottky diodes are available for
super-fast switching). But even a 2pF 1n5711 would not be much
of a problem, 10mA applied to 2pF will slew 5 volts in just 1ns.
A Schottky diode is often worth its small extra capacitance.

But that's a requirement of 10mA of DRIVE current.
Click to expand...
Right, but provided by the speed-up cap or whatever, for a few ns.


--
Thanks,
- Win
 
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