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'[EE]: powering LEDs from AC power line.'
2001\09\28@072504 by antoniasse

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Hello all,
I needing some help!
How is the best way to power a Led from 220VAC and 24VAC?
The led has to be powered with a minimal current.
Thanks in advanced.

Luis F.

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2001\09\28@090751 by Olin Lathrop

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> How is the best way to power a Led from 220VAC and 24VAC?
> The led has to be powered with a minimal current.
> Thanks in advanced.

A capacitive charge pump driven from the AC voltage would be fine if the LED
doesn't need to be isolated from the line.


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2001\09\28@164329 by M. Adam Davis

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Place a capacitor and resistor in series with the LED.  Figuring out the
needed values is left to you, but make sure the cap is rated for 200v,
non polarized.

-Adam

antoniasse wrote:

{Quote hidden}

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2001\09\28@165158 by David VanHorn

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At 04:41 PM 9/28/01 -0400, M. Adam Davis wrote:
>Place a capacitor and resistor in series with the LED.  Figuring out the
>needed values is left to you, but make sure the cap is rated for 200v,
>non polarized.

And what happens when the voltage reverses?

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2001\09\28@172508 by Herbert Graf

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POP I would assume! :) TTYL

{Quote hidden}

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2001\09\28@175039 by David VanHorn

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At 05:26 PM 9/28/01 -0400, Herbert Graf wrote:
>POP I would assume! :) TTYL

I think it would be "bang", without a reversed diode across the LED.

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2001\09\28@175633 by Spehro Pefhany

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At 04:48 PM 9/28/01 -0500, you wrote:
>At 05:26 PM 9/28/01 -0400, Herbert Graf wrote:
>>POP I would assume! :) TTYL
>
>I think it would be "bang", without a reversed diode across the LED.

Could be much worse- it could seem to work until a line transient hits
it. Maybe I'll give it a try and report back.

Best regards,
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2001\09\28@175637 by Lasse Madsen

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> And what happens when the voltage reverses?

You must have a regular diode in anti-parallel with the LED

Best regards
Lasse Madsen

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2001\09\28@180052 by David VanHorn

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At 05:56 PM 9/28/01 -0400, Spehro Pefhany wrote:
>At 04:48 PM 9/28/01 -0500, you wrote:
> >At 05:26 PM 9/28/01 -0400, Herbert Graf wrote:
> >>POP I would assume! :) TTYL
> >
> >I think it would be "bang", without a reversed diode across the LED.
>
>Could be much worse- it could seem to work until a line transient hits
>it. Maybe I'll give it a try and report back.


Wear your safety goggles :)

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2001\09\28@181751 by Spehro Pefhany

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At 04:57 PM 9/28/01 -0500, you wrote:
>At 05:56 PM 9/28/01 -0400, Spehro Pefhany wrote:
>>At 04:48 PM 9/28/01 -0500, you wrote:
>> >At 05:26 PM 9/28/01 -0400, Herbert Graf wrote:
>> >>POP I would assume! :) TTYL
>> >
>> >I think it would be "bang", without a reversed diode across the LED.
>>
>>Could be much worse- it could seem to work until a line transient hits
>>it. Maybe I'll give it a try and report back.
>
>
>Wear your safety goggles :)

Not so bad, the LED has a reverse breakdown of something like 30V.

I use the following circuit; Ther would normally also
be a high-valued resistor in parallel with the capacitor
if nothing else is connected to the circuit (for obvious
safety reasons).

                                  Generic green LED
                                        //
L------[270R]------[1uF/250V]------x---|>|----------x
                                  |                |
                                  x---|<|----------x
                                     UF4005        |
                                                   |
N---------------------------------------------------x

This should give an average forward LED current of
22mA.

With the UF4005 (hey, I had them around) removed, the LED was
distinctly more yellow in color and dimmer. It also got
quite warm. After 10 random on/off cycles it was still working.
After 15 more it failed. Just the kind of design fault that
is most bothersome! If I'd picked a more conservative value for
the capacitor it might have worked even longer.

Best regards,


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2001\09\28@183043 by Olin Lathrop

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> Place a capacitor and resistor in series with the LED.  Figuring out the
> needed values is left to you, but make sure the cap is rated for 200v,
> non polarized.

And a diode in the right place else the LED will only work once.


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2001\09\28@190529 by Olin Lathrop

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> > And what happens when the voltage reverses?
>
> You must have a regular diode in anti-parallel with the LED

I would put the diode on the capacitor side of the resistor, not the LED
side.


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2001\09\28@204418 by Spehro Pefhany

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At 06:17 PM 9/28/01 -0400, you wrote:
>> > And what happens when the voltage reverses?
>>
>> You must have a regular diode in anti-parallel with the LED
>
>I would put the diode on the capacitor side of the resistor, not the LED
>side.

You need the diode in parallel with the LED, if it's in series, it will
just charge the capacitor up to 170V or so and you'll only get a brief blip
of light. The diode allows the capacitor to charge to -170V.

Or use a WO2M bridge on the LED and you can use half the capacitance for
a given brightness because the current flows on both 'alf cycles.
In any case the diode does not have to withstand more than few volts of
PRV, but should be reasonably rugged because of the turn-on transient and
line transients.

Best regards,
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2001\09\28@232743 by M. Adam Davis

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David VanHorn wrote:

> At 04:41 PM 9/28/01 -0400, M. Adam Davis wrote:
>
>> Place a capacitor and resistor in series with the LED.  Figuring out the
>> needed values is left to you, but make sure the cap is rated for 200v,
>> non polarized.
>
>
> And what happens when the voltage reverses?

How about a red/green LED, it'll glow amber when it's on, and as an
added bonus you'll know if the power company ever switches to dc!

-Adam

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2001\09\29@061129 by Andrew E. Kalman

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Adam Davis wrote:

>How about a red/green LED, it'll glow amber when it's on, and as an
>added bonus you'll know if the power company ever switches to dc!

Now THAT is funny!


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2001\09\29@061352 by Lasse Madsen

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> Could be much worse- it could seem to work until a line transient hits
> it. Maybe I'll give it a try and report back.

You really shoudnt because LED's does not have the capability of 230Vrmax
at most a few volts.

Doing it will destroy the led thats certain, transient's or not.

Regards
Lasse Madsen

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2001\09\29@075135 by Peter L. Peres

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> Place a capacitor and resistor in series with the LED.  Figuring out the
> needed values is left to you, but make sure the cap is rated for 200v,
> non polarized.

And a antiparallel diode with the LED...

Peter

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2001\09\29@081346 by Bob Ammerman

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> David VanHorn wrote:
>
> > At 04:41 PM 9/28/01 -0400, M. Adam Davis wrote:
> >
> >> Place a capacitor and resistor in series with the LED.  Figuring out
the
{Quote hidden}

Yeah but if it switches to DC then the LED will go out because we are using
a series capacitor in this circuit.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\09\29@081959 by Olin Lathrop

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> >> You must have a regular diode in anti-parallel with the LED
> >
> >I would put the diode on the capacitor side of the resistor, not the LED
> >side.
>
> You need the diode in parallel with the LED, if it's in series, ...

I didn't say to put it in series.  You're right, that would be stupid.  OK,
I give up and try some ASCII art:

                                 LED
     ---||---*------/\/\/\-------|>|----
     |       |                         |
             |                         |
   AC in     _                         |
             ^ diode                   |
     |       |                         |
     --------*--------------------------


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2001\09\29@111613 by M. Adam Davis

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Doh!  Back to the drawing board...  ;-)

-Adam

Bob Ammerman wrote:

{Quote hidden}

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2001\09\29@115240 by Bob Barr

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Bob Ammerman wrote:

<snip>

> > How about a red/green LED, it'll glow amber when it's on, and as an
> > added bonus you'll know if the power company ever switches to dc!
> >
> > -Adam
>
>
>Yeah but if it switches to DC then the LED will go out because we are using
>a series capacitor in this circuit.
>

If the power company ever switches the grid over to DC, I think the LED will
be the least of your worries. :=)

Regards, Bob

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'[EE]: Powering LEDs from AC power line.'
2001\10\02@011903 by Bala Chandar
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Hi everyone,

Here's a practical and reliable circuit to power an LED from the mains
voltage. I have been using the 240V version for the past 18 years - YES,
from Sep 1983 onwards without any problems!

I was using a neon lamp with a series resistor to indicate the status of a
mains switch. The problem was that every two years or so, the tiny neon lamp
had to be replaced. Ever since I started using the LED circuit, it has been
working reliably and I have not had any reason to replace any component in
the circuit.

240V Version:

       0.22uF 400V      220 Ohms       LED
        Polyester       1/4W            //
  ---------||----------/\/\/\----------|>|-------
  |                              |              |

  |                              |              |
240V AC                           |-----|<|------|
  |                                   1N 4001   |
  |                                             |
  -----------------------------------------------


120V Version:

       0.47uF 250V      120 Ohms       LED
        Polyester       1/4W            //
  ---------||----------/\/\/\----------|>|-------
  |                              |              |

  |                              |              |
120V AC                           |-----|<|------|
  |                                   1N 4001   |
  |                                             |
  -----------------------------------------------

Needless to mention, adequate precaution is to be taken to avoid electric
shock since high voltage is present on all points in the circuit.

I would love to hear your suggestions and comments.

Regards,
Bala

Mumbai, India

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2001\10\02@013456 by Spehro Pefhany

picon face
At 11:31 PM 10/1/01 -0500, you wrote:
>
>Needless to mention, adequate precaution is to be taken to avoid electric
>shock since high voltage is present on all points in the circuit.
>
>I would love to hear your suggestions and comments.

- This is fine, given your cautions  about insulation.

- A WO4 instead of the diode (LED conected to +/- of the bridge)
 will allow the capacitor size to be halved with the same brightness

- If it's on a power bar or other item where there could conceivably
 be no load, you should have a reliable bleeder resistor across the
 capacitor, otherwise the plug prongs could give someone a shock.

- On a 120V circuit, consider just using a series resistor of adequate
 voltage rating and a super-bright LED with 1N4148 parallel. 51K will
 give pretty reasonable brightness and is small/cheap compared to a
 capacitor.

Best regards,

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2001\10\02@061320 by Russell McMahon

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Note that the capacitor should not only have the voltage ratings shown but
also should be an "X rated" part intended for across mains operation. A
lesser rated may survive for an indefinite period. Or may not.

Mains Neutral / Ground (if ground referenced) should be on the non-capacitor
side of the mains input but treat all points as being at mains voltage at
all times.




     Russell McMahon
_____________________________


> Here's a practical and reliable circuit to power an LED from the mains
> voltage. I have been using the 240V version for the past 18 years - YES,
> from Sep 1983 onwards without any problems!
>
> I was using a neon lamp with a series resistor to indicate the status of a
> mains switch. The problem was that every two years or so, the tiny neon
lamp
> had to be replaced. Ever since I started using the LED circuit, it has
been
{Quote hidden}

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2001\10\02@075444 by Olin Lathrop

face picon face
>         0.47uF 250V      120 Ohms       LED
>          Polyester       1/4W            //
>    ---------||----------/\/\/\----------|>|-------
>    |                              |              |
>
>    |                              |              |
> 120V AC                           |-----|<|------|
>    |                                   1N 4001   |
>    |                                             |
>    -----------------------------------------------
>
> Needless to mention, adequate precaution is to be taken to avoid electric
> shock since high voltage is present on all points in the circuit.
>
> I would love to hear your suggestions and comments.

I would move the anode of the 1N4001 to the capacitor side of the resistor
instead of the LED side and make it a 1N4004.  This will result in a bit
higher efficiency.


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2001\10\02@080945 by Allen Mahurin

picon face
But if you move the anode side, without moving the
cathode, the diode is no longer in reverse parallel
with the LED.  For tat matter, it wouldn't be parallel
with the LED at all.  Wouldn't that defeat the purpose
of putting it in the circuit?

ATM

--- Olin Lathrop <RemoveMEolin_piclistEraseMEspamspam_OUTEMBEDINC.COM> wrote:

> I would move the anode of the 1N4001 to the
> capacitor side of the resistor
> instead of the LED side and make it a 1N4004.  This
> will result in a bit
> higher efficiency.

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2001\10\02@105104 by Olin Lathrop

face picon face
> But if you move the anode side, without moving the
> cathode, the diode is no longer in reverse parallel
> with the LED.  For tat matter, it wouldn't be parallel
> with the LED at all.  Wouldn't that defeat the purpose
> of putting it in the circuit?

The diode is still reversed accross the LED with a resistor in between.
With the diode directly accross the LED, the cap charges/discharges both
ways thru the resistor.  With the diode accross the resistor and LED instead
of just the LED, the cap charges without the resistor on the negative slope.
The cap current then goes thru the resistor and LED on the positive slope.
This is a little more efficient because the current only goes thru the
resistor once.


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2001\10\02@121814 by adastra

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Olin,

I think what you meant to say originally was that the CATHODE should be
moved to the other side of the resistor.

Foster

> {Original Message removed}

2001\10\02@134136 by Dwayne Reid

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At 01:39 AM 10/2/01 -0400, Spehro Pefhany wrote:

>- On a 120V circuit, consider just using a series resistor of adequate
>   voltage rating and a super-bright LED with 1N4148 parallel. 51K will
>   give pretty reasonable brightness and is small/cheap compared to a
>   capacitor.

On the other hand, if you toss the parallel 1n4148 and instead add a 1n4005
diode in series, the resistor sees only half the power dissipation.  In
other words, a simple half wave series circuit.

A resistor in parallel with the LED helps tailor the turn on voltage if the
LED turns on too easily.

dwayne



Dwayne Reid   <spamBeGonedwaynerEraseMEspamplanet.eon.net>
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2001\10\02@151131 by Olin Lathrop

face picon face
> I think what you meant to say originally was that the CATHODE should be
> moved to the other side of the resistor.

Oops, yes that's what I meant.  Here is the circuit I was envisioning:


                                    LED
  ----||------*-------\/\/\/--------|>|-------
  |           |                              |
              |                    1N4004    |
120V AC in     ----------------------|<|------*
                                             |
  |                                          |
  --------------------------------------------

This allows the cap to charge on the negative slope with essentially no
loss.  On the positive slope, current is driven thru the LED and the
resistor.  With proper choice of cap you don't need much of a resistor.  The
maximum current is a function of the cap and the dV/dt of the AC input.  The
main purpose of the resistor is to protect the LED in case of line spikes,
which have high dV/dt and could fry the LED.  The diode is presumably more
robust and can handle the abuse much better.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, RemoveMEolin@spam@spamspamBeGoneembedinc.com, http://www.embedinc.com

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2001\10\02@225509 by Josh Koffman

flavicon
face
I hate to tag on to the end of this conversation, but I remember once
seeing a circuit for a wiring tester based on three LEDs. It worked like
one of those 3 neon bulb jobbies that when the outlet is wired
correctly, 2 bulbs light and one stays dim. Anyone have the schematic
for one of these? And I suppose as well, the table that shows what the
various combinations of lights mean?

Thanks,

Josh Koffman

{Quote hidden}

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2001\10\03@061410 by Vasile Surducan

flavicon
face
On Tue, 2 Oct 2001, Olin Lathrop wrote:

> >         0.47uF 250V      120 Ohms       LED
> >          Polyester       1/4W            //
> >    ---------||----------/\/\/\----------|>|-------
> >    |                              |              |
> >
> >    |                              |              |
> > 120V AC                           |-----|<|------|
> >    |                                   1N 4001   |
> >    |                                             |
> >    -----------------------------------------------
> >
> > Needless to mention, adequate precaution is to be taken to avoid electric
> > shock since high voltage is present on all points in the circuit.
> >
> > I would love to hear your suggestions and comments.
>
> I would move the anode of the 1N4001 to the capacitor side of the resistor
> instead of the LED side and make it a 1N4004.  This will result in a bit
> higher efficiency.

 No Olin, the efficiency will be still pour. The led will flicker in the
same way like in the original schematic... but will work enough to light.
Vasile

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2001\10\03@080408 by Roman Black

flavicon
face
Olin Lathrop wrote:
{Quote hidden}

Don't mean to sound picky, but I would
use a 1N4007 (1000v) diode, and really
would keep the resistor before any of the
semiconductors. Yes it is 5% less efficient
but when you get those lightning strikes
and other frequent AC mains disasters it
will probably survive. :o)
-Roman

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2001\10\03@143916 by Harold M Hallikainen

picon face
On Fri, 28 Sep 2001 23:55:43 +0200 Lasse Madsen
<RemoveMELasse.madsenspamspamBeGoneELEKTRONIK.DK> writes:
> > And what happens when the voltage reverses?
>
> You must have a regular diode in anti-parallel with the LED
>
> Best regards
> Lasse Madsen

       Or another LED...

Harold


FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

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2001\10\05@055734 by Roman Black

flavicon
face
M. Adam Davis wrote:
>
> Doh!  Back to the drawing board...  ;-)
>
> -Adam
>
> Bob Ammerman wrote:
>
> >Yeah but if it switches to DC then the LED will go out because we are using
> >a series capacitor in this circuit.


We've been using the high-brightness leds
a lot now, you can get them quite cheaply in
quantity especially the "medium" range like
900mCd, 1200mCd and 1500mCd.

You can get these for 12c US or even less in
quantity, and they are really high-EFFICIENCY
leds. So for 1mA you get a lot of light, and
this is much better than many leds at 20mA.
So in most cases you can scrap the high voltage
ac capacitor, saving more than 12c, then just use
a series resistor, 1mA at 120v is about 120k
and 0.12w. You gain all thr way around.

Now, i'm just waiting for a led manufacturer
to make AC LEDs. :o)
Simple, reverse-parallel high efficiency red
leds in a standard package. One resistor, one
led, twice the light from very little AC mains
current.

Oh well, when some boffin patents it i'll
remember the day when I though of it first.
Maybe i'll just sue them... ;o)
-Roman

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2001\10\05@060758 by Spehro Pefhany

picon face
At 07:54 PM 10/5/01 +1000, you wrote:

>Now, i'm just waiting for a led manufacturer
>to make AC LEDs. :o)
>Simple, reverse-parallel high efficiency red
>leds in a standard package. One resistor, one
>led, twice the light from very little AC mains
>current.

They exist in the form of bipolar (Red/Green)
LEDs. You can actually get most any color you
want, so perhaps they could make Red/Red super-
bright if you would but ask (and order 50K pcs.)

There are also "AC input" optocouplers that have
inverse parallel IR Leds internally. Popular for
some applications, such as AC voltage input to
microcontrollers (even PICs).

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speffspam_OUTspam@spam@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
     /.-.\
    (( * ))
     \\ //     Please help if you can:
      \\\      dailynews.yahoo.com/fc/US/Emergency_Information/
     //\\\
    /// \\\
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2001\10\05@071942 by antoniasse

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face
What is the part number of this AC input optocouplers?

Regards



{Quote hidden}

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2001\10\05@072746 by Spehro Pefhany

picon face
At 08:19 AM 10/5/01 -0300, you wrote:
>What is the part number of this AC input optocouplers?

Try Toshiba TLP626-4 (quad unit in a 16 pin DIP, phototransistor out)
There are many others, and other mfrs. as well. Single, dual, quad,
and with darlington out.

Best regards,
Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spamBeGonespeff@spam@spaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
     /.-.\
    (( * ))
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     //\\\
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2001\10\05@170406 by Bob Ammerman

picon face
> Now, i'm just waiting for a led manufacturer
> to make AC LEDs. :o)
> Simple, reverse-parallel high efficiency red
> leds in a standard package. One resistor, one
> led, twice the light from very little AC mains
> current.
>
> Oh well, when some boffin patents it i'll
> remember the day when I though of it first.
> Maybe i'll just sue them... ;o)
> -Roman

How about a standard package LED with a built in bridge rectifier?

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\10\05@172936 by Spehro Pefhany

picon face
At 10:10 AM 10/5/01 -0400, you wrote:
>
>How about a standard package LED with a built in bridge rectifier?

That would work too, with an extra 1.4V Vf.  Some advantage in some
non-indicator applications because the light output would be the
same at the same current, regardless of polarity.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
RemoveMEspeffEraseMEspamKILLspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
     /.-.\
    (( * ))
     \\ //     Please help if you can:
      \\\      dailynews.yahoo.com/fc/US/Emergency_Information/
     //\\\
    /// \\\
    \/   \/

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2001\10\05@174912 by Bob Ammerman

picon face
I suggest it because then you wouldn't get the visual oddness often produced
by having two emitters in the package (especially in non-diffused LEDs).

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2001\10\07@151819 by hard Prosser

flavicon
face
Just make sure that the resistor has an appropriate voltage rating as well
as the power rating - including likely spike/surge conditions. Series
connection of several resistors may assist.

Richard P




M. Adam Davis wrote:
>
> Doh!  Back to the drawing board...  ;-)
>
> -Adam
>
> Bob Ammerman wrote:
>
> >Yeah but if it switches to DC then the LED will go out because we are
using
> >a series capacitor in this circuit.


We've been using the high-brightness leds
a lot now, you can get them quite cheaply in
quantity especially the "medium" range like
900mCd, 1200mCd and 1500mCd.

You can get these for 12c US or even less in
quantity, and they are really high-EFFICIENCY
leds. So for 1mA you get a lot of light, and
this is much better than many leds at 20mA.
So in most cases you can scrap the high voltage
ac capacitor, saving more than 12c, then just use
a series resistor, 1mA at 120v is about 120k
and 0.12w. You gain all thr way around.

Now, i'm just waiting for a led manufacturer
to make AC LEDs. :o)
Simple, reverse-parallel high efficiency red
leds in a standard package. One resistor, one
led, twice the light from very little AC mains
current.

Oh well, when some boffin patents it i'll
remember the day when I though of it first.
Maybe i'll just sue them... ;o)
-Roman

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