led's

Guest
I need help with a way to light up my SWR meter with internal led which would be really close to RF passing thru the SWR meter. That way it would only light up the meter when I transmit. if anyone could point me to a circuit that would do this, probably need two leds one on each side of the meter, would be really grateful. I know there are ways using 12V but I want to stay away from batteries or having to plug/unplug cables. My email is k4wi@earthlink.net. Thanks, Cort K4WI
 
On Sat, 27 Jul 2013 12:54:07 -0700 (PDT), my2004vette@gmail.com wrote:

I need help with a way to light up my SWR meter with internal led which would be really close to RF passing thru the SWR meter. That way it would only light up the meter when I transmit. if anyone could point me to a circuit that would do this, probably need two leds one on each side of the meter, would be really grateful. I know there are ways using 12V but I want to stay away from batteries or having to plug/unplug cables. My email is k4wi@earthlink.net. Thanks, Cort K4WI
Click to expand...
---
Do you have the drawings for your SWR meter?

--
JF
 
On Sat, 27 Jul 2013 12:54:07 -0700 (PDT), my2004vette@gmail.com wrote:

I need help with a way to light up my SWR meter with internal led which would be really close to RF passing thru the SWR meter. That way it would only light up the meter when I transmit. if anyone could point me to a circuit that would do this, probably need two leds one on each side of the meter, would be really grateful. I know there are ways using 12V but I want to stay away from batteries or having to plug/unplug cables. My email is k4wi@earthlink.net. Thanks, Cort K4WI
Click to expand...

You could pick off the RF with a small capacitor or a gimmick.

Then go to an RF choke to ground. From the junction, a schottky diode (1N5711
maybe) drives the LED anode, with the led cathode grounded. Tweak the cap or the
gimmick to tune the brightness.

Most LEDs have a lot of capacitance, so may not work directly from the RF.

A lot depends on your frequency and RF power level.

A good LED is bright at 1 mA, especially green ones.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
 
On 28/07/2013 10:02 AM, John Larkin wrote:
A good LED is bright at 1 mA, especially green ones.
Click to expand...
Just 1 mA? You talking about surface-mount LEDs?

--
@~@ Remain silent. Nothing from soldiers and magicians is real!
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (Fedora 19 i686) Linux 3.10.3-300.fc19.i686
^ ^ 17:27:02 up 22:53 1 user load average: 0.02 0.05 0.08
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On Sun, 28 Jul 2013, Mr. Man-wai Chang wrote:

On 28/07/2013 10:02 AM, John Larkin wrote:
A good LED is bright at 1 mA, especially green ones.

Just 1 mA? You talking about surface-mount LEDs?

LEDs have gotten more efficient, which is how there are now the
Click to expand...
superbright.

Forty years ago, you'd put 15mA into an LED and get a bit of light, good
for display but not for lighting anything up.

Now you can put that current through some "average" LED and get a lot more
light.

He also factored in the sensitivity of the eye, apparently more sensitive
in the green spectrum so you can see it better than another color, thus
lower output is needed to be a bare minimum.

You drop the current through an LED that has great output at 15mA, and you
get a decent indicator at much lower current.

MIchael
 
On Sun, 28 Jul 2013 17:42:22 +0800, "Mr. Man-wai Chang"
<toylet.toylet@gmail.com> wrote:

On 28/07/2013 10:02 AM, John Larkin wrote:
A good LED is bright at 1 mA, especially green ones.

Just 1 mA? You talking about surface-mount LEDs?
Click to expand...
They all have a chip inside.

I have some Avago high-efficiency green LEDs, in T1-3/4 packages. Greens are not
just efficient, they coincide with the eye's sensitivity curve.

These are bright a 1 mA and visible in room light at 1 uA. I tried to determine
the minimum current that would produce discernable light up close, in total
darkness, dark-adapted. It was about 800 picoamps.



--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
 
On 29/07/2013 6:41 AM, John Larkin wrote:
Just 1 mA? You talking about surface-mount LEDs?

I have some Avago high-efficiency green LEDs, in T1-3/4 packages. Greens are not
just efficient, they coincide with the eye's sensitivity curve.
These are bright a 1 mA and visible in room light at 1 uA. I tried to determine
the minimum current that would produce discernable light up close, in total
darkness, dark-adapted. It was about 800 picoamps.
Click to expand...
Do you have the picture and datasheet of that 1mA LED? Could I read them?

--
@~@ Remain silent. Nothing from soldiers and magicians is real!
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (Fedora 19 i686) Linux 3.10.3-300.fc19.i686
^ ^ 01:15:02 up 3:47 0 users load average: 0.00 0.01 0.05
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
 
On Tue, 30 Jul 2013 03:28:23 +1000, Mr. Man-wai Chang
<toylet.toylet@gmail.com> wrote:

On 29/07/2013 6:41 AM, John Larkin wrote:
Just 1 mA? You talking about surface-mount LEDs?

I have some Avago high-efficiency green LEDs, in T1-3/4 packages.
Greens are not
just efficient, they coincide with the eye's sensitivity curve.
These are bright a 1 mA and visible in room light at 1 uA. I tried to
determine
the minimum current that would produce discernable light up close, in
total
darkness, dark-adapted. It was about 800 picoamps.

Do you have the picture and datasheet of that 1mA LED? Could I read them?
Click to expand...
Just get a high efficiency LED and run about 1mA and see! - everyone else
are not going to do all your work for you
 
On Tue, 30 Jul 2013 01:28:23 +0800, "Mr. Man-wai Chang"
<toylet.toylet@gmail.com> wrote:

On 29/07/2013 6:41 AM, John Larkin wrote:
Just 1 mA? You talking about surface-mount LEDs?

I have some Avago high-efficiency green LEDs, in T1-3/4 packages. Greens are not
just efficient, they coincide with the eye's sensitivity curve.
These are bright a 1 mA and visible in room light at 1 uA. I tried to determine
the minimum current that would produce discernable light up close, in total
darkness, dark-adapted. It was about 800 picoamps.

Do you have the picture and datasheet of that 1mA LED? Could I read them?
Click to expand...
They were a gift from James Arthur, and I don't know the part number.
Just browse the Avago web site, or Digikey, for high-output green
LEDs.

I was surprsded by the sub-nA light output. At roughly 100 mV/decade
current, I'd have guessed that the voltage drop would be so low that
it wouldn't have enough energy to make photons.

It would be fun to use a PMT and some signal averaging to see how
little current would still make some light.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
 
On Tue, 30 Jul 2013, David Eather wrote:

On Tue, 30 Jul 2013 03:28:23 +1000, Mr. Man-wai Chang
toylet.toylet@gmail.com> wrote:

On 29/07/2013 6:41 AM, John Larkin wrote:
Just 1 mA? You talking about surface-mount LEDs?

I have some Avago high-efficiency green LEDs, in T1-3/4 packages. Greens
are not
just efficient, they coincide with the eye's sensitivity curve.
These are bright a 1 mA and visible in room light at 1 uA. I tried to
determine
the minimum current that would produce discernable light up close, in
total
darkness, dark-adapted. It was about 800 picoamps.

Do you have the picture and datasheet of that 1mA LED? Could I read them?


Just get a high efficiency LED and run about 1mA and see! - everyone else are
not going to do all your work for you
Click to expand...
I think he's still trying to wrap his mind around the idea that putting
more current through an LED won't automatically increase the light output.


If only, all those Poly-Pak type LEDs forty years ago, that were dim with
15mA going through them, would have been fine.

Michael
 
On Mon, 29 Jul 2013 18:30:07 -0400, Michael Black <et472@ncf.ca>
wrote:

On Tue, 30 Jul 2013, David Eather wrote:

On Tue, 30 Jul 2013 03:28:23 +1000, Mr. Man-wai Chang
toylet.toylet@gmail.com> wrote:

On 29/07/2013 6:41 AM, John Larkin wrote:
Just 1 mA? You talking about surface-mount LEDs?

I have some Avago high-efficiency green LEDs, in T1-3/4 packages. Greens
are not
just efficient, they coincide with the eye's sensitivity curve.
These are bright a 1 mA and visible in room light at 1 uA. I tried to
determine
the minimum current that would produce discernable light up close, in
total
darkness, dark-adapted. It was about 800 picoamps.

Do you have the picture and datasheet of that 1mA LED? Could I read them?


Just get a high efficiency LED and run about 1mA and see! - everyone else are
not going to do all your work for you

I think he's still trying to wrap his mind around the idea that putting
more current through an LED won't automatically increase the light output.
Click to expand...
It does, up until the LED dies.


--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
 
On Mon, 29 Jul 2013, John Larkin wrote:

On Mon, 29 Jul 2013 18:30:07 -0400, Michael Black <et472@ncf.ca
wrote:

On Tue, 30 Jul 2013, David Eather wrote:

On Tue, 30 Jul 2013 03:28:23 +1000, Mr. Man-wai Chang
toylet.toylet@gmail.com> wrote:

On 29/07/2013 6:41 AM, John Larkin wrote:
Just 1 mA? You talking about surface-mount LEDs?

I have some Avago high-efficiency green LEDs, in T1-3/4 packages. Greens
are not
just efficient, they coincide with the eye's sensitivity curve.
These are bright a 1 mA and visible in room light at 1 uA. I tried to
determine
the minimum current that would produce discernable light up close, in
total
darkness, dark-adapted. It was about 800 picoamps.

Do you have the picture and datasheet of that 1mA LED? Could I read them?


Just get a high efficiency LED and run about 1mA and see! - everyone else are
not going to do all your work for you

I think he's still trying to wrap his mind around the idea that putting
more current through an LED won't automatically increase the light output.

It does, up until the LED dies.

"But does it short out, or open up?"
Click to expand...

Michael
 
On 30/07/2013 5:03 AM, David Eather wrote:
Just get a high efficiency LED and run about 1mA and see! - everyone
else are not going to do all your work for you
Click to expand...
To get to 1mA means I would need to buy another resistor. That's money. :)

--
@~@ Remain silent. Nothing from soldiers and magicians is real!
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (Fedora 19 i686) Linux 3.10.3-300.fc19.i686
^ ^ 16:48:02 up 19:20 0 users load average: 0.00 0.01 0.05
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
 
On 30/07/2013 8:43 AM, Michael Black wrote:
It does, up until the LED dies.
"But does it short out, or open up?"
Click to expand...
1. Would a 3V resistor short itself when connected to a 3V DC input?

2. If answer to (1) was "no", then why do I need a current-limiting
resistor connecting 2 3V LEDs in series to a 5V DC input？

3. If answer to (1) was "yes", then what current-limiting resistor
should I use in (1)?

--
@~@ Remain silent. Nothing from soldiers and magicians is real!
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (Fedora 19 i686) Linux 3.10.3-300.fc19.i686
^ ^ 16:48:02 up 19:20 0 users load average: 0.00 0.01 0.05
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
 
On 30/07/2013 7:13 AM, John Larkin wrote:
I think he's still trying to wrap his mind around the idea that putting
more current through an LED won't automatically increase the light output.

It does, up until the LED dies.
Click to expand...
Are you two talking about 3mm/5mm LEDs or hi-power LEDs here?

--
@~@ Remain silent. Nothing from soldiers and magicians is real!
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (Fedora 19 i686) Linux 3.10.3-300.fc19.i686
^ ^ 16:48:02 up 19:20 0 users load average: 0.00 0.01 0.05
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
 
On 30/07/2013 5:25 AM, John Larkin wrote:
They were a gift from James Arthur, and I don't know the part number.
Just browse the Avago web site, or Digikey, for high-output green
LEDs.

I was surprsded by the sub-nA light output. At roughly 100 mV/decade
current, I'd have guessed that the voltage drop would be so low that
it wouldn't have enough energy to make photons.

It would be fun to use a PMT and some signal averaging to see how
little current would still make some light.
Click to expand...
If it's a military grade LED, then I was NOT supposed to be able to find
anything about it! :)

--
@~@ Remain silent. Nothing from soldiers and magicians is real!
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (Fedora 19 i686) Linux 3.10.3-300.fc19.i686
^ ^ 16:48:02 up 19:20 0 users load average: 0.00 0.01 0.05
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
 
On Tue, 30 Jul 2013 19:03:54 +0800, "Mr. Man-wai Chang"
<toylet.toylet@gmail.com> wrote:

On 30/07/2013 5:03 AM, David Eather wrote:
Just get a high efficiency LED and run about 1mA and see! - everyone
else are not going to do all your work for you

To get to 1mA means I would need to buy another resistor. That's money. :)
Click to expand...
---
So is time, but you don't seem to have a problem wasting everybody
else's.

--
JF
 
On Tue, 30 Jul 2013 19:07:39 +0800 "Mr. Man-wai Chang"
<toylet.toylet@gmail.com> wrote in Message id:
<kt86do$kjq$1@dont-email.me>:

1. Would a 3V resistor short itself when connected to a 3V DC input?
Click to expand...
WTF is a 3V resistor?
 
On Tue, 30 Jul 2013 07:45:56 -0400 JW <none@dev.null> wrote in Message id:
<tq9fv8ti2s1nfu9776u4bkaj5vupnqn7ic@4ax.com>:

On Tue, 30 Jul 2013 19:07:39 +0800 "Mr. Man-wai Chang"
toylet.toylet@gmail.com> wrote in Message id:
kt86do$kjq$1@dont-email.me>:

1. Would a 3V resistor short itself when connected to a 3V DC input?

WTF is a 3V resistor?
Click to expand...
For that matter, WTF is a 3V DC input?
 
On 30/07/2013 8:16 PM, JW wrote:
1. Would a 3V resistor short itself when connected to a 3V DC input?

WTF is a 3V resistor?
Click to expand...
I repost the questions. Thanks!

--
@~@ Remain silent. Nothing from soldiers and magicians is real!
/ v \ Simplicity is Beauty! May the Force and farces be with you!
/( _ )\ (Fedora 19 i686) Linux 3.10.3-300.fc19.i686
^ ^ 20:57:02 up 21:22 0 users load average: 0.00 0.01 0.05
不借貸! 不詐騙! 不援交! 不打交! 不打劫! 不自殺! 請考慮綜援 (CSSA):
http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
 
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