How to make an LED light regardless of polarity?

J

Joe Strout

Guest
Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?

Thanks,
- Joe

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| Joseph J. Strout Check out the Mac Web Directory: |
| joe@strout.net http://www.macwebdir.com |
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"Joe Strout" <joe@strout.net> wrote in message
news:joe-6BBC93.14035910092004@comcast.dca.giganews.com...
Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?
Click to expand...
Just put two leds back to back so they share the same current limiting.

Works!
 
"Joe Strout" <joe@strout.net> wrote in message
news:joe-1A2846.14284710092004@comcast.dca.giganews.com...
In article <Oan0d.18524$AY1.4676@newssvr29.news.prodigy.com>,
"Clarence" <No@No.Com> wrote:

"Joe Strout" <joe@strout.net> wrote in message
news:joe-6BBC93.14035910092004@comcast.dca.giganews.com...
Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?


Just put two leds back to back so they share the same current limiting.

Sorry, I wasn't clear: I need to light *one* LED regardless of polarity.
Two won't do; the spec allows for just one.
Click to expand...
No way I know of. You do know you can get dual Leds in one package don't you?
 
In article <Oan0d.18524$AY1.4676@newssvr29.news.prodigy.com>,
"Clarence" <No@No.Com> wrote:

"Joe Strout" <joe@strout.net> wrote in message
news:joe-6BBC93.14035910092004@comcast.dca.giganews.com...
Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?


Just put two leds back to back so they share the same current limiting.
Click to expand...
Sorry, I wasn't clear: I need to light *one* LED regardless of polarity.
Two won't do; the spec allows for just one.

Thanks,
- Joe

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| joe@strout.net http://www.macwebdir.com |
`------------------------------------------------------------------'
 
"Clarence" <No@No.Com> wrote in message
news:vfn0d.18527$X%1.15679@newssvr29.news.prodigy.com...
"Joe Strout" <joe@strout.net> wrote in message
news:joe-1A2846.14284710092004@comcast.dca.giganews.com...
In article <Oan0d.18524$AY1.4676@newssvr29.news.prodigy.com>,
"Clarence" <No@No.Com> wrote:

"Joe Strout" <joe@strout.net> wrote in message
news:joe-6BBC93.14035910092004@comcast.dca.giganews.com...
Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC
polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?


Just put two leds back to back so they share the same current limiting.

Sorry, I wasn't clear: I need to light *one* LED regardless of polarity.
Two won't do; the spec allows for just one.


No way I know of. You do know you can get dual Leds in one package don't
you?
Click to expand...
You can also get the four diodes (bridge rectifier) in one package.
 
"Clarence" <No@No.Com> wrote in message
news:Oan0d.18524$AY1.4676@newssvr29.news.prodigy.com...
"Joe Strout" <joe@strout.net> wrote in message
news:joe-6BBC93.14035910092004@comcast.dca.giganews.com...
Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?


Just put two leds back to back so they share the same current limiting.

Works!
Click to expand...
I think you mean in parallel (so they share the same current limiting
 
Joe Strout wrote:

Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC
polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?

Thanks,
- Joe

,------------------------------------------------------------------.
Joseph J. Strout Check out the Mac Web Directory: |
joe@strout.net http://www.macwebdir.com |
`------------------------------------------------------------------'
Click to expand...
what is your source voltage?
use a bridge rectifier and connect the LED to
the + and - terminal.
 
On Fri, 10 Sep 2004 14:03:59 -0500, Joe Strout <joe@strout.net> wrote:

Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?
Click to expand...
---
What's it worth to ya?

--
John Fields
 
Joe Strout wrote:
Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?
Click to expand...
You could use a two-colour LED--but then the colours would be different in
different polarities.

Cheers,

Phil Hobbs
 
In article <g6r0d.1121$Z_k.636@news04.bloor.is.net.cable.rogers.com>,
"Ryan Wheeler" <mojo@nospam_netscape.com> wrote:

what is your source voltage?
Click to expand...
9 VDC, though of course I use a current-limiting resistor.

use a bridge rectifier and connect the LED to
the + and - terminal.
Click to expand...
Thanks, that's exactly what I was looking for!

Best,
- Joe

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| joe@strout.net http://www.macwebdir.com |
`------------------------------------------------------------------'
 
On Sat, 11 Sep 2004 18:53:38 -0500, Joe Strout <joe@strout.net> wrote:

In article <g6r0d.1121$Z_k.636@news04.bloor.is.net.cable.rogers.com>,
"Ryan Wheeler" <mojo@nospam_netscape.com> wrote:

what is your source voltage?

9 VDC, though of course I use a current-limiting resistor.

use a bridge rectifier and connect the LED to
the + and - terminal.

Thanks, that's exactly what I was looking for!
Click to expand...
---
Amazing! a bridge rectifier _is_ four diodes, which you said you had
no room for...

--
John Fields
 
John Fields wrote:

Amazing! a bridge rectifier _is_ four diodes, which you said you had
no room for...
Click to expand...
And four diodes are usually smaller than a bridge rectifier. Though I
haven't looked at SMD models that may be out there.


Thomas
 
Joe Strout <joe@strout.net> writes:

In article <Oan0d.18524$AY1.4676@newssvr29.news.prodigy.com>,
"Clarence" <No@No.Com> wrote:

"Joe Strout" <joe@strout.net> wrote in message
news:joe-6BBC93.14035910092004@comcast.dca.giganews.com...
Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC polarity?

I can imagine a way to do it involving four additional diodes, but
that's more than I have room for in this application. Is there some
clever way to do it with only two (or less)?


Just put two leds back to back so they share the same current limiting.

Sorry, I wasn't clear: I need to light *one* LED regardless of polarity.
Two won't do; the spec allows for just one.
Click to expand...
Try to find those two-color LEDs that have two different color
LEDs in one LED package, those two are installed on different
directions. Installing such LED would make the LED to light
on different colors on different polarity power, and third
(combination of those first two) when AC is feed to it.
This could be one option to consider if you specification
allows it.

--
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at
http://www.epanorama.net/
 
In article <mao9k0h5e3p8daul0il90f7ne33ktpp1kd@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:

On Sat, 11 Sep 2004 18:53:38 -0500, Joe Strout <joe@strout.net> wrote:

In article <g6r0d.1121$Z_k.636@news04.bloor.is.net.cable.rogers.com>,
"Ryan Wheeler" <mojo@nospam_netscape.com> wrote:

what is your source voltage?

9 VDC, though of course I use a current-limiting resistor.

use a bridge rectifier and connect the LED to
the + and - terminal.

Thanks, that's exactly what I was looking for!

---
Amazing! a bridge rectifier _is_ four diodes, which you said you had
no room for...
Click to expand...
But it's one component instead of four. Is it so amazing that I have
room for one more component (possibly even two), but not four? Or have
I missed something?

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| joe@strout.net http://www.macwebdir.com |
`------------------------------------------------------------------'
 
Joe Strout wrote:

But it's one component instead of four. Is it so amazing that I have
room for one more component (possibly even two), but not four? Or have
I missed something?
Click to expand...
An 1n914/1n4148 with leads is very small and 4 of them mounted behind
the LED will make it a bit longer but not wider.


Thomas
 
On Mon, 13 Sep 2004 14:47:44 -0500, Joe Strout <joe@strout.net> wrote:


But it's one component instead of four. Is it so amazing that I have
room for one more component (possibly even two), but not four? Or have
I missed something?
Click to expand...
---
I think you've missed something.

You said, in essence, that you didn't have room for four motorcyles,
but that a Honda Civic would be fit in the same volume.

That is, not that there aren't any, but I haven't seen any full-wave
bridges in packages smaller that four tiny diodes, and they're both
four diodes. There is another possibility, though, and that's that
there are lots of tiny dual diodes out there, so you could make up
your bridge that way if you could fit two of them in there and the
full-wave bridge wouldn't.

--
John Fields
 
"Joe Strout" <joe@strout.net> schreef in bericht
news:joe-3411EA.14474313092004@comcast.dca.giganews.com...
In article <mao9k0h5e3p8daul0il90f7ne33ktpp1kd@4ax.com>,
John Fields <jfields@austininstruments.com> wrote:

On Sat, 11 Sep 2004 18:53:38 -0500, Joe Strout <joe@strout.net> wrote:

In article <g6r0d.1121$Z_k.636@news04.bloor.is.net.cable.rogers.com>,
"Ryan Wheeler" <mojo@nospam_netscape.com> wrote:

what is your source voltage?

9 VDC, though of course I use a current-limiting resistor.

use a bridge rectifier and connect the LED to
the + and - terminal.

Thanks, that's exactly what I was looking for!

---
Amazing! a bridge rectifier _is_ four diodes, which you said you had
no room for...

But it's one component instead of four. Is it so amazing that I have
room for one more component (possibly even two), but not four? Or have
I missed something?

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| joe@strout.net http://www.macwebdir.com |
`------------------------------------------------------------------'
Click to expand...
Have a look at the size of the components mentioned. A diode bridge
requires (much) more space then four small diodes (1N4148 for instance.)

petrus bitbyter


---
Outgoing mail is certified Virus Free.
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"Michael A. Covington" <look@ai.uga.edu.for.address> wrote in
news:414224c3@mustang.speedfactory.net:

"Clarence" <No@No.Com> wrote in message
news:vfn0d.18527$X%1.15679@newssvr29.news.prodigy.com...

"Joe Strout" <joe@strout.net> wrote in message
news:joe-1A2846.14284710092004@comcast.dca.giganews.com...
In article <Oan0d.18524$AY1.4676@newssvr29.news.prodigy.com>,
"Clarence" <No@No.Com> wrote:

"Joe Strout" <joe@strout.net> wrote in message
news:joe-6BBC93.14035910092004@comcast.dca.giganews.com...
Please excuse the newbie question:

How can I make an ordinary LED light up regardless of the VDC
polarity?

I can imagine a way to do it involving four additional diodes,
but that's more than I have room for in this application. Is
there some clever way to do it with only two (or less)?


Just put two leds back to back so they share the same current
limiting.

Sorry, I wasn't clear: I need to light *one* LED regardless of
polarity. Two won't do; the spec allows for just one.


No way I know of. You do know you can get dual Leds in one package
don't you?


You can also get the four diodes (bridge rectifier) in one package.
Click to expand...

yup!!! an example is old radio shack part number 276-065 commercial
equivalent is 369HHd. A single jumbo LED with common cathodes and two
separate anode leads.



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"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote:


Have a look at the size of the components mentioned. A diode bridge
requires (much) more space then four small diodes (1N4148 for instance.)
Click to expand...
The Siemens BAV99S has 4 doides which can be bridge connected in a 6 pin
SOT-363 package which is about 2mm square.
 
Thank you all for your input. I've already got some bridge rectifiers
on order from Mouser, but if none of them fit the task, I'll try four
separate diodes (or two dual diodes) instead.

Thanks,
- Joe

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| joe@strout.net http://www.macwebdir.com |
`------------------------------------------------------------------'
 
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