Connect with us

led's

Discussion in 'Electronic Basics' started by [email protected], Jul 27, 2013.

Scroll to continue with content
  1. 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 onlylight 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 . Thanks, Cort K4WI
     
  2. Just 1 mA? You talking about surface-mount LEDs?

    --
    @[email protected] 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
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  3. LEDs have gotten more efficient, which is how there are now the
    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
     
  4. Do you have the picture and datasheet of that 1mA LED? Could I read them?

    --
    @[email protected] 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
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  5. 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
     
  6. "But does it short out, or open up?"

    Michael
     
  7. To get to 1mA means I would need to buy another resistor. That's money. :)

    --
    @[email protected] 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
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  8. 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)?

    --
    @[email protected] 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
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  9. Are you two talking about 3mm/5mm LEDs or hi-power LEDs here?

    --
    @[email protected] 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
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  10. If it's a military grade LED, then I was NOT supposed to be able to find
    anything about it! :)

    --
    @[email protected] 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
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  11. JW

    JW Guest

    WTF is a 3V resistor?
     
  12. JW

    JW Guest

    For that matter, WTF is a 3V DC input?
     
  13. I repost the questions. Thanks!

    --
    @[email protected] 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
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  14. 1. Would a 3V LED 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)?

    --
    @[email protected] 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
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  15. Ahh, but it's those electrons on the far end of the exponential 'Boltzmann tail' that have enough extra thermal energy to make it into the depletion region. (I'll have to try I-V curves for LED's at low temperatures someday,dunking into LN2 should be pretty easy.)

    George H.
     
  16. Just guessing.... :)

    I googled "1mA LED", not

    --
    @[email protected] 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
    ^ ^ 21:00:02 up 1 day 21:25 0 users load average: 0.08 0.05 0.08
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  17. .... and found this link:

    Avago Technologies
    Red non-diffuse round LED,1mA 1.6V
    http://uk.rs-online.com/web/p/visible-leds/0826521/

    Is it the one you were talking about?

    --
    @[email protected] 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
    ^ ^ 21:00:02 up 1 day 21:25 0 users load average: 0.08 0.05 0.08
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  18. He might be right.... Scroll down for the table in the following link:

    http://www.marutsu.co.jp/user/led.php


    This link is actually quite useful to people using LEDs. Too bad it's
    Japanese...

    --
    @[email protected] 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
    ^ ^ 21:00:02 up 1 day 21:25 0 users load average: 0.08 0.05 0.08
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
  19. Grin.. well lots of electronics looks like a branch of science to me.
    There was some news 'splash' from (maybe) mit of someone getting more lightout of an led than power in.. at some ridiculously low current.

    (The good thing about electrons is there are a whole lot of them, so there are a few with many kT's of kinetic energy.)

    There's also this 'common' physics demo where they look at the led wavlength and forward voltage drop for a bunch of different color leds and plot things up to get a measure of Planck's constant. (A bit of a bogus experimentwhen you look at the details.)
    Ouch.. the only thing more expensive than optics is high vacuum.

    Speaking of modulating diode lasers, Cliff Stoll (who's quite a lovable 'character'.) Was visiting the other day. He does a bunch of educational outreach and uses a modulated diode laser, beam splitter, and cheap corner cube reflector to measure the speed of light. But what he needs is a cheap (fast) photodiode detector. I put him on to Phil's book... but I've been thinking it might be a nice project.

    George H.
     
  20. Have you ever touched a real one? :)

    --
    @[email protected] Remain silent. Nothing from soldiers and magicians is real!
    / v \ Simplicity is Beauty!
    /( _ )\ May the Force and farces be with you!
    ^ ^ (x86_64 Ubuntu 9.10) Linux 2.6.39.3
    ä¸å€Ÿè²¸! ä¸è©é¨™! ä¸æ´äº¤! ä¸æ‰“交! ä¸æ‰“劫! ä¸è‡ªæ®º! è«‹è€ƒæ…®ç¶œæ´ (CSSA):
    http://www.swd.gov.hk/tc/index/site_pubsvc/page_socsecu/sub_addressesa
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Similar Threads
Loading...
Electronics Point Logo
Continue to site
Quote of the day

-