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driving LED from 115vac — Parallax Forums

driving LED from 115vac

Erik FriesenErik Friesen Posts: 1,071
edited 2009-04-17 20:31 in General Discussion
Any opinions on the best way to do an indicator light powered from 115vac?

options -

series resistor to bipolar led

series resistor to diode to led

small capactior to resistor to bipolar or diode-led

Comments

  • PJAllenPJAllen Banned Posts: 5,065
    edited 2009-04-17 14:15
    http://www.marcspages.co.uk/tech/6103.htm

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  • BeanBean Posts: 8,129
    edited 2009-04-17 15:16
    Erik,
    Just aware that the link PJ gave is using 230V mains not 115V mains. So you'll have to adjust the value accordingly.

    Bean.

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  • Erik FriesenErik Friesen Posts: 1,071
    edited 2009-04-17 15:34
    I am looking for minimal components here. Can that be done with one diode only?
  • LeonLeon Posts: 7,620
    edited 2009-04-17 16:05
    You need something else to reduce the voltage!

    Leon

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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2009-04-17 16:35
    As the article in the link states, you can ditch the bridge rectifier circuit and add a reverse protection diode (or a second, reverse-connected LED) across the LED instead. This protects the LED from high reverse voltages. You still need the series components for current limiting, though. A milliamp-range fuse is necessary, too, in case one of the components fails short.

    -Phil
  • Mike2545Mike2545 Posts: 433
    edited 2009-04-17 16:35
    This will work...It's been drawn for an opto-isolator but will work well for an LED smile.gif

    Or use a neon with resistor.

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    Mike2545

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    Post Edited (Mike2545) : 4/17/2009 4:40:45 PM GMT
    pdf
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    120V AC turn on led.pdf
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  • Erik FriesenErik Friesen Posts: 1,071
    edited 2009-04-17 16:48
    @ leon. I meant using a resistor and or cap first. I don't wish to use a bunch of components as I have 7 - 115v out relays that I want to indicate.
  • Erik FriesenErik Friesen Posts: 1,071
    edited 2009-04-17 16:53
    @ mike - is that millifarads or microfarads?
  • Mike2545Mike2545 Posts: 433
    edited 2009-04-17 17:37
    Eric, its microfarad 160 Vac found here www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMvOcEq4GH1AAjFenWuujJ69ZmewO7woKe4%3d

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    Mike2545

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  • Erik FriesenErik Friesen Posts: 1,071
    edited 2009-04-17 20:31
    Thanks for the ideas. I think a mb4s from fairchild will do the trick.
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