You may have reached the maximum output possible with this LED. =A0It is no=
rmal for an LED's output to level off or dim above a certain current input.=
 =A0You can confirm this by powering it from a variable supply.

----------------------------------------
> Date: Tue, 21 Jan 2014 11:12:04 -0500
> From: cdenk@windstream.net
> To: piclist@MIT.EDU
> Subject: [EE] AC powered LED brightness
>
> From a thread several weeks ago, I am powering numerous LED's from 24
> VAC. The majority brightness is as desired, but one LED is very dim. The
> method is:
>
> 24 VAC> 332 NF capcitor> (LED and 1n4004 parallel anode to cathode)>
> 1.5k resistance> VAC common
>
> The LED of the topic is a Digikey 516-1330-ND.
>
> Parameter HER/Orange
> Peak Forward Current 90 mA
> Average Forward Current[1] 25 mA
> DC Current[2] 30 mA
>
> In a 5 VDC circuit with desired brightness, 191 ohm resistor series, 15
> ma, 1.96 volt across LED. Normally I would use as first choice a 470 ohm
> resistor.
>
> In the AC circuit, across the LED only 1,5 ma. I have tried various
> bigger and smaller resistors and caps with not desired results. I have
> other LED's that I have adjusted the brightness by changing the
> Resistance, but this LED is different.
>
> Any comments appreciated.
>
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