simple LED fade on / off

M

mofotron

New Member

• May 4, 2003

• #1

:shock:

Allo,

I'm pretty new to the world of circuitry, so please forgive me if this question has a rediculously simple answer:

is there and easy way to make an led fade on and then stay at a constant brightness until the circuit is broken? (it would also be nice if there were a way to make the light fade out when the circuit is broken)

If so, what parts should i use and can any of them control how long the fade lasts?

THanK you FOr youR tImE, i really appreciate any help i can get


- chip

 

Sebi

Active Member

• May 4, 2003

• #2

Try this...

 

Attachments

• LED_127.gif

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daviddoria

New Member

• May 5, 2003

• #3

is that just a standard capacitor?

if i'm not mistaken, is this called a choke circuit?

 

M

mofotron

New Member

• May 5, 2003

• #4

thanx much! i'll give it a shot as soon as i get the parts

 

bogdanfirst

New Member

• May 5, 2003

• #5

hey Sebi, are you sure you have written correct? i think that is saw 10,000uF there......why couldn you use a transistor instead and a smaller value capacitor?

 

daviddoria

New Member

• May 5, 2003

• #6

why do you even need a transistor? can't you just use like a 10uF cap? and again, is this called a choke circuit?

 

P

Phoenix

New Member

• May 5, 2003

• #7

Would it not be better to put the capacitor across both the LED and the resistor? Reason being that once power is removed, you will get a large surge current through the LED if the resistor isn't there to limit the current drain, which could destroy the LED...

 

Sebi

Active Member

• May 5, 2003

• #8

Phoenix, here cant flow higher discharge current as normal,because the LED -as zener - limiting the cap.voltage. If the capacitor prallel with supply,no fade-on effect...

 

J

john1

Active Member

• May 5, 2003

• #9

cap has to be pretty large in that arrangement,
because the voltage drop to extinguish the led
is only a little below the lit voltage.

how about if the cap was at a slightly higher
voltage, but not supply voltage, which could
be considered to be grounded or near, after
switch-off.

This might allow a smaller cap to be used.

 

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• Led_Fader.jpg

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