how to dim an LED

jimbo1968 · 21st July 2011, 10:57 PM

sorry for off-topic, but I know someone here will know the answer.

I just bought a cambridge audio P500 amplifier, the single green LED is way too bright.

What size resistor should I put in series to dim it?
'Really dim' is what I'm aiming for.

If you need to know the voltage I will measure it.

thanks

Andrew Eckhardt · 11:03 PM

Nobody knows what really dim is going to take, but you'd be off to a decent start by finding the value of whatever dropping resistor is currently in series with it and replacing it with 4 or 5 times the resistance.

If you need it dimmer add more resistance.

jimbo1968 · 21st July 2011, 11:11 PM

Thanks,

I haven't opened it yet, but from this picture it looks like an easy job. even for a mechanical engineer.

Someone will probably tell me the resistor value before I can measure it

danFrank · 21st July 2011, 11:15 PM

Brown, Black, red? 1K ohms. Just put a small 5K or 10K trimmer in series with the resistor, adjust till you get the desired brightness and then forget about it.
Daniel

jimbo1968 · 21st July 2011, 11:19 PM

Good idea. I can probably find one of those.

21st July 2011, 10:57 PM	#1
jimbo1968 diyAudio Member Join Date: Nov 2004 Location: UK, bristol	how to dim an LED sorry for off-topic, but I know someone here will know the answer. I just bought a cambridge audio P500 amplifier, the single green LED is way too bright. What size resistor should I put in series to dim it? 'Really dim' is what I'm aiming for. If you need to know the voltage I will measure it. thanks

21st July 2011, 10:59 PM	#2
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	Nobody knows what really dim is going to take, but you'd be off to a decent start by finding the value of whatever dropping resistor is currently in series with it and replacing it with 4 or 5 times the resistance. If you need it dimmer add more resistance. Last edited by Andrew Eckhardt; 21st July 2011 at 11:03 PM.

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21st July 2011, 11:15 PM	#4
danFrank diyAudio Member Join Date: May 2005 Location: California	Brown, Black, red? 1K ohms. Just put a small 5K or 10K trimmer in series with the resistor, adjust till you get the desired brightness and then forget about it. Daniel

21st July 2011, 11:19 PM	#5
jimbo1968 diyAudio Member Join Date: Nov 2004 Location: UK, bristol	Good idea. I can probably find one of those.