LED lights...Surprised

gmphadte · 2nd March 2007, 04:46 AM

I was experimenting the LED-LDR for an indigenous attenuator. At one point, I connected one of the psu lead to the blue LED, with the power switch off. The other lead of the LED was in my hand. I saw the blueish reflection on the clear LED dome. I thought it was some ambient light reflection. On investigating, I found that the LED was lighting, very dim, off course.
Next I thought, I am connected to ground through the feet and is the reason for the LED's glow. I lifted my feet from the floor while sitting on a wooden chair with plastic bases on the leg ends, and the LED still glows, a little dimmer.

Then I went measuring with DMM(Fluke77)
The voltage across the LED is about 7 Vdc with line cord in one direction and about 17Vdc with the cord the other way round.

The PSU is linear with 317.
The RED LED also glows.

Can all this be used constructively...

Gajanan

cpemma · 5th March 2007, 11:09 PM

You can easily (and safely) test LEDs with just a 9V PP3 battery to (a) check they work, (b) sort out which lead is which.

Grip one lead, touch the other to a battery terminal, touch the other battery terminal with a finger. Swap terminals if nothing happens. You may need to lick your fingers first.

LEDs will glow on a few micro-amps.

gmphadte · 6th March 2007, 02:53 AM

The LED was even going dim-full. This indicated that the mains voltage was fluctuating.

Gajanan Phadte

cpemma · 6th March 2007, 02:23 PM

Quote:

Originally posted by gmphadte
The LED was even going dim-full. This indicated that the mains voltage was fluctuating.

More likely your grip was fluctuating.

gmphadte · 7th March 2007, 02:57 AM

cpemma wrote

Quote:

More likely your grip was fluctuating.

No, it was going on cyclically.

Gajanan Phadte

2nd March 2007, 04:46 AM	#1
gmphadte diyAudio Member Join Date: Jul 2003 Location: Dona paula, Goa	LED lights...Surprised I was experimenting the LED-LDR for an indigenous attenuator. At one point, I connected one of the psu lead to the blue LED, with the power switch off. The other lead of the LED was in my hand. I saw the blueish reflection on the clear LED dome. I thought it was some ambient light reflection. On investigating, I found that the LED was lighting, very dim, off course. Next I thought, I am connected to ground through the feet and is the reason for the LED's glow. I lifted my feet from the floor while sitting on a wooden chair with plastic bases on the leg ends, and the LED still glows, a little dimmer. Then I went measuring with DMM(Fluke77) The voltage across the LED is about 7 Vdc with line cord in one direction and about 17Vdc with the cord the other way round. The PSU is linear with 317. The RED LED also glows. Can all this be used constructively... Gajanan

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5th March 2007, 11:09 PM	#2
cpemma diyAudio Member Join Date: Jul 2003 Location: S Yorkshire OK	You can easily (and safely) test LEDs with just a 9V PP3 battery to (a) check they work, (b) sort out which lead is which. Grip one lead, touch the other to a battery terminal, touch the other battery terminal with a finger. Swap terminals if nothing happens. You may need to lick your fingers first. LEDs will glow on a few micro-amps.

6th March 2007, 02:53 AM	#3
gmphadte diyAudio Member Join Date: Jul 2003 Location: Dona paula, Goa	The LED was even going dim-full. This indicated that the mains voltage was fluctuating. Gajanan Phadte

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