Electronics > Beginners
LED strip lighting even without a positive terminal connection
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Adhith:

--- Quote from: exe on July 22, 2018, 03:08:28 pm ---
--- Quote from: Adhith on July 22, 2018, 02:52:23 pm ---I haven't seen this type of disturbance before but now I did. any how its only noticeable at dark and so probably I would have missed before

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Are you sure it's not leakage to ground? That's totally different from AC coupling through the body.

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Thank you for your kind reply.well the leds are driven by a seperate led driver. small lighting up problem is only seen when my hand goes near it and also when the VU meter starts operating all the led strips are lighted up in a very low brightness just like the picture that i have attached before. This problem is solved through the 10k resistor to the ground at each of the 10 output pins form VU meter. But I'm a bit confused of this weird behavior.
Adhith:

--- Quote from: Gyro on July 22, 2018, 03:14:47 pm ---
--- Quote from: Adhith on July 22, 2018, 02:52:23 pm ---I haven't seen this type of disturbance before but now I did. any how its only noticeable at dark and so probably I would have missed before

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Some modern LEDs can be seen glowing at insanely low currents in a dark environment...

https://www.eevblog.com/forum/projects/led-visibility-optimization-at-very-low-currents/

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Thank you for your kind reply. In my case the led light up seems more over like a single dot of light.
Zero999:

--- Quote from: exe on July 22, 2018, 01:14:22 pm ---
--- Quote from: Psi on July 20, 2018, 12:10:18 pm ---yep, pretty normal, you are acting as an antenna and coupling in some 50/60hz AC mains.  Doesnt take much to light up an led

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I don't think so. Never seen an LED lit this way. A good 50Hz must be huge.

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I have seen this before. If I take a single high efficiency green LED, connect one to an earthed object, such as a tap or radiator and hold the other in my hand, I the LED lights dimly.


--- Quote from: Adhith on July 21, 2018, 11:47:02 am ---Thank you again for your suggestion. To be specific the leds are powered by a separate led driver through the 10 transistors seen in the circuit which i have attached previously.
1) Since its a RGB led strip with common anode, by "Putting a resistor in parallel with the LED strip"  and "Put a capacitor in parallel with the LED strip" did you mean connecting the positive terminal of the strip to any one of the R or G or B terminal or to the power ground??
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You effectively have three LED strips, so of course you need a separate resistor for the red, green and blue elements.


--- Quote ---2) since the DC adapter is having only 2 pins there is no earth pin from it to make it earthed

3)one thing which i couldn't figure out was that, why is the strip so sensitive to the things near it. the strip is even lighting up when I just approach my hand around it and not even touching it. would there be any interaction to worry about between the terminals  +, R, G, B on the LED strips since they are very close to each other and to be on the safe side should I just insulate these pins with some hot glue??

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As long as you use a resistor per red, green and blue set of LEDs, then it shouldn't cause any problems.
Adhith:
Thank you Hero999 for your valuable reply. So you were saying that since its an R,G,B led strip i want to use 3 such resistors one for each colour. But when I shorted the +ve terminal of a strip to the ground through a 10K resistor the problem was solved. Does this also work?? or its a wrong thing to do??
Zero999:

--- Quote from: Adhith on July 25, 2018, 08:17:06 am ---Thank you Hero999 for your valuable reply. So you were saying that since its an R,G,B led strip i want to use 3 such resistors one for each colour. But when I shorted the +ve terminal of a strip to the ground through a 10K resistor the problem was solved. Does this also work?? or its a wrong thing to do??

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Thinking about this again. I was wrong about needing a separate resistor for each colour. A single resistor on the +V rail is all that's needed and as it works, keep it as it is.
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