Forum: Analog Circuits Voltage drop consequences in led strips

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Hi

I would like to understand how voltage drop in a power cable affects led
pixels.
Is there a way to figure out when they start fading and when the logic
drops out?

I am using 12v pixel control strips with 144px per meter. I will feed in
extra power every meter, but I would like to keep my power lines as slim
as possible (1mm) so the strip and power lines fit in slim alumninum
extrusions.

LED chip gs8202 datasheet:

Strip manufacturers recommendations: 20w  12v  1.6A per meter,
My total length per strand: 7m plus 3m extension.

A total of 140W @ 12v = 11.2 A

I am using an online calculator and these are my results:

- 10m @ 1,5mm² drops 23,15% to 9.22v
- 10m @ 1,0mm² drops 34,72% to 7,83v

So assuming that this accurate enough, what are the consequences for the
last meters that now have to make do with for example 9.22. Some fading?
Logic malfunction?

Thankful for any knowledge on how this can be derived from the
datasheet, or any experience on the subject

Ciao

fuberator

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Hi!
Let's considere a LED. A single one, fed by an adjustable power supply
(capable of of both constant current or constant voltage). LEDs are
powered by a current (20 mA for the cheapest ones), that's how you can
modify their brightness. But there is a minimum voltage so they can
light up (Vf, forward voltage). Too low voltage, nothing will light up
(NO conduction) and too high (leading to a too high current) will fry
the LED.
So for a known and stable voltage, a series resistor is inserted:
R=(Vsupply-Vf)/I
If Vsupply is 12V on one end and 9V on the other end, you can either:
-change R in series with your LEDs along the entire path (requires
-de-soldering of SMT components). High R close to the power supply,
lower R away from it. Err... not easy.
-use larger wires (Rwire=rho*length/section). Errr... not easy.
-use "dual end feeding". Run a pair of electrician wires, as the ones
used for a lamp(2.5 mm2?), from your power supply to the remote end.
Near end and far end power cables will share load-> reduced current in
each->lower loss->brighter remote LEDs. Easy and cheap !

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