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Topic: Voltage drop problem(trying to power on a WS2812 led strip) (Read 220 times) previous topic - next topic

akiskaps

Hello, I am making a project using ws2812 led strips. I have soldered 90 leds.Measuring the voltage from my power supply is 4.99V but when I am conecting it to the led strip I see a voltage drop to two volts. When I am adding a diode to the +5V of the led strip it gets hot.When I am connecting the strip to the power supply, only the first led flickers once and then is off.Can you please help me troubleshoot the voltage drop? Should it be causing from wires? From bad soldering?

P.S. I dont think a Schematic or code is neccesary. I am absolutelly sure the conections are fine and I am not dealing problems with code. I am just trying to power on the strip.

Thanks for your time.

runaway_pancake

short circuit?
post some quality pictures of your connections
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

akiskaps

short circuit?
post some quality pictures of your connections
Thanks a lot for your fast reply and your interest. I have 3D printed a nanoleaf replica and put 3 leds in each 30 corners which means I have to upload a 30 photos :( .If there is any way to have it checked by myself let me know or should I upload 30 photos.

runaway_pancake

"Hot diode", in this instance, indicates a short circuit or similar mis-wiring.
Like it says in my signature - "When all else fails, check your wiring".
"Eyeball" everything super-critically (solder blobs, stray strands).
 
A) Try disconnecting everything and re-connect each section till the fault returns
or
B) Try disconnecting each section, one at a time, till the problem goes away. (Less preferred.)
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

akiskaps

"Hot diode", in this instance, indicates a short circuit or similar mis-wiring.
Like it says in my signature - "When all else fails, check your wiring".
"Eyeball" everything super-critically (solder blobs, stray strands).
 
A) Try disconnecting everything and re-connect each section till the fault returns
or
B) Try disconnecting each section, one at a time, till the problem goes away. (Less preferred.)

I have checked everything very carefully with a multimeter and none of the conections are shorted(touching each other if that means shorted). Only one wire in the end of the led strip have been disoldered from it's Din pin but i think this is not causing the problem as none of the leds till there are working.Now about the soldering i am not sure what could be wrong. It was really hard to solder all those leds inside the case and the pins are small enough so it's not really good soldered everywhere but having it checked with my multimeter each pin is connected.

runaway_pancake

So with the strip disconnected from the power supply (enitrely) you can use your multimeter's ohmmeter function.
What is the resistance from +V to GND (red probe on +V, black probe on Gnd)?

Maybe you should show a picture or two of some of the corners.

If there is a problem then you have to hunt it out (no matter how big a pain that might be), specifically Method A or Method B (previous).

"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

runaway_pancake

There's the half-split method. Disconnect the downstream half, leaving the half closest to the power supply connected. If the problem goes away, it's in the disconnected half. If not, disconnect at the remaining halfway point and repeat the process.
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

DrAzzy

Why would you conclude that a hot diode is due to a short circuit, not just that the load is excessive for the diode used? a 1A diode will indeed get hot if you try to push 4A through it!

When I use that sort of LED (the 50-led 2811 based strings that look like christmas lights) I inject 5v with a DC-DC converter at the start of every strip (being buck converters, at low load they won't care that one's output setpoint might be a little higher, and at high load, the resistance of the wires in the light string keeps it from being a problem). These are powered by 19v (from a laptop power supply) carried by a pair of wires ziptied along the length of the string. Can run 200 LEDs this way from a 19v 3.5A common laptop supply (though it can't quite handle all LEDs on at 100% brightness - I prevent that in software - they're usually run with overall avg like 50% loading). They've worked extremely reliably - I've used them at half a dozen wild house parties, and sent them with my friends' camp to firefly twice, and have had no hardware failures.
ATTinyCore for x4/x5/x61/x7/x8/x41/1634/828/x313 megaTinyCore for the megaavr ATtinies - Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

runaway_pancake

"Why would you conclude that a hot diode is due to a short circuit, not just that the load is excessive for the diode used?"
Fair point, I suppose, but there was, as I read it, a problem and later a diode was introduced and it got hot, leading me to figure the PS is limiting.
('Hot' meaning what to whom, warm-ish, hot as hell, it's all relative.)
Get rid of the diode, it's not a fuse.
I noted a few ways to go about isolating (troubleshooting) the problem.
So what are your views on the problem/s with the "LED strip"?
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

runaway_pancake

"a 1A diode will indeed get hot if you try to push 4A through it!"

If all he has is a "led strip" connected to a PS, as the OP has stated, then current ought to be minimal (not 1A, let alone 4A). Agree or Disagree?
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

DrAzzy

"a 1A diode will indeed get hot if you try to push 4A through it!"

If all he has is a "led strip" connected to a PS, as the OP has stated, then current ought to be minimal (not 1A, let alone 4A). Agree or Disagree?
My interpretation was that it was a diode in series with the LED strip (which doesn't really make sense, as it would make the voltage drop worse by adding it's own). Some people think you need to do this when injecting power at multiple places - in fact, you generally don't.
ATTinyCore for x4/x5/x61/x7/x8/x41/1634/828/x313 megaTinyCore for the megaavr ATtinies - Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

akiskaps

So with the strip disconnected from the power supply (enitrely) you can use your multimeter's ohmmeter function.
What is the resistance from +V to GND (red probe on +V, black probe on Gnd)?

Maybe you should show a picture or two of some of the corners.

If there is a problem then you have to hunt it out (no matter how big a pain that might be), specifically Method A or Method B (previous).


Ok! having it checked with the multimeter as you said I noticed a problem :) . Indeed as you said there was a short I had connected a single led wrong!Now it works but some leds are still off. Doesn't seem any wrong connection here.from this led strip and on the multimeter reads -0.01 Moh instead of 0.01 which the working leds have.

Thanks a lot for your interest and help. You made my day :)

Here are two pictures of what is going on on the not working part.


runaway_pancake

The 2nd picture looks like there's a blob from the red to the green wire connected to that dark LED. And over on the left (can't tell if it's on or not), the solder looks unacceptable.

These things aren't tolerant of reverse voltage.

Between the Arduino data pin and the first LED in the string, I believe there is supposed to be a resistor (if you haven't done that). Going without can result problems.
https://learn.sparkfun.com/tutorials/ws2812-breakout-hookup-guide/hardware-hookup
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

DrAzzy

Between the Arduino data pin and the first LED in the string, I believe there is supposed to be a resistor (if you haven't done that). Going without can result problems.
As it happens, you can get away with this if the data line is short - you need the resistor if the data line is of non-negligible length.
ATTinyCore for x4/x5/x61/x7/x8/x41/1634/828/x313 megaTinyCore for the megaavr ATtinies - Board Manager:
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

akiskaps

Ok, i got it working. Thanks a lot for your help, but now I have another problem. The data is reading is not right. Most times is flickering, some times the most leds are off and not the correct color. As I read from searching there must be a noise? I have a resistor between arduino's and strip's data pin. Should I open a new post?

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