Help- Soldering LED to Wire not working

[byoo]

So I’m doing a project where I have to solder NeoPixel individual leds together using wires. But whenever I try to power it, the conduction or whatever doesn’t go through and the next led doesn’t light up. Here are some pictures. I don’t think it’s my soldering because the connection from my Arduino to the first led worked.

https://imgur.com/gallery/gsBcnXT

And these are materials I used

Make jumper wires (for wires; cut the head off): Breadboard Solderless With Jumper... https://www.amazon.com/dp/B073X7GZ1P?ref=yo_pop_ma_swf

NeoPixels: HKBAYI 4M 5V 60Leds/M 240pixels... https://www.amazon.com/dp/B00K7UHPEC?ref=yo_pop_ma_swf

WYCTIN 60-40 Tin Lead Rosin Core... https://www.amazon.com/dp/B071G1J3W6?ref=yo_pop_ma_swf

Soldering Iron 60W, Electric... https://www.amazon.com/dp/B078THBNB3?ref=yo_pop_ma_swf

Also this may be the problem but the temp of the solder iron is 350 (which other people usually do 400~600) but it worked on attaching the cable to the first led from the programming system (arduino) so I’m not too sure.

I know cold solders are a problem too. How do you know if you have one?

Any help would be greatly appreciated!

[alsetalokin4017]

Hmmm.... a 60 watt non-adjustable iron is kind of overkill for small circuit board pads. Your soldering will improve with practice, but I don't see any "fatal" solder joints in your photo. For future reference the soldering of the Red wire on the Input side of the Middle LED is the best one, so that's what you should go for in further soldering. Cold solder joints are dull in appearance, lumpy and don't make good physical contact. There may be one or two actual cold solder joins in your photo where reflowing might be appropriate, but let's check other stuff first.

How are you supplying power to the neopixel string?  Are you sure that the #2 Neopixel is still good? What Arduino code are you using to drive them? Can you post your code please? Also please show your power supply and your connections to the Arduino.

[KL27x]

I know cold solders are a problem too. How do you know if you have one?

A continuity tester (one of the many functions of a DMM) is one of the most basic sanity checkers you can have. This is why my most used DMM is just a cheap pen meter.

For starters, you could check continuity on your power and ground rails. There might be a defect/break in one of the first two boards? Not too likely, but when debugging things, it is way way wayyyy better to start at the beginning. It might feel redundant and wasteful. And a bit like swimming in molasses. But 9 times out of ten, you will get to the finish line just as quickly, but with less stress and fewer curse words.

Not sure what it's supposed to do, what with the Din/out lines. Knowing that would help in the debugging. That would be high on my radar, though. Maybe a short between the D line and power/ground somewhere between the first and second Data line? That would be much more likely than you broke a power or ground trace. And I reckon that could stop the rest of the dominoes from falling.

That said, never underestimate your own stupidity. You ought to consider the possibility that it is doing exactly what it's supposed to do. If you haven't already, give a good once over on the documentation. Sometimes called RTFM.

Not sure what scale you are on, but 350C would be just about perfect for electrical soldering. 400-600C would be hella hot for most electrical work. And much under 600F would be too low to do much with an iron.

[alsetalokin4017]

NeoPixels aren't normal LEDs you know. They are controlled by precise data signals coming over the Data line. If the Arduino isn't programmed properly... strange things can happen.

I don't have enough information to sort this problem as either hardware, or software. Let's see the code please.