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Tips for Soldering SMD Capacitor Directly onto 5mm Neopixel
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Tips for Soldering SMD Capacitor Directly onto 5mm Neopixel

by scuby on Sun Aug 11, 2019 5:41 pm

I’m putting a string of waterproof lights together based on 5mm through-hole neopixels - wired together with glued heat-shrink around each to keep them reasonably waterproof (to survive out in the rain all year round - not underwater).

Given each pixel (ideally) needs its own 0.1uF capacitor, I’ve tried a couple with a 0603 SMD capacitor soldered directly between the two middle legs. Seems to work well, keeps the size and complexity down.

However, soldering (manually, with iron) is taking me ages - very fiddly and hard to get it lined up. I wondered if anyone else had done it like this, or had any tips on how best to do that type soldering relatively quickly and easily? It’s just for personal project at home so doesn’t need to be massively efficient - just a bit easier than my current approach!

Thanks a lot,

Dave

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Re: Tips for Soldering SMD Capacitor Directly onto 5mm Neopi

by XRAD on Sun Aug 11, 2019 8:09 pm

why not one appropriate capacitor on the main power 'in', and one resistor on the data 'in' ? That would significantly reduce your soldering time and reduce hardware footprint.....

if the 'chain' is long enough, you may have to add another capacitor at a second power feed....

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Re: Tips for Soldering SMD Capacitor Directly onto 5mm Neopi

by chemdoc77 on Sun Aug 11, 2019 8:42 pm

Try using the following from Adafruit to hold parts together when soldering:

Helping Third Hand Magnifier W/Magnifying Glass Tool - MZ101 PRODUCT ID: 291

Also, put a drop of solder on each wire that you are going to solder together before you solder them together. Are you using 60/40 solder? It works the best.

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Re: Tips for Soldering SMD Capacitor Directly onto 5mm Neopi

by scuby on Mon Aug 12, 2019 5:34 am

XRAD wrote:why not one appropriate capacitor on the main power 'in', and one resistor on the data 'in' ? That would significantly reduce your soldering time and reduce hardware footprint.....

if the 'chain' is long enough, you may have to add another capacitor at a second power feed....


Thanks - I guess I could just skip them, but the spec and almost every guide emphasises the importance of the 0.1uF capacitor next to every pixel. They are doing a completely different job to the capacitor and resistor at the start of the chain (which I also have).

For SMD LEDs I’ve switched exclusively to the WS2813, which has the capacitor built-in, but there are fewer options for through-hole LEDs hence trying this approach.

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Re: Tips for Soldering SMD Capacitor Directly onto 5mm Neopi

by scuby on Mon Aug 12, 2019 5:38 am

chemdoc77 wrote:Try using the following from Adafruit to hold parts together when soldering:

Helping Third Hand Magnifier W/Magnifying Glass Tool - MZ101 PRODUCT ID: 291

Also, put a drop of solder on each wire that you are going to solder together before you solder them together. Are you using 60/40 solder? It works the best.


I’ve not got that particular model of helping hands, but for these SMD capacitors I found I couldn’t get any useful grip - just too small!

I’ve just ordered some 0805 sized capacitors to see if they make it any easier, to get a grip - assuming it’s not too big.

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Re: Tips for Soldering SMD Capacitor Directly onto 5mm Neopi

by XRAD on Mon Aug 12, 2019 7:40 pm

from adafruit through hole neopixel guide:

1938-00 (1).jpg
1938-00 (1).jpg (105.52 KiB) Viewed 61 times

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Re: Tips for Soldering SMD Capacitor Directly onto 5mm Neopi

by adafruit_support_bill on Tue Aug 13, 2019 6:10 am

from adafruit through hole neopixel guide:

For small arrays like that, you can sometimes get away with no bypass caps. But all our boards are designed with a cap-per-pixel as recommended.

Each pixel has 3 internal PWM drivers to control the R, G and B LEDs. The switching noise from those PWM drivers can couple back through the power and ground rails and disrupt the control signals.

The large electrolytic cap at the main power feed is both too slow and too far away to filter that noise. Ceramic caps are faster, so they are much better at filtering the higher frequencies. And placing them close to the pixels allows them to suppress the noise at the source - before it can propagate and start to cause problems elsewhere.

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Re: Tips for Soldering SMD Capacitor Directly onto 5mm Neopi

by scuby on Tue Aug 13, 2019 7:29 am

Thanks Bill, yes I just re-read the specs and they’re very clear that those capacitors are very strongly recommended so I’ll stick with them, even if it means a bit more soldering. If I do a bunch of them together I’ll probably speed up!

Do you know if there are any upgraded through-hole neopixels in the pipeline, with a built-in capacitor like the WS2813s?

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Re: Tips for Soldering SMD Capacitor Directly onto 5mm Neopi

by adafruit_support_bill on Tue Aug 13, 2019 8:02 am

I'm not aware of any at this time from our suppliers. But I'm pretty sure we'd stock them if and when they are available.

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