Addressable RGB LEDs without going nuts - Page 1
Forum section: electronics / projects

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 03, 2017, 09:17:24 am
content: I really like NeoPixel (WS2812b et al) and I have a couple of home projects with my kids that use them but the wiring is driving me nuts!So for example I have a panel with 27 Neopixels.... each pixel has +,-, DataIn and Data Out. The Neopixels I bought come on a mini PCB and I have been soldering wires to these one at a time and slowly losing my will to go on... particularly as I would eventually like quite a few of these panels.So... I am obviously doing this WRONG!The LEDs I have don't look PCB friendly... all the contacts are on the bottom and if I tried to reflow these wouldn't all the bits on the top start to float around.Please can someone suggest an alternative? I think I am happy to pay the PCB cost (even though it is quite big) just to save me the time but I would need PCB friendly neopixels.I DO need each pixel to be individually addressable but no other constraints... I'm not necessarily bound to WS2812.e.g Can you buy the components separately.... do you need a C and R at each like the mini-board?(I tend to buy my stuff via Farnell... but I never seem to see WS2812 et al there??)Thanks in advance

author: Ian.M
author_rank: Super Contributor
timestamp: June 03, 2017, 09:56:09 am
content: Each Neopixel needs the 0.1uF decoupling cap but only the first in the chain needs the resistor.You can buy 'bare' Neopixels in either SMD or through hole packages. Seehttps://cdn-learn.adafruit.com/downloads/pdf/adafruit-neopixel-uberguide.pdf

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 03, 2017, 10:48:09 am
content: I checked EBAY and Farnell....It looks like buying the chips on the mini circular boards might be the cheapest even if I need to have the additional hassle of flowing them off (and I do have a track record of distorting/melting LEDs on reflow)Do you think it actually would be feasible to SMD the circular boards... solder paste and heat?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 03, 2017, 11:02:20 am
content: Quote from: NivagSwerdna on June 03, 2017, 10:48:09 amWhy would you do that rather than just using the LEDs on their own?pretty sure there are a few options for pre-wired strings - try Aliexpress

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 03, 2017, 11:05:36 am
content: I am fussy about the geometry so pre-made won't work.I am yet to find a source of cheap vanilla/unsoldered 5050 addressable LEDs.... the mini-board type I have are £5 for 50 on the slow boat.

author: CJay
author_rank: Super Contributor
timestamp: June 03, 2017, 11:06:16 am
content: First ideas off the top of my head:Plated through hole double sided board where the PTH holes are large enough to get the tip of an iron into?The holes align with the pads on the Neopixel board, flux it up and fill the hole with solder while clamping the neopixel to the other side?Better would be a slot but I'm not sure if you can get the edge of a slot plated?Another alternative might be to solder header pins to the neopixel to convert them to a 'DIL' package and use either a PCB or prewired sockets.*edit* attached a pic of one of my prototyping Neopixels, would need the header pins to be perpendicular for your needs but you get the idea...

author: janoc
author_rank: Super Contributor
timestamp: June 03, 2017, 11:09:10 am
content: Quote from: NivagSwerdna on June 03, 2017, 11:05:36 amYou aren't looking in the right places. AliExpress is full of these:https://www.aliexpress.com/item/10-1000pcs-SK6812-4pins-5050-SMD-similar-with-WS2812B-Individually-Addressable-Digital-RGB-Full-Color-LED/32550663121.htmlI have ordered them from the above seller and no problem whatsoever. Actually those LEDs use a slightly different driver that is a local Chinese improved (!) version of WS2812B, but are compatible.You can also get self-adhesive strips, through-hole LEDs with this driver and what not, just search for WS2812b on AliExpress.Do notsearch for "Neopixel" - that is a business name that only Adafruit (and the "maker" community) uses, you won't find much under that name.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 03, 2017, 11:11:26 am
content: Quote from: janoc on June 03, 2017, 11:09:10 amThanks for the SK6812 suggestion. There seem to be much more options there. Sorry our posts crossed.

author: Ian.M
author_rank: Super Contributor
timestamp: June 03, 2017, 11:26:20 am
content: One thing to be cautious about - I believe there have been some reports of high defect rates for the Chinese WS2812B clones. You may have to either do a lot of rework or set up to test individual ones before assembly.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 03, 2017, 11:30:58 am
content: Quote from: Ian.M on June 03, 2017, 11:26:20 amFair point. Since these are for home use only, i.e. not production, that should be OK but a pre-assembly test makes a lot of sense.

author: janoc
author_rank: Super Contributor
timestamp: June 03, 2017, 07:17:21 pm
content: Quote from: Ian.M on June 03, 2017, 11:26:20 amHaven't heard about that. It could have well been simply a dodgy seller selling dodgy parts - e.g. rejects. However, it is possible to find also the original WS2812Bs there.OTOH, if you don't want to risk AliExpress, you can buy from Digikey:https://www.digikey.fr/product-detail/fr/1655/1528-1104-ND/5154679?curr=eur&WT.z_cid=ref_octopart_dkc_buynow&site=usHowever, even Digikey states that:"LED RGB WS2812 OR SK6812" - those are the Adafruit parts and Adafruit is taking them from China.

author: endevor100
author_rank: Contributor
timestamp: June 04, 2017, 01:50:25 am
content: Could you make premade addressable strips work for your panel geometry? They would be the easiest to wire up. There are many options if you search "individually addressable led strip" and the first one off the google pile I liked is this product:https://www.amazon.com/240pixels-programmable-Individually-addressable-Waterproof/dp/B00K7UHPEC

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 04, 2017, 07:08:18 am
content: Quote from: endevor100 on June 04, 2017, 01:50:25 amNo. I have a very custom design using laser cut geometry, every millimeter matters for the aesthetics.I spent the afternoon wiring up my first panel and it looks good. For any quantity I would have to consider a new approach... a single custom PCB would be very expensive (although I could use the other side for the microcontroller etc) since with my current design it is 271.5mm x 63mm... I could perhaps have modules... groups of six or nine. (I find anything greater than 100mm x 100mm gets £££)In any case this version is a prototype so my final dimensions might change.I also foundhttp://pi-plates.com/the-problem-with-neopixels/which has some comments about the sensitivity of the internal parts to agressive soldering.

author: ebclr
author_rank: Super Contributor
timestamp: June 04, 2017, 07:40:06 am
content: This is the wiring you need to doAnd here case you wana use Arduino

author: hamster_nz
author_rank: Super Contributor
timestamp: June 04, 2017, 08:42:18 am
content: I found them to be very sensitive to handling while breadboarding, with the first of the chain blowing. Maybe ESD, maybe dodgy +5V conmection allowing DI to get much higher than Vdd.

author: Ian.M
author_rank: Super Contributor
timestamp: June 04, 2017, 09:31:48 am
content: Quote from: hamster_nz on June 04, 2017, 08:42:18 amAdafruit recommends a series resistor of between 300 and 500 Ohms in the data line, adjacent to the first LED to damp ringing, and provide such a resistor on most of their PCB mounted Neopixel products. They also recommend a very large bulk decoupling cap across +5V and ground, to damp transients.I suspect they suffer from the same problem as many LDO regulators - the supply lead inductance can ring with the ceramic decoupling cap and over-voltage the chip if the power-up rise rate isn't controlled.

author: chris_leyson
author_rank: Super Contributor
timestamp: June 04, 2017, 11:25:33 am
content: QuoteLast time I used a string of WS2812Bs I needed 330 ohm series resistor otherwise they just wouldn't work. I should have had a close look with a scope.

author: Buriedcode
author_rank: Super Contributor
timestamp: June 04, 2017, 12:27:58 pm
content: Like others I'll just ad comments.- There are TH addressable 5mm RGB LED's available. This may or may not be preferable to the SMT type.- I'm sure I have seen large (120x450mm) stripboard prototype boards on ebay. You can solder the 6-pin 5050 or the 4-pin 5050 Addressable LED's directly to these, but will still require soldering an awful lot of jumpers on the back to hook the DOUT to DIN of the next one for either the 4-pin or 6-pin. For long runs you might want to use more than one strip for the power rail and ground, but the layout means its very easy to add decoupling caps distributed along the lines. If you insist on having a custom laysout for the LED's, this is probably the best combination of cheapness and convenience, whilst keeping functionality.- As has been suggested, why not LED strips? They generally have decoupling caps on the strip, and the cheapest have low densities, ~30 LED's per metre which is ~1 5/16" spacing. Looks similar to what you have on those boards. They have self adhesive, easy-to-use connectors, and you can break them up into strips of only 8 LED's, and have 4 of those stuck to your MDF blocks. You would only have to wire connectors between strips (wiring three 4-wire connectors, rather than 4x8 =32). They are also dirt cheap, available everywhere, and have more options (RGBW, low profile - SK6812, waterproof etc..).- 'Neopixel' is the brand for Adafruit Addressable LED's. You mentioned you get 50 for $5 which is a great price. Adafruit are often much more expensive. It seems like getting LED's on individual boards might be cheap, but as you found out is making life *more* difficult in terms of wiring.Conclusion: Seriously, get some WS2812B strips. For ~ $20 you can get a few metres, which means you'll have lots spare should any LED's die - and replacing the strips will be easy if you use the snap-in connectors. It will greatly reduce the wiring time whilst still allowing the pattern you have in that pic, should be more reliable (less fannying about worrying about decoupling) and let you spend more time on other parts of the project. The cons? You're not doing something entire from scratch. but if that was the point of the project, then I'm sure you would be happy to do all that wiring.

author: tooki
author_rank: Super Contributor
timestamp: June 04, 2017, 02:19:01 pm
content: Why not just get the same modules you already have, but pre-wired, like this?https://www.aliexpress.com/item/50-x-SK6812-Pre-soldered-Addressable-Individully-RGBW-led-string-Neutral-white-WWA-pixel-module-light/32749443892.html

author: Flenser
author_rank: Regular Contributor
timestamp: June 04, 2017, 02:39:59 pm
content: They do make clip-on connectors for the flexlble RGB LED strips:http://www.ebay.com.au/itm/Weldless-Clipon-Coupler-Connectors-2pin-4pin-RGB-for-3528-5050-LED-Strip-Lights-/282214429792?var=&hash=item41b54a7460:m:myzXT4lOEk26hhxx9MMyHxghttp://www.ebay.com.au/itm/2pcs-4pin-LED-Strip-connectors-5050-RGB-10mm-PCB-board-wire-No-Soldering-/162535648487?hash=item25d7e12ce7:g:qQsAAOSwH09ZLnJ7http://www.ebay.com.au/itm/5x-10mm-4-pin-Solderless-Clip-on-Coupler-Connector-for-5050-RGB-LED-Strip-Light-/292139734832?hash=item4404e29730:g:ZDEAAOSwr7ZW6KDPhttp://www.ebay.com.au/itm/L-Shape-RGB-Led-Strip-Light-Connector-Ribbon-String-Corner-Female-Adapter-/222533922570?hash=item33d00e2f0a:g:8xIAAOSwPh5ZMvWPhttp://www.ebay.com.au/itm/No-soldering-3528-8mm-5050-10mm-T-L-X-Shape-Adapters-LED-Strip-Connectors-RGB-FT-/131779786020?var=&hash=item1eaeaff524:m:mEC4EsWBkpMC85E4Jhf8qwAand plug-in connectors:http://www.ebay.com.au/itm/L-Shape-RGB-Led-Strip-Light-Connector-Ribbon-String-Corner-Female-Adapter-/222533922570?hash=item33d00e2f0a:g:8xIAAOSwPh5ZMvWP