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Topic: Wiring advice for 10A adafruit project with WS2812B (Read 280 times) previous topic - next topic

athompson395

Hello board,

Could you help me with some advice on what components I need to do this safely?

I want to use WS2812B LED strips with an external power source. I will need them all on simultaneously for one part of the project (on the 24th Dec, it's an advent calendar dolls house). At 2/3 brightness (40mA per LED) I estimate 10V for ~250 LEDs.

Sketch below of what I think I need to do. Questions:

1)  Does this look right or do I need to use a transistor as well?
2) How can I physically put together the 5V wires without using a breadboard? Do I need to solder or can I use some screw joints?
3) Do I reallly need the 1000uF capacitor?
4) What rating wire do I need to do the 5V 10A part safely?
5) Are there any limitations on soldering for 10A current?
6) I know I need to also link the WS2812B strips with Arduino ground - is it safe to do that part on a breadboard (i.e. what is the largest current that would flow to Arduino ground rather than the 5V ground?

Context on me / this project - long time coder, revisiting electronics after a 15 year gap from school physics. I have tested the code at low brightness of this setup using a 5V supply with a 700mA rated external power supply successfully. I now want to increase the brightness hence this question. I have not yet learned to solder so prefer to avoid if a safe workaround exists

Thanks in advance!
Alice


athompson395


Railroader

5 Amps per LED strip is a lot of current rushing at switch on. The 1000 microFarads will dampen electrical noice and possible trouble in the 5V 10A pwr supply. However Your drawing looks not good to me. Those capasistors must be connected as + to 5V and - to GND.
I would use 1,5 Square millimimeter cable minimum for that amount of current.
Use screw connectors for those cables.
Connect the pwr GND to the Arduino GND in one place well outside the Arduino. Don't let those high currents run in loops around the controller.
Use Your knowledge. If that's not enough, look for education.
Having knowledge, think outside the box to gain more of it. Only trains run like the train, on the rails. The rest run between the rails.

DrDiettrich

You can run solid + and - wires along the strips, and conect them to the strip e.g. every 10..20 LEDs. If you feed power to one strip end only, and it doesn't smoke when fully on, measure the remaining voltage at the other end.

Railroader

@DrDiettrich
Do You have a link so I can learn and see what those LED strips look like and how they are arranged?
Lots of question come about that stuff. Those strips didn't exist when I experimented with similiar builds.
Use Your knowledge. If that's not enough, look for education.
Having knowledge, think outside the box to gain more of it. Only trains run like the train, on the rails. The rest run between the rails.

DrDiettrich

I don't refer to a specific strip. Usually the WS2812B are daisy-chained, with thin printed wires carrying the signals and power. The strips can be cut after each or three chips, depending on the model. While the signal is refreshed by each chip, the voltage can derate significantly after a meter or so.

Railroader

@WS2812B
Thanks. I've got some idea about it. It looks like all the LEDs are loading the 5V in parallell making currents to add up.
Use Your knowledge. If that's not enough, look for education.
Having knowledge, think outside the box to gain more of it. Only trains run like the train, on the rails. The rest run between the rails.

SteveMann

#7
Oct 13, 2019, 10:27 pm Last Edit: Oct 13, 2019, 10:41 pm by SteveMann
Circuit schematic
In my 50+ years of programming and circuit design, this is the first time I saw a real "back of the envelope" drawing.

As Railroader said, the capacitors are in the wrong place.  You run the 5V from the Power Supply to each of the LED strips.  Same with the ground, but you got this right in your drawing.  Then at each LED strip put your capacitor between 5V and Ground.  Everything else looks right.

Railroader

@SteveMann
I once got a project specificasion written during a "happy friday" in a restaurant. Okey, the copy I got was not on restaurant towels or similiar.
In England, according to the law, one could, or still can write out a check, on the back of a fish!
Use Your knowledge. If that's not enough, look for education.
Having knowledge, think outside the box to gain more of it. Only trains run like the train, on the rails. The rest run between the rails.

Paul__B

In England, they write out a cheque!



OK, big problem with circuit theory here!  :smiley-eek:

MorganS

The 5V and ground don't have to follow the direction arrows on the strips. So if it is more convenient to wire to the other end then do so.

I have one big WS218 project which is like a square grid. The strips are arranged head-to-tail so the dsta line snakes through the whole square. But the power and ground are only connected along one side of the square.

Usually it is easier to have only one data pin instead of the two you show. The length of the data line is unlimited, if you have at least one LED to boost the signal each 10-30 meters. That LED may be left dark if necessary.
"The problem is in the code you didn't post."

athompson395

All many thanks for your detailed and quick responses - very much appreciated!

Railroader thanks for your detailed response. One follow up if I may... what counts as "well outside the arduino" is that in centimeters or some other measurement? Thanks! This was a good starting point for me on Neopixels but may well be too basic for you: https://learn.adafruit.com/adafruit-neopixel-uberguide/powering-neopixels. Have never seen a cheque on a fish... will need to ask around about that one!

DrDiettrich thank you

SteveMann I had limited scrap paper at home and was in a rush... but I have to say I did think about making that joke...

Paul__B not sure what you mean but happy to take any advice :)

MorganS thanks. Can I ask, in the case of using one data input do I need to solder the connecting wire from the end of one strip to start of the other (i.e. it sees the next strip as 131, 132 etc)? I avoided this for the sake of avoiding soldering (never tried this before) and because i have spare arduino pins in my design

Thanks all for your helpful replies!
Alice

MorganS

Yes, you can link together an unlimited number of strips, nose-to-tail.
"The problem is in the code you didn't post."

Paul__B

Paul__B not sure what you mean but happy to take any advice :)
You had the capacitors shown in series with the power lines.  :smiley-eek:   Need to study up on what series and parallel are, and what capacitors do.

I note various comments about where to connect the power to the strip, which end, one end of arrays and so on.  I would say you need to connect the power - in parallel(!) - to the strip every 2 or three Amps and that means every 30 to 50 LEDs, always including both ends.

Also an important note:  the power wires - 5 V and ground - must run together - as a pair - from the power supply to (each part of) the strip, and the data and ground wires must also run together as a pair from the Arduino to the strip.  The resistor in question should be at the strip, not the Arduino and the capacitor in question should be mounted across 5 V and ground at the point where the data connects in.

athompson395

Sorry to bother you again but I had set everything up, tested bit by bit, but I seem to have damaged the neopixels somehow - only the first one of each strip lights, and it's very very dim (just so you can see the red blue green).

Any ideas if there is a way to fix this damage and what might cause it so I don't do it again...?

Thanks in advance!
Alyson

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