dchurch24
Posts: 50
Joined: Thu Dec 06, 2012 7:29 pm

WS2812B Led Matrix 8x32

Fri Jun 14, 2019 10:44 am

Hi,

I recently purchased one of these: https://www.amazon.co.uk/gp/product/B07 ... UTF8&psc=1

I have a 5v 6amp psu, and I have some sample code to run an 8x32 LED matrix, but I can't work out where or what the connectors are.

I have the two power wires - those I understand :p

There are two other connectors with the matrix kit: a 3 pin male, and a 3 pin female.

Unfortunately, there's no wiring diagram with the matrix, so am unsure what each of these wires does.

Has anyone done anything similar that could point me in the right direction?

Andyroo
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Location: Lincs U.K.

Re: WS2812B Led Matrix 8x32

Fri Jun 14, 2019 11:08 am

Normally you have a power, ground and data in at one end and the other end its power, ground and data out to allow chaining of these units together.

I assume the connectors are designed to be soldered to the ends for this chaining but without pictures of the connectors and ends of the LEDs I’m a bit stuck :D as the Amazon pick does not give you a clue as to which connector is in or out!

If you know the LED type (the Amazon page has a link) you could try to trace the pins back from the LEDs to the end to give you the solder points if nothing is marked...
Need Pi spray - these things are breeding in my house...

dchurch24
Posts: 50
Joined: Thu Dec 06, 2012 7:29 pm

Re: WS2812B Led Matrix 8x32

Fri Jun 14, 2019 11:16 am

Hi, thanks for that.

Of course! One end (not sure which) would be used to daisy-chain them!

I don't have the matrix with me at the moment, but I did take some photos earlier. The wire colours, are, of course: black, green and red. Hopefully, when I get back to it, it will be obvious which is in/out.

It's a tad annoying to be honest. I was assuming that there would be some kind of datasheet, or at least a rudimentary wiring diagram - but it's simply the matrix and nothing else.

I've left a question for the seller, but I'm not holding out much hope. This might become a matter of trial and error!

Andyroo
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Re: WS2812B Led Matrix 8x32

Fri Jun 14, 2019 12:04 pm

Green will be data unless they have gone really away from red/black for power :lol:

Looking at the Amazon page this link here gives you a basic code example (Arduino I think) but no cabling other than the LED pin out :roll: but another question states this needs an external power supply so I would GUESS the connector with the two extra leads is the start of the chain.
Need Pi spray - these things are breeding in my house...

dchurch24
Posts: 50
Joined: Thu Dec 06, 2012 7:29 pm

Re: WS2812B Led Matrix 8x32

Fri Jun 14, 2019 12:54 pm

Ah - good stuff...getting closer (in my head at least!). Thank you.

I found this: https://tutorials-raspberrypi.com/conne ... ed-strips/

The diagram (about half way down), has the power going through so my guess is that these are split out as there are many more of them, requiring more power.

My guess is that I would ground both the black wires, use the green data wire (on pin 12 (GPIO18) - PWM?) , and simply pass the live down the external red.

Does that sound feasible?

Andyroo
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Re: WS2812B Led Matrix 8x32

Fri Jun 14, 2019 4:06 pm

Do not forget to ground the Pi to the same ground as the LEDs and make sure the Pi does not get any power from the external supply via the green wire.

Some of these can draw 60mA so you will need a beefy supply - 15+ Amps at max draw (all white) and a good in rush protection capacitor (and a pair of sun glasses :lol:) - not sure about the max current there - I know that’s the calculated figure for max brightness when white but it’s hard to believe the unit would not melt at that draw... Can anyone help here give a rough guide for actual use?

I would hunt Github for a library to drive the LED chipset as timing data to these is very very fussy esp. if you want to change the colour / patterns. I think the Adafruit ‘neopixel’ software may work (though they are WS2812 not 12b I think) - just pass the data stream through a 470 ohm resistor and level shifter (assuming these need 5V) before the first LED.
Need Pi spray - these things are breeding in my house...

dchurch24
Posts: 50
Joined: Thu Dec 06, 2012 7:29 pm

Re: WS2812B Led Matrix 8x32

Fri Jun 14, 2019 5:19 pm

Yep. Got the grounding thing :)

I have a variable psu (0-30v 0-10A), so as long as I don't turn them all white I should be fine, I think.

Am back at home now, so have had a proper look.
There are two sets of three wires and one set of 2.
The 2 are red/black power, seemingly in-line with the red and black of one of the set of three.
1st set of three (male)
Red: 5v
Green: DO
Black: GND

2nd set (female):
Red: 5v
Green: DI
Black: GND

That has baffled me properly now!

Ps. Thanks for your time and effort on this. Really appreciated.

Andyroo
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Re: WS2812B Led Matrix 8x32

Fri Jun 14, 2019 5:29 pm

By the markings then it’s the female connector that the Pi would connect to then.

I’ve seen warnings about variable power suppliers taking a moment to settle down hence the capacitor.

The location of the power should not be an issue - I’ve seen videos of Christmas decorations made from these where the power is connected in the middle rather than the end to help reduce voltage drop over long runs.

Good luck. If the Pi is too busy to give a clean signal, it gives you a good excuse to buy another :shock: or get an Arduino board :lol:
Need Pi spray - these things are breeding in my house...

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rpdom
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Location: Chelmsford, Essex, UK

Re: WS2812B Led Matrix 8x32

Fri Jun 14, 2019 7:44 pm

I'd connect the DI and GND wires to the Pi. Don't connect the 5V wire to the Pi.

Connect the power supply, set to 5V, to the pair of red and black wires.

dchurch24
Posts: 50
Joined: Thu Dec 06, 2012 7:29 pm

Re: WS2812B Led Matrix 8x32

Sat Jun 15, 2019 4:04 am

Will do. Thank you.

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