Neopixel wiring?

Hi, I'm a newbie and I might have chucked myself in the deep end of Arduinos.
The project to cut years of explanation is: I need to control 3 of these: NeoPixel Jewel - 7 x 5050 RGB LED with Integrated Drivers : ID 2226 : $5.95 : Adafruit Industries, Unique & fun DIY electronics and kits from an Arduino uno but it has this shield: Adafruit 16-Channel 12-bit PWM/Servo Shield - I2C interface : ID 1411 : $17.50 : Adafruit Industries, Unique & fun DIY electronics and kits this shield has stacking headers so the Arduino pins are replicated on top. So my question is where do I put the wires for the LED's and I cant stress enough to explain with a circuit diagrams please. All 3 LED's will be the same colour at the same time so using the same command pin (if you could do that) is an option. I don't currently have an external power pack but I intend to so make one up if it helps.

I apologise in advance for my lack of knowledge, stubbornness or general noobery.
Thanks for reading, Gig

Have you read this:

Do you understand every thing said there?

Just wire your displays in series and treat them as one long string of neopixel LEDs.

(Yes, he was given that link before).. :slight_smile: (different forum)

and also explained about the requirements when using Neopixels.. (he also have some other leds and 6+ servos, and linear actuator..etc and other stuff going on). (never have used an Arduino before as well, and hasnt listened to advice about breaking things up into steps first) :expressionless:

It was suggested that using Dot Stars might be easier for his experience level as well (to avoid the 800Mhz update/timing)

also.. as noted before..

a neopixel strips really just needs +, - (+5v) ....and a control wire going to the Arduino.. doesnt matter what one as you define it in the sketch.

read that link carefully and do not forget the resistor and cap.. or you'll blow your Neopixel strip)

to avoid the 800Mhz update/timing)

I think that might be out by three orders of magnitude though.

You can control three strips with three instances of the library on separate pins if you like.

Ok, so what about this, I know the wires don’t connect to the LED’s correct places but you should know what I’m on about. Oh and we meet again xl97. Thanks for the quick replies.

Well given that what you drew will draw just over 1A then you can't power it from the USB at all.

I know the wires don't connect to the LED's correct places

So if the wires do connect in the right place then hey it is fine. But you don't have to ask to know when it is correct it is correct. Is there a real question here?

Grumpy_Mike:
I think that might be out by three orders of magnitude though.

oops....

800 kilobits per second for timing

Grumpy_Mike:
You can control three strips with three instances of the library on separate pins if you like.

yes you can.

however he has much stuff going on..(static leds, 6+ servos,. actuator..etc) (and having never even used an Arduino before..it was suggested maybe using the Dot Stars might be easier for him to work with)

Here’s the image attached to reply #4.

b726e0f56d08e96ee9eebed6035c87d4601a086e.jpg

How to insert uploaded images.

I don’t see what the big problem is.

You should be able to power 7 NeoPixels from the Arduino’s 5V line. If you’re worried about pulling too much current then set the colors to low brightness settings.

Get the code to work with one set of seven and then start adding the other LEDs.

Have you used one set of NeoPixels by itself yet?

You just connect 5V for Arduino (or shield) to the Jewel’s “PWR” connection. One of the two “GND” connections on the Jewel connects with the Arduino’s ground and the Jewel’s “IN” connection connects with whatever I/O pin you’re using to control the NeoPixels from code.

If you post the code you’re using, I could help make sure the brightness settings are low enough to safely use from the Arduino’s power supply.

Ok, confession time! I don’t know a lot about electronics. I am a mechanical engineer and took electronics club many years ago, I also took physics and this bit still remains a mystery. I know things like circuit diagrams and how electricity works I.e. electrons and all but what components drawing what and how not to get the magic smoke I am in another world and am asking for you help. When I ask “would this work?” its because I don’t know if it will, I took that drawing from google as that was the only lead I had as to how to do this. I tried to keep this project simple for now xl97 as I see this brings confusion. I will deal with all its aspects individually, If that’s ok? Thank you DuaneDegn for the explanation. It helps a lot. I am currently getting my head around the Arduino by doing all the small projects and the code? well I’ve just played with the numbers knowing they will work. not written code yet, again my code background comes from making command block contraptions in minecraft so not C but I’m just tackling the physical wiring aspect first. Ill do some research on the code today and tomorrow and get back.

This is how you wire those three up.
jewl.png

Grumpy_Mike:
This is how you wire those three up.

Except the OP wants to wire them in parallel, with all three data in lines connected directly to the Arduino.

My guess is the the Arduino’s logic signal should be able to drive three NeoPixels at once but I personally think wiring it like you show would be more practical and offer more possibilities.

It would be trivial to replicate the color data so it’s transmitted three times.

Here’s the diagram for using the pixels in parallel.

neo exB.png

I don’t know if one is better off using three separate resistors or if it would be better to use a single resistor. I slightly favor using three separate resistors over using a single resistor.

I’ve used NeoPixels lots of times myself and I never use a resistor on the signal line.

The best way to wire the power lines will depend on the physical layout of the boards. It would certainly be possible to chain the power lines while using the data lines in parallel.

Again, it sure seems like chaining the boards would be a more practical approach than wiring them in parallel.

Thank you so much, This is many helpfulness's in value. I cant thank you enough. Ill do a shopping trip to get the wires and mock up some bread board prototypes after I've done the tutorial. Thanks again.

Yes he might have wanted them connecting in parallel, but he is much better off making a seriese connection. There is more flexibility and a lot more learning potential and I suspect he did not know you could connect them in seriese. Still he has the choice now.

I was always told to do them in parallel as is one blows then you don't loose the circuit, and the capacitor is relevant and the correct uF? (sorry if that's a stupid question, I guessing the answer is duh, why would they include it) but it was taken of the neopixle ring so things might change. Thank you all for your help. I could NOT have done it with out you. No seriously.. I couldn't.

I was always told to do them in parallel as is one blows then you don't loose the circuit

Yes but they are not like Christmas tree lights. The light itself can fail but the electronics that pass on the signals often still works.

Yes that capacitor is fine, the exact value is not critical.

Gigatrix:
I was always told to do them in parallel as is one blows then you don't loose the circuit,

Who told you this? The only way I can see blowing the whole circuit would be by using the wrong power source. In this case it would blow the circuit whether or not the data was wired in parallel.

It is possible to blow the first LED in the chain if your ground is disconnected. If the ground line becomes unattached, the LEDs will still work for a very short time. During this time the returning current from the LEDs will flow through the signal line of the NeoPixel. At least this is my present theory.

I had a hairbrained idea of trying to power some NeoPixels on my robot's wheels. My "power transfer" system apparently had some glitches.

The first pixel of my 16 pixel ring kept dying when using this setup. The OSHPark PCBs are good quality but after replacing the LED on the ring a few times, one of the traces was damaged.

Here's my "blue wire" repair.

So technically, your parallel wiring scheme places the first LED on each of your PCBs at risk. If you wire them in series only the LED with its data line connected to the Arduino would be at risk.

I bet the series resistor AdaFruit now recommends reduces the likelihood the first LED would be damaged. I'll probably start using a series resistor myself and see if I can reduce the abuse I give to my NeoPixels.

My power transfer setup is an extreme example. Under normal use, the NeoPixels should work fine.

Gigatrix:
and the capacitor is relevant and the correct uF?

I don't have have an answer for this. I think AdaFruit generally does a good job with their tutorials and I'm sure they have a lower kill ratio when using NeoPixels than myself. I don't think the exact value of the cap matters much. I'd think a few hundred uF would likely work okay.

My one concern with using a 1,000uF cap is the in rush current when power is turned on. I think a 1,000uF cap could damage a USB port if you tried to power your setup from the USB supply. I'm not sure about this myself.

As I mentioned earlier, I don't use a series resistor (though I'll likely start using them) and I don't use a 1,000uF cap in my NeoPixel projects.

I've had trouble when controlling NeoPixels from a 3.3V microcontroller. NeoPixels don't appear to like 3.3V logic when powered from 5V. You can see glitches in this video caused by using 3.3V logic.

Fortunately there are lots of logic level converter options and another option is to power the NeoPixels from 3.3V. Either of these solutions fixes the glitches.

Of course the Leonardo is a 5V controller so you don't have to worry about this. (So why did I tell you? Oh, that's right, so I could post the "hypno rings" video.)

Grumpy_Mike:
Yes but they are not like Christmas tree lights. The light itself can fail but the electronics that pass on the signals often still works.

This hasn't been my experience. When I've had the first LED fail, it completely failed and didn't pass on the signal. Still this is actually an argument against using the boards in parallel since in series only a single LED is at risk of damage from a bad ground connection.

This hasn't been my experience. When I've had the first LED fail, it completely failed and didn't pass on the signal

Yes that is because you were damaging the electronics by incorrect powering / driving. I was talking about the event of the LED failing. In your system the LED was probably fine but in damaging the drive circuit it would not light as well.

and the resistor? sorry to be a pain. Thank you all.

and the resistor

What about it?

I would use three close the the Arduino.

The capacitor is there to smooth out current surges created by the fact that each little neopixel apparently has its own little PWM devices, asynchronuous with all other neopixels in the chain. So it isn't the case that capacitance must always increase as neopixels increase. As you get more neopixels in the sequence, the increasing number of PWM processes will actually act as a smoothing mechanism. So 1000 uF, is probably more than enough capacitance, no matter how many neopixels.