neopixel power

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HunterDarkwolf
 
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neopixel power

Post by HunterDarkwolf »

This might be a bit of a stupid question, and I'm sorry if it is, I'm very new to this. I'm looking at getting a meter strip of neopixels (https://www.adafruit.com/product/1376) and run them from an Arduino Uno R3 board, can I safely power this all with a 9v battery connected to the arduino's power socket, or should I be looking at something else. I ask, because I don't want to damage the strip, and it says not to go above 6vdc, and 5 is the recommended.

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adafruit_support_bill
 
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Re: neopixel power

Post by adafruit_support_bill »

A 9v battery does not have the capacity to power a meter of Neopixels. And even if it did, you would risk overloading the 5v regulator on your UNO.

What are the requirements of your project. Doe it require a portable power source? If so, how long does it need to run on a charge?

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HunterDarkwolf
 
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Re: neopixel power

Post by HunterDarkwolf »

wanting to do a flame looking setup on an arm (think scorch from rogue company). So portable would be needed.

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adafruit_support_bill
 
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Re: neopixel power

Post by adafruit_support_bill »

For portable projects with Neopixels, I'd recommend switching to a 3.3v processor like one of the Feather series. In addition to being more compact, it will simplify your power requirements.

Using a 3.3v processor, you can power both the Neopixels and the processor using a 3.7v LiPo cell. These come in various capacities and have the highest power density of all the commonly available battery types. https://www.adafruit.com/category/574

The Feather 32U4 is from the same Atmega processor family as the Atmega 328 used in the Arduino UNO. https://www.adafruit.com/product/2771

I'd also recommend reading through this guide on power management for portable Neopixel projects. https://learn.adafruit.com/sipping-power-with-neopixels

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JohnHind
 
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Re: neopixel power

Post by JohnHind »

This is a request/suggestion for LadyAda when she is laying out new 3.3v CircuitPython boards with USB power and a NeoPixel on-board:

Rather than powering the NeoPixel from 3.3V, power it from USB 5V and include a level shifter on the IO pin used to drive it. Take the data out pin from the NeoPixel out on the board pinout. This way more NeoPixels can be added off-board with out taking any extra IO or regulated power.

The problem with driving the NeoPixels from 3.3V, apart from being out of spec, is that it adds a lot of extra load to the voltage regulator and also will increase the voltage drop limiting the length of the off-board chain. Best to drive the chain from 5V taking full advantage of the current available on the USB socket, but then 3.3V volt is likely too low to drive the data in reliably, so a level shifter is required. A 74LV1T86 is a good solution for this, being a tiny SOT353 package that would take very little board space.

I've been having difficulty getting a good RP2030 board for a keyboard project based on two of Adafruit's splendid NeoKey 5x6 Ortho Snap-Apart. In the end I just used a Feather modded to bring out USB 5V and with an off-board level-shifter. I'm keeping an eye on the new Scorpio, but unsure if it will have enough 3v3 IO for the key matrix (I need 14 GPIO on top of the 5V ones for the NeoPixels).

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adafruit_support_bill
 
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Re: neopixel power

Post by adafruit_support_bill »

Rather than powering the NeoPixel from 3.3V, power it from USB 5V and include a level shifter on the IO pin used to drive it.
That would violate the Feather power specification: https://learn.adafruit.com/adafruit-fea ... 2861841-12

Feathers are designed to be powered by USB or LiPo and are widely used in portable projects under battery power. In those cases, you can power your pixels at 3.7v direct from the BAT pin with no added stress on the regulator.

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JohnHind
 
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Re: neopixel power

Post by JohnHind »

adafruit_support_bill wrote:
Rather than powering the NeoPixel from 3.3V, power it from USB 5V and include a level shifter on the IO pin used to drive it.
That would violate the Feather power specification: https://learn.adafruit.com/adafruit-fea ... 2861841-12

Feathers are designed to be powered by USB or LiPo and are widely used in portable projects under battery power. In those cases, you can power your pixels at 3.7v direct from the BAT pin with no added stress on the regulator.
The board could be designed to take power for the NeoPixels (and the level shifter) from the input to the 3v3 regulator although the upstream diodes might need to be beefed up to allow say the full 2A USB power spec. The battery will not be the full 5V, but I believe the NeoPixel spec. goes down to a little under 4V so it would certainly be closer if not quite there, and avoiding the losses and limits of the regulator. In common with most USB keyboard builders, I had no need of the Feather's battery capability and in fact had to remove the battery socket as it made the board too thick to fit in the case! The recent 'Kee Boar' board was a miss for me because it did not bring out all the RP2040 IO and it did not have a level shifter for the NeoPixels. We still need a good board to pair with the superb and innovative NeoKey product!

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adafruit2
 
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Re: neopixel power

Post by adafruit2 »

you're pretty much talking about an itsybitsy board - it has a level shifted 5V signal output specifically for
https://www.adafruit.com/product/4888
and 23 GPIO pins
for kb2040 we cannot turn any of the GPIO into output-only because folks expect each pin to be able to handle key inputs

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JohnHind
 
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Re: neopixel power

Post by JohnHind »

adafruit2 wrote:you're pretty much talking about an itsybitsy board - it has a level shifted 5V signal output specifically for
https://www.adafruit.com/product/4888
and 23 GPIO pins
for kb2040 we cannot turn any of the GPIO into output-only because folks expect each pin to be able to handle key inputs
Yes, I considered the Itsybitsy. The problem with that is the Micro-B USB. I wanted a modern USB-C and in the end it was easier to modify a Feather than fit in an adapter cable. If I'd been happy with Micro-B, an original RP Pico board would actually have been a better choice: all the GPIO and a good deal thinner!

I addressed the GPIO issue in my original post: most of the boards (including KB2040) have a single NeoPixel on-board for feedback so that already consumes a dedicated GPIO. Drive that NeoPixel from battery or USB power and a level shifter and make its data out available on the pinout. We can then extend the NeoPixel chain without taking another GPIO.

The KB2040 is hobbled by using a pre-defined pinout with insufficient pins to bring out all the GPIO. I get that this makes it a drop-in replacement on some third-party keyboard matrixes, but it also makes it a poor choice for keyboards built on Adafruit's own NeoKey boards! It would be possible to drop the STEMMA socket and put a row of solder pads along that edge on the top of the board only. This would preserve pinout compatibility whilst providing connectivity for the rest of the GPIO and the NeoPixel data out. For my own use however I do not care about matching the pinout or even have a problem with a larger footprint. However height of the board is critical as it has to fit under the NeoKey boards without raising the typing surface too far above the desk.

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JohnHind
 
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Re: neopixel power

Post by JohnHind »

I've just been thinking, I'd love to collaborate on this. My proposal is that Adafruit would design and market a RP2040 board with my conceptual input. I already have a prototype full keyboard based on a Planck-inspired 12x4 grid which I would adapt to use the new processor board and write a Learning Guide for. The CircuitPython code is already done (I am typing on the Feather-based prototype now!) and has many useful teaching points including a state-machine implementation for the multi-function Planck operating mode.

The basic concept is the board would have the same grid layout as the NeoKey Ortho Snap-Apart. It would be some multiple of the grid of this board, ideally 1x4. This way it could sit under the back row of the KB with the USB-C socket emerging back-left or right allowing a layout similar to what Apple use with the processor board in a bar under the rear of the KB which also serves to raise the back up to a comfortable typing angle.
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rKercher
 
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Re: neopixel power

Post by rKercher »

Hey there John,

I am completely new to circuitry and similar projects. I've been wanting to do my own ortho 5x12 board, and stumbled upon the snap apart by Adafruit. Been thinking of using two together, but have no idea of how they should be connected. I got a RP pico for Christmas from a friend, and wondering if I can bother you for suggestions on how to connect the two PCBs, and then how to connect them to a pico. Eventually I also want to make it wireless, so if you think any of the microcontrollers Adafruit has could do, manage a battery and power the LEDs, I would be appreciative of your time. I saw your post about wanting a Choc board, and I hope they eventually do that as well. A truly LP 5x12 ortho with Bluetooth and backlighting is my dream. Hope they can spin up a PCB design for it!

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JohnHind
 
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Re: neopixel power

Post by JohnHind »

Kattni's guide here: https://learn.adafruit.com/adafruit-neo ... snap-apart covers the basics. It is a project that requires soldering though. For two boards, probably the easiest way is to link the five 'Row' terminals on the right side of one to those on the left side of the other. Then take five wires (a ribbon cable is easiest) from any of the row terminals on each row to any five GPIO terminals on the micro. Now you will need to connect twelve wires from the 'col' terminals to any twelve more GPIO. In CircuitPython, you use the 'keypad' library and specify the row and column pins in two lists. This is all you need for the keys.

Neopixels only need one more GPIO, but the wiring is more involved. Looking from the top (key-face side) of the board, you need a wire from the 'OUT' terminal on the bottom-right key to the 'In' terminal of the top-left key of the other board. You also need to connect one of the GND terminals and one of the VIN terminals between the two boards. Now you will need to connect the 'In' terminal top-left of the first board to GPIO via a level shifter (unless you are using a 5V micro) and any VIN pin to 5V and any GND pin to the microcontroller Ov or GND. Use reasonably thick wires for GND and 5V, the sort you would find on a battery clip. Check out JP's guide here: https://learn.adafruit.com/neopixel-levelshifter.

For radio, checkout JP's guide here: https://learn.adafruit.com/ble-hid-keyb ... cuitpython (I have not tried this myself, but generally 'HID Keyboard' examples can be extended to full-size keyboards).

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rKercher
 
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Re: neopixel power

Post by rKercher »

Thank you so much for that answer and resources, this seems so much more doable now!

I join you in hoping for a choc version for low profile goodness haha... I want to be able to have a 50-60% at my desk and a 30% that I can slip in my pocket for the road lol

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