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Thread: help understanding batteries with neopiexls & espixelstick

  1. #1
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    Default help understanding batteries with neopiexls & espixelstick

    Im ready to take my espixstick project wireless. I built a neopixel tube light and I am able to program it with espixelstick but after so much reading, I can't wrap my head around batteries. I have 60 pixels in my tube and based on adafruits power guide I should have a battery with 3.6a. Now what is confusing is voltage I believe. I understand pixels should have 5v power to run and that guide says they should run on 3.7v since 5v batttery don't exist? The pixelstick can take in either a 5v or 12v power supply but what about with a battery voltage? I've been looking at batteries on custom light saber websites because they would fit in my tube. The batteries here: https://www.thecustomsabershop.com/Li-ion-74V-C85.aspx are 7.4v. Does that mean its really just two 3.7 v batteries together and still outputs at 3.7v or do they use something to regulate it down to 5v for the pixels? Would the espixel stick be able to take the 7.4 to 5v? I also have so nodemcu boards, do they have anything built in that helps with power? Power and all these boards just so confusing for me.

    Just really confused on what I would need to run the 60 pixels for a few hours on battery that would fit in a tube with 1.2" diameter.

    Any guidance that would give me a better understanding of batteries and what to look for would be appreciated. Once I wrap my head around the concept, I'm sure I'll be able to find one.

    Thanks in advance.

  2. #2
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    Default Re: help understanding batteries with neopiexls & espixelstick

    Hi
    You may want to give these a look as they are designed for high output . Your 60 leds @60ma per
    for a couple of hours can be very taxing on power depending on usage of course .

    POWER

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    Default Re: help understanding batteries with neopiexls & espixelstick

    Quote Originally Posted by angus40 View Post
    Hi
    You may want to give these a look as they are designed for high output . Your 60 leds @60ma per
    for a couple of hours can be very taxing on power depending on usage of course .

    POWER
    Thank you for the link. Does the espixelstick take the 7.2v of that battery and turn it to 5v? Trying to understand how using more than 5v works.

    Thanks

  4. #4
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    Default Re: help understanding batteries with neopiexls & espixelstick

    I am not overly familiar with the espixelStick , but I would gather that it is regulated to output 5v data regardless of input voltage .

    Depending on your pixel input voltage requirement 7.2V may be safe ( check data sheet to verify ) otherwise
    you could use a dc-dc buck converter to shed excess voltage .
    Alternatively you could add a resistor to drop a volt or 2 as per your requirement .

  5. #5
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    Default Re: help understanding batteries with neopiexls & espixelstick

    My understanding is that the espixelStick and similar controllers regulate the voltage of the DATA output but do not regulate the positive line. Your pixels will be exposed to the full voltage of the battery. You should look for a buck converted that can handle sufficient current for the pixels.

    Sent from my moto z4 using Tapatalk

  6. #6
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    Default Re: help understanding batteries with neopiexls & espixelstick

    Why not use a cell phone battery bank? Those bricks you charge to then charge your cell phone when you don't have power. They are a source of 5v, no conversion needed. This is what I used to power my top-hat matrix. I am driving 256 Pixels and the controller for at least an hour or longer. I used an old USB cable, cut off the end and connected it to my controller. The other end plugs directly to the power bank.
    Last edited by mikeh65; 05-19-2020 at 11:04 AM.

  7. #7
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    Default Re: help understanding batteries with neopiexls & espixelstick

    Quote Originally Posted by mikeh65 View Post
    Why not use a cell phone battery bank? Those bricks you charge to then charge your cell phone when you don't have power. They are a source of 5v, no conversion needed. This is what I used to power my top-hat matrix. I am driving 256 Pixels and the controller for at least an hour or longer. I used an old USB cable, cut off the end and connected it to my controller. The other end plugs directly to the power bank.
    I can definetly do that in some setups but my goal was to have the battery fit in the pixel tubes so that's why wanted to go with the saber one listed above due to its form factor. I guess those saber guys use some sort of resistor or buck converter? Trying to post on their forum but they still haven't activated my account.

  8. #8
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    Default Re: help understanding batteries with neopiexls & espixelstick


    Something like this?

    It was built in/around a 30mm pvc pipe. 60leds/m ws2811 and one 1W or 3W 12V led on top. 3 dc-dc converters built in. 2 for 5V, 1 for 12V. I built a 4S1P battery from recuperated 18650 batteries. The leds were controlled by an nodemcu, via wifi. Controller was FPP. In te video the battery is not inserted yet.
    Errors for fun only.

  9. #9
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    Default Re: help understanding batteries with neopiexls & espixelstick

    Just a note on batteries in general. I do have some pixel strings that are very PICKY. If the voltage is too high, they will start messing up.

    Case in hand: 12v WS2812 pixels that refuse to operate correctly @ 12v. I had to drop the voltage between 11.5-11.75v IDLE for them to be stable.

    Batteries: 12v Lead Acid standing voltage: 12.6v To charge lead acid, 13.8 is the minimum for charging. Between 8.5-9.5v the battery is pretty much depleted and needs to be recharged.

    Lithium Ion: 3.7v cells. Full charge is 4.2v Minimum discharge voltage is 3.2v. Below 3.2v and the cell is usually DEAD. Internal safety mechanisms will prohibit recharging.

    A good choice for Lithium Ion batteries would be in the RC car/truck/air plane hobby. Built and ready to go. I have used many from 2AH to 10AH (2000-10,000mah) @ 20-80A constant output. Match a balancing charger and low voltage cut-off for long battery life.

    NiMh is a good choice too. They will tolerate all sorts of abuse much better than Lithium Ion. Building a power source is a bit easier @ 1.2v per cell.

    One note: Lithium Ion is temperature sensitive because it is a WATER BASED battery AND will not work when the internal electrolyte freezes. I do not recall the freezing temperature. Lead-acid, NiMh and NiCd batteries have reduced current capacity as the temperature gets colder - significantly noticeable from ZERO to MINUS 60
    Last edited by RGB_Mixer; 05-28-2020 at 11:46 AM.
    -Eddie

    The missus wants to ride!

  10. #10
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    Default Re: help understanding batteries with neopiexls & espixelstick

    Quote Originally Posted by DaveMcK View Post
    My understanding is that the espixelStick and similar controllers regulate the voltage of the DATA output but do not regulate the positive line. Your pixels will be exposed to the full voltage of the battery. You should look for a buck converted that can handle sufficient current for the pixels.

    Sent from my moto z4 using Tapatalk
    It is not so much that the data line voltage is regulated, it is that the WS281x chips all use a 5v Data signal which means you need to provide 5v to the WS281x chips. They do not actually run at any voltage other than 5v. Your 12v pixels all have some sort of voltage regulation (resistor, Integrated regulator, buck converter) to convert input voltage to 5v. As for the LEDs that the chips drive, the chips use a current sink model on the outputs so you can use (almost) any voltage on the three LEDs and the device does not care.


    2020 Full sized show reworked for the new location. Only adding (famous last words) 13 RBLs that I finally got converted to using pixels
    2019 - Just moved into a new home (yet another change of plans). Will be dim but not dark. Too much to do at the new place to leave time for a show. Dim show (3000 pixels) had regular visits most nights.
    https://www.youtube.com/channel/UCyX...ttrsZNARkUce0Q

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