Ambilight setup, why do we need (we think) extra electronics in there like capacitors/resistors, experiences thoughts and explanations

  • hello folks,



    after being here for quite a time i see that people intend to use extra electronics in his/hers Ambilight setup.

    my question is why,


    don't get me wrong, each to his own. ;)


    but....


    I never understood why the Ambilight guys think they need a capacitor soldered between the +5volts line and GND on the strip.

    the only thing a capacitor does in this typical setup is "buffering" and storing power when its needed, this capacitor used ( in microfarrad) is so tiny that it only works for milli seconds

    that is if it even works at all. ( do you know its actually doing something at all, or you can do without?)



    in my world/eyes and out of the engineeringfield, if you have a powerfull PSU that delivers a steady/clean rectified AC to DC then the use of extra capacitors isn't necessary

    the good quality PSU is more then capable to be "powerdrained" without having a problem in rectifier circuit.


    and then the resistor in the dataline before connected to the strip ( mostly 3 line strips)

    the resistor in series is only meant to protect the first LED in the strip and only if the strip is powered from one side this has use.

    for the rest of it it does absolutely nothing.

    i am talking about this>>>



    power from both sides ( the ledstrip) is the way to go in that setup,

    less electronics is always better then a lot. Why use that capacitor is it really really necessary??

    in my eyes, when u need to solder capacitors between the powerlines then something isn't already quite right from the start..


    my only two cents. ( or prove me wrong, i might learn something) :D



    note; i am not using them no capacitor/resistor

  • great topic lol - I think it boils down to each hardware setup in all honesty.


    I had no resistor or capacitor it all worked, i fitted both, it still works and i don't notice any difference, I only picked the capacitors up as i was getting other things from that place and they were cheap and i was curious more than anything else as WLED has it on their main diagram.


    but im still on the if you have a decent psu that can put out the proper current and voltage required - it should be on tap to use, as and when the LEDS require it, whether the capacitor does provide the litlle burst at the right time - who knows but as most vids or tutorials use the barrel connectors as they plug into the brick psu im happy believing that you only need it if you have one of those unstable PSU's


    Resistor on the 1st led to protect it - could be the case if your running slightly higher than 5v and your MCU is out putting 5v , resistor could pull that signal down to a more cleaner stable level but meh im quite happy to chop it off if needed and move the wiring down 1 led.


    Just my thoughts on it

  • i 've read a story when only with starting of the (bad quality) PSU spikes in the voltage will occur and possibility is without using the capacitor > can damage your ledstrip.

    but thats only when booting up the powersupply.


    when powersupply already runs and then ledstrip is powered up nothing can happen i would say... :whistling:


    oh, and also don't forget to fuse correctly like davieboy explained in his topic, RE: Protect you Build because this can also mean a way to high current ( unwanted) trough your electronics. ;)

  • Both are in adafruits best practices for neopixels/WS2812b
    https://learn.adafruit.com/ada…-uberguide/best-practices


    They go on to bold a section stressing the importance.

    - Any project with a lot pixels or a large power source should definitely include the power capacitor and data line resistor.


    and even give a big red bold warning on the "Powering Neopixels" section
    - Adding a 300 to 500 Ohm resistor between your microcontroller's data pin and the data input on the first NeoPixel can help prevent voltage spikes that might otherwise damage your first pixel. Please add one between your micro and NeoPixels!

    as well as give some information about why you should use caps
    - Before connecting a NeoPixel strip to ANY source of power, we very strongly recommend adding a large capacitor (1000 µF, 6.3V or higher) across the + and – terminals. This prevents the initial onrush of current from damaging the pixels.


    Edit: It's really easy to add both so I've never questioned it. They may not make a night and day difference, but they certainly don't hurt anything. And as the old adage goes, better safe than sorry.

  • D34DC3N73R


    thanks for the input, i know that site ( looked in there before) from beginning with ambilight project.


    The resistor data line surge i get, i think its also mostly for 3 -line strips that only have 1 data line. :)

    i think also for Raspi you don't need them ( can't hurt if used) because dataline output isn't higher than 3,3 volts.


    the capacitor story all comes back to the use of a weak/not steady powersupply and/or not clean and rectified enough.

    that said;


    -i am not convinced ( yet) about the capacitor


    -i am about the resistor, but only if used in a MCU/controller thats not a Raspi.




    i think and thats the mainreason why they will repeat that, most people are not experienced in electronics and buy the cheapest stuff from Amazon or AliExpress they can find like powerbricks and such.., if you use that stuff then chance is big you will fry the neopixels strip from them and they dont want that of course. ;)

    so ( how i see it) its a precausion to use that capacitor to RULE OUT bad PSU thats on the market.


    ;)

  • D34DC3N73R


    i am a oldschool guy, i think that we have come far into electronics from 30 years ago untill now.


    PSU's thats fabricated now ( the better ones/brands) are way way better than 20/30 years ago, they are all electronic, have safety in them and switch off if it detects mallfunction and/or to high power drainage like shortcutting.


    So to be short; no it can't hurt to use the capacitors of course not.

    but you can do without is my 2 cents.



    i never used capacitors/resistor in my build and it runs flawless for already 1,5 years. ;)

  • Absolutely, but to offer a counter-argument, quality has become less important vs eliminating manufacturing costs. If they can cut some corners and the product still "works" but is cheaper to produce, that's almost certainly the direction they'll take. And, how much quality will remain based solely on reputation? Thinking I don't need to test anything, I've got a meanwell PSU! There is a lot of variance in the manufacturing process, and not all PSU's (even the same brand and model) are created equally.


    To summarize, yes, you'll probably be fine without using caps and a resistor if you're very careful during installation, and are using quality parts/LEDs. But on the flip side, they're so easy to integrate that if they save me having to chop off an LED, or make the LEDs brighter in the center of my strip for that split second, then IMO they're worth it.

  • In many cases helped this...

    especially for cheap high current china power supplies. Maybe a little oversized... 8o

    Also, APA102 never worked properly without a level shifter in my setups. ;(

    Grüße aus Österreich / Greetings from Austria !

    - Don't wanna miss it anymore !

  • mostly it is just a prevention, just to be sure that the risk is at a minimum if something goes wrong...


    some old datasheets wanted all those components....


    but i think those are mostly old pictures, where the leds had no protection and everthing else...


    if you look at world semi homepage (world semi is from WS28xx) you will see that most of those things are now all included!



    http://www.world-semi.com/solution/list-4-1.html#141


    If you want more Information, look at the presentation on their site. http://www.world-semi.com/DownLoadFile/141


    also the apa102 has some protection




    http://www.christians-bastel-l…ocs/datasheets/APA102.pdf


    if you have a look at the sk6812, you would need for every led a cap...



    http://www.normandled.com/uplo…%20LED%20%20Datasheet.pdf

  • To summarize, yes, you'll probably be fine without using caps and a resistor



    good argument, but..

    I think that a big brand like Meanwell ( the real one) where we do purchase a lot at the company, cannot afford bad quality.


    A big brand like that can not take the chance into a "bad production or cheaper costs" , the professional installations depend on hassle free and no mallfunction environment. If it was the case that a PSU will die fast then they get a bad reputation fast also :)


    so i will stand by this, most problems with builds/setups if its ambilight or something else will most the time come back to the person who build it and has a flaw in the build. Its not the PSU but


    • bad connections in general
    • gauge of wire not thich enough, has more resistance in wire like AWG18 ( its only 1mm thick)
    • not soldered joints/PINS or connections in general
    • Grounding trough GND pins/ledstrip/PSU isn't done properly or not at all.
    • using two diffrent powersources and not grounded correctly to each other
    • PSU is a cheap knock off or even worse powerbrick" with no earth connection to powergrid.
    • PSU is bad, to much AC running trough DC signal and not rectified properly ( believe me that happens a lot )
    • the list goes on and on.

    especially for low voltage and high currents soldered joints become really important to reduce resistance into the joints as much as possible.

    so you see before this is all not correct you can use as much capacitor as you want but you never get the results you are hoping for.

    thatswhy i myself am not a big believer into adding electronics that shouldn't be necessary in the first place.


    call me old fashion, and... each to his own.


    advice is free. ;)

  • if you have a look at the sk6812, you would need for every led a cap...

    1 microfarrad each LED, i wonder what it does and >> is it also implemented into the strip type of the sk6812?

    i think it should be there to flatten out the curve . if it even excist > to protect the led and also make it possible to run at lower voltage, i think thats the mainreason they implement it.


    • just to be safe
    • make it possible run on 3,5 volts ( capacitor works as a storage container for power needed)


    something like that, still i am convinced if i see the schedule that the led will run on 5 volts without the c2 104 cap.



    And in general when you think about it then if the capacitor is needed into the schematics if you are using the led without a strip.

    whats the purpose then to use a 1000 microfarrad 16volts capacitor for the whole line at the beginning?

    its impossible for that capacitor to hold and flatten out a curve for all the leds simultaniously ( because they are mounted in voltage parallel, so equal 5 volts applied)

  • especially for cheap high current china power supplies. Maybe a little oversized... 8o

    Also, APA102 never worked properly without a level shifter in my setups. ;(



    hahaha something similar i used in car-hifi installations, the 1,5 Farrad cap > carefull with installments! always use a lightbulb in series to load. :P


    Really never worked? i made already 3 setups now,


    • ws2801 first build
    • apa102 for myself, second build
    • apa102 for a friend

    not any of the builds needed level shifter/caps or resistors.

    maybe i am just lucky ;)

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