leds And resistors

I'm a chemist by training and for me if someone gave me two five gram bags of something I'd assume that 5g = 5g. I naively thought it would be the same with volts.

If you want to use that analogy then you must also figure amps as volume. If your bags are sized for 5g of Pb, surely you cannot fit 5g of feathers in it.

tinman13kup:
If your bags are sized for 5g of Pb, surely you cannot fit 5g of feathers in it.

Depends…

lfba.GIF

Have a look at thread here

https://forum.arduino.cc/index.php?topic=524448.0

Conveniently, it contains all of;

  1. a suggestion to use imagebin
  2. The reason I’m using imagebin
  3. Two requests for the details on power surge protection, specifically resistors and capacitors.

Looked at that that thread, so you think the advice from one member overrides the rules of How to use this forum. Pasting you images as attachment keeps everything in house and no one has to venture off into potentially malware ridden sites.

Power surge protection means something on mains supplies but very little about the sort of things we are dealing with here which is probably why no one received an answer.

It is not being pedantic it is helping you get the best answer but you seem to be hell bent on wasting peoples time here. I did see your initial post before you had any answers and refrained from kicking off the twenty questions quiz because I know you have a negitave attitude towards me. So when I saw something I could comment on sensibly this morning I decided to. Looks like I only antagonized you even more.

Point is if you are told something on one thread about using a data resistor and capacitor on those LED strips and then ignore it in later posts, it shows you are not up to the correct level to be attempting what you are doing and are only being a troll and total waste of space. You need to do more tutorials, examples and background reading. What you are doing is like someone asking about the nuances of Latin grammar when you don’t even know what the words mean.

I will leave it up to others to tell you what you are doing is stupid and not bother answering your posts again because you seem to resent me telling you what you have done wrong. From personal messages from other members I know I am not the only one who you have pissed off in your 111 posts here. So goodbye.

groundFungus:
What makes you assume that? What risk are you trying to mitigate? How is the Arduino powered?

First two questions;

Grumpy_Mike:
If you have wired it up like that it is a great way to damage your WS2812 LEDs. This is because the data signal from the Arduino will be much higher than the supply applied to the WS2812s

I inferred that this meant it was the separating of the power supply that caused the problem. The risk is explicitly stated by Mike “great way to damage your WS2812 LEDs”

The Arduino when I’m testin with this setup is powered through the USB by a portable mobile phone charger.

Still trying to get some info on the size of both capacitor and resistor required for use with the Arduino.

As my knowledge is so small, every time I try and add more info I just seem to confuse things, so assume I know nothing and you won’t be far wrong. With that in mind;

  1. Why do I need a capacitor?
  2. What size do I need? Does it depend on the project? If so it’s a pro Trinket controlling between 45-60 WS 2812b LEDs (the 8-led circuit is just a test rig)
  3. Where does the capacitor go? (Detailed please, I’ve become aware that I misinterpret things like “in-line” etc

Same three questions apply to the resistor requirement.

The circuit is basically the same as my terrible diagram, but without the indicative “normal” LED and resistor and obviously more LEDs. In practice the power supply will be a 5v portable phone charger. I’ve been using one for over two months and it hasn’t caused me any problems yet...it’s impossible that all the LEDs will be on and with all three RGB channels powered at the same time due to the software running on the Arduino. This isn’t a sustained lighting source, the LEDs flash on for a few seconds (less even) with a much longer (up to 10 seconds) intervening period of darkness, so the maximum power drawn isn’t as high as the approx 18w with a 3.6A maximum that powering them all would require (source of calculation https://www.audectra.com/guides/power-consumption-of-rgb-led-strips/).

Also, can someone recommend an image size reduction app for an iPad?

Hi, Is there a graphics app on the smarty phone? Check what it can do..

Tom... :)

I refer you to the Adafruit guide for cap size, resistor size and wiring details.

strip.jpg

groundFungus:
I refer you to the Adafruit guide for cap size, resistor size and wiring details.

strip.jpg

Thank you!

TomGeorge: Hi, Is there a graphics app on the smarty phone? Check what it can do..

Tom... :)

Everything apart from reducing size as far as I can see...

Referring to groundfungus’ Diagram...

Is it okay to take power for the neopixels from the +5v and GND terminals of the Trinket, with the Trinket powered by USB?

If so, the power and GND would enter from the same “end” as the data. I know Adafruit recommend having the resistor as near to the pixels, not the controller...does it matter where the capacitor is sited in the same fashion?

Once again, thanks.

You can power the LEDs from the Trinket as long as you are very careful to not draw too much current (< about 500mA total for USB).

Actually the location of the resistor is not that important. The cap should be as near the strip power input as possible for the least wiring voltage drop. It doesn’t matter which end the power is fed to the strip. You can feed power to both ends. If you have long strips you can inject power in the middle and both ends.

Did a bit of reading. A dedicated charging USB port is rated at 1500mA, the power packs I have are I believe 1200mA (I may be confusing mA and mAh though, will check tomorrow).

If the above info is right, would it be better to wire the LEDs and the Arduino directly from the powerpack, rather than take the LEDs from the +5v on the Arduino, i.e. as per your original diagram?

If i do inject power at more intervals, does each connection require the capacitor?

Grumpy_Mike: But you should never turn off the power to a string of WS2812s when the data pin is connected up anyway or you will damage them.

Regarding the above...is there a way to turn off the LEDs safely? I’d rather they weren’t on all the time...

Hi,

GreyArea: Regarding the above...is there a way to turn off the LEDs safely? I’d rather they weren’t on all the time...

If you need the controller to be still operating, then get it to command all the LEDs to turn OFF. Tom... :)

Where in the diagram did I indicate that the 5V strip supply is from the Arduino 5V? I certainly did not mean that as the strips that I use are all powered by an external 5V supply. USB 2.0 ports can supply 500mA, USB 3.0 can supply 900mA, a charging port can supply more. As to the 5V regulator, it depends on the amplitude of the source of the supply voltage to the regulator how much current the regulator on an Arduino can supply. The more voltage that the regulator must drop, the less current the regulator can supply before it overheats. For instance, on an Uno the regulator can handle about 1W of power dissipation. With a 12V supply that means that the regulator can not supply more than about 150mA to stay under 1W dissipation. With 7.5V to the regulator about 400mA.

I would distribute the capacitance between the taps. Divide the 1000uf by the number of taps and use the closest standard value at each tap, as close to the strip as possible. But no lower than 100uf on each.

groundFungus: Where in the diagram did I indicate that the 5V strip supply is from the Arduino 5V?

You didn’t. I worded my statement poorly. Please see below with added parentheses to try and clarify, sorry.

“If the above info is right, would it be better to wire the LEDs and the Arduino directly from the powerpack, (rather than take the LEDs from the +5v on the Arduino) i.e. as per your original diagram?”

Or to be perfectly clear;

“If the above info is right, would it be better to wire the LEDs and the Arduino directly from the powerpack, (...), i.e. as per your original diagram?”

TomGeorge: Hi,If you need the controller to be still operating, then get it to command all the LEDs to turn OFF. Tom... :)

So, if I have a power switch that kills power to BOTH the Arduino and the LEDs, that’s okay? Or if I do power from usb, with +5v and GND from the Trinket to the LEDs, just pulling the USB cable out doesn’t risk harm?

Take the power for the LEDs from the power pack, not the Arduino 5V.

groundFungus:
Take the power for the LEDs from the power pack, not the Arduino 5V.

+1 Karma for clarity!

Is the attached diagram a correct interpretation of what you’ve all told me so far?

The power packs I have are rated at 1.0A output and are 1200mAh. Adafruits guidance is to assume 20mA per LED, so absolute maximum would be 50, but in practice my animations run maybe 10 to 20 at a time and only at a maximum brightness of 100 (not 255), so hopefully I am covered.