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LED Strip - Power supply

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Reply #30 — Posted 2yr ago
by MikeMoy | Newbie | 50 exp
Reply #30 — Posted 2yr ago
by MikeMoy | Newbie | 50 exp
For the record I know I am going to get slammed for saying this, so screw it. I know many of you have thought the same thing just never said it to anyone here.

@DeathBloom, I don't mean to discourage you, but I have to ask you an others in this same boat.

It's clear you know very, very little about electronics, and that's ok, we all have to start somewhere. Why in the world would you jump in both feet into something way above your head? Electronics is not like legos in that if the connector fits another your good to go. Why would you spend your money on something, and have no idea what your really doing?

I am all for people learning something new like you are, but why so many of them try to blink a led, spin a motor without ever at least learning first the absolute basics in electronics, like how to calculate a current resistor for a led or for that matter even know a led has a polarity. Understand current draw on a I/O pin, know what a transistor does and how to use it, and calculate the base current resistor properly. Let alone not own a $8 el'cheapo meter just blows my mind. Many don't even know that I2C needs pull-up resistors, and moreover what value to use on a 3.3V system compared to a 5V system.

Many more yet that play with I2C and SPI done even own a cheap scope. The copy and paste code examples, plug in these modules and get the gizmo to work and then get all excited and then go full throttle into thinking of something larger to make, and when they do and it does not work they are scratching their heads wondering why it worked on the bench but after i put 50' of cable to it, it stopped. Then all the forum questions start why this and why that, and did you do this and did you do that. Hey, just pull your scope out and probe the lines and you will quickly see what the problem is.

LEARN BASIC ELECTRONICS first people, and for the love of pete get some testing equipment if you plan to do more than the basics.
I hate it when I see people make things that don't know jack, and just because it's working they think all is well. Start selling it to their friends and such and then there is a fire at night because of it.
4 likes
Reply #31 — Posted 2yr ago
by Terrence | Hero | 12,056 exp
Reply #31 — Posted 2yr ago
by Terrence | Hero | 12,056 exp
@MikeMoy - No one is forcing you to read, let alone contribute to, these help sessions for the non EE's among us.

I applaud Mr. Smith and Brett's generous efforts to guide us in our blind path into electronics via tiny boards. Clapping

This is a great forum of experts and novices alike, please don't try to shape it into an experts only forum.
1 like
Reply #32 — Posted 2yr ago
by Mr. John Smith | Legend | 42,263 exp
Reply #32 — Posted 2yr ago
by Mr. John Smith | Legend | 42,263 exp
@MikeMoy - There are many reasons why I answer the questions of newbies on the forum. I'll use my personal experience as an example.

First off, there is nothing wrong with exploring. Don't know how to blink an LED in a 5V system? No problem, you'll learn after the first few blow out on you. Not everyone has the time/money to do 3 years of information technology design (programming), 3 years of Electronics Design, and 3 years of Mechanical Engineering; I certainly do not but I'm still trying to do a project that requires all those skills. Even after the schooling, you'll learn practical skills in the industry of each of the aforementioned bodies of knowledge that you won't learn in school. So to be well rounded in each would require a master level (post-graduate) degree. That's 15 years! So your suggestion of learning the basics before hand just isn't always practical for everyone's situation. I for example started learning electronics in primary school. I learned about transistors, current, voltage, logic gates etc all before college. Even after that, during my career I keep learning about digital electronics and µC programming (in assembly btw). Then along came GHI and Fez Domino.

Secondly, it helps the person who's asking learn faster when I mention things like, the difference between how current flows in a diagram vs how it flows in physics; and the difference between GND and Ground. This is not something that a new person may know straight out of the block. I do remember the pain learning which way was which back in the early 2000's from blowing many an IC and transistor. But learn I did.

Thirdly, these forums are constantly crawled by search engines. If in the future some twelve year old is trying their hand at something similar and they happen upon these knowledge base articles, it will benefit them to see what has been tried before, and the explanations of why and why not.

Lastly, GHI as a company benefits from having an advanced and active community, where at least two disciplines meet. Anyone trying to determine if purchasing GHI products is a good investment, will happen upon these articles and realize that there are many knowledgeable (and helpful) people around them, who can sometimes answer questions before even the manufacturer can. Even seemingly off topic ones like which way to Ground. The forum acts in a way like industry experience which some of us (i.e myself) may lack in electronics.

P.S. Just because I have a scope, doesn't mean I know how to use it to diagnosis transmission line problems; oh and thanks for the tip about I2C needing pull up resistors. I didn't know that either Cheesy
Reply #33 — Posted 2yr ago
by Brett | Superhuman | 125,590 exp
Reply #33 — Posted 2yr ago
by Brett | Superhuman | 125,590 exp
I'm still suspicious of your code playing a part, but the easy way to eliminate this is to do exactly the same test, run exactly the same code with completely isolated devices (no USB connection to a PC), and powering both the Panda and LEDs off the same power source, and testing your 5v and your ~4.5v one (although this may be slightly too low for the LDO to work, but try it). The behaviour of your code should be the same in both scenarios, so all things being equal and operating correctly, the LEDs should work the same
Reply #34 — Posted 2yr ago
by Dave McLaughlin | Legend | 58,471 exp
Reply #34 — Posted 2yr ago
by Dave McLaughlin | Legend | 58,471 exp
Just so we can be sure of the GND's being correct, can you show a simple drawing of your setup?

If your code works with the small strip on the same power setup, then the issues has to be down to voltage levels and possibly the rise and fall times are not good when more LED's are fitted. It may also be that the voltage dips low enough when you try to illuminate more LED's and the supply can't handle this although as it is designed for LED driving this should hopefully not be the case. A scope would show this but something you don't yet own. Smiley
Reply #35 — Posted 2yr ago
by DeathBloom | Junior | 772 exp
Reply #35 — Posted 2yr ago
by DeathBloom | Junior | 772 exp
Terrence says:

I applaud Mr. Smith and Brett's generous efforts to guide us in our blind path into electronics via tiny boards. Clapping

I second this.

Brett says:
Panda and LEDs off the same power source, and testing your 5v and your ~4.5v one (although this may be slightly too low for the LDO to work, but try it).
Will try this out today and let you know the results.
I still suspect the logic level voltage here. I'll get the shifter today.
Dave McLaughlin says:

Just so we can be sure of the GND's being correct, can you show a simple drawing of your setup?

Will be also my homework for today.

Dave McLaughlin says:

If your code works with the small strip on the same power setup...

I want to emphasize that I have 2 identical set ups which are only different in terms of power supply used: 4.5v vs 5v, the LED number is the same. The first set up works well and the second fails.

The fail may be characterized like: LED strip fails to get the correct data from the controller.
It's not like the second set up fails to light the LEDs up as I told already that when accidentally touching the Data Input of LED strip with mult-meter I was able to light up the whole strip with the second set up.
Reply #36 — Posted 2yr ago
by Brett | Superhuman | 125,590 exp
Reply #36 — Posted 2yr ago
by Brett | Superhuman | 125,590 exp
let me reiterate the test conditions too - you use one Panda and LED strip, connected to the 4.5v supply. It works. You only change out the 4.5v supply with the 5v supply, nothing else, no other changes Smiley

I'm going to go to find a P2 and some LEDs and some voltage regulators to play with
Reply #37 — Posted 2yr ago
by DeathBloom | Junior | 772 exp
Reply #37 — Posted 2yr ago
by DeathBloom | Junior | 772 exp
Brett says:

let me reiterate the test conditions too - you use one Panda and LED strip, connected to the 4.5v supply. It works. You only change out the 4.5v supply with the 5v supply, nothing else, no other changes Smiley

I'm going to go to find a P2 and some LEDs and some voltage regulators to play with

This is totally true with one remark: both times Panda2 was powered via USB but it was common grounded with both supplies.

One question in return: the digital outputs of PANDA2 work at 3.3V, correct? Meaning Hi and Lo signals corresponds to 3.3V "interface"
Reply #38 — Posted 2yr ago
by Brett | Superhuman | 125,590 exp
Reply #38 — Posted 2yr ago
by Brett | Superhuman | 125,590 exp
So please test it without USB Smiley Yes, the USB GND connection should remove the influence of any bias between the GND reference voltages, but we really need to get away from that as a diagnosis tool. Just deploy a simple pattern that's easy to see when it's running correctly on the LEDs.

I didn't have a P2 that I could lay my hands on easily, and my LED strip was connected to a Gadgeteer screw terminal breakout board, so I connected up a 5v source to my LED set and connected it back to a Cobra2, and I proved that powering the board was fine - haven't yet written code to get the LEDs going but I'll get to that in the morning

And your 3v3 question. A HI signal means 3v3 on that pin, a LO signal means 0v on that pin.
Reply #39 — Posted 2yr ago
by Mr. John Smith | Legend | 42,263 exp
Reply #39 — Posted 2yr ago
by Mr. John Smith | Legend | 42,263 exp
@DeathBloom - On another note, I suggest that you get a book on electronics. Preferably one that a tutorial about building circuits.

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