daisy chaining 74HC595's

Ruffsta:
never mind, i get it... but where does uF capacitors go? i thought you needed 1 for every 74HC595? also, they may not be using 10 leds... but i'd like to know where the pnp goes as well (because i will be using 10 leds per row in a lot of my stuff)..

You need a decoupling capacitor (0.1uF usually) as close as possible to the power leads of every chip. Its perfectly possible to share
one between two neighbouring chips, if they are adjacent, the important thing is that the leads between the chip's supply pins and
the capacitor are short... The purpose of the capacitor is to stop the voltage dropping as currents switch on a time scale of a few ns to us,
it far faster than the power supply can adapt to load changes.

With lots of LEDs the currents being switched are larger and extra decoupling capacitors (10uF or so) are probably a good thing -
these don't have to be as close to the chips as they handle a somewhat longer timescale. Adding a few might be needed.

You mention PNP transistors - are you planning a multiplexed array? Are you commoning the anodes then?

most of my projects will involve ATLEAST 100 leds - (some 50)... whether they be single color, bi-color or RGB - (most are RGB), but i have a few projects that are single color..

right now for this specific project, i have a sheet of pegboard - it will hold 1,012 RGB leds.. so, 1 uF capacitor for every 74HC595 and 1 pnp for every 10 leds is what i'm told...

i may do the same project using just blue leds, but for that i can use max7219's - as each one can drive 64 leds - requiring less than the one with RGB leds.... may even try one with bi-color leds.. haven't decided if i want to build a third project of it.. but the RGB one and the single color one - i am interested in doing right now.

Ruffsta:
.. so, 1 uF capacitor for every 74HC595 and 1 pnp for every 10 leds is what i'm told...

Oh ? ? ?
So, who's The Authority?

Ruffsta:
... i am a chef by trade!

How many cloves of garlic does chicken get cooked with?
How much baking powder should I use with flour?

Catch my drift?

[quote author=Runaway Pancake]
Oh ? ? ?
So, who's The Authority?[/quote]
if you must know... CrossRoads... mod and 22 yr engineer on here...

depends on what kind of chicken dinner/lunch you are making.. but atleast i was being specific on my project!

here we go again with the sarcasm...

k, i'm taking a break from arduino and the bs sarcasm... it's really starting to piss me off and i don't need anyone's crap anymore

anyways, thanks for not making me feel welcome on this forum everyone.. wish i could say it was a blast.. but i won't lie, it wasn't thanks to all the bs sarcasm that has been dished out to me more than once.. i hope this isn't how you treat all new people to arduino and the forum.

Ruffsta:
starting to feel sorry i bought this damn thing for my son and i to have something to do together and joining this forum.. since day 1 i never felt welcomed here... and i still feel the same way. glad i won't let my son join this forum... i can imagine how he would be treated.

and for all of you "experts" on here.. shame on you for not remembering what it was like being new and/or not having the patience to those that are new.. and you should also stop talking to all the new people like they know as much as you.

Maybe you've been disappointed because you're so hostile. There's a LOT to learn when getting into electronics. You can't just go to the forums and demand that someone show you how to do things. When the first poster suggested checking the datasheets you got mad. But that's step 1 when using ANY new component. You ALWAYS start by looking up the datasheet, as it's filled with info that will help you use their product properly. All you have to do is look at the part number.

74HC595 is a type of IC made by lots of manufacturers, but they all have their own unique part number. For example, the ones I got from TI are SN74HC595N. By looking up that datasheet, I found that the maximum current it can handle is 50ma. If you use 180 ohm resistors as shown in the image in the OP, lighting up more than 3 rows of lights will fry the chip. And that's with a PNP transistor switching their current. Just the gate current drawn by the transistors will put you over the top.

So try not to get frustrated. There's a lot to learn, but all it really takes is a bit of research. Engineers spend years learning this stuff in college. Don't be afraid to spend an hour with your nose buried in a datasheet. You'll be a lot more successful and things will make a lot more sense when you come back to the project armed with knowledge about how it works and why each component is needed.

Also, the first image that you posted leaves the output enable pin floating. That's not good. But you'd know that if you had read the datasheet. 8)

Ruffsta is actually referring to a 0.1uF cap that will go on the VCC pin of every 74HC595.

TI is the authority:

CrossRoads:
Ruffsta is actually referring to a 0.1uF cap that will go on the VCC pin of every 74HC595.
TI is the authority:
http://processors.wiki.ti.com/index.php/General_hardware_design/BGA_PCB_design/BGA_decoupling

Well, that's nice but
vs.

Ruffsta:
so, 1 uF capacitor for every 74HC595 and 1 pnp for every 10 leds is what i'm told...

I didn't see anything in the TI link about the "1 pnp per 10 LEDs Rule".

And he got a perfectly reasonable answer to his capacitor question (twice). Maybe going without decoupling is akin to going resistorless to some people - but you could sure fool me. Not being enough, evidently, we got the "argument from intimidation."

Ruffsta:
here we go again with the sarcasm...

k, i'm taking a break from arduino and the bs sarcasm... it's really starting to piss me off and i don't need anyone's crap anymore

anyways, thanks for not making me feel welcome on this forum everyone.. wish i could say it was a blast.. but i won't lie, it wasn't thanks to all the bs sarcasm that has been dished out to me more than once.. i hope this isn't how you treat all new people to arduino and the forum.

Your frequent use of the word "piss" in your posts coupled with your reliance on tantrums in an effort to get your way sets the table.

The PNPs also refers to the multiplexing I proposed in a different thread, for rows of LEDs with cathodes sunk by shift registers and anodes sourced from PNP.

He must have lost track of that subject (thread).

Kama to JoshD

What a great shame :frowning: I hope his son is not put off, nor indeed Ruffsta himself. Maybe after he's had a think he'll come back, maybe with a new alias, chill out and enjoy what he's doing?

Not really wanting to dwell, but I have to say that after the number of posts statement I went off and looked at his posts. I'll not comment further.

It can be very frustrating when starting any new hobby, but nothing pays off like getting down and dirty with the basics. Learning how to find info is probably one of the most useful things to learn. You struggle for a while then all of a sudden you're no longer the new boy, and there you are, helping people.

What encourages me the most when helping people, is evidence that they are helping themselves, and the odd please & thank you goes such a long way.

I have to say that I've not come across another forum with so many angry members nor as many new members who approach the subject with so much over inflated optimism. I'm not saying that the latter is a bad thing, but peeps are brought down to earth with a bump when their overly complicated first project fails.

Ruffsta:
anyways, thanks for not making me feel welcome on this forum everyone.. wish i could say it was a blast.. but i won't lie, it wasn't thanks to all the bs sarcasm that has been dished out to me more than once.. i hope this isn't how you treat all new people to arduino and the forum.

Wow, this thread spiraled totally out of control while I was asleep.

This page might help:

... i'm not going to take advice from someone new who has less posts than i do ...

You might want to go easy on the aggressive tone. Someone with few posts (now) might be a retired engineer or professor, who just joined the forum, and knows just as much about things as anyone.

... you get told different things by different people and when you look at tutorials ...

That's the nature of the Internet, I'm afraid. However on the "official" support site (here), you can expert good advice, and if someone does suggest something that may not work, someone else will likely correct it.

i bought this damn thing for my son and i to have something to do together and joining this forum.. since day 1 i never felt welcomed here... and i still feel the same way. glad i won't let my son join this forum... i can imagine how he would be treated.

Your son will be most welcome here. If he treats us with respect and courtesy, I'm sure everyone will reciprocate.

If somebody posts garbage here, they usually get corrected in no time (and if you're sensible you'll thank them for correcting you, not start arguing!)

You can't say the same for some random page on the Internet, or even the official tutorial pages on this site (there's some major errors in some of the tutorials and apparently no way to get anybody to correct it).

fungus:
even the official tutorial pages on this site (there's some major errors in some of the tutorials and apparently no way to get anybody to correct it).

and that's a good way to run an official site/forum? surely there must be a way to correct the tutorials..

There are a lot of tutorials in the Playground. Some were written for older versions of the IDE, and prior to some function call changes. Plus, some were written before newer hardware was released and may not mention something like "does not work on Leonardo" or something like that.

Some authors may have moved on, and you can appreciate it would be a lot of work for someone to make sure every tutorial is absolutely correct, for all available hardware, operating systems, versions of the IDE and so on. It's a moving target, after all.

To be honest, I don't understand where all this anger is coming from. In your first post in this thread you said:

so can someone please explain (and show if possible) the right way of doing it as far as pnp's and capacitors go.

What PNPs? Do you mean transistors? There aren't any in the circuit. On the bildr page you linked (http://bildr.org/2011/02/74hc595/) there is no reference to PNP at all.

So, your question doesn't make a lot of sense. And, if I may ask, why not ask at the bildr page? Surely it's not our fault you are having trouble with a circuit on another web site?

Your posts are coming across as very negative. You ask again: "i just want to know where the freaking pnp's and capacitors go! that's all i'm asking for!!! damn..".

Well, swearing aside, again, what PNPs?

Then: "glad i won't let my son join this forum... i can imagine how he would be treated".

Sorry you feel like that. Perhaps find a friendlier forum ... if you can.

In any case, you might want to "let" your son join and form his own opinions.

These were both posted already and clearly show where the PNP and capacitors go.
You can re-draw them in fritzing if you want.

Ruffsta:
that's not very helpful.. i have 74HC595's from different sources.. i don't know who the actual manufactures are nor am i going to track them down... (like i don't have other things to do)... and honestly, i don't know your skill level, but i'm not going to take advice from someone new who has less posts than i do.. no punt intended.

Fortunately, 74HC devices are supposed to meet certain specifications no matter who the manufacturer is. Therefore, just about anyone's data sheet will do. That may not be true for other devices so if someone tells you to get a data sheet, then it's probably good advice. Nevertheless, it is your responsibility to either look up the data sheet or reveal the manufacturer's name when designing with a part or asking for help with that design... whether or not you're too busy doing other things.

You can take that advice or leave it as I probably don't have enough posts to be relevant. This is the Internet and anyone can have any qualifications they can type but if we're counting, I have been designing and building electronic circuits since I was ten (57 years), and have had a degree in electrical engineering (electronics not power) for 46 years. When I have 15,000 posts I will have skill as well I guess. :slight_smile:

or carpal tunnel syndrome 8)

CrossRoads:
or carpal tunnel syndrome 8)

Yeah, that's a definite danger! :slight_smile:

Fortunately, 74HC devices are supposed to meet certain specifications

Hence my suggestion to read the DS. I once became very unstuck when a bucket load of chips turned up with NC where there was supposed to be an inverted output! Once bitten....

FYI Ruffsta, many chips are supplied without (or unreadable) part numbers, but they will usually have the manufacturers name/logo (logos are another learning curve) (hint, dampen with a whetted finger tip and angle to light)

I would suggest (to anyone who hasn't yet) getting hold of some data sheets of components you are familiar with (LEDs, Transistors, even Resistors) because it does take a while before you "get your eye in". They are filled with information that is of little interest to the average punter unless you want to push the envelope. You will find details of the package, soldering criteria, operating and storage minima & maxima, more graphs than you can shake a stick at, exemplar circuits, test circuits. But you will also find pin-outs, application notes, sometimes circuit layout advice (more so for high frequency, crystals/resonators etc.), de-coupling advice, table of operating voltages, source/sink current, operating and quiescent current etc. PRINT THEM OUT, write all over them, they are your best friend, a well fondled data sheet should have coffee rings and dog ears. If you go though my filing cabinets and pull job folders, you will find data sheets by the score! You have to learn to sort the wheat from the chaff.

Some slightly off topic advice that will pay dividends...
Breadboards : Treat them with love and care, a damaged board will cause you grief and have you chasing your tail.

Soldering Irons : Forget them! Get a soldering station! I just picked one up from ebay for a few quid for my son. Ensure that it is temperature controlled (not just variable voltage) 40-60W with a selection of tips, but I personally hardly ever use anything other than a fine pencil tip.
You could of course make one using an Arduino, but seriously, for the money....
Again, treat with love! A tinned tip is a happy tip. Keep your sponge damp, use good quality solder and use the lowest temperature that allows you to solder confidently. Cleanliness is next to shinieness!

Sarcastic Hint: If you were supposed to carry the solder to the joint on the tip of the iron, they would be equipped with little ladles! If your iron has a little ladle, it's past time to change the tip :wink:

One last tip: Break your project down and joy it! If daisy chaining 20 chips, first prove that you can drive one, that it does everything you want, then two, again, test it! Then twenty, you will find success will be matter of fact, not a rarity and the same goes for your code, break it down in to simple, testable blocks. And don't just copy, understand! edit, fiddle, play.

Oh, and have fun!